exaust pipe size question

ahunt01 · 08-08-03, 01:18

I recently gave away a radar detector to a friend that mendrel bends exaust pipes for cars and he's going to bend + install wider pipes for me for free.
Anyways, I was wondering what size should I have installed?
I have a 2000 automatic Civic EX with stock pipes and an universal Arospeed bomb muffler, and an AEM SRI. I'm leaning towards 2 1'4 in because I've heard that it won't lose too much backpreassure, it will sound better and will give me an incy wincy bit of more power in the top end without having an impact on my low end torque. Any sugestions?
Thanks

FUEL · 08-08-03, 01:22

Yeah dont make a ricer out of it =)

ahunt01 · 08-08-03, 01:33

Hehe I'm trying not to.

AkronSi · 08-08-03, 02:40

I think that anything in the 2-2.5 range would be fine. I assume you're replacing the entire mid-pipe (b-pipe) and resonator with the new larger pipe, right? A lot of people with the new K20 engines have been getting good gains with a new straight mid-pipe and the stock exhaust. You should be fine. Sounds like a nice trade.

ahunt01 · 08-08-03, 02:50

Umm, I really don't know anything about the mid-pipe (b-pipe) lol. But I will replace all the pipes from the cat to the muffler, so it'll probably replace the mid-pipe and the resonator. I finally got a hold of the performance shop that I plan to get a motor swap done after I get my master's degree and they recommend 2.5 as the max, and 2.25 as a more safer size. They said 2.5 would be better for an SI, but with an automatic EX they said that 2.5 might be on the verge of losing too much backpressure, making the car lose HP.
Hopefully the wider pipes will make it sound better. It sounds cool now but it sounds kinda funny with a hi flow muffler on stock pipes.

IndigoGTI · 08-08-03, 03:59

I would go with the 2.25. That is the pipe size I had on my Accord (2.2l). The muffler shop that installed it does a lot of work on imports and the installer told me that anyting above 2.25 would not be beneficial unless I was running nitrous or forced induction. You may also want to consider a resonator to keep the volume down and smooth out the exhaust tone.

FUEL · 08-08-03, 04:05

Just remember it doesnt do much good to replace the pipe from the cat back with larger pipe if you are not going to replace the pipe to the larger stock from the exhaust manifold to the cat. .I would say 2 1/2 would be great for you. I am having a custom built exhaust in trade for detailing labor and I am going with 2 1/2 I think you will be happy with it

4DSC · 08-09-03, 01:43

You have a friend that does REAL mandrel bending with an (expensive!) mandrel bending machine??

Anyway, search around the internet. There are rough guidelines or charts that relate exhaust pipe size to engine displacement and power output. I don't know where to find one, but I've seen such things in hot rodding magazines. Good luck in looking.

Backpressure is not desirable actually, but it's important to keep exhaust gas velocity up, which is why people tell you not to get too large a size of pipe. I'm not sure how well this setup works in practice, but some exhausts have tubing of different sizes in stages. For example, a V8 car might run dual exhausts with 2.5" tubing for about 1/3 the distance, then switch to 2.25" tubing, and then end up at the tailpipes with 2" tubing.... The rationale behind this is that the exhaust gases cool (transfer their heat to the piping I presume) as it travels along the exhaust system and as it does so it reduces in volume, and thus velocity, if it's a pipe of constant diameter. Might be something worth considering.

Good luck!

ahunt01 · 08-09-03, 05:31

Well I'm not 100% sure it's real mandrel bent pipes. I've seen his work on another car and I looked at the bends and it was smooth as a babies arse, no ripples, marks or anything. I just assumed it's mandrel bent.

Stl_GT · 08-16-03, 07:01

Ok here's my .02 If it's for looks than it's your preference. You are only going to see small if any gains ( read no gains here )by replacing the mid pipe and cat backs.....and headers if you car has them. I assume all cars have some type of headers. That's a big debate in the mustang community, dyno numbers just don't prove out any gains based on exhaust systems. Having said that, I would just replace the tips and be done with it. Anything else IMO is just wasted. As for the sound, yes mid pipes can change the sound considerably as can the mufflers. Just goto a car show and listen to different engines and ask the guy what's he's got. Good luck!

Dinzdale40 · 08-16-03, 07:11

its "header" not "headers", it's a 4 cylinder...lol

Stl_GT · 08-16-03, 07:36

LOL, haha....yea like I said I don't usually work with 4 cylinders.