SuperCharger Vs. Turbo...
05-19-2004, 12:43 PM
#161
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Originally posted by gq_626
GREDDY safety issue update:
I spoke to kenji at Greddy today. Couple of things here
1) The airbag sensor does work.
That is good...whew.
2) The aluminum brace will fit...even with the intercooler in place. woohoo! That is the good news. The bad news is that you need to custom fabricate some piping, and replace the left side IC end tank with a single lower unit. The upper intake pipe blocks the mounting points for the brace. That is the reason we cant install the brace...its not the thickness of the FMIC that is an issue. Greddy tried to design the kit to keep the brace in place, but the elabroate piping was too complex for a bolt-on it...and they said it would require too much welding and cutting.
But this is certainly an option for those that want to reinstall that brace. I am going to look into the costs myself...it couldnt be too terribly expensive.
GREDDY safety issue update:
I spoke to kenji at Greddy today. Couple of things here
1) The airbag sensor does work.
That is good...whew.2) The aluminum brace will fit...even with the intercooler in place. woohoo! That is the good news. The bad news is that you need to custom fabricate some piping, and replace the left side IC end tank with a single lower unit. The upper intake pipe blocks the mounting points for the brace. That is the reason we cant install the brace...its not the thickness of the FMIC that is an issue. Greddy tried to design the kit to keep the brace in place, but the elabroate piping was too complex for a bolt-on it...and they said it would require too much welding and cutting.
But this is certainly an option for those that want to reinstall that brace. I am going to look into the costs myself...it couldnt be too terribly expensive.
05-19-2004, 12:46 PM
#162
Sanderman....your sacasm is witty...but ludicirous.
BELIEVE me....that last thing i want in my first gear is any more power....thank GOD there is a bit of lag until 4500rpm. It is virtually still impossible for me to get a good start without completely smoking the tires!!
Until you've driven a TT....and compare it to an SC....I dont think you'll fully appreciate what I am talking about.
BELIEVE me....that last thing i want in my first gear is any more power....thank GOD there is a bit of lag until 4500rpm. It is virtually still impossible for me to get a good start without completely smoking the tires!!
Until you've driven a TT....and compare it to an SC....I dont think you'll fully appreciate what I am talking about.
05-19-2004, 12:58 PM
#163
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Originally posted by gq_626
Sanderman....your sacasm is witty...but ludicirous.
BELIEVE me....that last thing i want in my first gear is any more power....thank GOD there is a bit of lag until 4500rpm. It is virtually still impossible for me to get a good start without completely smoking the tires!!
Until you've driven a TT....and compare it to an SC....I dont think you'll fully appreciate what I am talking about.
Sanderman....your sacasm is witty...but ludicirous.
BELIEVE me....that last thing i want in my first gear is any more power....thank GOD there is a bit of lag until 4500rpm. It is virtually still impossible for me to get a good start without completely smoking the tires!!
Until you've driven a TT....and compare it to an SC....I dont think you'll fully appreciate what I am talking about.
In a typical road track there wont be very many times you will have the car under 2500 rpms...and from 2500 rpms up the TT is just so superior in TQ and HP. Below 2500 rpms neither system is much better than stock N/A (maybe 10-15%)
GQ when you are crusing on the highway 65mph roughly 3000 rpms in 5th and roughly 1/3 to 1/2 throttle....describe what happens when you down shift and floor it .....my guess is the throttle response is almost instant.
05-19-2004, 01:11 PM
#164
in your senario....I have full boost in 1/2 sec...max. And becuase the engine is so wonderful in N/A form.....if you were sitting in passenger seat and not looking at the guages, you would not even notice "lag". I swear...people that ride in my car cant even tell there is a turbo per sec......it just feels disgustly fast and torque everywhere.
And becuase the engine is so wonderful in N/A form.....if you were sitting in passenger seat and not looking at the guages, you would not even notice "lag". I swear...people that ride in my car cant even tell there is a turbo per sec......it just feels disgustly fast and torque everywhere.
05-19-2004, 01:59 PM
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Originally posted by gq_626
in your senario....I have full boost in 1/2 sec...max. And becuase the engine is so wonderful in N/A form.....if you were sitting in passenger seat and not looking at the guages, you would not even notice "lag". I swear...people that ride in my car cant even tell there is a turbo per sec......it just feels disgustly fast and torque everywhere.
in your senario....I have full boost in 1/2 sec...max.
And becuase the engine is so wonderful in N/A form.....if you were sitting in passenger seat and not looking at the guages, you would not even notice "lag". I swear...people that ride in my car cant even tell there is a turbo per sec......it just feels disgustly fast and torque everywhere.
And because the power curve is a nice gradual one this means superior accelaration in street/track because you get more power sooner in the power band than S/C and a huge advantage in TQ!
If you look at some of the small motors with massive turbos running high boost they can have a huge spike in power like 100 hp increase in 1000 rpm which can be tricky to control out on a track with the curves however the greddy kit has a good streetable power curve which is easier to control out on a track as the power is more gradual. It closely resembles N/A dyno charts with the same kind of power.
05-19-2004, 07:17 PM
#167
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Originally posted by SQUILL
GQ when you are crusing on the highway 65mph roughly 3000 rpms in 5th and roughly 1/3 to 1/2 throttle....describe what happens when you down shift and floor it .....my guess is the throttle response is almost instant.
GQ when you are crusing on the highway 65mph roughly 3000 rpms in 5th and roughly 1/3 to 1/2 throttle....describe what happens when you down shift and floor it .....my guess is the throttle response is almost instant.
I don't think it is a bad thing, just part of a turbo. But seems like some of you guys are in denial of this lag issue. You can use all the terms you want, but the fact of the matter is in everyday driving, you will have that hesistation(lag). Yes, it maybe small, but it is still there.
In this trend, the weaknesses of an SC have been said and noted. But when it comes to turbos, the only weakness that has been accepted is price(and that is argued), and that is just not true. The only reason why the lag is low on the Z is the fact that the compression is high and the boost is low.
Last edited by little_rod; 05-19-2004 at 07:20 PM.
05-19-2004, 08:05 PM
#168
Originally posted by little_rod
The only reason why the lag is low on the Z is the fact that the compression is high and the boost is low.
The only reason why the lag is low on the Z is the fact that the compression is high and the boost is low.
