SuperCharger Vs. Turbo...
05-20-2004, 11:36 PM
#181
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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.
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.
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.
Anyway, you're right that it doesn't make sense, but somehow it works. I don't think GReddy planned it like this, but this kit seems to be effective.
05-21-2004, 04:56 AM
#182
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hey squill let me make this very clear to you.
if i am at 3000 rpms and barely touching the gas in a greddy tt <25% throttle, then i have no boost at all. none. if i throttle 50% i will have some maybe 1-2 psi. if im at full throttle then i will make full boost. quit telling us that if your at 3000 rpms the tt will make boost no matter what. turboes rely on throttle to make boost otherwise it vents it out. plz understand this. a greddy tt car at 4000 rpms with no throttle is making the same power as an na car until he significantly presses the gas. then he gets positive boost
if i am at 3000 rpms and barely touching the gas in a greddy tt <25% throttle, then i have no boost at all. none. if i throttle 50% i will have some maybe 1-2 psi. if im at full throttle then i will make full boost. quit telling us that if your at 3000 rpms the tt will make boost no matter what. turboes rely on throttle to make boost otherwise it vents it out. plz understand this. a greddy tt car at 4000 rpms with no throttle is making the same power as an na car until he significantly presses the gas. then he gets positive boost
05-21-2004, 07:41 AM
#183
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Originally posted by PoWeRtRiP
hey squill let me make this very clear to you.
if i am at 3000 rpms and barely touching the gas in a greddy tt <25% throttle, then i have no boost at all. none. if i throttle 50% i will have some maybe 1-2 psi. if im at full throttle then i will make full boost. quit telling us that if your at 3000 rpms the tt will make boost no matter what. turboes rely on throttle to make boost otherwise it vents it out. plz understand this. a greddy tt car at 4000 rpms with no throttle is making the same power as an na car until he significantly presses the gas. then he gets positive boost
hey squill let me make this very clear to you.
if i am at 3000 rpms and barely touching the gas in a greddy tt <25% throttle, then i have no boost at all. none. if i throttle 50% i will have some maybe 1-2 psi. if im at full throttle then i will make full boost. quit telling us that if your at 3000 rpms the tt will make boost no matter what. turboes rely on throttle to make boost otherwise it vents it out. plz understand this. a greddy tt car at 4000 rpms with no throttle is making the same power as an na car until he significantly presses the gas. then he gets positive boost
Please try to under stand to drive a car at 3000 rpms it requires some throttle imput be it small or not you are burning gas and making exaust flow through the turbos ...please understand you will be making some boost even if it is 1/4 psi...whatever.
the only way to not make boost @4000 rpms would be if you had 0 throttle imput like coasting down a hill for example while still in gear.
the point is if you allready have the turbine spinning getting it spinning faster takes alot less time than going from the turbines not spinning at all to spinning fast enough to create boost.
the point is if you are driving the car @3000 rpms you will have the turbines spinning no matter what the throttle imput unless you are coasting with no throttle imput ... if you are pressing on the gas to keep the car at 3000 rpms you will be making some boost be it a tiny amount or whatever and from there if you go WOT the mitsu turbos will give you power and throttle response almost instantly .
05-21-2004, 08:06 AM
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Great points, everyone; this is a really great thread....
On the bit about throttle and rpm and turbo spool-up: let me give you a way to understand the issue. The amount of air/fuel flowing through the motor determines the amount of torque/power it produces. If you are driving along at 50MPH at low RPM in 4th gear, versus driving along the same road at the same 50MPH but downshifted to higher RPM in 2nd gear say, you will have a different throttle position, but the engine will have the same net power output because the load is the same. (Different torque, because the transmission is transforming the torque/rpm into power -- torque at road wheel rpm for both situations.) Now here's the amazing part: in the two situations, net airflow (and thus fuel) will be (almost exactly) the same in the two situations! Mass airflow determines power output. (That's why the MAF sensor is sometimes called the load sensor.)
Downshifting to higher rpm's helps lag because the engine assembly responds faster at high rpms -- cycle time is lower. But the turbos still have to spool up: the spindle speed needs to change, because they are being asked to flow more air at higher pressure. The lag is from the time it takes that spindle with the compressor and turbine wheels to spin up and produce mass flow efficiently. You can plot this on the turbo map.....
