Dual to single?

[direction88]

It has come time for me to get a new exhaust made and I want to hear some opinions on my idea. I have a stroked 2.7 and I want to go with a Hartge header, Y pipe and possibly a single 3" to a Borla muffler. Is 3" a good size or should I go smaller?

[StereoInstaller1]

2.5" maximum on a 2.5 liter motor, in fact, you will lose a tiny bit of torque compared to a 2.25".

[direction88]

Technically its a 2.7 so in that case would 2 1/2 or 2 3/4 be right? The guy who is building it suggested 3.

[JasonC]

It isn't a heavy breathing V8 or boosted car. So 2 1/2" would be more then plunty.

[StereoInstaller1]

My wifes bone stock but good condition 325i has a tiny bit more torque than mine, but I definitely have more top end. Both cars are 3.73, stock M20B25 with a G260.

Mine has an aftermarket cat, 2.5" poorly done cheap crap catback into an ebay muffler.

Noisy as hell, raspy and LOUD, I would never recommend it to anyone.

[direction88]

My wifes bone stock but good condition 325i has a tiny bit more torque than mine, but I definitely have more top end. Both cars are 3.73, stock M20B25 with a G260.

Mine has an aftermarket cat, 2.5" poorly done cheap crap catback into an ebay muffler.

Noisy as hell, raspy and LOUD, I would never recommend it to anyone.

Ok so just to clarify, you converted your car from a stock dual exhaust to a 2.5 single pipe?

[StereoInstaller1]

Ok so just to clarify, you converted your car from a stock dual exhaust to a 2.5 single pipe?

It was on the car when I bought it, but yeah, it has a single 2.5" "Y" just behind the headers, before the cat.

The cat is a cheapo ebay POS too, just single 2.5" in and out, then an ebay "catback", all welded with no flanges anywhere. Makes working on the car way harder when the exhaust doesn't come apart.

The sound was pretty good before the muffler crapped out. Too loud, but really aggressive.

The ricer kids LOVE the sound of the thing. I have had several kids offer to buy my old muffler, since htey think it will make their Honda sound like a mighty mighty 2.5 liter M20.....har-har-har.

[direction88]

All done! I had my Hartge headers ceramic coated, a custom Y pipe with O2 bung made, high flow 2.5" in/out cat installed, 2.5" SS pipe to a Borla muffler and a 3" polished SS tip. Here a couple of pics and a link to a video of the sound (sounds way better in person). The car revs much more freely now and makes a noticeable amount more power.

http://www.youtube.com/watch?v=n4wddSBG-v4

[moatilliatta]

I like that oil cap!

[elsabor67]

Sound pretty good. Does it get a lit loud at 2500 rpms?

[direction88]

I like that oil cap!

LOL ya I know its lame. I needed a new one and that was like $5, it will do until I find a more presentable one but I need to spend my cash elsewhere right now. ^ It is loud, maybe even too loud for some but I like it.

[tonytony]

it sounds nice, has it been broken in yet? It'll probably get quite a bit deeper in tone. Post some driving videos too

[nando]

3" is way too big for an N/A M20, thats the size the 300whp+ turbo guys use. stick to 2.25-2.5" max.

also you don't lose torque from having lower backpressure, you lose torque from lower exhaust velocity and gain torque from less backpressure. However backpressure and exhaust velocity are inversely related - bigger pipes lower backpressure, but they slow down the exhaust gasses - so you want to maximize velocity and minimize backpressure. there is a sweet spot.

[Van Westervelt]

Every E30 I have heard that converted to single pipe anywhere in the system, has rasp. Unless its just an X or H pipe, or single resonator. Not bad, just contains rasp.

What Nando said about the backpressure vs torque myth is true.

Yours does sound pretty good.

[gearheadE30]

nando, that's 2.5" piping. he just has a 3 inch tip on it. Sounds pretty good, but I prefer the sound of duals.