Just talking with a guy on facebook who has a custom one on his car (he has it on a big turbo LNF) .

I know they don't make them but would there be any gain from having one custom made? More turbo noise? I remember I rode in a 4" open DP 04 STI and it sounded insane!!!!


4" turbo 20g:

https://www.facebook.com/photo.php?v...type=3&theater

 

Not on a 20g. I was thinking about a 4 inch exhaust however that way I could re-route the dump into the exhaust and not loose to much power.

 

Why you think its not a 20g?

 

A 4" inch dp on a 20g is not worth it is what I mean

 

Any cons? Im basically wondering if you used it on a K04 what would happen? Just more turbo noise?

 

Why would there be cons?

 

Well off the top of my head, Cons would be:

too little back pressure
boost spikes

not sure though for our cars.

not sure what else, that's what a guy who had it on a WRX told me (not the same STI that I rode in that had it)

 

get rid of that back pressure idea right now, its a turboed car, you want the exhaust heat to leave a quickly as possible for better spooling

 

^but I have heard the opposite in relation to electric cutouts, saying exactly what I said, zero backpressure is bad for the turbo, needs just a little bit.

 

Ever see a honda with the exhaust out the hood at the strip? zero back pressure

EDIT: I say zero back pressure but that is impossible, there is such a thing as to big to soon if you're trying to flow the air out of a long tube, all the exhaust air will not flow very well and actually cause more issues. If youre wanting to run a 4inch dp off a tubro it better be open to the air quickly

 

turbo cars should not have back pressure. that's for na cars

 

Do you have an **** poor base model?

What's your concern with this topic?

 

You really don't have to be an ass. It's a discussion whether it pertains to himself personally or not. Since you can't read I'll post the section.

2.0L LNF Performance Tech 260hp and 260 lb-ft of torque Turbocharged tuner version.
Technical Discussions ONLY!

Please reread the last line and don't be an ass.

 

Turbos make the back pressure. Don't need any more then that. Any real cons? Prolly not. But you get made fun of prolly lol. I was going to do a whole 4 inch exhaust.

 

atmospheric pressure is fictitious.

but seriously, id imagine there would be fitment issues with a 4" on a cobalt. my 3" looks awfully cramp back where it bolts to the cat-back

 

But you would have a full 4" exhaust, if you went that route and you use a different flange or use the same as stock but flipped upside down

 

On a TT built supra 4" exhaust makes sense... on our cars with stock turbo - not so much..

 

Everyone thinks in terms of back pressure when they should be focusing on exhaust gas velocity. Too big of a dp slows exhaust gas velocity which hurts overall performance and turbo spool in the process. Engines hate backpressure and also hate very large inlet or outlet pipes.

 

Exact answer I was looking for. I will be buying a HHR SS soon, and my buddy just got a 09 LNF so this question applies to both, and now I finally can add that doucherag to my ignore list.

 

Even on some of the Crazy Turbo Jeeps builds some of us have. We only step up to a 4" DP when we go 88mm or higher. There are guys running 76mm with a 3.5 and that is all that is required.

I would not recommend going 4" on this car ever unless your doing a crazy hybrid huge turbo build thats only running a 1/4 mile at a time.

Term hit it on the nose.

 

3" is more then big enough for almost all cobalts. My buddies evo has 780awhp and still on 3"down pipe/external waste gate. 4"=lots of wasted money and time

 

Good answers, thanks! Now that I blocked Plees or whatever his name is this thread stayed on track!

 

I did the same. That asshat never has anything constructive to say in all 300 posts he has he is always mocking people for no reason. I guess he never got hugged enough as a child.

 

This.

I always mention this to the LSJ guys as well. Good exhaust gas velocity is key.

Slowing down exhaust gas velocity with too large of a pipe can create unwanted turbulence.

I'm sorry, but a 4" downpipe is way overkill. That car in the video is from my area.

I've seen him driving around every now and again.

 

Changing the subject here a bit....I knew a guy that had a 2.5" header back exhaust on a 3.0V6 with about 200hp, then he downsized from the resonator back splitting to 2 2" pipes with no rear mufflers, said it helped back pressure.

Any truth there?