On the big turbos Greddy is using: I have no doubt that the Greddy turbos can work at both 4psi and 25psi; my point was simply that they must be inefficient at one of those extremes. I found a map on the 'net (well, it was a synthetic map, built by modifying another map, but close enough for government work), and it does seem that they are large units! So I would think that they have significant lag when used at the low end, but again, the proof is in the pudding, and I've never driven one of these.
It does all go back to what you want out of the car. For me, I'm mostly intersted in track use, and analyzing things a bit more, I had been thinking of waiting for the Dreamworkes SC unit (if it ever shows up), or maybe the Stillen if I can come around to liking the hood. But now I'm thinking JWT -- the 530HP max rating means they will be using nice small turbos, the bb aspect means quick response, and the native ECU reprog (rather than add-ons) is the right way to control things. But I wonder about the $$$$ and wish they would identify which turbos they will be using.
Squill, for me the lag issue is important b/c I'm interested in track use, and I think the Z will be very hard to get the suspension set up right for a turbo car with big lag. This car has an excellent suspension that really seems tuned for carving turns with nice steady power transitions, so I'd like to up the power without fundamental changes. So to me, that's an SC (either type) or small turbos.....
On GQ man's point about turbos being the path to the biggest possible HP, I would completely agree. The centri SCs have a major problem if you start to drop the CR (no low end at all, may not even have enough power to get the car to the high end to get boost in an extreme situation). As the boost is raised to extreme levels, the Roots SC will hit major thermal probs (the low efficiency of external compression gets you) requiring water injection and refrigerated intercooler arrangements in the extreme situations. In contrast, turbos at the extreme high end just require big intercooling and lots of engine tuning/management -- and maybe a big shot of nitrous to get past the lag....
G3po, good point about the Roots SC boost; yes, I figure 2k rpm is "just off idle" as the Roots blower is rpm-linked and 2k is below the useful powerband on a track. And water injection is the devil's work my friend! (But definitely can be put to good use!)
-frank
On the bit about throttle and rpm and turbo spool-up: let me give you a way to understand the issue. The amount of air/fuel flowing through the motor determines the amount of torque/power it produces. If you are driving along at 50MPH at low RPM in 4th gear, versus driving along the same road at the same 50MPH but downshifted to higher RPM in 2nd gear say, you will have a different throttle position, but the engine will have the same net power output because the load is the same. (Different torque, because the transmission is transforming the torque/rpm into power -- torque at road wheel rpm for both situations.) Now here's the amazing part: in the two situations, net airflow (and thus fuel) will be (almost exactly) the same in the two situations! Mass airflow determines power output. (That's why the MAF sensor is sometimes called the load sensor.)
Downshifting to higher rpm's helps lag because the engine assembly responds faster at high rpms -- cycle time is lower. But the turbos still have to spool up: the spindle speed needs to change, because they are being asked to flow more air at higher pressure. The lag is from the time it takes that spindle with the compressor and turbine wheels to spin up and produce mass flow efficiently. You can plot this on the turbo map.....
On the big turbos Greddy is using: I have no doubt that the Greddy turbos can work at both 4psi and 25psi; my point was simply that they must be inefficient at one of those extremes. I found a map on the 'net (well, it was a synthetic map, built by modifying another map, but close enough for government work), and it does seem that they are large units! So I would think that they have significant lag when used at the low end, but again, the proof is in the pudding, and I've never driven one of these.
It does all go back to what you want out of the car. For me, I'm mostly intersted in track use, and analyzing things a bit more, I had been thinking of waiting for the Dreamworkes SC unit (if it ever shows up), or maybe the Stillen if I can come around to liking the hood. But now I'm thinking JWT -- the 530HP max rating means they will be using nice small turbos, the bb aspect means quick response, and the native ECU reprog (rather than add-ons) is the right way to control things. But I wonder about the $$$$ and wish they would identify which turbos they will be using.
