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Back pressure

Posted: Fri May 17, 2002 6:29 pm
by Guest
Someone please correnct me if i am wrong, but I was always led to believe that these motors that we have (especcially the 4 cyl) required a certain amount of back pressure from the exhaust. Im looking to go right through the exhaust on my '92 GTZ and I wanted to know if taking out the cat and going with a 2.25 piping with a new downpipe would work well on the quad 4 setup. (Dont kow that much about the exhaust side....)

Back pressure

Posted: Fri May 17, 2002 11:02 pm
by gar187er
UH OH!!! some one said the B-word!!!!!  :0

:D im not even going to comment on that word ;)

....the 2.25" and a new downpipe(possibly 2.5") is the best setup for the Q4's.....removing a cat is an option if you dont have strict emissions where you live.....

Back pressure

Posted: Sat May 18, 2002 7:06 pm
by Guest
what B-word.... backpressure???

Back pressure

Posted: Sat May 18, 2002 10:26 pm
by Canada
backpressure is the devil, just dont go to large of a diameter of pipe and you will lose velocity in the exhaust gas and the cylinder wont empty as well

Back pressure

Posted: Sun May 19, 2002 12:37 am
by Guest
yeah, there is zero emmisions testing in NH, so im all set there. Would that help out much, by removing the cat?

Back pressure

Posted: Sun May 19, 2002 8:22 am
by rweatherford
Quote (kev415 @ May 18 2002,11:37)
yeah, there is zero emmisions testing in NH, so im all set there. Would that help out much, by removing the cat?

Remove the stock cat if you are going to go with 2.25 or 2.5 inch exhaust.

You should also port your exhaust manifold collector and flange at the downpipe to match the exhaust size.

Back pressure

Posted: Sun May 19, 2002 10:07 am
by 90BerettaGTZ
i agree with Rex but ill add that you should go with the 2.5 with mandrel bends. 2.5 is fine for the quad, i felt gains all the way down to 2500 rpm and anything over 4800 rpm ALOT more pronounced. i did however put a high flow cat back on just cause i like breathing.

Back pressure

Posted: Sun May 19, 2002 8:57 pm
by Guest
how do these gains compare to any gains i would get with the 2.25?

Back pressure

Posted: Sun May 19, 2002 10:18 pm
by Guest
mandrell bent 2.25 inch pipe flows better than 2.5 inch regular crimp bending does.  I bought mandrell bends from jegs in 2.5 inch and modified my flange to 2.5 inch, with a smooth transition, like rex's, then 2.5 inch cat and then 2.25 mandrell all the way back, gas welded, ill have new quarter mile times soon,

Back pressure

Posted: Mon May 20, 2002 10:11 pm
by Kevskate99
Hey Kev, where do you live? I live in Nashua and travel on 101 everyweekend and I'm going to mt monadnock this weekend probably. I travel everywhere from lakes region-south all the time. BTW my name is Kevin also.  :D

Oh yeah, Did you hear about the motorcycle accident in greenland on friday night? If you did I witnessed it the guy died instantly. I was the 2nd car behind the car that got hit head on. the guys brains and guts and crap were all over the road. I was like 10ft from the guy.

Here's a link.

http://www.exeternewsletter.com/news/05 ... s/5176.htm

Back pressure

Posted: Tue May 21, 2002 12:28 am
by Guest
yeah, i did hear about that accident, its prety scary.
Anyways, i live in a little town called Northwood. I dont know If you have ever heard of Coe-Brown, but I went to High School there. Its about half way between concord and portsmouth, rt 4 runs straight through it. If you are ever in the area, stop in Heritage True Value and ask for me, we own the place.

Back pressure

Posted: Tue May 21, 2002 10:12 am
by Kevskate99
My g/f's step brother goes there I think. My g/fs dad lives right off route 28 in center barnstead. He live right off lock lake.

Back pressure

Posted: Thu May 23, 2002 12:16 am
by Guest
No kiddin'   small world!! I have a bunch of friends from barnstead, what's your g/f's dad's name, I prolly know him!!

Back pressure

Posted: Thu May 23, 2002 12:47 am
by Kevskate99
He just moved there. My g/f lives in Exeter with her mom. But her dad's name is Rod I won't say the last name since its on the board itself but he's been there for a year or so, His stepson's name (I think he goes to coe brown) is Dustin I don't remember his last name though so I couldn't tell you either way. He lives right down the road from the Alton circle. I always end up going to the country store off 28 to get food when I spend the weekend up there. I'm actually going next weekend not this weekend but the one after. Send me an E-mail at Kevskate99@hotmail.com Maybe if you don't live to far from the Mcdonalds in the Alton Circle we could meet up there, since I'll be like 15 mins down the road from there.  :)

Back pressure

Posted: Thu May 23, 2002 2:41 pm
by gar187er
**cough cough** off topic **cough cough**

;)  PM each other if you two wanna meet up, k?  :)