PupleDiesel

When I bought my truck, the exhaust was bad and I replaced it w/ a 4" MBRP turbo back system. I just spoke to a dealer who specializes in Dodge/Cummins PU's. He said going to a 4" exhaust will hurt my bottom end torque, esp. since I have an auto tranny. If this guy is right what do I need to change to reverse this problem? Different turbo, injectors, etc. I really don't want to bomb the truck.

Dinner

I don't think I've ever heard of 4" exhaust hurting performance. Some people say they noticed a little more torque, some people say they didn't notice anything other than sound and lower EGT's...

dieselfuelonly

Some people will say that you lose a little bottom-end spoolup with a free(er) flowing exhaust.

Don't worry about it. You won't notice a thing... but other people will notice your truck .

PupleDiesel

Ah...lower EGT that's important. I know w/ motocross bikes (2 stroke) when you increase the exhaust size you lose bottom end torque, but gain top end. I didn't think this applied to 4 stroke engines.

essgeetee

You will not lose anything going to a bigger pipe, this is a turbo diesel not a gasser. Look at all the sled pullers with hoodstacks!

Dinner

Well it depends where you increase/decrease the diameter of the pipe allowing more low-mid-top end

Lary Ellis (Top)

Find yourself another expert, that one is a little confused

Box5

i just put on a 4" straight pipe to 6" tip and it's probably just me, but it felt stronger, but maybe I was just loving the deeper tone it had so my foot was in it.

1-2-3

I agree with Box5. I simply took out the muffler and resonator. I really don't think my performance got any better, but it did seem to run better, but I attribute that to the better sound that makes you tend to push your foot further tot he floor. With just a muffler delete, mine is not really loud at all, in fact, most people are surprised to find out that I have no muffler. I do find myself unrolling the passenger window when driving next to a concrete wall or divider, and turning th radio down.

Too bad I can't set a preset on the radio to silence the music and unroll the passenger side window. That's music to me. It'll really be music when I can hide enough cash from the wife for a full blown, 4" all the way system.

PupleDiesel

Great! So I can forget about low end torque loss.

Let me add a word to "I really don't want to bomb the truck". The word is...YET. All I need is time and $$$$.

Thanx for all your input.

Dinner, I over-simplified the 2 stroke exhuast thing (expansion chambers, etc.) sometime I'm just a little simple like that ;-). Thanx for your input!

Box5

once u see the cloud of black roll out of ur tailpipe..u'll never stop

Dinner

I thought I would just throw that in there for kicks

ofcmarc

If you figure that trick out, SHARE IT!

I have a long list that's caught up in the house appropriations commitee.

XLR8R

A 5" exhaust can compromise bottom end torque due to decreased flow velocity, especially if the engine isn't Bombed for high RPM & HP.

tx_2500

the guy is thinking from a NA standpoint, not from forced induction. in a non turbo engine yes, going bigger on the exhaust will lessen your low end torque and give you a little more breathing room up top. in a turbo application your exhaust piping wont play quite so much a part.