Throttle body rebore
10-16-2002, 07:35 PM
#16
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RSAErick,
We have played with a lot of UK 964RS's with some success. Specifically regarding the throttle body, the standard one is 68mm, and the maximum practical bore size that you can use is 70mm which is the same diameter as the intake manifold mounting flange, so no air flow gains can be had beyond 70mm.
As for power gains, my thoughts are that up to 300bhp all you will see is improved response. Even with mass flow, I do not think that you will show any gains, but the car will feel quicker.
We do a regular Motec engine management conversions for the RS and have done two identical systems, one with the standard throttle body, one with a 70mm. The performance difference came out in favour of the 70mm unit at +6bhp and +3Nm @ flywheel: the 70 posted 324bhp/401Nm (295lbft), the 68 posted 318bhp/398Nm (293lbft). Both engines has K&N on tube (no air flow measurement), cat bypass, cup pipe, larger injectors and Motec M48 ecu. This is the only comparison that I have done, hope it helps.
We have played with a lot of UK 964RS's with some success. Specifically regarding the throttle body, the standard one is 68mm, and the maximum practical bore size that you can use is 70mm which is the same diameter as the intake manifold mounting flange, so no air flow gains can be had beyond 70mm.
As for power gains, my thoughts are that up to 300bhp all you will see is improved response. Even with mass flow, I do not think that you will show any gains, but the car will feel quicker.
We do a regular Motec engine management conversions for the RS and have done two identical systems, one with the standard throttle body, one with a 70mm. The performance difference came out in favour of the 70mm unit at +6bhp and +3Nm @ flywheel: the 70 posted 324bhp/401Nm (295lbft), the 68 posted 318bhp/398Nm (293lbft). Both engines has K&N on tube (no air flow measurement), cat bypass, cup pipe, larger injectors and Motec M48 ecu. This is the only comparison that I have done, hope it helps.
10-19-2002, 08:31 AM
#17
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Would an enlarged TB be a waste of money for an '84 944 with a non stock airbox, headers, test pipe, and a performance chip ? The head is stock as well as the cam.
tanx !!
tanx !!
10-23-2002, 06:51 PM
#18
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For a fairly stock car it sounds like a waste of money. Has anyone measured any improvement in throttle response? Do you think Porsche put in too small a throttle body to what, save money? Not likely. Most likely they picked a size that would have good air velocity at low rpms and nice throttle response. (Bigger = less velocity)
Engines are systems. If the exhaust is the most restrictive link, improving intake air flow might not make a big difference. Even Ninemiester's built up motor only showed a 2% improvement.
The same money spent on track events would make a lot more sense IMO.
grouchy old man
Engines are systems. If the exhaust is the most restrictive link, improving intake air flow might not make a big difference. Even Ninemiester's built up motor only showed a 2% improvement.
The same money spent on track events would make a lot more sense IMO.
grouchy old man
