Civic-EG.com Forum 3.3.1

- Sun Aug 22, 2010 4:21 pm #210044 I was told not to go bigger then 2½inch. Going 3inch you will lose back pressure. I'm not sure what your guys setup is in the states, but I was told theres a science behind it.

So I have a few questions.

Apparently for a 4cylinder car, 2inch piping is good.
Can anyone clear this up for me?

Also, do you guys have a catalytic converter or do yous delete it?

What do you benefit better, using 4-2-1 headers or 4-1?

- Sun Aug 22, 2010 8:01 pm #210057 Most people that I know go with a 2.25" system. But 2.5" would be ok. I know of a few guys running it and they've never had any issues. I've never personally known anyone who has had 2" but I've seen a few cars with 2". There isnt a whole lot of back pressure so I'm going to guess 2" wouldn't be a problem. It might sacrifice a little power and would sound a little different then if you were to go 2.25" or w/e

The difference between a 4-2-1 and a 4-1 is that the 4-1 is better for higher RPM power and the 4-2-1 is better for the lower to mid range power. So it all depends on what you want.

You can delete your cat or keep it in. A high flow cat is never a bad idea. They also make test pipes but I think those are more for cars that are going to be raced, not too sure tho.

Hope this helps you out a little.

R.I.P. Coty "CoCo" Swanson
7-9-91 to 8-16-09
Free Gabe Lorenz!

- Sun Aug 22, 2010 10:56 pm #210081 stock
d series is slow anyways lol may as well save gas

he's a rim whore, he'll have different ones on there in a few weeks.

- Mon Aug 23, 2010 11:48 am #210150 a friend told me .... unless your engine is modified inside.. like aftermarket parts, pistons.. etc.. you can go not higher than 2.5"

- Mon Aug 23, 2010 8:50 pm #210203 Thats what I've always said. No higher than 2.5" unless your pushing some power. I had the bolt ons (I/H/E) and ran 2.5" piping and had 0 problems

R.I.P. Coty "CoCo" Swanson
7-9-91 to 8-16-09
Free Gabe Lorenz!

- Mon Aug 23, 2010 11:20 pm #210223 none vtec 2.5 would be over kill not that it would rob you power but would not gain over having 2 - 2.25

if it has vtec you may gain 2-7hp in top end going 2.5inch.

after that your going to need turbo or something that helps the air push throw fast to see any gains.

2.5inch with not much of a muffler will sound really tiny!! I have 2 inch cat back on my 99 hatch and it has a good sound to it. could feel a difference in top end. but It's factory cat/header combo so it's restricted there still.

doing header and all will really help. but you will notice a mpg difference being worse

- Tue Aug 24, 2010 12:18 am #210235

stock
d series is slow anyways lol may as well save gas

Exhaust and header gained MPG for me

D15b7 w/ eghey 4-2-1, stock cat, and 2.5" exhaust = 28 - 32 MPG city ... 42 MPG Highway.

Oh yeah and that's with the EX transmission. Just sayin'


To OP 2.5" feels pretty good, maybe a little bit of loss on the bottom end, but honestly not very noticeable.

4-1 vs. 4-2-1 we could debate this until the end of time, but unless you are racing your car and putting doing some serious N/A tuning (and spending a lot of money for a proven, tuned header) ... it really doesn't matter. For a street/strip build it's not going to make a difference which one, especially on these tiny engines ... the powerband shift is very minimal.

Straight lines are for sissies.

- Sun Sep 12, 2010 4:37 am #213208 So what do you guys run or recommend, canon exhaust or muffler, like spoon or something?

- Sun Sep 12, 2010 4:41 am #213210

So what do you guys run or recommend, canon exhaust or muffler, like spoon or something?

Personally I liked the sound of my ebay special massive coffee can muffler. But have since upgraded to the vibrant stealth turbo muffler ... I love the sound or that as well. Whatever you get just make sure it doesn't make the stupid ricer "brrraaaaaap" noise and I think you will be happy with it.

Straight lines are for sissies.

- Sun Sep 12, 2010 2:23 pm #213241 Personally, I think something like mugen or spoon would be the best brand mufflers

[suspendedHatch]

- Sun Sep 12, 2010 4:37 pm #213247 This topic has been beat to death. Extensive testing by just about every Honda magazine out there has consistently shown this:

N/A 2.25 and follow the oem exhaust path
FI as big and as straight as is practical

If you go larger than 2.25 on a naturally aspirated engine, all you are doing is shifting your power band beyond the rev limit. Same thing if you shorten the exhaust or delete the cat converter.

It has nothing to do with backpressure btw.

- Mon Sep 13, 2010 10:24 am #213379

This topic has been beat to death. Extensive testing by just about every Honda magazine out there has consistently shown this:

N/A 2.25 and follow the oem exhaust path
FI as big and as straight as is practical

If you go larger than 2.25 on a naturally aspirated engine, all you are doing is shifting your power band beyond the rev limit. Same thing if you shorten the exhaust or delete the cat converter.

It has nothing to do with backpressure btw.

Best answer

- Mon Sep 13, 2010 11:37 am #213387 I think we can all agree that the 2.25. It's the most practical and you don't need to go any higher unless going turbo. Also don't get a test pipe unless you are tracking it. Go with a high flow cat and all will be good.

- Mon Sep 13, 2010 9:32 pm #213482

This topic has been beat to death. Extensive testing by just about every Honda magazine out there has consistently shown this:

N/A 2.25 and follow the oem exhaust path
FI as big and as straight as is practical

If you go larger than 2.25 on a naturally aspirated engine, all you are doing is shifting your power band beyond the rev limit. Same thing if you shorten the exhaust or delete the cat converter.

It has nothing to do with backpressure btw.

Best answer

Well that's because he knows hondas.....

It says it under his name...

i pitty the foo who aint got vtec......
EM1 build http://civic-eg.com/viewtopic.php?t=17256

- Tue Sep 14, 2010 7:51 am #213588 aww what! how can I change mine under my name?