I have a 2002 cummins 3/4 ton.. Would ditching the small factory exhaust make my truck run cooler when towing, and or help milage??? Thanks for any help and thoughts..

 

If I were to guess..it would make it run cooler..more air flow..
when I'm towing 7k its hard to get to 1100F..
MPG - don't know..

-dkenny

 

Thanks DKenny

 

Should do both, but I'm just guessing. I would like to hear on this subject too. I would also like to know what a good towing exhaust would be. One that would lower EGT's & not have a drone or be too loud. Also how much of an improvement in MPG's people have actually seen after an exhaust change.

 

A freer flowing exhaust will help get the heat away from the turbo outlet faster, thus lowering outlet gas temperature; which is a good thing regarding turbocharger life.

The factory 3" exhaust necks down to about 2" or less at the rear axle bend, which can create a backpressure issue when higher rpms are reached.

Cummins suggested a 4" system to Chrysler, for efficiency and turbo life. Chrysler opted for a 3 incher with a 4 inch tip...go figure.

MPG may be affected slightly in your favor, but hard to measure!

The resonator whichthe factory added behind the muffler helped quiet the droning you will experience from a more open exhaust system. My MBRP is a little drony at speed because the muffler is a straight thru design with no baffles. I have read on here that some guys like the Silverline Muffler for quieter running.

 

mine lowered egts greatly, mileage idk cause i love listening to it

 

4" exhaust is one of the first things I did. It is a bit louder, but only for those outside the truck. I can't really hear a difference in the truck, the engine takes care of that. As far as fuel economy, I never really saw a difference, at least not one worth mentioning. I will say that Every diesel mechanic told me to do it. I did remove the resonator too. I actually like the sound.

As far as running cooler, I did not have gauges prior to replacing the 3", but most chip and programmers suggest to get a 4" exhaust minimum to reduce EGT's. The highest I have seen mine under load is 1100, but I don't try to win any races while pulling and take my time getting up to speed.

 

We put a Silverline 4" turbo-back exhaust kit on ours (in the siggy line) and are pleased - it reduced backpressure, didn't make THAT much difference in the noise (well, in the cab anyhow and overall the quality was good - installation not any worse than other exhaust work I've personally done, and A LOT better to work with than that darn little Geo Metro.....
Got a screamin deal from an ebay seller in Tennessee, whose name escapes me. The mitered tip was thrown in for part of the deal. Only hitch was that even ordering for the long frame option, (ours is C&C) the tubing parts didn't quite work out - my son had a leftover shorter piece, I swapped him for the too-long "in the middle" one that came with.

Be aware that going to a larger diameter tube right at the turbo does put it pretty doggone close to the floorboards, we had to do some creative tweaking to get airspace between that hot exhaust and the floor insulation, and you still feel it a bit with your foot (only on passengers side) when running hard.

 

The smallest dia. my factory exhaust is at any point is 3". In stock form there is no need for larger exhaust. Under 300hp you may see a 100egt drop and by 400hp a 200 degree drop going to a 4" system. The main restriction creater of higher egts is in the hy35 turbo exhaust housing which is equal to a 1.5" exhaust.

 

It does run cooler my pyro dropped 200 degrees and better mileage and bottom end power with a STRAIGHT PIPE. Cost $40 bucks.

 

To answer the OP question, the factory exhaust is not small. Its a full 3" mandrel bent system with a 4" tip. The factory muffler is restrictive but the resonator in front of it is a straight through 4" open design thats free flowing. So if you're wanting to lower your EGT's then you can remove the OEM muffler to eliminate the actual restrictiveness or go totally straight and remove both the muffler and the resonator to increase the sound but then you will gain an annoying drone at about 2k RPM which also gets exaggerated while towing. Straight piping the stock 3" system will sustain more HP than the average guy will ever need but buying a quality 4" system with a muffler will be about the same as the straight piped 3", without the drone and be a bit quieter too. The 4" with muffler will be the one your wife and kids will want if you change the exhaust any.

Any gain in HP will be minimal and unnoticeable unless you're putting some serious power to the ground. Then you will need a 4" or possibly a 5" depending on how much power you have.

You wont notice any increase in fuel mileage either.

 

I was trying to find 5" Silverline exhaust for 2nd gen but seems like all they have is 4"....?

 

Installing an exhaust system thats to big for the amount of power your engine makes can be counter active and actually reduce your low end power, let alone change the rest of the power curve. Exhaust size needs to be tuned to the engine application just like any other component.

 

I do understand that. However I'm planning on upgrading my truck later on. Already have Edge j/a in a box. I'll be getting injectors, bigger turbo (maybe hx35 hybrid) and a few other bolt ons

 

Thanks for all the info guys and gals... This truck is mostly going to be used for daily driving commuter truck.. I will slowly put some power goodies on it but not a lot all at once.. I wanted to start with the exhaust due to its in rough shape.. I'm still wanting to keep it sounding nice... Its getting new tires this coming week.. The previous owner stuck 245/75/16's on it.. it revs a bit hi on the highway.. For pulling duties i have a 04 cummins 1ton...