Squill, for me the lag issue is important b/c I'm interested in track use, and I think the Z will be very hard to get the suspension set up right for a turbo car with big lag. This car has an excellent suspension that really seems tuned for carving turns with nice steady power transitions, so I'd like to up the power without fundamental changes. So to me, that's an SC (either type) or small turbos.....
On GQ man's point about turbos being the path to the biggest possible HP, I would completely agree. The centri SCs have a major problem if you start to drop the CR (no low end at all, may not even have enough power to get the car to the high end to get boost in an extreme situation). As the boost is raised to extreme levels, the Roots SC will hit major thermal probs (the low efficiency of external compression gets you) requiring water injection and refrigerated intercooler arrangements in the extreme situations. In contrast, turbos at the extreme high end just require big intercooling and lots of engine tuning/management -- and maybe a big shot of nitrous to get past the lag....
G3po, good point about the Roots SC boost; yes, I figure 2k rpm is "just off idle" as the Roots blower is rpm-linked and 2k is below the useful powerband on a track. And water injection is the devil's work my friend! (But definitely can be put to good use!)
-frank
05-21-2004, 09:46 AM
#185
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from what 's shown on the JWT website
http://www.jimwolftechnology.com/cus...asp?PartID=410
the kit should ship with "WZ321-BB530" turbos, I haven't found and A/R curve for this one yet. Really does look sweet for dual street/race use. I am considering just replaceing the OEM Rod with Pauters and leaving most else internally alone. With 100 octane,~12-14psi , 10.3:1 CR it would make a pretty snappy track ride and the bottom end should hold together well.
Note: It is probably upgradeable (same flanges and downpipe)
to "WZ320-BB700s" for the gimme mo power and lag junky.
Of course the OEM internals could never handle this much boost.
from what 's shown on the JWT website
http://www.jimwolftechnology.com/cus...asp?PartID=410
the kit should ship with "WZ321-BB530" turbos, I haven't found and A/R curve for this one yet. Really does look sweet for dual street/race use. I am considering just replaceing the OEM Rod with Pauters and leaving most else internally alone. With 100 octane,~12-14psi , 10.3:1 CR it would make a pretty snappy track ride and the bottom end should hold together well.
Note: It is probably upgradeable (same flanges and downpipe)
to "WZ320-BB700s" for the gimme mo power and lag junky.
Of course the OEM internals could never handle this much boost.
05-21-2004, 10:04 AM
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Originally posted by ct roadster
Great points, everyone; this is a really great thread....
On the bit about throttle and rpm and turbo spool-up: let me give you a way to understand the issue. The amount of air/fuel flowing through the motor determines the amount of torque/power it produces. If you are driving along at 50MPH at low RPM in 4th gear, versus driving along the same road at the same 50MPH but downshifted to higher RPM in 2nd gear say, you will have a different throttle position, but the engine will have the same net power output because the load is the same. (Different torque, because the transmission is transforming the torque/rpm into power -- torque at road wheel rpm for both situations.) Now here's the amazing part: in the two situations, net airflow (and thus fuel) will be (almost exactly) the same in the two situations! Mass airflow determines power output. (That's why the MAF sensor is sometimes called the load sensor.)
Downshifting to higher rpm's helps lag because the engine assembly responds faster at high rpms -- cycle time is lower. But the turbos still have to spool up: the spindle speed needs to change, because they are being asked to flow more air at higher pressure. The lag is from the time it takes that spindle with the compressor and turbine wheels to spin up and produce mass flow efficiently. You can plot this on the turbo map.....
On the big turbos Greddy is using: I have no doubt that the Greddy turbos can work at both 4psi and 25psi; my point was simply that they must be inefficient at one of those extremes. I found a map on the 'net (well, it was a synthetic map, built by modifying another map, but close enough for government work), and it does seem that they are large units! So I would think that they have significant lag when used at the low end, but again, the proof is in the pudding, and I've never driven one of these.
It does all go back to what you want out of the car. For me, I'm mostly intersted in track use, and analyzing things a bit more, I had been thinking of waiting for the Dreamworkes SC unit (if it ever shows up), or maybe the Stillen if I can come around to liking the hood. But now I'm thinking JWT -- the 530HP max rating means they will be using nice small turbos, the bb aspect means quick response, and the native ECU reprog (rather than add-ons) is the right way to control things. But I wonder about the $$$$ and wish they would identify which turbos they will be using.
