I drove the twin turbo
10-11-2007, 11:12 AM
#31
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Mike,
I believe he is running GT28's in 71 trim. The car has 2 large front mounted intercoolers in front of the wheels. He is running 12lbs on the stock high-mileage motor.
I believe he is running GT28's in 71 trim. The car has 2 large front mounted intercoolers in front of the wheels. He is running 12lbs on the stock high-mileage motor.
10-11-2007, 12:58 PM
#32
Three Wheelin'
I sold an ITB intake system to an engine builder in Canada. It's going on a 7.0L 928 which will be a twin turbo. I don't know any of the details. I did suggest that he put a sort of basket under the car to catch the driveline parts.
10-11-2007, 01:11 PM
#33
Three Wheelin'
Might as well extend it under the passenger seat as well, as while the car is in one piece there will be stuff to catch under the passenger too.
10-11-2007, 02:13 PM
#34
Rennlist Member
Thanks for the info! GT28s seem a little small; typically good for a twin turbo application though; I run a custom Mitsu TE-05 in my 88 SPG (16G wheel); supposedly one is good for 400 hp; x2 would be, well, fun. 12 psi is a good mark; 15 psi should be doable, if not more (the high mileage cautions against going too high, though). Two ICs? Interesting; seems like that would add an unnecessary pressure drop to the system (unless two were used for spatial concerns). A single high-flow IC with water injection would be my choice.
10-11-2007, 02:35 PM
#35
Man of many SIGs
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He uses one intercooler for each turbo. They are A/A and mounted in the fenders so that the air flow to the engine cooling system and A/C is not impeded.
10-11-2007, 05:16 PM
#36
Race Director
It's going to be kind of hard to get real comparisons. In the above comparison, the Murf car is an S4 with an automatic transmission, and was run on a Superflow dyno. The twin turbo car is an S4 with a 5-speed, was run on a DynoJet dyno, and the numbers are using the higher resulting STD correction factor, instead of the SAE correction. The stroker is a 5-speed with aftermarket cams, engine management, individual throttle bodies, etc., was run on a Dynocom brand dyno, and also using the STD correction factor.
Below is an overlay comparison of the twin turbo car's chart and the very first Murf customer car's chart, from almost four years ago now. There are still some differences, but at least less of them, and it's about the closest to a really even comparison that I could come up with using the data I've got. Both cars are '87 S4 5-speeds, both runs were done on a DynoJet, both charts are using the STD correction factor, and both are stated as being internally stock engines. The Murf car is intercooled and using the stock engine management with just the FMU (stage 2 kit). The twin turbo car is intercooled and using the stock engine management with SharkTuned chips. The Murf car is using stock exhaust manifolds, an X-pipe, and stock 928 exhaust pipes. The twin turbo is using a custom dual 3" exhaust after the turbo exhaust manifolds and other turbo stuff. The most significant difference between the two is probably that the Murf car is at 10psi of boost and the twin turbo is at 12psi of boost. The thinner blue lines are the Murf car, and the thicker gray lines are the twin turbo car. It's too bad that the boost wasn't the same for both cars, but even so, I think it makes for an interesting comparison.
Below is an overlay comparison of the twin turbo car's chart and the very first Murf customer car's chart, from almost four years ago now. There are still some differences, but at least less of them, and it's about the closest to a really even comparison that I could come up with using the data I've got. Both cars are '87 S4 5-speeds, both runs were done on a DynoJet, both charts are using the STD correction factor, and both are stated as being internally stock engines. The Murf car is intercooled and using the stock engine management with just the FMU (stage 2 kit). The twin turbo car is intercooled and using the stock engine management with SharkTuned chips. The Murf car is using stock exhaust manifolds, an X-pipe, and stock 928 exhaust pipes. The twin turbo is using a custom dual 3" exhaust after the turbo exhaust manifolds and other turbo stuff. The most significant difference between the two is probably that the Murf car is at 10psi of boost and the twin turbo is at 12psi of boost. The thinner blue lines are the Murf car, and the thicker gray lines are the twin turbo car. It's too bad that the boost wasn't the same for both cars, but even so, I think it makes for an interesting comparison.
Could you add a twinscrew run to that too?? My homemade dyno is far from perfect......since I made it all in paint..... I find it ver interesting that the turbo makes ALOT less torque down low than the vortech kit.....the twinscrew would be even better on the bottom!
10-11-2007, 05:33 PM
#37
Captain Obvious
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Easy there…..We are getting really close to “magazine racing” here.
I bet at these hp levels, both boosted cars would feel very much the same.
I bet at these hp levels, both boosted cars would feel very much the same.
10-11-2007, 06:04 PM
#38
Three Wheelin'
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Z
Could you add a twinscrew run to that too?? My homemade dyno is far from perfect......since I made it all in paint..... I find it ver interesting that the turbo makes ALOT less torque down low than the vortech kit.....the twinscrew would be even better on the bottom!
Could you add a twinscrew run to that too?? My homemade dyno is far from perfect......since I made it all in paint..... I find it ver interesting that the turbo makes ALOT less torque down low than the vortech kit.....the twinscrew would be even better on the bottom!
LOL: Bench racing > Magazine racing >>>>> TEH INTRAWEB RACING!!!!111
I'll bet they both feel a hell of a lot faster than a certain English "202 mph" S4...
~~~~~~~~~~~~~~~~~~~~~~~~
You know what we need? Like the big magazines do, invite all the 928 tuners to a showdown. Have them bring their best creations to a track and run some instrumented tests, then some back-to-back dyno pulls. Maybe even invite some of the full-race cars for kicks.
10-11-2007, 07:43 PM
#40
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10-11-2007, 09:20 PM
#42
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So slap a 50-75HP shot of giggle gas to the turbo. Common system for the ricers. The N2O ramps backwards and turns off as the turbo kicks in. No lag anymore!
10-11-2007, 10:21 PM
#44
Supercharged
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Oh yeah... and that was at less than 7psi vs 10~12psi.
I'll have a dyno sheet of my improved setup soon. Oh crap, I was supposed to call the dyno guy today...
I'll have a dyno sheet of my improved setup soon. Oh crap, I was supposed to call the dyno guy today...
10-11-2007, 11:16 PM
#45
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Z
Could you add a twinscrew run to that too?? My homemade dyno is far from perfect......since I made it all in paint..... I find it ver interesting that the turbo makes ALOT less torque down low than the vortech kit.....the twinscrew would be even better on the bottom!
Could you add a twinscrew run to that too?? My homemade dyno is far from perfect......since I made it all in paint..... I find it ver interesting that the turbo makes ALOT less torque down low than the vortech kit.....the twinscrew would be even better on the bottom!
The second comparison chart is of the same two cars. It's the same GT twin-screw run compared to a run from the same S4 centrifugal car done on the same dyno about six weeks later. The only change made to the centrifugal car from the earlier run was increasing the boost to what I think the current Murf stage 3 kit is now. The red lines are the centrifugal car, and the blue lines are the twin-screw car again.