I ran into a mustang driver the other day that mentioned that he did not think I needed a muffler at 15lbs of boost. He was wondering why I didn't just run the 2.5 exhaust all the way back with no muffler. I said that I needed the back pressure. He insisted that I didn't.

Please educate me! What do you think and why?

P.S. If you have an opinion please have facts to back it up!

Eddie

 

You don't need back pressure ever

 

Ok so the muffler is not needed then?

 

the muffler is only there to suppress noise. you never "need" backpressure, infact, it is not wanted. the only reason why a smaller exhaust would be better is because of exhaust gas velocity. a smaller one might be more efficient lower in the powerband while up top might suffer. however, a larger exhaust might be more efficient up top while suffering down low. this is why many exhaust systems gain power up top while losing power down low.

sorry, this is probably confusing. someone can clear up but please, no posts saying that backpressure is needed to make power. thats just a myth.

 

Let me lay it out for you. On a FI car the best exhaust is no exhaust. Look at it this way, there is a turbo bolted to your exhaust manifold. that is a ton of restriction/backpressure and to make it worse; it's like 8inches from the head.

after the turbine housings you want as free-flowing as possible.

i use to run open DP and i always made more power, the TQ curve will shift a tad do to the loss of velocity, but the HP is there.

if you want to see where your at, drill a small hole in the middle of your exhaust, run a pressure gauge to it. anything over 3-4psi of backpressure and your hurting performance.


in layman's terms,, blow through a coffee straw; then a burger king straw. which one is easier to blow through.. same goes for your engine. it's nothing more than a big air pump.

 

you dont need a muffler on a turbo'd car, you would make more power without it.

i mean your not losing power by having a muffler, but you arent gaining any either.

 

you dont *need* the muffler, but it helps sound supression as stated above. Look at the srt-4 for instance. it has no muffler, but if you've ever heard on, you know that it spits, and gargles whenever your not on the throttle.

what you could think about doing is getting a cutout welded to your downpipe hooked to an electronic valve opener. run through the stock exhaust for supreme sound supression daily, and then when the need arises, open up the valve for a loud but power gaining time!

 

Ok sounds good. Thank you for the info..... I will wait for a couple more opinions but it looks like there will be a ZPI axle back for sale real soon!!! any offers?

 

I was just thinking today about a 2.5" all the way back with no muffler. I want that "spit and gargle" sound that the srt and some sti's have. ZPI's full exhaust makes a similar sound (at least on whocares car).

 

eliminate your resonators and you'll get that sound.

 

isnt that spit and gargle from fuel popping in your exhaust system.

thats what i have learned, when you dont have a resonator you have excess unburnt fuel and that causes a popping sound.

i have experienced first hand with two of my cars, sounds great.

 

Looks like I have a ZPI exhaust for sale....

 

I was running a Full 2.5 inch exhaust plus a TRD axel back and I got that SRT-4 sound I think your talking about.

 

YUCK YUCK... don't like the sound at all!!!!! sooooooo I"m putting the muffler back on! OH well.

 

Why go 2.5 inch? I'd say go 3 inch all the way. I have a full 3 inch with resonator and Greddy 80mm muffler going on. As others mentioned you want as little backpressure as possible while maintaining decent velocity.

 

I think a lot of people say it's a no no for the 3" on the tC unless your going for big numbers (400+whp).

 

Well if he is pushing 15lb of boost im assuming he is going for high HP and would probably benefit from a 3" exhaust. Although I do believe its been stated that 3" all the way back has some fitment issues under the car. But im sure something could be fabbed up to fix the problem.

 

Yes sir, my car Spits and gargles when daily driving. i like it , lol

 

Just to clarify.....I was not asking if I should go with 2.5" exhaust....I already have it. I was just asking if I need the muffler or not. I have already put it back on because i did not like the sound without it. Thanks for all your help.
Eddie

 

Fitment issues? Naw, plenty of room. Mine has plenty of clearance everywhere and it is full 3 inch all the way from the downpipe back.