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#1 |
Super Moderator
Join Date: May 2007
Location: Billings, Montana
Posts: 1,034
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Well, I wouldn't really be able to say for sure; never drove anything with a high-flow cat on it. Exhaust systems are tricky, too much free flow and you don't build the pressure differences between outside air and the gases within the pipes that is required to help suck the exhaust out of the system, too little flow and exhaust backs up in the pipes and chokes the engine. Both scenarios will hinder performance.
I feel it should be noted that it's not about how much hp you can gain, but how the car drives. That extra 2 hp at XXXX rpm for a split second could translate to less hp throughout the powerband. In this scenario, you have more peak hp but performance will suffer due to the lower overall hp. Oh, I also forgot to mention that the Supra I was referring to above had an unknown brand 2 1/2" cat-back system on it, both before and after the cat change.
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1989 7MGTE R154 Targa Top White Package w/Blue Interior Driftmotion 57trim CT26, Upgraded Intercooler, 2.25" Hard Pipes, 3" Turbo Back Exhaust with Test Pipe, HKS VPC w/GM 3 bar MAP sensor, APEXi S-AFC, Walbro 255lph fuel pump, ProSport EVO Series Boost / Fuel Pressure / AFR gauges, Lotek a Pillar Gauge Pod, HKS Type 0 Turbo Timer, Eibach Lowering Springs, Tokico Illumina II TEMS struts, custom powder coated Motegi Racing TrakLite wheels |
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#2 | |
3" Exhaust
Join Date: Feb 2010
Location: Oregon
Posts: 225
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#3 |
3" Exhaust
Join Date: Feb 2010
Location: Oregon
Posts: 225
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Thanks for all your input.. I have decided the only way to find out if I will in fact lose or gain will come down to trying the high flow cat and the test pipe on a dyno. This way I can see where I gain or lose along the power band...
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#4 |
Super Moderator
Join Date: May 2007
Location: Billings, Montana
Posts: 1,034
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That's a good idea, be sure to post your results once you're able to do this
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1989 7MGTE R154 Targa Top White Package w/Blue Interior Driftmotion 57trim CT26, Upgraded Intercooler, 2.25" Hard Pipes, 3" Turbo Back Exhaust with Test Pipe, HKS VPC w/GM 3 bar MAP sensor, APEXi S-AFC, Walbro 255lph fuel pump, ProSport EVO Series Boost / Fuel Pressure / AFR gauges, Lotek a Pillar Gauge Pod, HKS Type 0 Turbo Timer, Eibach Lowering Springs, Tokico Illumina II TEMS struts, custom powder coated Motegi Racing TrakLite wheels |
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#5 |
3" Exhaust
Join Date: Oct 2010
Location: kansas
Posts: 166
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Nice 87 Supra, Pearl white, targa top, 5 spd, 7mgte ![]() ARMY STRONG !! La fiebre Boricua Puerto Rico!!! ![]() |
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#6 |
Intake
Join Date: Apr 2010
Location: Montana
Posts: 40
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Do keep in mind that the changing of the cat will only heavily influences N/A's on powerband issue. With a Turbo, all of the back pressure required by the car is supplied by the turbo, no further back pressure is needed.
So, If you got a turbo, sure, you can take the cat off and see a considerable gain. With an N/A, I wouldnt, the car runs alot smoother with it on and it smells better. One more thing to keep in mind, the oxygen sensor on this car is not heated, I have been to told by mechanics that beack pressure created by the cat helps to heat up the oxygen sensor, and that little guy controls up to about 8% of your fuel economy...
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1987 Toyota Supra 7MGTE AUTO 1987 Toyota Supra 7MGE MANUAL 1990 Toyota Supra 7MGTE AUTO-> MANUAL |
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#7 | |
3" Exhaust
Join Date: Feb 2010
Location: Oregon
Posts: 225
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#8 |
12psi boost
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I took my Supra without cat for a run down the mother road on Saturday. Had the top off and the engine sounds get annoying real quick. I do not think he has any more power than my Supra with the CAT. If anything there seems to be less power. Well put enough money into her, suppose it is time to replace the exhaust system or at least from the block to the cat.
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1986 Mk III MA70 7MGE Targa Top 5 Speed Stock Exhaust ![]() |
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#9 |
3" Exhaust
Join Date: Oct 2010
Location: kansas
Posts: 166
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so you feel more power with the cat?
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Nice 87 Supra, Pearl white, targa top, 5 spd, 7mgte ![]() ARMY STRONG !! La fiebre Boricua Puerto Rico!!! ![]() |
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#10 |
12psi boost
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I would have to do a series of objective tests. I do hope to get transferred to Hawaii or return home to Japan. The Cat is needed for both, do wonder if I can get in trouble for running without the cat.
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1986 Mk III MA70 7MGE Targa Top 5 Speed Stock Exhaust ![]() |
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