Exactly....but that is the nature of the Z. I am not reinventing the car. Lag is much bigger factor on smaller displacement engines, lower compression, and lower trq motors. I conceded there is lag....but it is imperseptible under normal driving conditions on the Z. I'd be happy to give anyone a ride in my car to demonstrate...just make sure you change your pampers.
In my opinion...and the opinion of many of the folks even with SC's...is that the two main drawbacks of TT are the cost (both parts and labor), and the more difficult installation and reversibility of a TT kit. This isnt something you can slap on and off your car in a day or two.
Once that 1/2 sec or so spool up takes place, you are in a world of significantly more TRQ and HP and any given RPM point. That is a trade off that almost any will make.....all things being equal of course.
And little_rod......I forgot to tell you...i dont even have to downshift.....the boost still comes on in 1/2 sec on the freeway in 5th gear.
05-19-2004, 09:18 PM
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Originally posted by little_rod
Well, I don't really care what happens when you downshift
Well, I don't really care what happens when you downshift
Originally posted by little_rod
of course the power should be pretty instant then. What is being ignored over and over again is that second that the turbo hesistates(which is lag).
of course the power should be pretty instant then. What is being ignored over and over again is that second that the turbo hesistates(which is lag).
https://my350z.com/forum/attachment....&postid=772477
And compare to this:
https://my350z.com/forum/attachment....&postid=752370
Graph here:
https://my350z.com/forum/attachment....&postid=752366
(thanks to those who posted this stuff earlier in the year)
Looks like your SC dont hit peak till redline, whooohoo so unless your at 5800rpm all day the TT will have boost in a much more usable band (gee sounds like a broken record)
Originally posted by little_rod
I don't think it is a bad thing, just part of a turbo. But seems like some of you guys are in denial of this lag issue
I don't think it is a bad thing, just part of a turbo. But seems like some of you guys are in denial of this lag issue
Originally posted by little_rod
You can use all the terms you want, but the fact of the matter is in everyday driving, you will have that hesistation(lag). Yes, it maybe small, but it is still there
You can use all the terms you want, but the fact of the matter is in everyday driving, you will have that hesistation(lag). Yes, it maybe small, but it is still there
Originally posted by little_rod
In this trend, the weaknesses of an SC have been said and noted. But when it comes to turbos, the only weakness that has been accepted is price(and that is argued), and that is just not true
In this trend, the weaknesses of an SC have been said and noted. But when it comes to turbos, the only weakness that has been accepted is price(and that is argued), and that is just not true
Originally posted by little_rod
The only reason why the lag is low on the Z is the fact that the compression is high and the boost is low.
The only reason why the lag is low on the Z is the fact that the compression is high and the boost is low.
05-19-2004, 11:37 PM
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Originally posted by little_rod
Well, I don't really care what happens when you downshift, of course the power should be pretty instant then. What is being ignored over and over again is that second that the turbo hesistates(which is lag).
Well, I don't really care what happens when you downshift, of course the power should be pretty instant then. What is being ignored over and over again is that second that the turbo hesistates(which is lag).
Originally posted by little_rod
I don't think it is a bad thing, just part of a turbo. But seems like some of you guys are in denial of this lag issue. You can use all the terms you want, but the fact of the matter is in everyday driving, you will have that hesistation(lag). Yes, it maybe small, but it is still there.
I don't think it is a bad thing, just part of a turbo. But seems like some of you guys are in denial of this lag issue. You can use all the terms you want, but the fact of the matter is in everyday driving, you will have that hesistation(lag). Yes, it maybe small, but it is still there.
Originally posted by little_rod
In this trend, the weaknesses of an SC have been said and noted. But when it comes to turbos, the only weakness that has been accepted is price(and that is argued), and that is just not true. The only reason why the lag is low on the Z is the fact that the compression is high and the boost is low.
In this trend, the weaknesses of an SC have been said and noted. But when it comes to turbos, the only weakness that has been accepted is price(and that is argued), and that is just not true. The only reason why the lag is low on the Z is the fact that the compression is high and the boost is low.
Yes the lag is low...so low in fact that the TT kit is superior on the VQ35DE than a Supercharger in every way except for price. The fact is that when the sc is in the low revs (2500-3000) the power it is making is considerably less than a TT. IT takes the SC till 4500 rpms untill it is really making some big power gains. Although this is not called "LAG" it is comparble. The s/c may deliver a very smooth feeling throughout the 6800 rpms of the VQ motor however the time between 0 rpms and 4500 rpms the SC is slowly building up to its power potential and because it is a smooth transition it doesnt feel like there is lag but that is exactly what is going on ..the S/C cars dont start to really pull hard untill the engine is high in the revs ...in the mean time the TT car has been dominating since 2500 rpms.
the comment you made about the high compression low lag....this is why on a VQ35DE Twin Turbos are superior over superchargers.
05-20-2004, 03:04 AM
#171
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First of all, I never argued the power curves of a turbo. I pointed out two things that were problems with a TT, lag and price. Now, I can point out more, such as difficulty of installation, heat, and such, but I didn't and I really don't care to do that.
I think both systems have their pluses and minuses, the funny thing is, I am neither pro-SC or pro-TT. What is interesting though is how much the power aspect of FI is talked about, yet the price is somehow not as important. I have been quoted a price on a greddy TT installed, but that is just for the base kit. To get all the bells and whistles you need to make sure it does well for you will cost more. Some of these things are just not needed by an SC.
I have neither system, but if I were to purchase one, price would be high on the list, after all, money does make the world go around. No matter how much money you have, no reason to spend more than you need in order to get the results that you desire.
The reason I bought up that the lag is low cause of the high compression and low boost of the TT setup is because of this, if you change those variables (compression & boost) to get to the potential of a TT, then you run into guess what, more lag!!! I just don't see the reason to get a TT if you are not going to take advantage of its potential, but I might be the only one in the world that thinks that, lol.
I think both systems have their pluses and minuses, the funny thing is, I am neither pro-SC or pro-TT. What is interesting though is how much the power aspect of FI is talked about, yet the price is somehow not as important. I have been quoted a price on a greddy TT installed, but that is just for the base kit. To get all the bells and whistles you need to make sure it does well for you will cost more. Some of these things are just not needed by an SC.
I have neither system, but if I were to purchase one, price would be high on the list, after all, money does make the world go around. No matter how much money you have, no reason to spend more than you need in order to get the results that you desire.
