diesel exhaust

[thomas89]

alright i own a 1990 suburban 2500, 6.2 litre engine... it gets on average 16.5 mpg in the city and 14 mpg highway. i was wondering if i got straight open exhaust on it if it should get better mileage... i've heard that diesels don't require any back pressure from the exhaust to run right but i had exhaust on it a while back and it seemed to get 10 mpg anywhere!?!

[GasSavers_Red]

Welcome to the site thomas

In high school I had a friend with a diesel F250, upping to a full 4" brought his MPG from 10 to 12-14ish or so. Might help, not too sure. What kind of tires and when was the last time you had your diff fluids changed?

[2TonJellyBean]

What kind of highway speeds?

[theclencher]

Oh yes, I and everyone else you bless with that contraption can hardly wait to listen to that thing rattle past. I definitely recommend no mufflers for everyone wanting to increase fe, or wanting to harrass their neighbors, or make a redneck statement.

[skewbe]

LOL, those loud a$$ harleys suck major a$$ too.

And it is especially dumb because the bozos riding them probably think they are "all american".


There are tons of faster/quieter/lighter/far less expensive/better looking/reliable bikes out there (thanks Mr Suzuki!).

[SVOboy]

There are always rumors floating around about bigger exhausts being better for mileage, but I think it really depends on the vehicle.

Only thing I would caution is not to eliminate your cat.

Welcome to the site.

[Sludgy]

I've thought about a bigger exhaust on my 6.0 Powerstroke, but I always come back to the same thing:

Bigger exhaust pipes help most at high rpms. But for fuel economy, I want to keep engine RPMs as low as I can. At low RPM and gas flow, backpressure should be negligible in the stock exhaust.

I just can't see doing a $500 experiment with so little chance of success.

Yanno, I just thought of something. Maybe I sould actually test the backpressure in the stock exhaust......

[thomas89]

the truck is a 3 spd th400 i usualy go about 70mph on the freeway...i also have highway tread 265/75 r16 tires nothing real aggressive...the truck doesnt have a turbo or a cat all it has are the mufflers

[GasSavers_Red]

Swap a 4 speed auto or a manual gear box?

[rh77]

BTW, welcome to the site...

Diesels need to breathe to be efficient. Unfortunately without the turbo, any exhaust treatment is going to be loud. "Dealer's Choice" on that one...

Biggest thing -- try to slow down. You have a big brick cutting through the air, which takes a lot of fuel. No matter what kind of mod you have, this could get you the biggest savings.

Consider an engine block heater to get things moving from a cold start. At 130 hp and 240 lb-ft of torque, you may be on the low-end of the power-weight-FE ratio. Does it seem to really need some throttle to get it going? If/when it's time for a replacement, an Isuzu turbo-diesel may be a good option. Otherwise, keep it tuned-up and look for signs of wear.

On a side note: Clench -- we all know you dislike loud exhausts, but do you have a suggestion to help this man's FE?

Instead of throwing our arms up in the air because, OMG, someone with a large vehicle is asking for help -- let's take the time to address the challenge.

As always, I throw-in the caveat: for the next purchase, think "what's the smallest vehicle that can fit my needs". Until then, we're here to help. Even after then too, I guess

RH77