Squill, for me the lag issue is important b/c I'm interested in track use, and I think the Z will be very hard to get the suspension set up right for a turbo car with big lag. This car has an excellent suspension that really seems tuned for carving turns with nice steady power transitions, so I'd like to up the power without fundamental changes. So to me, that's an SC (either type) or small turbos.....
On GQ man's point about turbos being the path to the biggest possible HP, I would completely agree. The centri SCs have a major problem if you start to drop the CR (no low end at all, may not even have enough power to get the car to the high end to get boost in an extreme situation). As the boost is raised to extreme levels, the Roots SC will hit major thermal probs (the low efficiency of external compression gets you) requiring water injection and refrigerated intercooler arrangements in the extreme situations. In contrast, turbos at the extreme high end just require big intercooling and lots of engine tuning/management -- and maybe a big shot of nitrous to get past the lag....
G3po, good point about the Roots SC boost; yes, I figure 2k rpm is "just off idle" as the Roots blower is rpm-linked and 2k is below the useful powerband on a track. And water injection is the devil's work my friend! (But definitely can be put to good use!)
-frank
Great points, everyone; this is a really great thread....
On the bit about throttle and rpm and turbo spool-up: let me give you a way to understand the issue. The amount of air/fuel flowing through the motor determines the amount of torque/power it produces. If you are driving along at 50MPH at low RPM in 4th gear, versus driving along the same road at the same 50MPH but downshifted to higher RPM in 2nd gear say, you will have a different throttle position, but the engine will have the same net power output because the load is the same. (Different torque, because the transmission is transforming the torque/rpm into power -- torque at road wheel rpm for both situations.) Now here's the amazing part: in the two situations, net airflow (and thus fuel) will be (almost exactly) the same in the two situations! Mass airflow determines power output. (That's why the MAF sensor is sometimes called the load sensor.)
Downshifting to higher rpm's helps lag because the engine assembly responds faster at high rpms -- cycle time is lower. But the turbos still have to spool up: the spindle speed needs to change, because they are being asked to flow more air at higher pressure. The lag is from the time it takes that spindle with the compressor and turbine wheels to spin up and produce mass flow efficiently. You can plot this on the turbo map.....
On the big turbos Greddy is using: I have no doubt that the Greddy turbos can work at both 4psi and 25psi; my point was simply that they must be inefficient at one of those extremes. I found a map on the 'net (well, it was a synthetic map, built by modifying another map, but close enough for government work), and it does seem that they are large units! So I would think that they have significant lag when used at the low end, but again, the proof is in the pudding, and I've never driven one of these.
It does all go back to what you want out of the car. For me, I'm mostly intersted in track use, and analyzing things a bit more, I had been thinking of waiting for the Dreamworkes SC unit (if it ever shows up), or maybe the Stillen if I can come around to liking the hood. But now I'm thinking JWT -- the 530HP max rating means they will be using nice small turbos, the bb aspect means quick response, and the native ECU reprog (rather than add-ons) is the right way to control things. But I wonder about the $$$$ and wish they would identify which turbos they will be using.
Squill, for me the lag issue is important b/c I'm interested in track use, and I think the Z will be very hard to get the suspension set up right for a turbo car with big lag. This car has an excellent suspension that really seems tuned for carving turns with nice steady power transitions, so I'd like to up the power without fundamental changes. So to me, that's an SC (either type) or small turbos.....
On GQ man's point about turbos being the path to the biggest possible HP, I would completely agree. The centri SCs have a major problem if you start to drop the CR (no low end at all, may not even have enough power to get the car to the high end to get boost in an extreme situation). As the boost is raised to extreme levels, the Roots SC will hit major thermal probs (the low efficiency of external compression gets you) requiring water injection and refrigerated intercooler arrangements in the extreme situations. In contrast, turbos at the extreme high end just require big intercooling and lots of engine tuning/management -- and maybe a big shot of nitrous to get past the lag....
G3po, good point about the Roots SC boost; yes, I figure 2k rpm is "just off idle" as the Roots blower is rpm-linked and 2k is below the useful powerband on a track. And water injection is the devil's work my friend! (But definitely can be put to good use!)
