Turbo eff. and high boost applications
08-23-2005, 09:59 AM
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Turbo eff. and high boost applications
Hallo,
when you look around, you see a lot of high boost cars (30psi i.e.)
but when you look at the compressor maps you see that most (also big T4 turbos) loos efficiency when you past aprox. 20psi
so, is all the compressor map thing bullshit or do these turbos realy operate at such a low eff. level?
a lot of the real big ones are also left of the surge line when run i.e. 30psi at 6krpm on a b16 engine... how could that work?
Thanks
Malte.
when you look around, you see a lot of high boost cars (30psi i.e.)
but when you look at the compressor maps you see that most (also big T4 turbos) loos efficiency when you past aprox. 20psi
so, is all the compressor map thing bullshit or do these turbos realy operate at such a low eff. level?
a lot of the real big ones are also left of the surge line when run i.e. 30psi at 6krpm on a b16 engine... how could that work?
Thanks
Malte.
08-24-2005, 07:39 AM
#3
Re: Turbo eff. and high boost applications (mrx)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mrx »</TD></TR><TR><TD CLASS="quote">bump ... nobody?!?</TD></TR></TABLE>
You're reading these maps in a very "2 dimensional" way.
1) These maps that were created were al based upon testing and readings from truck applicationtions (after all that how most of these applications were started in the first place. The efficiency islands for a certain amount of displacement at a given time are going to read slightly differently, and must be compensated in your calculation.
2) These maps are tested without intercoolers, and efficiency changes slightly with given pressure drops of intercoolers in the setup that you want you use.
3) Turbine maps. These also account for a lot of the "misreading" that is used when you're calculating a particular application. You're not getting the full story.
Compressor and turbine maps can be read when one looks at it in a particular way. It's not just the math, but the experience, and intuition of the application used that makes them a useful tool.
Hope this helped a little.
You're reading these maps in a very "2 dimensional" way.
1) These maps that were created were al based upon testing and readings from truck applicationtions (after all that how most of these applications were started in the first place. The efficiency islands for a certain amount of displacement at a given time are going to read slightly differently, and must be compensated in your calculation.
2) These maps are tested without intercoolers, and efficiency changes slightly with given pressure drops of intercoolers in the setup that you want you use.
3) Turbine maps. These also account for a lot of the "misreading" that is used when you're calculating a particular application. You're not getting the full story.
Compressor and turbine maps can be read when one looks at it in a particular way. It's not just the math, but the experience, and intuition of the application used that makes them a useful tool.
Hope this helped a little.
08-24-2005, 07:47 AM
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Most T series turbochargers are pretty efficienct at 30+ PSI. You sure you have the correct formulas for airflow and pressure ratio?
Turbocharger efficiency and compressor flow maps don't tell the whole story, but they definitely give you a very good idea of how the turbo will preform.
From my experience, if you are using the correct equations and the compressor flow map says it will surge, it WILL surge. If you are just barely to the left of the surge line, you might not hear or feel it in the car, but outside of the car, it will be much eaiser to detect. Also, compressors will react differently to different compressor covers. If a compressor flow map is drafted using a .70 A/R T04S cover, and you are running the wheel in a .60 A/R T04E cover, the wheel will act a little differently then the compressor flow map.
I would be leary of any compressor flow map for a Garrett wheel you come across besides the Garrett Engineering flow maps however. I have seen maps printed by a couple different places that were FAR different then the actual Garrett map.
Turbocharger efficiency and compressor flow maps don't tell the whole story, but they definitely give you a very good idea of how the turbo will preform.
From my experience, if you are using the correct equations and the compressor flow map says it will surge, it WILL surge. If you are just barely to the left of the surge line, you might not hear or feel it in the car, but outside of the car, it will be much eaiser to detect. Also, compressors will react differently to different compressor covers. If a compressor flow map is drafted using a .70 A/R T04S cover, and you are running the wheel in a .60 A/R T04E cover, the wheel will act a little differently then the compressor flow map.
I would be leary of any compressor flow map for a Garrett wheel you come across besides the Garrett Engineering flow maps however. I have seen maps printed by a couple different places that were FAR different then the actual Garrett map.
