Hey quick q...

What's the largest exhaust system that you can put on the 2.2 before you start losing too much backpressure?

Thx

 

i'd say 2.25, heavy mods 2.5" turbo 3"

 

2.25" inner diameter is fine, any 2.5" exhaust is really 2.25 inch anyway...so looking from the way manf. rate it, 2.5" is the biggest i would go

 

From an V8 old schooler, 2.5" mandrel bent dual pipes will easily handle 400 ponies. So with single divide by two. ;-) 200 ponies with 2.5" 300 ponies 3.0"

 

for a stock 2,2 2.5" is the biggest i would go, ifyour boosted than 3" woudl be ok, 3" only if your turbo'd making 300+

 

Good info
Thx Guys

 

There is actually a multi page explination of that theory on cobbtuning.com

Good job bro.

 

Here it is: http://www.cobbtuning.com/info/?ID=3222


Good piece of writing.

 

you WANT to lose backpressure. backpressure = bad.

that being said, i would stick to either 2 1/4 or at the biggest 2.5

 

to a point yes, but your engine also needs some backpressure to function.

 

LOL same thing I tried!. I found that 2.25 or 2.5 worked best. I went the 3" route before my ss exaust change over, big mistake. I found it lost power and sounded horrible. Get yourself a 2.25 ss exhaust, which is a direct bolt in, a lightly used one can be had for cheap, with a good muffler, and you'd be good to go.

 

I have an 2 1/2. sounds great & a little more peppy too

 

Why would an engine need backpressure to function though? Thats like saying that your intake manifold needs restrictions and turbulence in order for your engine to run smoothly. In effect, backpressure "pushes down" on the piston during the exhaust stroke which takes velocity away from any piston in the power stroke. Backpressure = loss of power. The real issue is having the exhaust velocity high.

 

100%, completely and totally wrong. tell me why an engine needs backpressure?

i don't get why so many people still believe this myth.

 

so a 230ish hp supercharged 2.2 would run best with a 2.5 or 3?

 

3" is never for na unless you're making huge power. You'll want a 3" for any turbo application.

 

http://www.dsmtuners.com/forums/freq...kpressure.html

heres kind of an explaination of what i was trying to say. if you put a massive pipe on a basically stock 4 cyl engine, its gonna drive like crap because it just wont have the low end pep that everyone is looking for.

 

bro, the first thing in that article is that backpressure is always bad

of course putting a pipe that's too big is not good, but it's not because of backpressure.

 

Yeah, has a lot of good insight not only for Subi's but for automotive performance as a whole.
^^^ Let the flaming begin?
Werent you the one who did the spitball in a straw analogy?

 

Yes, it will drive like crap and have no low end pep, but its not because of the loss of backpressure. The reason it has no low end is because there is no exhaust gas velocity. So instead of having nice smooth exhaust pulses that help scavenge the cylinders, there will be turbulance. It won't be until the RPM's are high that the large exhaust will begin to help because there are sufficient cfm's to fill the exhaust properly resulting in the high exhaust gas velocity. This may be fine for a track only car, but for a DD it will be horrible.

 

I think I was one of the first to post the Cobb article, after all they are right out my back door of my shop. I have talked to a couple of the guys over there about exhaust and other things. That and have had a couple of my cars on there Dyno.

Quick physics lesson hot gasses flow faster to big of an exhaust and the gas cools down thus like XM15 stated you loose the scavenging effect loosing low end TQ.

 

yes.

 

Theres only 3 reasons we need exhaust pipes at all:

1.To carry spent gases safely away from driver/cockpit/enginebay

2. To keep atmosphere from entering the exhaust port, and burning the head/valves.

3. To tune the speed/scavenge quality of the spent gases for the application.



Cliff Notes: Dont need backpressure, backpressure is bad.


2.5" max on a streetable NA

 

2.25"-2.5" and you'll be fine.

 

just get some cheap used ss exhaust.