Shop owners - Tuners - opinions on SC parasitic loss
03-15-2007, 04:22 PM
#81
Dsport drove that T-trim to 19 psi and that air was probably fairly heated up and the compressor efficiency was probably in worse shape having to be spun so fast at 7400 rpms that he "only" achieved 510whp or so...at 19psi
I think he was running into a wall of parasitic loss limitations right around there, but you and me don't rev to 7400 rpms and we don't overdrive the blower as much as he was
Im not sure on the exact number and psi level he was at , but I believe they gave up because the belt kept snapping at a certain rpm level . He was shooting for 8000rpm . I think he said they reached 21psi and 7600rpm . not sure
EDIT...come to think about it ...Im thinking it was 18psi at 7600rpm that the belt kept snapping .
I think he was running into a wall of parasitic loss limitations right around there, but you and me don't rev to 7400 rpms and we don't overdrive the blower as much as he was
Im not sure on the exact number and psi level he was at , but I believe they gave up because the belt kept snapping at a certain rpm level . He was shooting for 8000rpm . I think he said they reached 21psi and 7600rpm . not sure
EDIT...come to think about it ...Im thinking it was 18psi at 7600rpm that the belt kept snapping .
Last edited by booger; 03-15-2007 at 04:39 PM.
03-15-2007, 04:29 PM
#82
I don't think that 8000rpms is the best way to go but hey, to each his own.
One thing that I have noticed is that the vortech impeller is not the most effeecient design. I am dead serious when I say that a redesigned billet impeller could be made if there was enough interest as an alternative to the t-trim. I already have one for a different brand of SC that flows 15% more flow then the original impeller within the same volute.
This also has to do with how the air is pushed off of the impeller. This can affect drag which also associates with parasitic loss due to the drag of the impeller against the air.
One thing that I have noticed is that the vortech impeller is not the most effeecient design. I am dead serious when I say that a redesigned billet impeller could be made if there was enough interest as an alternative to the t-trim. I already have one for a different brand of SC that flows 15% more flow then the original impeller within the same volute.
This also has to do with how the air is pushed off of the impeller. This can affect drag which also associates with parasitic loss due to the drag of the impeller against the air.
03-15-2007, 05:08 PM
#85
The parasitic loss I thought we were really talking about was the mechanical parasitic loss, or the act of a larger belt having to turn a blower. What I've been disagreeing with you about in regards to parasitic losses is how severe they are. You're using your belt slipping at 13 psi as an example to show the blower is harder to spin faster as boost rises, that's fine and I'm ok with that. I also think part of the reason the belt is slipping is the bad belt design, which you obviously acknowledge because you bought the Cog setup because you think it's a superior design. The thing I disagree with you on is how severe the mechanical parasitic loss is or isn't. At the end of the day it doesn't matter if you make power
The belt design was never meant to produce higher boost .
But lets just review a little to let you see where Im coming from
1- Dsport mag's article suggests running enough fuel for 150whp more at 600whp . This is ballpark and just an example . But at our whp it would come out to be around 100whp more fuel .
2- The link that talked about the Roll Royce motor that took 150hp to make 250 more usable hp . Again it ballpark figures . Im making 200whp + more than I did N/A , so Im guessing the loss to be simular , but again just giving the examples of how much is robbed from the motor to produce hp .
3- The guys at my shop that all say the parasitic loss was to great to continue to try to make usable hp with a centrifugal SC and switched to turbo's .
That is all I was looking at and all I was trying to debate
The belt design was never meant to produce higher boost .
But lets just review a little to let you see where Im coming from
1- Dsport mag's article suggests running enough fuel for 150whp more at 600whp . This is ballpark and just an example . But at our whp it would come out to be around 100whp more fuel .
2- The link that talked about the Roll Royce motor that took 150hp to make 250 more usable hp . Again it ballpark figures . Im making 200whp + more than I did N/A , so Im guessing the loss to be simular , but again just giving the examples of how much is robbed from the motor to produce hp .
3- The guys at my shop that all say the parasitic loss was to great to continue to try to make usable hp with a centrifugal SC and switched to turbo's .