The reason I bought up that the lag is low cause of the high compression and low boost of the TT setup is because of this, if you change those variables (compression & boost) to get to the potential of a TT, then you run into guess what, more lag!!! I just don't see the reason to get a TT if you are not going to take advantage of its potential, but I might be the only one in the world that thinks that, lol.
Last edited by little_rod; 05-20-2004 at 03:08 AM.
05-20-2004, 06:19 AM
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A properly sized turbo with proper plumbing on a lower compression motor will still build boost faster then a Vortech will. A centrifugal type SC is the exact same beast as a Turbo, except for what drives it (Turbo = exhaust / Centrifugal = rpm dependant) Now you can change your pulley on the SC, but at what cost, going outside the SC's rpm limit (avg 50-60krpm) This will get you boosted earlier and more of it at the top end. More tuning is required and of course if you turn up the boost on a turbo, the same results will happen, just with more TQ ...... 
If you want the best solution for this car, the TT is the way to go, if you just want to add some more power, the SC is a fine kit as well. If I am going to spend $5-7K I would want the best......
If you want the best solution for this car, the TT is the way to go, if you just want to add some more power, the SC is a fine kit as well. If I am going to spend $5-7K I would want the best......
05-20-2004, 06:22 AM
#173
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I don't have a FI system yet and here are the conclusions I have drawn from this thread that will help me make my choice:
Scenario 1
Two identical cars with identical drivers are rolling down the highway at the same speed. One car has a SC the other a turbo. Both cars running the same PSI. Both cars downshift to a gear that gives them 4800 RPMs or higher and floor it. The SC takes off right away being near peak boost. The turbo hesitates (lag) and takes off with equal force. The SC gets the jump on the turbo and the SC wins.
Scenario 2
Two identical cars with identical drivers are rolling down the highway at the same speed. One car has a SC the other a turbo. Both cars running the same PSI. Both cars floor it without downshifting. The SC starts methodically climbing in speed. The turbo hesitates (lag) and shoots forward under full boost catching the jump the SC had and passing the SC and the turbo wins.
Scenario 3
Two identical cars with identical drivers are at the drag strip. One car has a SC the other a turbo. Both cars running the same PSI. Each car is launched and driven in a manner that takes full advantage and potential of their respective systems. Both cars finish the race tied.
I have concluded that both systems as far as speed are essentially equal. They differ only in terms like cost, complexity, driving style, power sensation, and HP needs. All of these issues are personal in nature and have nothing to do with one system being better than the other.
I like the rush of power when the turbo kicks in but I like the cost, simplicity, and driving style of the SC.
Jeff
Scenario 1
Two identical cars with identical drivers are rolling down the highway at the same speed. One car has a SC the other a turbo. Both cars running the same PSI. Both cars downshift to a gear that gives them 4800 RPMs or higher and floor it. The SC takes off right away being near peak boost. The turbo hesitates (lag) and takes off with equal force. The SC gets the jump on the turbo and the SC wins.
Scenario 2
Two identical cars with identical drivers are rolling down the highway at the same speed. One car has a SC the other a turbo. Both cars running the same PSI. Both cars floor it without downshifting. The SC starts methodically climbing in speed. The turbo hesitates (lag) and shoots forward under full boost catching the jump the SC had and passing the SC and the turbo wins.
Scenario 3
Two identical cars with identical drivers are at the drag strip. One car has a SC the other a turbo. Both cars running the same PSI. Each car is launched and driven in a manner that takes full advantage and potential of their respective systems. Both cars finish the race tied.
I have concluded that both systems as far as speed are essentially equal. They differ only in terms like cost, complexity, driving style, power sensation, and HP needs. All of these issues are personal in nature and have nothing to do with one system being better than the other.
I like the rush of power when the turbo kicks in but I like the cost, simplicity, and driving style of the SC.
Jeff
05-20-2004, 06:40 AM
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Squill, continuing to repeat incorrect things won't make them correct!
You keep talking about RPM as being the factor in determining a turbo's boost; in fact, boost is much more determined by throttle (load) than by RPM. Please try to learn this and understand it: you *CANNOT* see lag on a dyno plot. Turbo boost is determined mostly by throttle, not by RPM; Roots boost is constant; and Centri SC boost is determined by RPM. Please, please, please learn this and keep it straight and stop saying incorrect things.
It simply does not matter if the motor is spinning at 2k or at 4k; if the motor is throttled, you are not making boost. When you open the throttle, there is a lag before the turbo spools up to make the boost that makes the power you see on the dyno plot. To make this simple and obvious, full power is not available from a turbo until the wastegate opens. We *KNOW* that you are not trying to tell us that the wastegate is always open when the motor is spinning over 2500 RPM! How long does it take when you step on the gas before the wastegate pops? It takes some amount of time, a half second according to GQ man, who aparently has the Greddy installed.
Second, you keep asserting that SC's don't make power until in the high RPM range. This is only true for the centri SC's (Vortec, ATI); it is completely incorrect for the Roots blowers (Stillen). The Roots blowers generate full boost just off idle, and maintain nearly constant boost irrespective of throttle through the entire rev range -- completely different than a turbo or centri SC. Come on, say it with me now: turbo boost is determined mostly by throttle, not by RPM; Roots boost is constant; and Centri SC boost is determined by RPM.
Third, I keep explaining to you how it takes power to drive a turbo, but you keep saying it's free -- please learn that this is false and demonstrates that you lack basic understanding of how machines work. It takes power to compress air; that power is robbed from the crank whether you take it off by a belt at the front of the motor (all SC's), or take it off the exhaust of the motor. Squill, you will learn this yet!
Fourth, you mentioned that the Greddy twin turbo has a stock boost of ~4 psi, but can be tuned to over 25 psi. It is not possible that a pair of turbos can maintain high efficiency across this broad a range of drive power -- thus either the system has significant lag when tuned to 4 psi (because the turbos are sized to deliver the cfm needed at 25psi), or it has major compressor surge at the 25 psi end (because the turbos are sized to deliver the cfm needed at 4psi). You can't have it both ways -- these are not variable inlet geometry turbos!! The VQ35 is a fairly large displacement motor for a turbo application, which definitely works against you in this regard: it needs a lot of air.
