Running W/O Cats....
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Joined: Dec 2002
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From: Irvine, CA
i was wondering the same ... right now im running w/ the two cats and nothing else from that point back. no muffler, no resonator, just a straight pipe that goes all the way back near the end of the car and shoots downwards the ground
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Joined: May 2003
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From: Closter, NJ
Originally posted by STLZ
Wouldn't you lose backpresssure which would lose you tq. I thought that running no cats was just an advantage it you had a FI setup and there was no adv for N/A.
Wouldn't you lose backpresssure which would lose you tq. I thought that running no cats was just an advantage it you had a FI setup and there was no adv for N/A.
backpreasure is not needed in 3.5L engine
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Joined: Mar 2003
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From: Rochester Hills, MI
Originally posted by racingdynamcs
cause u dont need it...no car engine needs backpreasure....
cause u dont need it...no car engine needs backpreasure....
New to this forum, Hello there.
First off, Turbo engines need no backpressure any backpressure at all slows down spooling of the turbos, this from experience on a turbo car. Turbo +backpressure= Bad, sloow spool. We are not talking about between engine and turbo thats a whole different world.
2nd it has been proven that NA motors also do not benefit from backpressure. The old agage of needing backpressure was because engines were not retuned with WB after removing all BP. Once Wide Bands came into use, and testing was done with an uncorked engine, at first there was a torque loss, but once A/F curves were fixed to compensate for the loss of BP, turque improves at least to previous levels and often a few Ft Lbs increase was seen.
I want to hear about how the VQ ECM isn't upset by the loss of the cats. This seems to contradict OBD2 specs, but I like the sound of it, makes uncorking that part of the exhaust easy
First off, Turbo engines need no backpressure any backpressure at all slows down spooling of the turbos, this from experience on a turbo car. Turbo +backpressure= Bad, sloow spool. We are not talking about between engine and turbo thats a whole different world.
2nd it has been proven that NA motors also do not benefit from backpressure. The old agage of needing backpressure was because engines were not retuned with WB after removing all BP. Once Wide Bands came into use, and testing was done with an uncorked engine, at first there was a torque loss, but once A/F curves were fixed to compensate for the loss of BP, turque improves at least to previous levels and often a few Ft Lbs increase was seen.
I want to hear about how the VQ ECM isn't upset by the loss of the cats. This seems to contradict OBD2 specs, but I like the sound of it, makes uncorking that part of the exhaust easy
No Prob, old school misconceptions abound, iut will just take time for people to realize that a PROPERLT tuned free flowing exhaust motor will outperform a PROPERLT TUNED motor with some backpressure. Until the availability of relatively cheap WB O2 sensors properly tuned was the problem .
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