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Downpipe Question.

G

GlocksGTP

New member
Would a 3" downpipe with highflow cat. make gas mileage increase or decrease? i have a 2001 GTP bone stock about to get exhaust soon though.
 


It'd increase you gas mileage...anything that lets the engine breathe better will increase it.

Dont just get a downpipe..you'd be much better off with a set of headers. Speed Daddy makes a decent set
1997 1998 1999 2000 PONTIAC GRAND PRIX 3.8L V6 HEADERS - eBay (item 170469647635 end time Mar-02-11 16:41:03 PST)

All you would need then is a highflow cat welded in.
The headers outflow the stock exhaust manifolds greatly, as well as the downpipe.
Plus, you'll pick up even more gas mileage, and help get rid of any knock retard you currently have.

Going from stock exhaust, to those headers, I grabbed about 5mpg in the city, and about 10 on the highway..seen over 35mpg on the interstate cruising.

But there are write-ups on how to install those headers. They are one of the single best "bang for the buck" mods you can do
 
i been reading about exhausts and i see alot of people taking out the resonator and putting in a glasspack? what does that do? sorry im a noob when it comes to cars.
 
well after headers these cars tend to get a lot of drone. a glasspack IS a resonator. personally i like the sound with them. Cherry Bombs are the way to go if you want a glasspack
 


Yeah, np.
For exhaust, the best setups tend to be

Headers, into either the stock cat back. Or if the mufflers/resonator are bad, get the longest, fattest glasspack you can for the resonator, and your choice of muffler.

There arent any performance gains to be had by replacing the cat-back, unless you are in a very high horsepower build.
 
Not to thread jack but a Catless downpipe. Will that hurt the MPGS? I know I have to get a tune to get rid of the code but wont the rear O2 read wayyy off still? How longcan I go on a Catless downpipe without a tune. Sorry same topic just catless pretty much
 


Ehhh I should just get Speed Daddy headers if is can get over the slip fit part. Not sure how that works. Well I get it the rtv seals it and the clamps in turn tightens it all down. Just seems more complicated in my mind
 
machinegunsquid said:
Nah, slip fit is simple....getting them welded is even simpler.

Mine are clamped with band clamps, and have never leaked.
Click to expand...

The whole welding thing = Money... Only if there was a writup with pics so I could play it out in my head............................... Oh and your car for some reason just screams RACE MEEEEEE. Anyway we will see gotta sell my GoPed pipe first lol. Apperently when you get married you have to choose what you want fast if I knew that before I woulda wore a..... anyway off topic AGAIN lol
 


You should be able to get the crossover welded on one end, and the downpipe welded for about 25-50bucks, depending on the shop, and how much you shoot the **** with the guy.

And yeah, my lady blew the motor up in my car...
she wants a different car now..
I told her "as long as I get mine back, and it runs, you can get one"

as far as the race me...its seriously the fender stripes...
before putting them on, I would never have people mess with me...after I did though, seems like 1/2 the cars im around do...
 
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