I am looking to install a B16 into my EK coupe.. In the future I will want to do some bolt on's but going from a SOHC to DOHC I know that factory piping will be restrictive..

What size piping should I do with this motor to be most beneficial? 2.25 or 2.5?

Also I was thinking of going str8 piping from the exhaust manifold into my stock muffler and not installing a cat. What will I gain or lose by not having a cat?

I'm going to be driving this thing home open header so I need to get some info because I cant ride this way for too long after.

 

Short answer:
- If you want to extract as much power as possible: 2.5" (or even 3").
- Run a good quality, metal core, high-flow catalytic converter to reduce noise (drone especially). The power loss (if any) will be negligible and your ears will be thankful.

Long answer:
I just swapped (like two weeks ago) a B18C in my 93 Hatch (CX) and the noise/drone has been driving me nuts (I do a lot of highway driving).

After some posting and much research it turned out that recently people have been getting the best numbers out of larger piping (so it seems like the "need for backpressure on NA motors" has become a myth).

I wound up getting a used Apex'I WS2 exhaust locally on Craigslist. I had the exhaust shop weld in a 2.5" Vibrant Stealth muffler and a test pipe. Even with the big resonator that comes with the exhaust (18" I believe) the car was a DRONE MACHINE. It was unbelievably loud to the point my ears would ring all evening if I drove the car on the highway during the day.

I went ahead and ordered a 2.5" high-flow catalytic converter from Vibrant. I got their "metal core" unit because it flows more than "ceramic core". I did a lot of research on this topic as well and it seems like good quality "metal core" cats don't restrict much at all. There are some bench-flowing tests, just search around on Google.

I got the cat welded in place of my testpipe yesterday and I am very pleased as it reduced drone by a LOT. The car is much quieter, but still louder than I would like. I would guess it's perfect for most people, though. I plan on taking a video of my setup and posting it on YouTube in a few weeks.

My recommendation is for you to pick a size (2.5" or 3"), then get a Tubing Kit from these guys. I got several exhausts for various cars from them over the past 10+ years, they do very good work and their prices are very reasonable. Once you picked size and ordered the tubing kit, get a matching muffler and high-flow metal core resonator from Vibrant and drive down to get it all installed/welded together and you've got yourself a sweet setup.

-Walter

PS= Amazon currently offers the best prices with free shipping on all the Vibrant stuff I mentioned above. eBay comes second (at the time of this writing).

 

Sweet... So a catalytic converter is the same as a resonator? And it would basically be, exhaust manifold-Hi flow cat-piping-muffler correct? I figured a test pipe would still be too loud, I want to keep it relatively quiet so everything is going into my stock muffler.. But I guess the cat is better for noise reduction.
The reason I'm going to keep my stock muffler is because I haven't officially decided what muffler I want to use. I'm considering a Greddy Evo or an apexi n1.
One thing I'm confused about that you said, you found an apexi ws2.. Did you use the piping from it or the muffler? Cause then you said you used a vibrant muffler.. Kinda threw me off..

 

No. A catalytic converter contains a "filtering" element that can either be ceramic or metallic (honeycomb style). The exhaust goes through this element, reacts with it and comes out "cleaner" than it would have if it didn't flow through it. Here's a good pic of the inside of a metal core high-flow cat. A resonator is like a "mini-pre-muffler". It's straight through but has a perforated core with fiberglass so it reduces rasp and some noise without interfering with flow. This picture of an old crappy one gives you an idea of its internals.

Yes, although most exhaust systems have a resonator before the muffler. Even aftermarket ones, like the WS2.

If you get aftermarket piping (2.25" and up), I think using the stock muffler will create an unnecessary restriction. I would use an aftermarket muffler. In my case, I bought a full Apex'I WS2 cat back exhaust with muffler. It came in three sections: 1 pipe from the cat going towards the rear axle (with resonator), one "bend" and the last section of pipe welded to the muffler. I wound up using the entire exhaust except for the last part. The exhaust shop made a pipe just like the one that came with the WS2 muffler and welded it to my Vibrant Stealth muffler.