Each half of the VQ35 is approx 1.74 liters, so you effectively have two single-turbo 1.7 liter motors. Audi and VW turbo apps that I'm familiar with in that size range had all sorts of lag issues, and it was very difficult to get the turbos sized just right for a given application. Different people had different turbo preferences for the same engine because they drove differently. Keep in mind that the Audi and VW apps had more cylinders driving the turbo (4, 5, or 6) than the VQ35 (3 per turbo), which means that the turbo in the VW/Audi application will be more responsive. OTOH, the VQ35 has a much higher CR, which greatly limits the max boost you can accept, but will help with the responsiveness.
GQ man, a half second of lag is an eternity on a track; in that time the car is most way through a corner!!
To me the FI alternatives break down to what you want the car to feel like:
Roots SC (Stillen): a bigger motor
Centri SC (Vortec): a peaky motor with a big rush near redline
turbo: regular motor with a big butt-kicking reserve of power after a small lag
It also comes down to the complexity of tuning:
Roots SC: simple tuning, its just like bigger displacement to the ECU
Centri SC: simple tuning, its just like wild cams/headers/exhaust to the ECU, RPM dependent fuel required at high boost
turbo: complex tuning, as fuel needs vary with boost which varies with throttle, no simple relationship to RPM
It also comes down to how hard it is to build the systems to higher boost:
Roots SC: new pulleys, easy ECU reprog/fuel enrichment, max boost limited by difficulty of intercooling (drop the CR and up the boost as much as you want, until you run out of cooling and get major detonation probs)
Centri SC: new pulleys, easy ECU reprog/fuel enrichment, max boost limited by the power difference between low RPM and high RPM (no cooling problem, but if you drop the CR, the low end drops major power)
turbo: just twist the **** to up the boost, and reprog the compensation maps; can drop the CR and up the boost until you hit compressor surge on the turbo, but lower CR and higher boost means increased lag.
It also comes down to complexity of install:
Roots SC: bolt on and go, but Stillen requires hood mods
Centri SC: bolt on and go, but a little more than Roots
turbo: big install
And of course price, which I have no basis to compare the systems.
I have absolutely no beef with anyone's choice of FI -- do whatever you want, whatever is appropriate to what you want to accomplish. Just don't go around spouting falsehoods.
-frank
You keep talking about RPM as being the factor in determining a turbo's boost; in fact, boost is much more determined by throttle (load) than by RPM. Please try to learn this and understand it: you *CANNOT* see lag on a dyno plot. Turbo boost is determined mostly by throttle, not by RPM; Roots boost is constant; and Centri SC boost is determined by RPM. Please, please, please learn this and keep it straight and stop saying incorrect things.
It simply does not matter if the motor is spinning at 2k or at 4k; if the motor is throttled, you are not making boost. When you open the throttle, there is a lag before the turbo spools up to make the boost that makes the power you see on the dyno plot. To make this simple and obvious, full power is not available from a turbo until the wastegate opens. We *KNOW* that you are not trying to tell us that the wastegate is always open when the motor is spinning over 2500 RPM! How long does it take when you step on the gas before the wastegate pops? It takes some amount of time, a half second according to GQ man, who aparently has the Greddy installed.
Second, you keep asserting that SC's don't make power until in the high RPM range. This is only true for the centri SC's (Vortec, ATI); it is completely incorrect for the Roots blowers (Stillen). The Roots blowers generate full boost just off idle, and maintain nearly constant boost irrespective of throttle through the entire rev range -- completely different than a turbo or centri SC. Come on, say it with me now: turbo boost is determined mostly by throttle, not by RPM; Roots boost is constant; and Centri SC boost is determined by RPM.
Third, I keep explaining to you how it takes power to drive a turbo, but you keep saying it's free -- please learn that this is false and demonstrates that you lack basic understanding of how machines work. It takes power to compress air; that power is robbed from the crank whether you take it off by a belt at the front of the motor (all SC's), or take it off the exhaust of the motor. Squill, you will learn this yet!
Fourth, you mentioned that the Greddy twin turbo has a stock boost of ~4 psi, but can be tuned to over 25 psi. It is not possible that a pair of turbos can maintain high efficiency across this broad a range of drive power -- thus either the system has significant lag when tuned to 4 psi (because the turbos are sized to deliver the cfm needed at 25psi), or it has major compressor surge at the 25 psi end (because the turbos are sized to deliver the cfm needed at 4psi). You can't have it both ways -- these are not variable inlet geometry turbos!! The VQ35 is a fairly large displacement motor for a turbo application, which definitely works against you in this regard: it needs a lot of air.
Each half of the VQ35 is approx 1.74 liters, so you effectively have two single-turbo 1.7 liter motors. Audi and VW turbo apps that I'm familiar with in that size range had all sorts of lag issues, and it was very difficult to get the turbos sized just right for a given application. Different people had different turbo preferences for the same engine because they drove differently. Keep in mind that the Audi and VW apps had more cylinders driving the turbo (4, 5, or 6) than the VQ35 (3 per turbo), which means that the turbo in the VW/Audi application will be more responsive. OTOH, the VQ35 has a much higher CR, which greatly limits the max boost you can accept, but will help with the responsiveness.
GQ man, a half second of lag is an eternity on a track; in that time the car is most way through a corner!!
To me the FI alternatives break down to what you want the car to feel like:
Roots SC (Stillen): a bigger motor
Centri SC (Vortec): a peaky motor with a big rush near redline
turbo: regular motor with a big butt-kicking reserve of power after a small lag
It also comes down to the complexity of tuning:
Roots SC: simple tuning, its just like bigger displacement to the ECU
Centri SC: simple tuning, its just like wild cams/headers/exhaust to the ECU, RPM dependent fuel required at high boost
turbo: complex tuning, as fuel needs vary with boost which varies with throttle, no simple relationship to RPM
It also comes down to how hard it is to build the systems to higher boost:
Roots SC: new pulleys, easy ECU reprog/fuel enrichment, max boost limited by difficulty of intercooling (drop the CR and up the boost as much as you want, until you run out of cooling and get major detonation probs)
Centri SC: new pulleys, easy ECU reprog/fuel enrichment, max boost limited by the power difference between low RPM and high RPM (no cooling problem, but if you drop the CR, the low end drops major power)
turbo: just twist the **** to up the boost, and reprog the compensation maps; can drop the CR and up the boost until you hit compressor surge on the turbo, but lower CR and higher boost means increased lag.
It also comes down to complexity of install:
Roots SC: bolt on and go, but Stillen requires hood mods
Centri SC: bolt on and go, but a little more than Roots
turbo: big install
And of course price, which I have no basis to compare the systems.