That is all I was looking at and all I was trying to debate
03-15-2007, 05:26 PM
#86
Quote:
Originally Posted by booger
If you had read the link I posted . You would also have noticed , in a two speed SC [ in a airplane ] that it took 400hp to turn the blower .
and you'd also notice that it says:
Quote:
The two-stage Merlin was losing 400 hp (300 kW) to turn the supercharger but developing between 1500 and 1700 hp (1125 to 1275 kW) at the propeller shaft, depending on model
seems inline with a regular SC parasitic loss to positive power trade off to me...how's that out of the ordinary? It's just a larger scale of power
Well ok...as you see then the motor above made 1500hp and it took 400 hp to turn that blower...thats huge and almost a 25% loss in power due to parasitic loss . Apply a 25% loss to our power level ? hmmmm 100hp go figure !!!!!! Its not quite 25% but close enough to get the point across
And to continue to beat the dead horse . The DSport mag article suggest a 25% increase in fuel to supply the same HP as a turbo . SO you see the thought of a huge parasitic loss isnt far fetched as you think . And a 20 to 25% loss is going to be more in line to our loss at 425whp .
Originally Posted by booger
If you had read the link I posted . You would also have noticed , in a two speed SC [ in a airplane ] that it took 400hp to turn the blower .
and you'd also notice that it says:
Quote:
The two-stage Merlin was losing 400 hp (300 kW) to turn the supercharger but developing between 1500 and 1700 hp (1125 to 1275 kW) at the propeller shaft, depending on model
seems inline with a regular SC parasitic loss to positive power trade off to me...how's that out of the ordinary? It's just a larger scale of power
Well ok...as you see then the motor above made 1500hp and it took 400 hp to turn that blower...thats huge and almost a 25% loss in power due to parasitic loss . Apply a 25% loss to our power level ? hmmmm 100hp go figure !!!!!! Its not quite 25% but close enough to get the point across
And to continue to beat the dead horse . The DSport mag article suggest a 25% increase in fuel to supply the same HP as a turbo . SO you see the thought of a huge parasitic loss isnt far fetched as you think . And a 20 to 25% loss is going to be more in line to our loss at 425whp .
Last edited by booger; 03-15-2007 at 06:02 PM.
03-15-2007, 06:31 PM
#87
booger, we really need to drop talking about airplane engines. Even at normal operating altitude, an 800hp engine at sea level will produce a lot less power at 15-24k feet above sea level. The supercharger not only makes additional power than it was when NA, but makes up for the power lost while at altitude. Wikipedia even said (and I quoted from earlier) that running the supercharger at sea level would damage the engine
The Dsport article is using an arbitrary 600whp number but doesn't disclose what the starting point of what the raw engine power is. I mean, are we talking about a small liter 200hp civic engine being supercharged to 600whp or are we talking about a 400hp 6 liter LS2 engine being supercharged to 600whp?
you can't just come on here and say "some guys with mustangs switched to turbos because the parasitic loss owned them, so that means it's really huge" despite whatever power level they're at vs what we're at. You'll need to give some examples like what car and what year it is, what psi they were running - with different psi dynos, if there was belt slipping, what hp numbers they ran, what rpm they rev to, what other mods they have like cams, exhaust, test pipes etc, what displacement, compression, etc
I know you seem to trust them, but as far as anyone here knows, they might have no idea what they're talking about
if parasitic loss due to creating 200whp is 20-25% then wouldn't that be 40-50whp? You can't count the power that the engine is naturaly making. While we're talking about that, what if you add 50whp via NA mods and 150whp via the supercharger? Then the parasitic loss is still 30-37whp...
The Dsport article is using an arbitrary 600whp number but doesn't disclose what the starting point of what the raw engine power is. I mean, are we talking about a small liter 200hp civic engine being supercharged to 600whp or are we talking about a 400hp 6 liter LS2 engine being supercharged to 600whp?
you can't just come on here and say "some guys with mustangs switched to turbos because the parasitic loss owned them, so that means it's really huge" despite whatever power level they're at vs what we're at. You'll need to give some examples like what car and what year it is, what psi they were running - with different psi dynos, if there was belt slipping, what hp numbers they ran, what rpm they rev to, what other mods they have like cams, exhaust, test pipes etc, what displacement, compression, etc
I know you seem to trust them, but as far as anyone here knows, they might have no idea what they're talking about
if parasitic loss due to creating 200whp is 20-25% then wouldn't that be 40-50whp? You can't count the power that the engine is naturaly making. While we're talking about that, what if you add 50whp via NA mods and 150whp via the supercharger? Then the parasitic loss is still 30-37whp...
Last edited by sentry65; 03-15-2007 at 06:41 PM.