-Walter

 

Ok.. I think I got what your saying...
I'm going to try and get some prices on that vibrant cat... because as I said, I cant ride open header, it will just be too much noise and attention... And once I get that, I'll go to a muffler shop and have them do some custom piping and install everything.

 

Best price I could find when I bought mine last week. Make sure you pick the right size.

This is a great page to get goodies from. You find what you need, get the part number, then search eBay, Amazon and Froogle for Vibrant + Part Number.

-Walter

 

would you reccomend stainless steel or aluminum for the tubing kit

 

Actually, i wouldnt go any larger than 2.5".... in the research ive done, bigger is not always better. I do agree that you want as much flow as possible, but you dont want to go too big... you need flow and velocity. while the 3" pipe may have a much larger capacity, these I4s just dont make enough exhaust gas to keep the pipe "full", so you loose speed as the gases expand to fill the space.... it would be like hooking a fire hose up you your garden faucet,

 

I have never seen aluminium exhaust piping. IC and Intake yes, but not exhaust. It's either steel or stainless steel (titanium for exotic cars). If you can swing it, stainless still is nice and you won't have to worry about rust/corrosion as much as plain steel. If you live in the North (salt, snow) I would definitely spend the extra money for SS.

I agree with you.
I have always messed with Turbo application, so I never worried about "needing" backpressure.

This article is excellent, you guys should read it if you have time (even if you don't have a Turbo as it explains the concept of backpressure well).

Based on that article, we would think we absolutely need some backpressure for our NA applications, right? That is what I thought, until I did some more research and found a LOT of posts where it was revealed that backpressure is bad even for NA applications. This is the exact reason why I wasn't 100% sold on the 3" piping kit and wound up getting the WS2 exhaust (close to 2.5").

-Walter

 

Don't go 3" unless its turbo. Yonaka Motorsports have a nice WS2 copy exhaust for around 200 bucks, and its 2.5" mandrel bent.

 

if you want the most power go 3 inch stainless steel piping high flow cat a resonator and muffler. but that might be a little loud. more then likely 2.5 will be fine.

it has been proven numerous times on this board alone. these little I4s put out plenty. it improved power throughout the whole curve. go look it up in the N/A section, dynos abundant to prove it.

don't get aluminum. you can get it but thats really more for race cars looking to save every little bit of weight they can.

backpressure is a lie. read more. anything after the header is restriction.

 

It all depends on how much power you plan on making. If you want a simple "peppy" dd, then 2.5" for you. If you have larger displacement, high redline, and higher compression get 3". You won't regret it.

 

I believe I am going to go with 2.5 from the headers str8 back.. no cat. I cant seem to find justification for one.

 

How about saving our lungs? Ill try and track down the artical, but a shop did dyno tests on a I4 motor (i think it was a civic, but i dont remember) and the difference between a high flow cat and a "Test Pipe" (no cat) was 1 maybe 2 HP... personally i would rather keep it legal and loose 1HP... its not like high flow cats are that expencive

 

ok, heres 2 different dyno tests...

http://www.delsolsource.com/2011/01/...pipe-vs-stock/

http://www.importtuner.com/features/...val/index.html

 

I've decided to go 2.5 inch into a resonator and then my muffler... I'll let you know the difference once I get the car back...

 

As mentioned above don't go 3 unless you're going FI...and keep a high-flow cat. 1 hp isn't going to be felt or seen in any times...keep the air clean and keep it legal.

 

The only reason im not running a cat right now is that my exhaust was made when the car still had a Y7 in it, and the cat was on the exhaust manifold. Now that I (finally, after 8 years) put a b series in, im going to be going 3" with high flow cat... like the guy before said, having the car legal is well worth 2hp.

 

2.5"

 

I'm in florida... no legality issues... No emissions or anything...

So I have the exhaust on.. It feels good.. Nice and quite but it opens up when you get higher in the RPMs...

Now I have a question.. Has anyone found a way from keeping the heat from under the car from coming into the car thru the opening where the e-brake goes into the arm rest?