Garrett GT turbo vs Modified K24's
05-09-2005, 05:01 PM
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Garrett GT turbo vs Modified K24's
This dyno is from two different cars with all of the same mods except turbos. The car that pulls stronger below 4,500 is the Garrett car.
Last edited by K24madness; 05-09-2005 at 09:32 PM.
05-09-2005, 06:39 PM
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Interesting comparison. I am kind of confused however If I understand correctly Kevin, he does not compare the GT Garretts to his modded K16s but rather K16 housings vs K24. I noticed that the Garretts are running leaner than the KKK below 5K at the point where the performance starts falling off somewhat, which is logical.
Can you please specify which compressor are the turbos using, which GT version are these, I would guess a GT25? The smaller turbine on the Garretts will increase back pressure, spool faster but loose efficiency at the high end.
Finally the conditions at which they were tested are not the same, the KKKs are suffering from double the humidity and both dyno runs are uncorrected.. Do you have boost pressure readings and dyno logs available?
Sorry but I am just trying to understand better the thread and make sure testing conditions are comparable.
Thanks
Interesting comparison. I am kind of confused however If I understand correctly Kevin, he does not compare the GT Garretts to his modded K16s but rather K16 housings vs K24. I noticed that the Garretts are running leaner than the KKK below 5K at the point where the performance starts falling off somewhat, which is logical.
Can you please specify which compressor are the turbos using, which GT version are these, I would guess a GT25? The smaller turbine on the Garretts will increase back pressure, spool faster but loose efficiency at the high end.
Finally the conditions at which they were tested are not the same, the KKKs are suffering from double the humidity and both dyno runs are uncorrected.. Do you have boost pressure readings and dyno logs available?
Sorry but I am just trying to understand better the thread and make sure testing conditions are comparable.
Thanks
05-09-2005, 08:09 PM
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No problem Jean. I am not trying to mislead anyone so let me try to clairfy.
The above Garretts are mounted into a K16 housing (both hot and cold). The inducer bore measures approx 48.09mm and the turbine bore measures 47.7mm. AR of .08 (not 100% sure)
My modified K24's have a inducer bore of 48.99 and a turbine bore of 54.53mm AR of 1.0 (not 100% sure)
Looking at both compressor wheels they look the same. Yet the AR and turbine whel size is very different. I would have expected better top end over the smaller Garrett/K16 combo.
Yes both of the dyno runs are uncorrected. I don't know why they do it that way. The temps and close and the pressure of 30.29 vs 30.32. The humidity is very different. If you feel this discounts the results then I will delete this post.
It is not often that you can compair 2 different cars with all of the same mods on the same dyno with the only difference being the turbos.
I was supprised to say the least.
I wecome your thoughts on the matter.
The above Garretts are mounted into a K16 housing (both hot and cold). The inducer bore measures approx 48.09mm and the turbine bore measures 47.7mm. AR of .08 (not 100% sure)
My modified K24's have a inducer bore of 48.99 and a turbine bore of 54.53mm AR of 1.0 (not 100% sure)
Looking at both compressor wheels they look the same. Yet the AR and turbine whel size is very different. I would have expected better top end over the smaller Garrett/K16 combo.
Yes both of the dyno runs are uncorrected. I don't know why they do it that way. The temps and close and the pressure of 30.29 vs 30.32. The humidity is very different. If you feel this discounts the results then I will delete this post.
It is not often that you can compair 2 different cars with all of the same mods on the same dyno with the only difference being the turbos.
I was supprised to say the least.
I wecome your thoughts on the matter.
Last edited by K24madness; 05-09-2005 at 09:33 PM.
05-09-2005, 08:14 PM
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this is interesting to me as well. Protomotive in NewJersey was recommending Garretts and said they were better than KKK hybrids. But, i really didnt have alot of confidence in these people as they were telling me things that was opposite to what Todd had told me the next day.
05-10-2005, 02:21 AM
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Not at all, I hope this is not what my post suggests. I do think that when you are comparing between two sets of turbos, the only reliable way to do it is on the same car, similar dyno conditions, and corrections should be made. They are not running the same AFRs and that will make a difference.
Humidity does play an important role with out turbo cars as you know, it is about double between the 2 different runs. If the difference between the 2 turbos is small I would not make a conclusions.
I do think however that what you are saying is correct, just wanted to raise some caution points.Thanks for sharing.
Not at all, I hope this is not what my post suggests. I do think that when you are comparing between two sets of turbos, the only reliable way to do it is on the same car, similar dyno conditions, and corrections should be made. They are not running the same AFRs and that will make a difference.
Humidity does play an important role with out turbo cars as you know, it is about double between the 2 different runs. If the difference between the 2 turbos is small I would not make a conclusions.
I do think however that what you are saying is correct, just wanted to raise some caution points.Thanks for sharing.