-frank
http://www.************************/350z/350z.htm
This kit looks like the most well put together kit ive seen using custom intercooler specifically designed for the 350z.. check it out
05-21-2004, 10:10 AM
#187
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Re: JWT
Originally posted by G3po
CT
from what 's shown on the JWT website
http://www.jimwolftechnology.com/cus...asp?PartID=410
the kit should ship with "WZ321-BB530" turbos, I haven't found and A/R curve for this one yet. Really does look sweet for dual street/race use. I am considering just replaceing the OEM Rod with Pauters and leaving most else internally alone. With 100 octane,~12-14psi , 10.3:1 CR it would make a pretty snappy track ride and the bottom end should hold together well.
Note: It is probably upgradeable (same flanges and downpipe)
to "WZ320-BB700s" for the gimme mo power and lag junky.
Of course the OEM internals could never handle this much boost.
CT
from what 's shown on the JWT website
http://www.jimwolftechnology.com/cus...asp?PartID=410
the kit should ship with "WZ321-BB530" turbos, I haven't found and A/R curve for this one yet. Really does look sweet for dual street/race use. I am considering just replaceing the OEM Rod with Pauters and leaving most else internally alone. With 100 octane,~12-14psi , 10.3:1 CR it would make a pretty snappy track ride and the bottom end should hold together well.
Note: It is probably upgradeable (same flanges and downpipe)
to "WZ320-BB700s" for the gimme mo power and lag junky.
Of course the OEM internals could never handle this much boost.
the only thing i dont like is the twin i/c design they chose. does anyone know if this is better than a single fmic? i understand they did it to make it fit on the g
Last edited by PoWeRtRiP; 05-21-2004 at 10:13 AM.
05-21-2004, 10:22 AM
#188
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JWT FMIC
I'd guess that hese 2 530bb are quite possible of produceing 600 crank on the VQ35 , but quite a few system items woudl nee upgrade to make that possible.
I'm sure a single huge FMIC would cost less and cool a little better, but yeh JWT targeted the G35 first which is good for me , 'cause that's what I have. If I had a Z and lots of extra dough I'd probably hold out for what APS has to offer. Sounds like APS is useing a base turbo similar to the 700bb.
I'm sure a single huge FMIC would cost less and cool a little better, but yeh JWT targeted the G35 first which is good for me , 'cause that's what I have. If I had a Z and lots of extra dough I'd probably hold out for what APS has to offer. Sounds like APS is useing a base turbo similar to the 700bb.
05-21-2004, 10:30 AM
#189
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and priced accordingly its like 8500 usd thats insane! im curious if he will offer an optional single fmic for z's. i just trust jim wolf more than most other companys so id like to see what hes got first.
05-21-2004, 10:39 AM
#190
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Someone earlier did has Jim W. about a single FMIC an he said he ahd no plans. He would offer the dual for Zs as well. At sub 600 crank I would expect his setup to be fine. However; the factory Z bumper facia is not ideally "open" were the ICs live. If this presents a problem, then I'm pretty sure JWT will be diligent and resolve. I've seen Z bumper facias tat have side openings. The JWT price tag won't be cheap either at ~$6800, but it will "look" OEM , I prefer sleepers.
05-21-2004, 10:46 AM
#191
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ah but i know i can get the jwt kit cheaper, whereas the abs kit will be sold only thru abs likely, just like how it is with the greddy kits that retail at 8000 but sell for 6000.
05-21-2004, 10:51 AM
#193
Guys, as you know....BB va. conventional, and the size of the turbo are just two of the varibles that contribute to a fast spooling/low lag turbo. How about the exhuast and compressor housing sizes and shape, the compressor wheel type and size, the weight of the compression shaft? You can't just say a TD05 has more lag than a BB turbo. You need to evalute all parts and specs of the turbo/wastgate assembly.
And squilll....actually, Ct and POWERTRIP are correct. The boost level is partly a function of throttle position, and partly a function of RPM. So at cruise, we are not making any boost at all....we are actualliy making vaccum...just like an N/A car. Once we give it the throttle, then I immediately make significant boost. But just cruising steady at 1/4 or 1/8 throttle doesnt produce any boost...this is how it should be.
