Do I need to buy a 4" exhaust?

[farnum]

I'm new to diesel and to this site. Got a 01 crew cab dually 6.6 and looking for better milage. Does my truck have 4" stock exhaust already?

[DmaxMaverick]

Welcome aboard, Farnum!

Your truck came stock with 3.5" exhaust. Do you need 4"? That's only for you to say. It won't help mileage. Your right foot is the best help there. Unless you are looking at power mod's or would like a different sound, you don't really need one. The stock exhaust does fine on a stock truck.

[Mark Rinker]

...plus, your 2001 likely does not have a cat (converter) - unless the truck was originally produced for sale in California.

I have left stock exhaust on all my Duramax trucks and never felt I was leaving power or mileage on the table. May replace the system on our 2006, since it is now turned up and seems to have a fairly restrictive cat and muffler that came with the cab/chassis setup.

[DmaxMaverick]

...plus, your 2001 likely does not have a cat (converter) - unless the truck was originally produced for sale in California......

None of the 2001 Duramax trucks had a cat. CA required them (along with EGR) for the 2002+ M/Y.

[Mark Rinker]

Thanks for the correction, DMax.

I cut the muffler out of my 2001 and replaced it with a chunk of straight pipe. Sound was a little on the loud side, but only when you really had your foot in it. Other than that, it wasn't noticable.

No change in power or mileage. Haven't touched one of the exhaust systems since.

[farnum]

Great tip! I'll remove the muffler and run a straight pipe.

[MaxACL]

Mark and DmaxMaverick,

My 02 was ordered from AAFES (The big BX of the military) while I was flying between Kuwait and the Pacific. Since the postal service for that area of the world goes through a California APO... I got the CA emissions added... thanks a lot, and though I have a vacuum pump and all the EGR bells, I don't have a cat. Why not?

Also, I have all stock exhaust with an unknown type of EGDE chip bought from someone that sold their 02 for an 06 and didn't need the chip. There are no adjustments on the chip, just a little black box with necessary connectors. I'm told the chip is set to the low level as all I do is towing. I assume that the stock exhaust is adequate and I don't really need a hotter chip???

One other problem: for the last month I keep smelling burnt ATF (???) fumes. I've checked, I have the levels checked each oil change and believe me, I'm at their elbows when they check, and there has been nothing missing. I even drained and refilled the ZF6 twice with the GM stuff ($22/qt). Still while on a warm to hot day I smell the smell and it's getting worst. Any suggestions?

'02 GMC, LB7, CA stuff, ZF6, 315,000 miles

Mike

[DmaxMaverick]

Interesting. Don't know why you didn't get a cat. Are you sure it's CA, and not NE emissions? There may or may not be a difference. Consider yourself lucky, in any case. A cat on a Diesel is about as useful as teats on a boar, as far as I'm concerned. The emissions RPO code and a sticker under the hood should tell the tale.

Your Edge Juice is programmable. A series of key on/off, T/H button operation, gear selection, etc. for auto trannies. It's different for manual trannies, and I have no idea how they are programmed. Get the manual from Edge to tell you how to do it (should be online). There are 4 or 5 tunes to choose from. It all depends on the release version and update revisions your box has.

ATF can be from several places. Check your PS/hydroboost system as well. The fluid smells like ATF when it gets burned. Coolant can also have a similar smell. It doesn't take much to burn and stink, so you may not notice the loss you are smelling. Could also be some residual from a spill you don't know about???

[Kennedy]

A quality 4" exhaust is definitely worthwhile for the performance gains, but not necessary when running lower level tunes. Straight pipes will gain a bit, but most get sick of the noise and change them to a muffled system.

[MaxACL]

DmaxMaverick,

My PS pump had run low one day and because of my location I refilled with ATF insted of PS fluid. Do you think that may be the smell? And how do you drain the PS pump?

ON a side note... My ex wife had those worthless teats long ago but they were on her back. Didn't look very good but she was fun to dance with.

John,

I'm confused. I want the performance gain of the 4 inch (if there will be one) but I would run the lower level tune while pulling trainers. Would the 4 inch gain be there in this case?

Mike

[DmaxMaverick]

DmaxMaverick,

My PS pump had run low one day and because of my location I refilled with ATF insted of PS fluid. Do you think that may be the smell? And how do you drain the PS pump?......

[I hate thread hijacking, and we'll move this if necessary]

Possible. Is it leaking/seeping anywhere? Maybe a spill? I use synthetic ATF exclusively in all my PS systems. I never noticed an odd smell, but it doesn't leak. If you had to add fluid, you have a leak or other curious condition. Look for fluid along both sides of the firewall, below the HB unit (engine and passenger compartments). Hot fluid leaking in the cab, even very little, would have a strong odor.

To drain the pump, remove and upturn it. Rotate the pump by hand to clear it. I wouldn't do this for "normal" service, but it can be done if that's what you want to do. A PITA, IMO.

It's easy to flush the system, which is what I do recommend. Remove the return line from the hydroboost unit, install an extended hose and route it to a container. Idle the engine until the hose stops pumping out fluid. refill the reservoir and repeat, pumping the brakes hard and rotate the wheel lock to lock during this. I usually cycle through a gallon or so before reinstalling the return hose and topping off. That's it. Very simple system.

[Kennedy]

While the dyno plot on my site is for my 4-5 system, the full 4 will be right there with it. This test was with the stock tuning.