03-15-2007, 06:48 PM
#88
The Rolls Royce motor and the DSport article are examples . This is all we have to go on . If the same % of loss applies to a aircraft engine as does what ever motor Dsport was refering to in its article , is the same . It isnt far fetched and it even makes it more believable that the same % of loss will apply to our motor . You have two totally different sources saying the same thing . That the parasitic loss is huge and is somewhere in the range of 20 to 25 % . So when comparing and the comparisons your using are all in the same % range . Why wouldnt it apply to another but different motor ?
And wouldnt you figure at 425whp our loss would be in the range of 70 to 100hp ? Dsport 600-150hp Roll Royce 1500hp -400hp both with in that same % of loss .
And wouldnt you figure at 425whp our loss would be in the range of 70 to 100hp ? Dsport 600-150hp Roll Royce 1500hp -400hp both with in that same % of loss .
03-15-2007, 07:08 PM
#89
did the Dsport article say what type of supercharger they're talking about????????
Centrifugals are pretty efficient and not as hard to turn as a roots blower.
I still don't think an airplane engine is a good example. The engine blows up with the supercharger at ground level by making too much power, but works fine at altitude
i'm a broken record at this point...how can you think the same % applies to a 24,000ft above sea level engine vs a sea level engine? At 24,000 ft above sea level, the supercharger's positive power is mostly used just to get the engine's power back up to 0 psi
at my shop's dyno, stock Z's are around 210-220whp. My NA Z was at 272whp. I added the vortech with 2.87 pulley and some other minor things and made 420whp with poor fuel pressure. So adding FI was about a 150whp difference.
Centrifugals are pretty efficient and not as hard to turn as a roots blower.
I still don't think an airplane engine is a good example. The engine blows up with the supercharger at ground level by making too much power, but works fine at altitude
i'm a broken record at this point...how can you think the same % applies to a 24,000ft above sea level engine vs a sea level engine? At 24,000 ft above sea level, the supercharger's positive power is mostly used just to get the engine's power back up to 0 psi
at my shop's dyno, stock Z's are around 210-220whp. My NA Z was at 272whp. I added the vortech with 2.87 pulley and some other minor things and made 420whp with poor fuel pressure. So adding FI was about a 150whp difference.
03-15-2007, 07:14 PM
#90
I'll keep finding examples if you like . But when they all say that the loss by turning the blower works out to be 20 to 25 % Does it really make a difference what type of motor and where it is used ?
Im tired of saying the same thing over and over . The examples are from different sources and different motors and different worlds . Why would our motor and car be different ?
Im tired of saying the same thing over and over . The examples are from different sources and different motors and different worlds . Why would our motor and car be different ?
03-15-2007, 07:27 PM
#91
here's why it makes a difference what altitude it's used at:
we don't know how much power is being lost because of how much less dense the air is. I can tell you that at 24,000 ft above sea level, the air is 38.8 % as dense as it is at sea level......but the air does get colder...but overall less power can be made
The fact that it can make 1500-1700hp at altitude is still an impressive gain over 1030hp when you consider the unknown, but significant loss in power due to high elevation.
You asked earlier how can they dyno it in the sky - they obviously don't, but it's not like they can't dyno it on the ground either, it'd blow the engine
we keep saying parasitic loss increases as boost increases
so if you take a 400hp engine and add 6 lbs of boost to get 600hp, that's going to have less parasitic loss than if you had a 200 hp engine adding 30 lbs of boost to get 600hp.
saying:
parasitic loss increasing as boost increases
conflicts with
saying parasitic loss is a constant 20-25%
meaning the Dsport magazine is leaving out some info...they're giving us the simplified dumbed down explanation/forumlas/percentages
we don't know how much power is being lost because of how much less dense the air is. I can tell you that at 24,000 ft above sea level, the air is 38.8 % as dense as it is at sea level......but the air does get colder...but overall less power can be made
The fact that it can make 1500-1700hp at altitude is still an impressive gain over 1030hp when you consider the unknown, but significant loss in power due to high elevation.
You asked earlier how can they dyno it in the sky - they obviously don't, but it's not like they can't dyno it on the ground either, it'd blow the engine
we keep saying parasitic loss increases as boost increases
so if you take a 400hp engine and add 6 lbs of boost to get 600hp, that's going to have less parasitic loss than if you had a 200 hp engine adding 30 lbs of boost to get 600hp.
saying:
parasitic loss increasing as boost increases
conflicts with
saying parasitic loss is a constant 20-25%
meaning the Dsport magazine is leaving out some info...they're giving us the simplified dumbed down explanation/forumlas/percentages
Last edited by sentry65; 03-15-2007 at 07:39 PM.