I have absolutely no beef with anyone's choice of FI -- do whatever you want, whatever is appropriate to what you want to accomplish. Just don't go around spouting falsehoods.
-frank
Last edited by ct roadster; 05-20-2004 at 06:51 AM.
05-20-2004, 07:07 AM
#175
Registered User
one other thing on the issue of lag that is misleading by what we have seen so far
these engines are pushing very low boost ~6.5-8 psi. almost any turbo car can make that kind of boost in no time. if they were pushing more boost its gonna be a while before they spool fully.
which would show more steep inclines on a dyno. when the z starts pushing one bar on the turbo motors it will likely not hit full boost until after 4k rpms, which will be extremely laggy considering the redline is at 6600. to fully appreciate this kind of boost you will need to increase the rpms as much as possible.
these engines are pushing very low boost ~6.5-8 psi. almost any turbo car can make that kind of boost in no time. if they were pushing more boost its gonna be a while before they spool fully.
which would show more steep inclines on a dyno. when the z starts pushing one bar on the turbo motors it will likely not hit full boost until after 4k rpms, which will be extremely laggy considering the redline is at 6600. to fully appreciate this kind of boost you will need to increase the rpms as much as possible.
05-20-2004, 10:42 AM
#176
This is a really good discussion...I hope we can keep the thread going.
I hope I am not sounding like a TT snob....becuase that is not my intention. As stated , there are benifits and drawbacks for each kit. But everyone that has an SC or TT is very happy with it..and mostly likely wouldnt change a thing.
One thing is that we keep talkiing hypotheicals and what-ifs. The fact is.....the TT's are running in the sub 10psi range on a very torqy motor with 10.3:1 compression. As a result, lag is very muted on the TT. But since the SC is parisitic, and being dirven by the crank, there is significnat less torque and HP down low...and a more gradually buildup of boost and power.
One drawback of the Roots style SC is heat.....how do you keep intake temps down signficnatly when running that car hard? I know some of them have front mount intercoolers and the like...but that roots unit on top of the motor is getting very very hot.......
Also, I think your max output and upside tuning potential is more limited with a roots vs. TT. That's my opinion....
Second, the Greddy kit use pretty large 18G turbos. You are correct, that at 6psi, there are running at the very bottom threshold of their efficiency...not ideal. But that is how Greddy designs their kits. There is plenty of room for exansion, and these turbos will hit their efficeicy sweetspot at about 15psi....whenever someone gets there.
My final point on this topic is that the TT gives tons of upside potential in terms of tuning, and for most street diriving conditions, offers more trq and power at a given RPM or thorrttle position. And yes, it takes 1/2 sec for full boost on the freeway, but it takes about 1/10 of sec to get some boost...just not max.....
Again, I am not bashing the SC's...just stating the facts. All of the SC's and TT';s are tons of fun. I just hope this dicussion will help people in making their own informed decisions on their purchase.
Also, note....both the SC's and TT's could stand for some upgrades once installed. The SC and TT are equally competent in the out-of-the-box state. But dont think that the the SC couldnt benifit from some extra tuning, guages, etc....just like the Greddy kit could benfit from those pieces as well.
Good luck to all...I've been enjoying and learning from this discussion.
I hope I am not sounding like a TT snob....becuase that is not my intention. As stated , there are benifits and drawbacks for each kit. But everyone that has an SC or TT is very happy with it..and mostly likely wouldnt change a thing.
One thing is that we keep talkiing hypotheicals and what-ifs. The fact is.....the TT's are running in the sub 10psi range on a very torqy motor with 10.3:1 compression. As a result, lag is very muted on the TT. But since the SC is parisitic, and being dirven by the crank, there is significnat less torque and HP down low...and a more gradually buildup of boost and power.
One drawback of the Roots style SC is heat.....how do you keep intake temps down signficnatly when running that car hard? I know some of them have front mount intercoolers and the like...but that roots unit on top of the motor is getting very very hot.......
Also, I think your max output and upside tuning potential is more limited with a roots vs. TT. That's my opinion....
Second, the Greddy kit use pretty large 18G turbos. You are correct, that at 6psi, there are running at the very bottom threshold of their efficiency...not ideal. But that is how Greddy designs their kits. There is plenty of room for exansion, and these turbos will hit their efficeicy sweetspot at about 15psi....whenever someone gets there.
My final point on this topic is that the TT gives tons of upside potential in terms of tuning, and for most street diriving conditions, offers more trq and power at a given RPM or thorrttle position. And yes, it takes 1/2 sec for full boost on the freeway, but it takes about 1/10 of sec to get some boost...just not max.....
Again, I am not bashing the SC's...just stating the facts. All of the SC's and TT';s are tons of fun. I just hope this dicussion will help people in making their own informed decisions on their purchase.
Also, note....both the SC's and TT's could stand for some upgrades once installed. The SC and TT are equally competent in the out-of-the-box state. But dont think that the the SC couldnt benifit from some extra tuning, guages, etc....just like the Greddy kit could benfit from those pieces as well.
Good luck to all...I've been enjoying and learning from this discussion.
05-20-2004, 10:58 AM
#177
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Facts
CT some input to your input.
WRT
"The Roots blowers generate full boost just off idle"
Not really unless you consider 2.-2.5k RPM just off idle, granted boost is there much quicker than a TT or Cent SC, but the pump is not perfect. Also unlike a roots a Twin screw doesn't drop off as quicky when spun at higer RPMs.
"One drawback of the Roots style SC is heat.....how do you keep intake temps down signficnatly when running that car hard?"
True but the air-water-ari intercoolers do a pretty good job , and I have personally had very good result with water injection, thouhg some consider it voodoo.
"You can't have it both ways -- these are not variable inlet geometry turbos!! "
True , and these these turbos do exist , but are still too expensive for this application. If someone here wants to drop another dime for a custom variable inlet turbo system have at it.
Personally I'm holding out for the JWT setup , since the 520BBs should be nearly laggless and produceing more power and tq than a roots over most of the RPM range at a comparable psi.
The 700BBs offer growth if needed in the future.
WRT
"The Roots blowers generate full boost just off idle"
Not really unless you consider 2.-2.5k RPM just off idle, granted boost is there much quicker than a TT or Cent SC, but the pump is not perfect. Also unlike a roots a Twin screw doesn't drop off as quicky when spun at higer RPMs.