And squilll....actually, Ct and POWERTRIP are correct. The boost level is partly a function of throttle position, and partly a function of RPM. So at cruise, we are not making any boost at all....we are actualliy making vaccum...just like an N/A car. Once we give it the throttle, then I immediately make significant boost. But just cruising steady at 1/4 or 1/8 throttle doesnt produce any boost...this is how it should be.
05-21-2004, 11:01 AM
#194
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BB Ts.
Noramly I woudl crap all over Turbos with integral Waste gate.
An integral WG usually slops up the ehxuat stream and increaeses the spool time.
However; the JWT design uses the improved 5 bolt downpipe flange which ehlps isolate WG steam from thru stream. Since these Turbos are designed specifially to reduce lag, I still expect the 530BBs and maybe the 700BBs to spool faster than a TD series turbo. I wouldn't expect a "huge" improvement, but there should be one. A vendor doesn't use BBs because greater cost sells more product.
An integral WG usually slops up the ehxuat stream and increaeses the spool time.
However; the JWT design uses the improved 5 bolt downpipe flange which ehlps isolate WG steam from thru stream. Since these Turbos are designed specifially to reduce lag, I still expect the 530BBs and maybe the 700BBs to spool faster than a TD series turbo. I wouldn't expect a "huge" improvement, but there should be one. A vendor doesn't use BBs because greater cost sells more product.
05-21-2004, 11:32 AM
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Here is my take... Keep in mind this is coming from someone who had a Stealth RT Turbo and a MKIV 600 hp Single Turbo Supra.
Both the turbo and S/C have positive and negative attributes. Both provide the Z with an acceptable amount of horsepower and torque. IMO, the turbo HP/ torque numbers are slightly jaded because most turbo guys run test pipes. Comparing apples to apples... A supercharger with a nice set of headers/ test pipes would produce much closer numbers. Maybe not the same but closer than what we have seen thus far. The difference as shown with ACP changing out the test pipes to H/F pipes lost him 20rwhp and XXrwtq.
My Z is an automatic and I will be running the 9lb pulley from ATI in the next couple days. I expect my new dyno numbers to be upwards of 415rwhp and 350rwtq. I chose the S/C for three reasons. 1) There is no chance of boost spikes like there is with the turbo (ask me how I know). 2) The supercharger runs much cooler and on an engine that was designed to be N/A (IE: no oil cooler and a small radiator). Longevity is something to factor. The last reason is the reliability of daily driving. There are fewer items to break or fail, so the chances are less likely it will occur with a S/C.
Again, these are my opinoins. Two nice things about a turbo would be the lack of sound (no belt moving). The second is the ability to change the boost pressure from inside the car. Please don't take this as I am downgrading turbos but on this car it was an easy choice to add a supercharger over a turbo.
Both the turbo and S/C have positive and negative attributes. Both provide the Z with an acceptable amount of horsepower and torque. IMO, the turbo HP/ torque numbers are slightly jaded because most turbo guys run test pipes. Comparing apples to apples... A supercharger with a nice set of headers/ test pipes would produce much closer numbers. Maybe not the same but closer than what we have seen thus far. The difference as shown with ACP changing out the test pipes to H/F pipes lost him 20rwhp and XXrwtq.
My Z is an automatic and I will be running the 9lb pulley from ATI in the next couple days. I expect my new dyno numbers to be upwards of 415rwhp and 350rwtq. I chose the S/C for three reasons. 1) There is no chance of boost spikes like there is with the turbo (ask me how I know). 2) The supercharger runs much cooler and on an engine that was designed to be N/A (IE: no oil cooler and a small radiator). Longevity is something to factor. The last reason is the reliability of daily driving. There are fewer items to break or fail, so the chances are less likely it will occur with a S/C.
Again, these are my opinoins. Two nice things about a turbo would be the lack of sound (no belt moving). The second is the ability to change the boost pressure from inside the car. Please don't take this as I am downgrading turbos but on this car it was an easy choice to add a supercharger over a turbo.