03-16-2007, 05:04 AM
#92
saying:
parasitic loss increasing as boost increases
conflicts with
saying parasitic loss is a constant 20-25%
meaning the Dsport magazine is leaving out some info...they're giving us the simplified dumbed down explanation/forumlas/percentages
It doesnt comflict at all . When boost rises , so does the whp and so does the P loss . And still stays at 25% .
I havent left out anything in the DSport article . I posted word for word [FOR YOU] the part of the article that talked about it in another thread . And because it was an import tuner mag. we can be safe to assume they were talking about a 4 cyl. or 6 cyl. motor .
ONE MORE TIME
The article suggests running enough fuel to support 25 % more whp then your total or intended whp . Why ? because the person that wrote the article said you need to make up for parasitic loss turning the blower .
The other example tells you straight forward that a Rolls Royce engine making 1500 to 1700 hp waisted another 400 hp turning the blower . Why ? parasitic loss turning the blower . and that 400hp is 25% of 1600 HP , right in the middle of the 1500 to 1700hp .
BOTH examples are worlds apart as far as where and when the motors are used . And worlds apart on how big the motors are . BUT they both share a 25% loss due to parasitic loss....GO FIGURE !!!!
parasitic loss increasing as boost increases
conflicts with
saying parasitic loss is a constant 20-25%
meaning the Dsport magazine is leaving out some info...they're giving us the simplified dumbed down explanation/forumlas/percentages
It doesnt comflict at all . When boost rises , so does the whp and so does the P loss . And still stays at 25% .
I havent left out anything in the DSport article . I posted word for word [FOR YOU] the part of the article that talked about it in another thread . And because it was an import tuner mag. we can be safe to assume they were talking about a 4 cyl. or 6 cyl. motor .
ONE MORE TIME
The article suggests running enough fuel to support 25 % more whp then your total or intended whp . Why ? because the person that wrote the article said you need to make up for parasitic loss turning the blower .
The other example tells you straight forward that a Rolls Royce engine making 1500 to 1700 hp waisted another 400 hp turning the blower . Why ? parasitic loss turning the blower . and that 400hp is 25% of 1600 HP , right in the middle of the 1500 to 1700hp .
BOTH examples are worlds apart as far as where and when the motors are used . And worlds apart on how big the motors are . BUT they both share a 25% loss due to parasitic loss....GO FIGURE !!!!
Last edited by booger; 03-16-2007 at 05:06 AM.
03-16-2007, 07:52 AM
#93
if i recall, there were two formulas in that article to calculate the fuel needed:
SC = hp/.70
turbo/NA= hp/.80
so if a SC requires 25% more fuel because of parasitic loss, than that means a turbo/NA is going to need 15% more fuel than hp.
arrived at this by: 600/.7 = 857
and 600/.8 = 750.
750/857 = about 60%
so 60% multiplied by the 25% SC figure = 15% for turbo/NA
We're talking about a 10% difference here between SC and turbo/NA's parasitic loss. So 10% of 420whp is 42whp is parasitic loss and additional fuel that the turbo/NA car doesn't need/use
So if a SC requires 25% more fuel than it makes power, did that article bother to mention how much more of a % fuel a turbo/NA setup would need for its power level?
Another thing is the 350Z/G35 engine one of the largest 6 cylinder engines made to grace the pages of Dsport. I'd be more inclined to assume Dsport had a smaller engine in mind. And unless they specify what the starting hp was of the raw engine vs how much of it is being made with boost, then we're only guessing what they meant
I don't really care what the parasitic loss is. My car makes power, your car makes power, and we can both tune the car to reach the proper A/F. If the parasitic loss is 100whp or way less than that doesn't change that
If you'd like to believe that there's just no more power left on the table to be gained because the parasitic loss is too great, then that's fine. I'm planning on sticking with my stock block for awhile so I'm not going to really get a chance for awhile to prove if 550+whp is possible or not with a SC on a Z/G. I actually think the power I'm making right now is plenty, but if I can manage to blow up my block, I'll be heading over to GT Motorsports for their stroker kit
thinking about it, I suppose it makes sense that even NA there's a whole bunch of parasitic loss happening with the accessories. The most ideal thing would be to not have the belt on the crankshaft at all or even a crank pulley. It's going to be harder to rotate the crankshaft of an 8 liter V12 than a small 1.2 liter inline 4
SC = hp/.70
turbo/NA= hp/.80
so if a SC requires 25% more fuel because of parasitic loss, than that means a turbo/NA is going to need 15% more fuel than hp.
arrived at this by: 600/.7 = 857
and 600/.8 = 750.