08-24-2005, 07:51 AM
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Re: (99_GS-T)
Hi,
yes i'am sure that i have the correct formulas... checked it with several turbo calculators too and get the same result...
i know that compressor maps are not the whole story but when i calculate a defined airflow at a given pressure level (like 30psi) i'am out of eff. at many many compressor maps... that is whats wondering me... i think that many turbos are good at this high pressure levels but if there is more math needed to see how good a turbo REALY is... let me know?!
this thread is for understanding why is is like it is...
Thanks
Malte.
yes i'am sure that i have the correct formulas... checked it with several turbo calculators too and get the same result...
i know that compressor maps are not the whole story but when i calculate a defined airflow at a given pressure level (like 30psi) i'am out of eff. at many many compressor maps... that is whats wondering me... i think that many turbos are good at this high pressure levels but if there is more math needed to see how good a turbo REALY is... let me know?!
this thread is for understanding why is is like it is...
Thanks
Malte.
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08-24-2005, 08:46 AM
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Re: (99_GS-T)
i did some math... and found that the most T3/T4 turbos are good enough at high boost levels around 30psi...
T3's are a bit inefficient at this pressures i think... just look at the T3 60trim ... its nearly out of the compressor map at above 6krpm
the T61 for example is all the way in surge until 6k and after that its not much eff. for the flow rates of out 1,6-2,0 Liter engines... so whats about ppl using a PT71 i.e. it is hard to understand that they have realy that amount of surge when using such a big turbo.
Best regards
Malte.
T3's are a bit inefficient at this pressures i think... just look at the T3 60trim ... its nearly out of the compressor map at above 6krpm
the T61 for example is all the way in surge until 6k and after that its not much eff. for the flow rates of out 1,6-2,0 Liter engines... so whats about ppl using a PT71 i.e. it is hard to understand that they have realy that amount of surge when using such a big turbo.
Best regards
Malte.
08-24-2005, 09:53 AM
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Re: (blundar)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blundar »</TD></TR><TR><TD CLASS="quote">*cough* Holset *cough*</TD></TR></TABLE>*cough* Let's see some compressor flow maps *cough*
Last PT71 I saw didn't get full boost until just shy of 7000 RPM, on a 1.9L. LAG helps keep the turbocharger from surging. A large turbine side helps with lag and power. You generally don't get a large compressor wheel without a large turbine wheel, so surge often isn't an issue if the turbo is sized correctly.
T3 compressors are pretty small. A T3 60-trim will be out of air long before 30 PSI, even on a 1.6L. A T04E 60-trim will make pretty decent power at less then 30 PSI, but will be running out of air at 30 PSI trying to rev high into the RPM range.
The T61 is pretty old school technology. It's a good wheel though. When I map it out for a 1.6L, revving out to 9000 RPM at 30 PSI for sea level, it's over 70% efficient from 6000 RPM to 9000 RPM. It's actually getting to its peak efficiency of 76% at 9000 RPM. It's no where near surging at 6000 RPM either.
Where did you get the compressor flow map for the T61?
The GT40 82mm 56-trim compressor wheel with the ported shroud cover maps out nicely for a 1.6L at sea level. It will be a bunch more responsive then the T61 as well. ~77% efficient at peak power on 30 PSI. It's even looking good at 33 PSI. Kind of interesting that 1.6Ls running that compressor wheel seem to make LOTS of power...
Last PT71 I saw didn't get full boost until just shy of 7000 RPM, on a 1.9L. LAG helps keep the turbocharger from surging. A large turbine side helps with lag and power. You generally don't get a large compressor wheel without a large turbine wheel, so surge often isn't an issue if the turbo is sized correctly.
T3 compressors are pretty small. A T3 60-trim will be out of air long before 30 PSI, even on a 1.6L. A T04E 60-trim will make pretty decent power at less then 30 PSI, but will be running out of air at 30 PSI trying to rev high into the RPM range.
The T61 is pretty old school technology. It's a good wheel though. When I map it out for a 1.6L, revving out to 9000 RPM at 30 PSI for sea level, it's over 70% efficient from 6000 RPM to 9000 RPM. It's actually getting to its peak efficiency of 76% at 9000 RPM. It's no where near surging at 6000 RPM either.
Where did you get the compressor flow map for the T61?
The GT40 82mm 56-trim compressor wheel with the ported shroud cover maps out nicely for a 1.6L at sea level. It will be a bunch more responsive then the T61 as well. ~77% efficient at peak power on 30 PSI. It's even looking good at 33 PSI. Kind of interesting that 1.6Ls running that compressor wheel seem to make LOTS of power...
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