"One drawback of the Roots style SC is heat.....how do you keep intake temps down signficnatly when running that car hard?"
True but the air-water-ari intercoolers do a pretty good job , and I have personally had very good result with water injection, thouhg some consider it voodoo.
"You can't have it both ways -- these are not variable inlet geometry turbos!! "
True , and these these turbos do exist , but are still too expensive for this application. If someone here wants to drop another dime for a custom variable inlet turbo system have at it.
Personally I'm holding out for the JWT setup , since the 520BBs should be nearly laggless and produceing more power and tq than a roots over most of the RPM range at a comparable psi.
The 700BBs offer growth if needed in the future.
05-20-2004, 11:01 AM
#178
New Member
Originally posted by PoWeRtRiP
one other thing on the issue of lag that is misleading by what we have seen so far
these engines are pushing very low boost ~6.5-8 psi. almost any turbo car can make that kind of boost in no time. if they were pushing more boost its gonna be a while before they spool fully.
which would show more steep inclines on a dyno. when the z starts pushing one bar on the turbo motors it will likely not hit full boost until after 4k rpms, which will be extremely laggy considering the redline is at 6600. to fully appreciate this kind of boost you will need to increase the rpms as much as possible.
one other thing on the issue of lag that is misleading by what we have seen so far
these engines are pushing very low boost ~6.5-8 psi. almost any turbo car can make that kind of boost in no time. if they were pushing more boost its gonna be a while before they spool fully.
which would show more steep inclines on a dyno. when the z starts pushing one bar on the turbo motors it will likely not hit full boost until after 4k rpms, which will be extremely laggy considering the redline is at 6600. to fully appreciate this kind of boost you will need to increase the rpms as much as possible.
When you raise the boost of both the turbo and an SC, THEN the lag issues of the turbo become more apparent. And yes, although it is ignored by some turbo guys, the SC can run more boost too.
Good info, frank, in this trend, they have mostly talked about the Vortech/ATI vs Greddy, but because there is more than one type of SC, the others should be talked about also.
Last edited by little_rod; 05-20-2004 at 11:13 AM.
05-20-2004, 03:46 PM
#179
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[QUOTE]Originally posted by ct roadster
[B]Squill, continuing to repeat incorrect things won't make them correct!
First of all thank you for your posts. Rpms in fact do play a big role in boost output in any turbo application. It is impossible to be driving a TT 350 Z at 3000 rpms without the turbos creating some boost at any throttle. Are turbos heavily dependant on throttle of course they are that is common knowledge. Everybody keeps making a big deal about the lag on a turbo ...please remember i am talking only the Vq35de when i am talking turbos in my posts
That is impossible if the motor has throttle imput no mater how slight at 2k or 4k it will make boost.
My contention is that the lag you are referring to is because of the immediate difference in power you can feel when the turbos begin to spool as this happens so fast that the power before and after is noticable. However you are discounting the fact that the turbos are still making power greater than the S/C during this time. For example during the "lag time" if the turbos at say 2lbs boost is making 200 hp and 260 ftlbs tq while the S/C is making 195 hp and 230 ftlbs of tq the TT system is generating more power although to the driver it doesnt feel like it due to the sensation of lag.
No i am not saying the waste gate is always open at 2500 rpms that is not possible what im saying while you are cruising at 2500 rpms you have whatever part throttle it requires to cruise at that rpm...while you are cruising the turbo is spinning just not making max boost since the turbos are allready spinning if you floor it the turbo rersponse will be allmost instant.
If the turbo takes 1/2 second to make peak boost the S/C takes longer it always will. (forget stillen in this argument im talking vortec , ati which is what the vast majority is running)
HA HA you know i really dont pay much attention to the stillen blower as it seems almost everybody here is running ati or vortec.
even though stillen has superior tourque i would choose the vortec blower if i was going to supercharge. Yes here i will say it with you "turbo boost is determined mostly by throttle" what you are not taking into consideration is that at and rpm above 2000 there is bost being made no matter how small the throttle input.
You cant even compare the effeciency of S/C vs turbo the turbo is vastly superior. Im sure i have a basic under stanting of how machines work ....you turn them on and then they work...right?LOL
you clearly have no idea what you are talking about here.
I didnt design the system however it is still superior to the blowers as it is now and these mitsu turbos can produce 25 psi.
Please try to understand the "lag" everyone is making a big deal about is insignificant.
Anyway nobody here is talking about audi turbos but since you mention it as an owner of 3 S4'S i can say I didnt experience any significant lag in my s4 as when driven correctly you wont get any even though they use out dated turbo technology (k03 turbos).
what do you mean more cylinders per turbo?? S4 is a v6 3 cyl per turbo ...anyway who cares about audi turbos we arent driving audis.
Who cares about the max boost it can accept people are getting 400 hp plus out of these bolt on turbo kits if you want more boost then build the engine. What do you want out of the vq35de ??? do you think you can bolt on 400 extra hp to any stock engine or something ????
you're joking right?
I have no beef with anybodys choice of FI either im just saying for the VQ35DE motor turbos are superior.
Turbos cant compete with S/C on price that is their only advantage that i see.
I want to accomplish the maximum amout of TQ and HP availible with the best posible amount of useable power through out the power band so i will bolt on some turbos....its really not as hard as everyone thinks the shop i got quotes from said install vortec 800 greddy 1300 so 500 bucks more...thanks again -SQUILL-
[B]Squill, continuing to repeat incorrect things won't make them correct!
Originally posted by ct roadster
You keep talking about RPM as being the factor in determining a turbo's boost; in fact, boost is much more determined by throttle (load) than by RPM. Please try to learn this and understand it: you *CANNOT* see lag on a dyno plot. Turbo boost is determined mostly by throttle, not by RPM; Roots boost is constant; and Centri SC boost is determined by RPM. Please, please, please learn this and keep it straight and stop saying incorrect things.
You keep talking about RPM as being the factor in determining a turbo's boost; in fact, boost is much more determined by throttle (load) than by RPM. Please try to learn this and understand it: you *CANNOT* see lag on a dyno plot. Turbo boost is determined mostly by throttle, not by RPM; Roots boost is constant; and Centri SC boost is determined by RPM. Please, please, please learn this and keep it straight and stop saying incorrect things.
Originally posted by ct roadster
It simply does not matter if the motor is spinning at 2k or at 4k; if the motor is throttled, you are not making boost.