05-11-2005, 03:04 AM
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We drive and modify these cars because we love em. But the factory has already done the developmental work with its racing programs on the 993 GT2. In some fashion the modificatios most of us undertake are a version of what the porsche factory did to the GT2 over the 993tt. Bigger turbos, ecu's, cams, twin plugs, intercoolers etc etc.
But why don't we listen to the guys who raced and developed these cars, like the factory! Most of the nickel rocket mods will last on the street, but not very long on a race track be it compition or drivers ed. Porsche Motorsport advises at 540 hp will be the line in the sand for a nice 40k rebuild with stock rods. Now I'm sure that many of these overboosted motors will live a long life because some owners will never see the true potential of their cars, because they will never drive them fast enough to generate the mechanical forces that will rip the engine apart. They and their internet tuner buddies will be right in their asscertion that stock rods will last through with continued use in a 550 hp car.
But why don't we listen to the guys who raced and developed these cars, like the factory! Most of the nickel rocket mods will last on the street, but not very long on a race track be it compition or drivers ed. Porsche Motorsport advises at 540 hp will be the line in the sand for a nice 40k rebuild with stock rods. Now I'm sure that many of these overboosted motors will live a long life because some owners will never see the true potential of their cars, because they will never drive them fast enough to generate the mechanical forces that will rip the engine apart. They and their internet tuner buddies will be right in their asscertion that stock rods will last through with continued use in a 550 hp car.
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05-11-2005, 05:34 AM
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Originally Posted by JJayB
But why don't we listen to the guys who raced and developed these cars, like the factory!
Had to share this pic from the 996tt board - the RS Tuning engined Alzen 996tt with 550-700hp. This illustrates the heat related safety margin which the racers have to build into their motors .
Last edited by TB993tt; 05-11-2005 at 06:59 AM.
05-11-2005, 08:06 AM
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OT.
TB, do you know what exactly happened to the alzen turbo this year at the 24h nurburgring?
they lost 2 hours due to a technical problem. i dont know if it was the motor ;-) or some other stuff.
they should have had more luck. but pole position with 8:30,846 minutes is not to bad...
manthey had a mis-shift and lost more than 2 hours - sad.
TB, do you know what exactly happened to the alzen turbo this year at the 24h nurburgring?
they lost 2 hours due to a technical problem. i dont know if it was the motor ;-) or some other stuff.
they should have had more luck. but pole position with 8:30,846 minutes is not to bad...
manthey had a mis-shift and lost more than 2 hours - sad.
05-11-2005, 08:43 AM
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Originally Posted by JJayB
We drive and modify these cars because we love em. But the factory has already done the developmental work with its racing programs on the 993 GT2. In some fashion the modificatios most of us undertake are a version of what the porsche factory did to the GT2 over the 993tt. Bigger turbos, ecu's, cams, twin plugs, intercoolers etc etc.
But why don't we listen to the guys who raced and developed these cars, like the factory! Most of the nickel rocket mods will last on the street, but not very long on a race track be it compition or drivers ed. Porsche Motorsport advises at 540 hp will be the line in the sand for a nice 40k rebuild with stock rods. Now I'm sure that many of these overboosted motors will live a long life because some owners will never see the true potential of their cars, because they will never drive them fast enough to generate the mechanical forces that will rip the engine apart. They and their internet tuner buddies will be right in their asscertion that stock rods will last through with continued use in a 550 hp car.
But why don't we listen to the guys who raced and developed these cars, like the factory! Most of the nickel rocket mods will last on the street, but not very long on a race track be it compition or drivers ed. Porsche Motorsport advises at 540 hp will be the line in the sand for a nice 40k rebuild with stock rods. Now I'm sure that many of these overboosted motors will live a long life because some owners will never see the true potential of their cars, because they will never drive them fast enough to generate the mechanical forces that will rip the engine apart. They and their internet tuner buddies will be right in their asscertion that stock rods will last through with continued use in a 550 hp car.
05-11-2005, 09:51 AM
#11
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The issue with the Garrett GT series turbos are not so much with the design of the turbine or the compressor, but with the bearing housing and it ability to be rebuilt and survive in an oil cooled environment.
Does anyone know if this was a single turbo CIS car? The air fuel ratio curve looks to be from that car, or from someone who does not know how to tune an EFI system. Allowing the AFRs to dip into the 10s is simply irresponsibley. Additionally, on a Dynojet dyno, it does not give the ability to control the lengh of time of the run, what this means is that the run will last a very short duration and the turbos will not spool as they would on the road. These runs probably lasted 6-8 seconds where you really would need about 18 seconds to cover that rpm range to accurately reflect the load on the turbo. The difference in torque may simply be a difference in the load between the runs. The Dynojet dynos are not a good tool for this type of analysis.