05-21-2004, 11:42 AM
#196
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Originally posted by gq_626
Guys, as you know....BB va. conventional, and the size of the turbo are just two of the varibles that contribute to a fast spooling/low lag turbo. How about the exhuast and compressor housing sizes and shape, the compressor wheel type and size, the weight of the compression shaft? You can't just say a TD05 has more lag than a BB turbo. You need to evalute all parts and specs of the turbo/wastgate assembly.
And squilll....actually, Ct and POWERTRIP are correct. The boost level is partly a function of throttle position, and partly a function of RPM. So at cruise, we are not making any boost at all....we are actualliy making vaccum...just like an N/A car. Once we give it the throttle, then I immediately make significant boost. But just cruising steady at 1/4 or 1/8 throttle doesnt produce any boost...this is how it should be.
Guys, as you know....BB va. conventional, and the size of the turbo are just two of the varibles that contribute to a fast spooling/low lag turbo. How about the exhuast and compressor housing sizes and shape, the compressor wheel type and size, the weight of the compression shaft? You can't just say a TD05 has more lag than a BB turbo. You need to evalute all parts and specs of the turbo/wastgate assembly.
And squilll....actually, Ct and POWERTRIP are correct. The boost level is partly a function of throttle position, and partly a function of RPM. So at cruise, we are not making any boost at all....we are actualliy making vaccum...just like an N/A car. Once we give it the throttle, then I immediately make significant boost. But just cruising steady at 1/4 or 1/8 throttle doesnt produce any boost...this is how it should be.
your boost guage reads 0 ?? You dont hear your turbines spooling or feel anything at all is this what your saying??
05-21-2004, 12:55 PM
#197
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Originally posted by SQUILL
I never argued that throttle position didnt have anything to do with a turbos boost function as it obviously does...GQ you are telling me that if you are cruising at 3000 rpm at say 1/4 throttle
your boost guage reads 0 ?? You dont hear your turbines spooling or feel anything at all is this what your saying??
I never argued that throttle position didnt have anything to do with a turbos boost function as it obviously does...GQ you are telling me that if you are cruising at 3000 rpm at say 1/4 throttle
your boost guage reads 0 ?? You dont hear your turbines spooling or feel anything at all is this what your saying??
Car and driver used to post how much HP it takes to cruise for a given car at 55mph or something, and most cars take like 20-30, so cruising really doesn't involve much load.
My only contest to the SC "instant power" is that the air column has to accelerate just like on a normal car and with the extra piping from the ICs, they will get a tiny bit of lag too. Now, I'll caveat that with saying I have never paid attention in a SC vehicle for this effect, so it's just a guess. AND, this same scenario applies for turbos as well- which have even more piping.
05-21-2004, 12:56 PM
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Originally posted by whosdady
Here is my take... Keep in mind this is coming from someone who had a Stealth RT Turbo and a MKIV 600 hp Single Turbo Supra.
Both the turbo and S/C have positive and negative attributes. Both provide the Z with an acceptable amount of horsepower and torque. IMO, the turbo HP/ torque numbers are slightly jaded because most turbo guys run test pipes. Comparing apples to apples... A supercharger with a nice set of headers/ test pipes would produce much closer numbers. Maybe not the same but closer than what we have seen thus far. The difference as shown with ACP changing out the test pipes to H/F pipes lost him 20rwhp and XXrwtq.
My Z is an automatic and I will be running the 9lb pulley from ATI in the next couple days. I expect my new dyno numbers to be upwards of 415rwhp and 350rwtq. I chose the S/C for three reasons. 1) There is no chance of boost spikes like there is with the turbo (ask me how I know). 2) The supercharger runs much cooler and on an engine that was designed to be N/A (IE: no oil cooler and a small radiator). Longevity is something to factor. The last reason is the reliability of daily driving. There are fewer items to break or fail, so the chances are less likely it will occur with a S/C.
Again, these are my opinoins. Two nice things about a turbo would be the lack of sound (no belt moving). The second is the ability to change the boost pressure from inside the car. Please don't take this as I am downgrading turbos but on this car it was an easy choice to add a supercharger over a turbo.
Here is my take... Keep in mind this is coming from someone who had a Stealth RT Turbo and a MKIV 600 hp Single Turbo Supra.