750/857 = about 60%
so 60% multiplied by the 25% SC figure = 15% for turbo/NA
We're talking about a 10% difference here between SC and turbo/NA's parasitic loss. So 10% of 420whp is 42whp is parasitic loss and additional fuel that the turbo/NA car doesn't need/use
So if a SC requires 25% more fuel than it makes power, did that article bother to mention how much more of a % fuel a turbo/NA setup would need for its power level?
Another thing is the 350Z/G35 engine one of the largest 6 cylinder engines made to grace the pages of Dsport. I'd be more inclined to assume Dsport had a smaller engine in mind. And unless they specify what the starting hp was of the raw engine vs how much of it is being made with boost, then we're only guessing what they meant
I don't really care what the parasitic loss is. My car makes power, your car makes power, and we can both tune the car to reach the proper A/F. If the parasitic loss is 100whp or way less than that doesn't change that
If you'd like to believe that there's just no more power left on the table to be gained because the parasitic loss is too great, then that's fine. I'm planning on sticking with my stock block for awhile so I'm not going to really get a chance for awhile to prove if 550+whp is possible or not with a SC on a Z/G. I actually think the power I'm making right now is plenty, but if I can manage to blow up my block, I'll be heading over to GT Motorsports for their stroker kit
thinking about it, I suppose it makes sense that even NA there's a whole bunch of parasitic loss happening with the accessories. The most ideal thing would be to not have the belt on the crankshaft at all or even a crank pulley. It's going to be harder to rotate the crankshaft of an 8 liter V12 than a small 1.2 liter inline 4
Last edited by sentry65; 03-16-2007 at 09:36 AM.
03-16-2007, 01:46 PM
#95
oh booger, we all know we can find various claims made by some guy who wrote a little blurb on the internet about a generallity showing one way or another.
Can we really say that's a creditable source? I mean, would that source hold up if you were writing a thesis in school or a scientific publication:
"some random guy who wrote an article on MSN says centrifugal's have 50% loss" therefore IT MUST BE TRUE. It doesn't even say anything about if he means that for all possible configurations at all possible boost levels or not
BTW, did you not read the last sentence of that paragraph where he says:
I had no idea that some guys example to get the point across was an actual mathmatically sound formula for all cases [/sarcasm]
Anyway, I'm all for you finding actual case studies of engines with superchargers where people seem to have found out the parasitic loss, but I'm still going to demand an explanation to the Dsport article that says:
fuel requirements are:
SC = hp/.70
turbo/NA= hp/.80
so there's a 10% difference between fuel requirements between a SC and turbo/NA
so that means:
if SC's need 25% more fuel
then turbo/NA need 15% more fuel
that's 10% difference in power/fuel being used up by parasitic loss that turbo/NA cars don't need to deal with
...and that's very different from a 25% total difference between SC and turbo/NA
turbos and NA engines don't get free lunches either just like Sharif said, they're just more free than a SC's lunch
Can we really say that's a creditable source? I mean, would that source hold up if you were writing a thesis in school or a scientific publication:
"some random guy who wrote an article on MSN says centrifugal's have 50% loss" therefore IT MUST BE TRUE. It doesn't even say anything about if he means that for all possible configurations at all possible boost levels or not
BTW, did you not read the last sentence of that paragraph where he says:
(these numbers are only examples but they illustrate the concept)
Anyway, I'm all for you finding actual case studies of engines with superchargers where people seem to have found out the parasitic loss, but I'm still going to demand an explanation to the Dsport article that says:
fuel requirements are:
SC = hp/.70
turbo/NA= hp/.80
so there's a 10% difference between fuel requirements between a SC and turbo/NA
so that means:
if SC's need 25% more fuel
then turbo/NA need 15% more fuel
that's 10% difference in power/fuel being used up by parasitic loss that turbo/NA cars don't need to deal with
...and that's very different from a 25% total difference between SC and turbo/NA
turbos and NA engines don't get free lunches either just like Sharif said, they're just more free than a SC's lunch
Last edited by sentry65; 03-16-2007 at 02:31 PM.
