| mfloren |
08-18-2007 10:17 PM |
Quote:
Originally Posted by nize
(Post 3399584)
what are you basing this on? do you have data?
i have before/after dynos and it shows absolutely no difference.
several other 951 owners i know who are dumping to atmosphere also have seen zero difference in power.
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its late, so i might have misspelled some of the words below. I might edit later.
Im refering to other cars. the 951 taps the WG back into the exhaust after the cat, so in essance, the backpressure that would have been increased in other cars, such as a turbo eclipse, EVO, Subaru, and most other japanese cars, is not a problem.
when upgrading to a 3" - 4" exhaust the 951 further decreases backpressure and a WG vented back into the system does not make much of a difference. I do not have any data on the difference in a 951, but alot of data on other car designs.
the best systems have a few inches of pipe after the turbo and imediatly vent to atmosphere. you do need back pressure in the exhaust system, fortunatly with a turbocharger in place all of the back pressure that is needed by the engine is supplied by the turbo it self. any and all back pressure post-turbo will degrade the spool up characteristics, and increase high RPM boost bleed off.
My 98 eclipse GSX gained a solid 8hp from venting to atmosphere. But if you look at the exhaust headder design there is only 10" of pipe from the exhaust port to the turbo. after the turbo most external WG's on these types of cars dump right back into the exhaust pipe within 8ish" after the turbo. this section, the down pipe, has the highest level of backpressure post-turbo out of the entire system. when you dump the WG pressure back into this section the turbo does not flow as much air at higher RPM's, which is typicaly part of the boost fade problem, bleed off.
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