Both the turbo and S/C have positive and negative attributes. Both provide the Z with an acceptable amount of horsepower and torque. IMO, the turbo HP/ torque numbers are slightly jaded because most turbo guys run test pipes. Comparing apples to apples... A supercharger with a nice set of headers/ test pipes would produce much closer numbers. Maybe not the same but closer than what we have seen thus far. The difference as shown with ACP changing out the test pipes to H/F pipes lost him 20rwhp and XXrwtq.
My Z is an automatic and I will be running the 9lb pulley from ATI in the next couple days. I expect my new dyno numbers to be upwards of 415rwhp and 350rwtq. I chose the S/C for three reasons. 1) There is no chance of boost spikes like there is with the turbo (ask me how I know). 2) The supercharger runs much cooler and on an engine that was designed to be N/A (IE: no oil cooler and a small radiator). Longevity is something to factor. The last reason is the reliability of daily driving. There are fewer items to break or fail, so the chances are less likely it will occur with a S/C.
Again, these are my opinoins. Two nice things about a turbo would be the lack of sound (no belt moving). The second is the ability to change the boost pressure from inside the car. Please don't take this as I am downgrading turbos but on this car it was an easy choice to add a supercharger over a turbo.
Did the huge difference in TQ not factor in to your decesion?
How many degrees above ambient is the intake charge with the ati intercooler?
was price or installation a factor or did you go with the ati siply because you thought it was the best option?
thnx-
05-21-2004, 12:57 PM
#199
Originally posted by SQUILL
you are telling me that if you are cruising at 3000 rpm at say 1/4 throttle
your boost guage reads 0 ?? You dont hear your turbines spooling or feel anything at all is this what your saying??
you are telling me that if you are cruising at 3000 rpm at say 1/4 throttle
your boost guage reads 0 ?? You dont hear your turbines spooling or feel anything at all is this what your saying??
That is correct...I show significant vaccum at cruise...any turbo or SC would show the same thing. Cruising equals vaccum.. I dont show positive manifold presure until I actually depress the acclerator pedel further..as if to accelerate. But under steady cruise....there is vaccum...as there should be. I cant hear the turbos or anything...sounds totally stock. I imagine they are spinning freely, but just not a level to create any boost effect...probably just idling slowly.
05-21-2004, 01:07 PM
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SC and TT
I can'r belive I keep geeting sucked into this thread , but here you go .
Whosdady: sure the TTs benefit from Testpipes or high flow cats, and yes this also can benefit S/Cs. However; aadding Testpipes or H/F cats in no way can meak the TQ curve of a Cent SC look even close to that of a properly sized TT setup.
Now on the other hand a Roots (or better yet a Twin Screw) provides a TQ curve that looks much closer to that of a TT setup accept at a higher comparable psi to compensate for the extra parasitic losses of the crank drive loss. The constant displacements SCs have an advantage over the Cents and even TTs at the lower half of the RPM curve.
So sure , comparable peak HP and TQ numbers are possible between both TTs and Cents , but the areas under the TQ curves will always be still vastly different regardelss of the exhaust used.
I would say one of the bigger challenges with a TT on a Z or G is getting that extra TQ at launch effectively to the pavement. So from a 1/4 mile perspective unless you can get the TQ to the ground it buys less WRT ET.
Whosdady: sure the TTs benefit from Testpipes or high flow cats, and yes this also can benefit S/Cs. However; aadding Testpipes or H/F cats in no way can meak the TQ curve of a Cent SC look even close to that of a properly sized TT setup.
Now on the other hand a Roots (or better yet a Twin Screw) provides a TQ curve that looks much closer to that of a TT setup accept at a higher comparable psi to compensate for the extra parasitic losses of the crank drive loss. The constant displacements SCs have an advantage over the Cents and even TTs at the lower half of the RPM curve.
So sure , comparable peak HP and TQ numbers are possible between both TTs and Cents , but the areas under the TQ curves will always be still vastly different regardelss of the exhaust used.
I would say one of the bigger challenges with a TT on a Z or G is getting that extra TQ at launch effectively to the pavement. So from a 1/4 mile perspective unless you can get the TQ to the ground it buys less WRT ET.