Thread: Question on 3" setups

Ok. Thanks a lot

So can anyone explain the myth that a large exhaust is "bad" for some motors? I realize it is untrue, but I remember hearing back when I was in highschool "large exhausts can hurt your valves" Where did this come from?

If this information is correct, I am going to have a hell of a time explaining this to my honda friends, and I just had them convinced the ve likes the 3inch, imagine what they are going to say when I tell them they all need to go three inch?


Dudeman

Quite a few Hondas in here in Jamaica - mostly those making over 200whp na - are using 3". But as a friend of mine found out, some will tell you that they are not.

Peace

Somewhere along the line the information related to header tech (smaller pipes are better for low end power all else being equal) got improperly placed on the entire exhaust. This may have gained popularity in the V8 world as back-to-back dyno sessions with and without an exhaust after the headers can show loss of low end power without an exhaust, or with a larger exhaust connected. This is due to the fact that most V8s (non flat plane V8s) see low end gains with an "X" pipe coupled with a smallish exhaust as scavenging effects take place all the way until you finally completely merge the exhaust. This does not translate at all to flat plane crank (all inline cylinder engines and some rare "V" configuration engines) header/exhaust design but that didn't stop the information from being carried over.
This of course is my own theory, and there's probably more to it.

I've sort of heard something similar. I've heard that running an engine with no exhaust manifold connected at all can cause damage (possible bending?) of the exhaust valves. I don't know if this is true or not, but the theory goes that if there is absolutely no exhaust back pressure, your valve could be damaged. I've seen videos of people on youtube running SR20s without exhaust manifolds on and revving them pretty high. I don't have an answer or even a theory for this one.

People don't test things. Common wisdom is commonly relied upon. They are the worst in ZA (in Doctor Gs case).

Here's my experience; I had a B12 with CA18DE motor down there. It was abused but anyway; They fought me to put a 2.25 primary back system (no cats there). I was like "WTF ! This thing rapps out to 8500-9000 rpm." They flat out refused to install a 60mm (2.36") system.

This system;



I was told it was overkill for a belt driven 1.8 liter 135fwhp engine with 10.5:1 compression ratio and an 8500-9000 rev limit.

noone has effectively answered how much a 3 inch gains over a 2.5 inch. If it is only 1-2 hp then the noise isn't worth it. If the gain is at least 5hp, then I could understand.

What noise? There shouldn't be a difference in volume, only frequency.

Thanks for all the info. Bennito has some experience of what I have to deal with, but at least there are a few guys who've stepped up their game.

My car is booked in for a full 3" mandrell bend system, with two silencers. Stainless steel, tig welded and fully polished. Will post pics as soon as it's done.

I have a full 3" with two silencers on my CA18DET s13 and it's almost as quiet as stock. The shops have many different lenths, volume and shapes (oval or round) silencers that you can pick from. Depending what you choose you can have a fairly quiet 3".

I'd prefer something a bit louder for my ve off course :-)

The question still stands. What are the gains of a 3inch over a 2.5? 2hp, 5hp, etc.

^^^ yup