Down Pipe Q

[hiballin]

Will installing a 3" THDP on a stock turbo/stock converter car decrease off idle and low speed torque? I did a search and can't find a discussion on this.

The reason I ask is because I have a down pipe looking for a car to be installed on. I'm concerned with off idle and low speed torque b/c the car is basically a grocery getter running 15lbs of boost and I don't want to hurt fuel mileage or bottom end power.

Has anyone studied the exhaust velocity dif between a stock and 3" THDP? Sometimes bigger is not always better.

 

[RUQWKNF]

I don't think you will find any studies or tests on this issue.
If anything, it should help promote slightly quicker spoolup due to less restrictive exhaust. As anyone that has ever uncapped their stock exhaust and run an open dump can attest, spool up is quicker.

It should not affect bottom end, nor gas mileage. Should help both. These cars were really choked up from the factory for a reason. Buick didn't want to really tick off Chevy, nor tip off the insurance companies with real world hp numbers, so they did everything they could to choke the little V6's power .

I'm a firm believer that every '86/'87 should have a 3" TH style downpipe on it, no matter the goal. I've run a 3" downpipe on every Turbo Buick I've ever owned since '94. It's a must have IMHO. Things that kill bottom end are Hooker headers on a stock torque converter, or a .82 or .85 A/R turbine housing on a stock torque converter. Now those kill spool up.
Just my O2's worth.

Patrick

 

[QUIP'6']

it is a great mod to a stock car!!!! a very noticable increase in power and spool up. you will be needing tires after a while!!! if gm did it i think insurance would have been higher do to unable to regulate horsepwer.

 

[SPOOLN]

It will soften your bottom end, and your car will sound louder. You do lose some exhaust velosity.

 

[notacarlo]

It will soften your bottom end, and your car will sound louder. You do lose some exhaust velosity.

Do you mean back pressure? Velocity is only a concern through the system pre-turbine.

 

[QUIP'6']

It will soften your bottom end, and your car will sound louder. You do lose some exhaust velosity.

NO, YES AND NO!!!!