It simply does not matter if the motor is spinning at 2k or at 4k; if the motor is throttled, you are not making boost.
Originally posted by ct roadster
When you open the throttle, there is a lag before the turbo spools up to make the boost that makes the power you see on the dyno plot. To make this simple and obvious, full power is not available from a turbo until the wastegate opens. We *KNOW* that you are not trying to tell us that the wastegate is always open when the motor is spinning over 2500 RPM! How long does it take when you step on the gas before the wastegate pops? It takes some amount of time, a half second according to GQ man, who aparently has the Greddy installed..
When you open the throttle, there is a lag before the turbo spools up to make the boost that makes the power you see on the dyno plot. To make this simple and obvious, full power is not available from a turbo until the wastegate opens. We *KNOW* that you are not trying to tell us that the wastegate is always open when the motor is spinning over 2500 RPM! How long does it take when you step on the gas before the wastegate pops? It takes some amount of time, a half second according to GQ man, who aparently has the Greddy installed..
No i am not saying the waste gate is always open at 2500 rpms that is not possible what im saying while you are cruising at 2500 rpms you have whatever part throttle it requires to cruise at that rpm...while you are cruising the turbo is spinning just not making max boost since the turbos are allready spinning if you floor it the turbo rersponse will be allmost instant.
If the turbo takes 1/2 second to make peak boost the S/C takes longer it always will. (forget stillen in this argument im talking vortec , ati which is what the vast majority is running)
Originally posted by ct roadster
Second, you keep asserting that SC's don't make power until in the high RPM range. This is only true for the centri SC's (Vortec, ATI); it is completely incorrect for the Roots blowers (Stillen). The Roots blowers generate full boost just off idle, and maintain nearly constant boost irrespective of throttle through the entire rev range -- completely different than a turbo or centri SC. Come on, say it with me now: turbo boost is determined mostly by throttle, not by RPM; Roots boost is constant; and Centri SC boost is determined by RPM...
Second, you keep asserting that SC's don't make power until in the high RPM range. This is only true for the centri SC's (Vortec, ATI); it is completely incorrect for the Roots blowers (Stillen). The Roots blowers generate full boost just off idle, and maintain nearly constant boost irrespective of throttle through the entire rev range -- completely different than a turbo or centri SC. Come on, say it with me now: turbo boost is determined mostly by throttle, not by RPM; Roots boost is constant; and Centri SC boost is determined by RPM...
even though stillen has superior tourque i would choose the vortec blower if i was going to supercharge. Yes here i will say it with you "turbo boost is determined mostly by throttle" what you are not taking into consideration is that at and rpm above 2000 there is bost being made no matter how small the throttle input.
Originally posted by ct roadster
Third, I keep explaining to you how it takes power to drive a turbo, but you keep saying it's free -- please learn that this is false and demonstrates that you lack basic understanding of how machines work. It takes power to compress air; that power is robbed from the crank whether you take it off by a belt at the front of the motor (all SC's), or take it off the exhaust of the motor. Squill, you will learn this yet!...
Third, I keep explaining to you how it takes power to drive a turbo, but you keep saying it's free -- please learn that this is false and demonstrates that you lack basic understanding of how machines work. It takes power to compress air; that power is robbed from the crank whether you take it off by a belt at the front of the motor (all SC's), or take it off the exhaust of the motor. Squill, you will learn this yet!...
Originally posted by ct roadster
Fourth, you mentioned that the Greddy twin turbo has a stock boost of ~4 psi, but can be tuned to over 25 psi. It is not possible that a pair of turbos can maintain high efficiency across this broad a range of drive power -- thus either the system has significant lag when tuned to 4 psi (because the turbos are sized to deliver the cfm needed at 25psi), or it has major compressor surge at the 25 psi end (because the turbos are sized to deliver the cfm needed at 4psi). You can't have it both ways -- these are not variable inlet geometry turbos!! The VQ35 is a fairly large displacement motor for a turbo application, which definitely works against you in this regard: it needs a lot of air.
Fourth, you mentioned that the Greddy twin turbo has a stock boost of ~4 psi, but can be tuned to over 25 psi. It is not possible that a pair of turbos can maintain high efficiency across this broad a range of drive power -- thus either the system has significant lag when tuned to 4 psi (because the turbos are sized to deliver the cfm needed at 25psi), or it has major compressor surge at the 25 psi end (because the turbos are sized to deliver the cfm needed at 4psi). You can't have it both ways -- these are not variable inlet geometry turbos!! The VQ35 is a fairly large displacement motor for a turbo application, which definitely works against you in this regard: it needs a lot of air.
I didnt design the system however it is still superior to the blowers as it is now and these mitsu turbos can produce 25 psi.
Please try to understand the "lag" everyone is making a big deal about is insignificant.
Originally posted by ct roadster
Each half of the VQ35 is approx 1.74 liters, so you effectively have two single-turbo 1.7 liter motors. Audi and VW turbo apps that I'm familiar with in that size range had all sorts of lag issues, and it was very difficult to get the turbos sized just right for a given application. Different people had different turbo preferences for the same engine because they drove differently. Keep in mind that the Audi and VW apps had more cylinders driving the turbo (4, 5, or 6) than the VQ35 (3 per turbo), which means that the turbo in the VW/Audi application will be more responsive. OTOH, the VQ35 has a much higher CR, which greatly limits the max boost you can accept, but will help with the responsiveness..
Each half of the VQ35 is approx 1.74 liters, so you effectively have two single-turbo 1.7 liter motors. Audi and VW turbo apps that I'm familiar with in that size range had all sorts of lag issues, and it was very difficult to get the turbos sized just right for a given application. Different people had different turbo preferences for the same engine because they drove differently. Keep in mind that the Audi and VW apps had more cylinders driving the turbo (4, 5, or 6) than the VQ35 (3 per turbo), which means that the turbo in the VW/Audi application will be more responsive. OTOH, the VQ35 has a much higher CR, which greatly limits the max boost you can accept, but will help with the responsiveness..
what do you mean more cylinders per turbo?? S4 is a v6 3 cyl per turbo ...anyway who cares about audi turbos we arent driving audis.
Who cares about the max boost it can accept people are getting 400 hp plus out of these bolt on turbo kits if you want more boost then build the engine. What do you want out of the vq35de ??? do you think you can bolt on 400 extra hp to any stock engine or something ????
