Optimal Exhaust Size

[WrickM]

3" should be more than big enough for anything you need. Engine size does not really matter, what really matters is the power (hp output) of the engine. Whatever the engine size hp is created by fuel in air igniting. True diesels do that more efficiently but really there isn't a huge difference between 300hp from a 2.5 liter engine with 25lbs of boost and a 7 liter engine making 300 hp when it comes to amount of exhaust created. (there are some differences ok, but when it comes to final exhaust size their aren't) 3" can support over 400 whp turboed and well over 300hp NA.

i know it's counter intuitive for a lot of people but engine does work (measured in hp) and that work is the simple output of fuel and air burning. A certain amount of fuel and air created x amount of power. there are variables and that does change the volume of exhaust but only slightly. really the only difference that matters is the efficiency of the engine. the higher the efficiency the small the amount of air/fuel needed to create x hp and hence a proportionally smaller amount of exhaust. so our somewhat efficient diesel actually produce a little less exhaust per hp than most gassers.

 

[alteredspeed]

I just installed a banks turbo on mine I had a 3" system including the down pipe. Now I just got 4" from the down pipe back to the bed and 5" stacks. The turbo spools quicker and the EGT's are noticeably different. Like 150 degrees different pulling a hill. So I say my truck benefited form the bigger system.

 

[7.3n/anut]

there is air fuel ratio. proper fueling is what yer lookin for the more air the more fuel you have to have to keep it running "efficiently". not wastin fuel and not making yer turbo useless by underfueling

 

[WrickM]

I just installed a banks turbo on mine I had a 3" system including the down pipe. Now I just got 4" from the down pipe back to the bed and 5" stacks. The turbo spools quicker and the EGT's are noticeably different. Like 150 degrees different pulling a hill. So I say my truck benefited form the bigger system.

Hey i am not arguing laws of thermodynamics here. There are still people that believe hydrogen generators work no matter how much science they see. One thing to remember is that EGT's are one method of trying to "approximate" cylinder temps, but they do not reflect a direct correlation. For example if you had a completely open exhaust your cylinder
temps would not be changed, but the exhaust temp would read only a few hundred degrees over ambient at most.

 

[smolkin]

Well, this thread has convinced me to put exhaust on my to-do list. I am certain that I'm losing hp and mpg esp. at higher rpms. So, if I wanted to replace my stupid exhaust (2" with massive muffler that is so quiet that the injector clatter and fan drown it out) with a 3" straight pipe, how loud would it be? Like, unable to hear my stereo loud or begging-for-a-ticket loud? Should I just budget in a decent flowing **** to begin with?

 

[7.3n/anut]

depends on how heavy yer foot is haha

 

[smolkin]

depends on how heavy yer foot is haha

Let's just say that my downshift rod is down 80% of the time. I do alot of around-town driving, and I am what you might call an aggressive driver. So I think I answered the muffler question just now...what's a good cheap 3"?

 

[7.3n/anut]

thrush welded series. my buddy had one not loud but had good tone

 

[damac]

I want to do an exhaust mod as well. For those of us that want to get a real world experience with the noise though, would it be safe to cut through the exhaust before the muffler, and then reattach if needed with one of those exhaust couplers that bolt on?

I am no techie but just wondering if that is safe or not. This would help me decide, I could go on a run and monitor noise levels and hopefully see if it gives me a performance upgrade before guying all the parts.

 

[7.3n/anut]

yea just make sure you eave yerself space to work underneath it. remember exhaust work SUCKS!!!! hahaha

 

[alteredspeed]

Anybody that needs a 3" system from the Y-pipe back, for a non turbo truck is welcome to my old system you can pick it up or I can cut it and put it in a box to ship. I just had it custom made about a year ago and now have a turbo. It is 3" all the way with a small 3" muffler. And it came off a 4 door long box truck so it should fit anything. and it exits out in the stock location. My zip is 22801 if anyone is interested. Best of all its free! I would like it to go to some one who can use it instead of the scrap heap.

 

[CDX825]

thrush welded series. my buddy had one not loud but had good tone

Thats what I have and I love it!

 

[GOOSE]

I would have to try srtaight piping it first. 30 sec with an 18volt saws all and its ready for a muffler if you do not like it.

 

[Compu Doc]

Mine is a 3" with a Gibson muffler. A lot of people have heard it and likes how it sounds.

 

[f-two-fiddy]

Straight Pipe NA sounds terrible on the interstate. Not so bad with a Turbo.

You'll get sick of the drone after a couple of 1 Hr+ interstate runs.