Kevin's turbos are based on the k16 turbine housings, however, he significantly modifies the A/R ratio as well as porting the casting. This allows it to perform like a K24 in terms of reduced back pressure, but retain the quick spool characteristics of the K16. Other hybrid manufacturers simply stuff a larger wheel into a stock K16 housing which cause the back pressure issues that TB is talking about. I have seen the differences in turbos built from Kevin and turbos built from another manufacturer and the back pressure differences have been significant.
Humidity does have some positive effects within an engine. Because the oxygen and fuel molecules are now between water molecules, the flame front speed is slowed down which helps prevent detonation.
The 993GT is not the holy grail it once was. It was built almost 10 years ago with technology from that age, and it was built to racing series specifications with restrictor requirements in some of them. Further it had a variety of engine management systems including TAG Electronics. The technology is OLD compared to what is available today, and we are not limited by racing series restrictions. It is possible to match or beat the GT2 performance and have reliability, many have done it.
Does anyone know if this was a single turbo CIS car? The air fuel ratio curve looks to be from that car, or from someone who does not know how to tune an EFI system. Allowing the AFRs to dip into the 10s is simply irresponsibley. Additionally, on a Dynojet dyno, it does not give the ability to control the lengh of time of the run, what this means is that the run will last a very short duration and the turbos will not spool as they would on the road. These runs probably lasted 6-8 seconds where you really would need about 18 seconds to cover that rpm range to accurately reflect the load on the turbo. The difference in torque may simply be a difference in the load between the runs. The Dynojet dynos are not a good tool for this type of analysis.
Kevin's turbos are based on the k16 turbine housings, however, he significantly modifies the A/R ratio as well as porting the casting. This allows it to perform like a K24 in terms of reduced back pressure, but retain the quick spool characteristics of the K16. Other hybrid manufacturers simply stuff a larger wheel into a stock K16 housing which cause the back pressure issues that TB is talking about. I have seen the differences in turbos built from Kevin and turbos built from another manufacturer and the back pressure differences have been significant.
Humidity does have some positive effects within an engine. Because the oxygen and fuel molecules are now between water molecules, the flame front speed is slowed down which helps prevent detonation.
The 993GT is not the holy grail it once was. It was built almost 10 years ago with technology from that age, and it was built to racing series specifications with restrictor requirements in some of them. Further it had a variety of engine management systems including TAG Electronics. The technology is OLD compared to what is available today, and we are not limited by racing series restrictions. It is possible to match or beat the GT2 performance and have reliability, many have done it.
05-11-2005, 09:51 AM
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Originally Posted by stockboost
Define Overboosted.
05-11-2005, 10:45 AM
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Jean,
It is the dip into the 10s that has me curious. The factory inductive ignition is weak and once the AFRs get below about 10.5:1 afr, the engines start to misfire because the spark energy is not sufficient.
It is the dip into the 10s that has me curious. The factory inductive ignition is weak and once the AFRs get below about 10.5:1 afr, the engines start to misfire because the spark energy is not sufficient.
Last edited by Geoffrey; 05-11-2005 at 11:06 AM.
05-11-2005, 12:15 PM
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Geoffrey both of the cars are 993tt.
The 993tt's I have seen equipted with GT series ball bearing turbos have been running strong for 1-3 years. The 3 year old car has 20k+ miles since install. I will not disclose what measures were taken to ensure long life as the shop may not what me to disclose it. Althoght they can't be repaired the replacement cartridge can be purchased about the same cost of rebuilding a KKK turbo.
These type of turbos do require extra care to warm up and cool down cycles. I don't know if I would want them in a track car. The quick spool advantage would not be realized. I agree that the KKK are more durable in extream situations.
Real world testing with a motec AF meter did not duplicate that fuel curve. As you know the "dyno jet" is not the best dyno out there. Not sure why the fuel curve was affected so much on the dyno vs the open road. I welcome you thoughts.
Lastly both cars have CDI ignition.
The dyno was used not to determin my true power levels only to chart my progress. Based on what I have seen I would not use this type of dyno as a tuning tool.
The 993tt's I have seen equipted with GT series ball bearing turbos have been running strong for 1-3 years. The 3 year old car has 20k+ miles since install. I will not disclose what measures were taken to ensure long life as the shop may not what me to disclose it. Althoght they can't be repaired the replacement cartridge can be purchased about the same cost of rebuilding a KKK turbo.
These type of turbos do require extra care to warm up and cool down cycles. I don't know if I would want them in a track car. The quick spool advantage would not be realized. I agree that the KKK are more durable in extream situations.
Real world testing with a motec AF meter did not duplicate that fuel curve. As you know the "dyno jet" is not the best dyno out there. Not sure why the fuel curve was affected so much on the dyno vs the open road. I welcome you thoughts.
Lastly both cars have CDI ignition.
The dyno was used not to determin my true power levels only to chart my progress. Based on what I have seen I would not use this type of dyno as a tuning tool.