Originally posted by ct roadster
GQ man, a half second of lag is an eternity on a track; in that time the car is most way through a corner!!..
GQ man, a half second of lag is an eternity on a track; in that time the car is most way through a corner!!..
Originally posted by ct roadster
To me the FI alternatives break down to what you want the car to feel like:
Roots SC (Stillen): a bigger motor
Centri SC (Vortec): a peaky motor with a big rush near redline
turbo: regular motor with a big butt-kicking reserve of power after a small lag
It also comes down to the complexity of tuning:
Roots SC: simple tuning, its just like bigger displacement to the ECU
Centri SC: simple tuning, its just like wild cams/headers/exhaust to the ECU, RPM dependent fuel required at high boost
turbo: complex tuning, as fuel needs vary with boost which varies with throttle, no simple relationship to RPM
It also comes down to how hard it is to build the systems to higher boost:
Roots SC: new pulleys, easy ECU reprog/fuel enrichment, max boost limited by difficulty of intercooling (drop the CR and up the boost as much as you want, until you run out of cooling and get major detonation probs)
Centri SC: new pulleys, easy ECU reprog/fuel enrichment, max boost limited by the power difference between low RPM and high RPM (no cooling problem, but if you drop the CR, the low end drops major power)
turbo: just twist the **** to up the boost, and reprog the compensation maps; can drop the CR and up the boost until you hit compressor surge on the turbo, but lower CR and higher boost means increased lag.
It also comes down to complexity of install:
Roots SC: bolt on and go, but Stillen requires hood mods
Centri SC: bolt on and go, but a little more than Roots
turbo: big install
And of course price, which I have no basis to compare the systems.
I have absolutely no beef with anyone's choice of FI -- do whatever you want, whatever is appropriate to what you want to accomplish. Just don't go around spouting falsehoods.
-frank
To me the FI alternatives break down to what you want the car to feel like:
Roots SC (Stillen): a bigger motor
Centri SC (Vortec): a peaky motor with a big rush near redline
turbo: regular motor with a big butt-kicking reserve of power after a small lag
It also comes down to the complexity of tuning:
Roots SC: simple tuning, its just like bigger displacement to the ECU
Centri SC: simple tuning, its just like wild cams/headers/exhaust to the ECU, RPM dependent fuel required at high boost
turbo: complex tuning, as fuel needs vary with boost which varies with throttle, no simple relationship to RPM
It also comes down to how hard it is to build the systems to higher boost:
Roots SC: new pulleys, easy ECU reprog/fuel enrichment, max boost limited by difficulty of intercooling (drop the CR and up the boost as much as you want, until you run out of cooling and get major detonation probs)
Centri SC: new pulleys, easy ECU reprog/fuel enrichment, max boost limited by the power difference between low RPM and high RPM (no cooling problem, but if you drop the CR, the low end drops major power)
turbo: just twist the **** to up the boost, and reprog the compensation maps; can drop the CR and up the boost until you hit compressor surge on the turbo, but lower CR and higher boost means increased lag.
It also comes down to complexity of install:
Roots SC: bolt on and go, but Stillen requires hood mods
Centri SC: bolt on and go, but a little more than Roots
turbo: big install
And of course price, which I have no basis to compare the systems.
I have absolutely no beef with anyone's choice of FI -- do whatever you want, whatever is appropriate to what you want to accomplish. Just don't go around spouting falsehoods.
-frank
Turbos cant compete with S/C on price that is their only advantage that i see.
I want to accomplish the maximum amout of TQ and HP availible with the best posible amount of useable power through out the power band so i will bolt on some turbos....its really not as hard as everyone thinks the shop i got quotes from said install vortec 800 greddy 1300 so 500 bucks more...thanks again -SQUILL-
05-20-2004, 10:05 PM
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Originally posted by jak
I don't have a FI system yet and here are the conclusions I have drawn from this thread that will help me make my choice:
Scenario 1
Two identical cars with identical drivers are rolling down the highway at the same speed. One car has a SC the other a turbo. Both cars running the same PSI. Both cars downshift to a gear that gives them 4800 RPMs or higher and floor it. The SC takes off right away being near peak boost. The turbo hesitates (lag) and takes off with equal force. The SC gets the jump on the turbo and the SC wins.
Scenario 2
Two identical cars with identical drivers are rolling down the highway at the same speed. One car has a SC the other a turbo. Both cars running the same PSI. Both cars floor it without downshifting. The SC starts methodically climbing in speed. The turbo hesitates (lag) and shoots forward under full boost catching the jump the SC had and passing the SC and the turbo wins.
Scenario 3
Two identical cars with identical drivers are at the drag strip. One car has a SC the other a turbo. Both cars running the same PSI. Each car is launched and driven in a manner that takes full advantage and potential of their respective systems. Both cars finish the race tied.
I have concluded that both systems as far as speed are essentially equal. They differ only in terms like cost, complexity, driving style, power sensation, and HP needs. All of these issues are personal in nature and have nothing to do with one system being better than the other.
I like the rush of power when the turbo kicks in but I like the cost, simplicity, and driving style of the SC.
Jeff
I don't have a FI system yet and here are the conclusions I have drawn from this thread that will help me make my choice:
Scenario 1
Two identical cars with identical drivers are rolling down the highway at the same speed. One car has a SC the other a turbo. Both cars running the same PSI. Both cars downshift to a gear that gives them 4800 RPMs or higher and floor it. The SC takes off right away being near peak boost. The turbo hesitates (lag) and takes off with equal force. The SC gets the jump on the turbo and the SC wins.
Scenario 2
Two identical cars with identical drivers are rolling down the highway at the same speed. One car has a SC the other a turbo. Both cars running the same PSI. Both cars floor it without downshifting. The SC starts methodically climbing in speed. The turbo hesitates (lag) and shoots forward under full boost catching the jump the SC had and passing the SC and the turbo wins.
Scenario 3
Two identical cars with identical drivers are at the drag strip. One car has a SC the other a turbo. Both cars running the same PSI. Each car is launched and driven in a manner that takes full advantage and potential of their respective systems. Both cars finish the race tied.
I have concluded that both systems as far as speed are essentially equal. They differ only in terms like cost, complexity, driving style, power sensation, and HP needs. All of these issues are personal in nature and have nothing to do with one system being better than the other.
I like the rush of power when the turbo kicks in but I like the cost, simplicity, and driving style of the SC.
Jeff