03-16-2007, 02:12 PM
#96
even if a full 50% of the power gained with the SC compared to the NA power, our cars have probably gained 150whp from the vortech alone, so that means roughly up to 75whp is being wasted turning the blower. That's a compromise on both our stances - under 100whp and over 25-40whp
I've typically read that it's less than 50% though, somewhere around 38-45% as a "rule of thumb"
but again, it isn't a constant because parasitic loss increases as psi rises - yours and my stance
I've typically read that it's less than 50% though, somewhere around 38-45% as a "rule of thumb"
but again, it isn't a constant because parasitic loss increases as psi rises - yours and my stance
Last edited by sentry65; 03-16-2007 at 02:33 PM.
03-19-2007, 03:55 PM
#98
yeah i read through that article a long time ago. I'm going to assume you're focusing on this line:
and I'm going to respond to that by saying how did they reach that 46% limit figure? because my car for instance on the dynodynamics dyno, makes 420whp with the vortech (as of last dyno) and 272whp when it was NA with my bolt on parts. That's a 55% improvement, so what's the deal with them saying 46% is the limit? We can't use a generality to define a specific situation with specific cars with specific types of superchargers
but I figure you're more focused on the 20% of total hp output part of that quote. And again I'm going to ask the writers of that article what type of supercharger were they refering to? That sentence they wrote implies that 20% is the max anyway
...I'm not going to let this go without some sort of explanation:
That Dsport article says
fuel requirements are:
SC = hp/.70
turbo/NA= hp/.80
so there's a 10% difference between fuel requirements between a SC and turbo/NA, not 25%
seems contradictory to me...
I can accept the 25% parasitic loss for a SC only if we agree then that turbo and NA has to deal with 15% parasitic loss
A supercharger can consume as much as 20 percent of an engine's total power output. But because a supercharger can generate as much as 46 percent additional horsepower, most think the trade-off is worth it.
but I figure you're more focused on the 20% of total hp output part of that quote. And again I'm going to ask the writers of that article what type of supercharger were they refering to? That sentence they wrote implies that 20% is the max anyway
...I'm not going to let this go without some sort of explanation:
That Dsport article says
fuel requirements are:
SC = hp/.70
turbo/NA= hp/.80
so there's a 10% difference between fuel requirements between a SC and turbo/NA, not 25%
seems contradictory to me...
I can accept the 25% parasitic loss for a SC only if we agree then that turbo and NA has to deal with 15% parasitic loss
Last edited by sentry65; 03-19-2007 at 04:10 PM.
03-26-2007, 08:13 AM
#99
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...I'm not going to let this go without some sort of explanation:
That Dsport article says
fuel requirements are:
SC = hp/.70
turbo/NA= hp/.80
so there's a 10% difference between fuel requirements between a SC and turbo/NA, not 25%
seems contradictory to me...
I can accept the 25% parasitic loss for a SC only if we agree then that turbo and NA has to deal with 15% parasitic loss[/QUOTE]
You keep assuming F.I. efficiency's are related to S/C parasitic losses. Don't compare system efficiency's they are obviously different and fuel usage can be a big part of the difference.
Parasitic loss is a drain on the engines output required to rotate all the additional mechanical assemblies pulleys/gears etc. It has NADA to do with Turbos. They have mass and this mass has to rotate which takes a fair amount of the engines output (tq) from the engine. The simple question remains How MUCH ???
That Dsport article says
fuel requirements are:
SC = hp/.70
turbo/NA= hp/.80
so there's a 10% difference between fuel requirements between a SC and turbo/NA, not 25%
seems contradictory to me...
I can accept the 25% parasitic loss for a SC only if we agree then that turbo and NA has to deal with 15% parasitic loss[/QUOTE]
You keep assuming F.I. efficiency's are related to S/C parasitic losses. Don't compare system efficiency's they are obviously different and fuel usage can be a big part of the difference.
Parasitic loss is a drain on the engines output required to rotate all the additional mechanical assemblies pulleys/gears etc. It has NADA to do with Turbos. They have mass and this mass has to rotate which takes a fair amount of the engines output (tq) from the engine. The simple question remains How MUCH ???
03-26-2007, 09:28 AM
#100
we don't even know the efficiencies of the generalities the article was talking about. It could have been talking about an efficient small turbo vs an inefficient roots blower for all we know
and what rpm range should we assume the article is talking about? What redline limit are we assuming a car should have?
and what rpm range should we assume the article is talking about? What redline limit are we assuming a car should have?
Last edited by sentry65; 03-26-2007 at 09:31 AM.
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