Do diesel engines require a different type of muffler, or will any muffler work? I was thinking of putting on a Flowmaster 50 series universal fit, and replacing the cat with a straight pipe in that section, and retaining the rest of the tailpipe and mid-pipe since they are all in good condition.

The truck just developed a new exhaust leak on the top left side of the crossover pipe at the flange where it connects to the left exhaust manifold. I ordered the Flowmaster crossover and downpipe kit, which should fix that problem. Does anyone know if there is a gasket there that goes between the crossover pipe and the exhaust manifold? The Flowmaster schematic doesn't show one or mention one.

I figured while I'm at it, I'll remove the cat and put a higher flowing muffler on with the intent of improving fuel economy and lowering EGT's (don't care about adding more power - just want to improve efficiency and durability). I believe the stock exhaust is a 3 inch, and I just don't see the point of adding one of those expensive 4" exhaust systems when the downpipe is a 3" pipe to begin with. Correct me if I'm wrong, but I think an exhaust system's efficiency is only as good as the smallest diameter pipe in the system. A 4" exhaust downstream of a 3" downpipe won't seem to do any good if the bottleneck is the 3" downpipe.

So upgrading the muffler with a universal fit Flowmaster and replacing the stock cat/soot trap with a universal straight pipe seems the be the best bang for the buck exhaust upgrade. If a special diesel muffler is needed, what are some good ones, and are any of them sold by themselves and not part of a whole exhaust system with pipes?

Thanks!

Don't need anything special as long as it is big enough (dia) to flow. Sounds like you are on the right track.:grd:

Yeah there is gaskets between the manifold and pipe. That is my same thought on the exhaust. If you turn a funnel upside down fluid doesn't flow any faster. But I ended up getting my exhaust from Warp Speed Perfromance anyway. I thought stock was 3" also. I guess it is like 2.75". When I got the stock downpipe out I measured it and outside dia. in some spots was 2.5". So the new downpipe alone should help a little. I do definitely hear the turbo better and earlier and the exhaust sounds sweet. I paid $269 for turbo back with a 5" tip, and $59 for the crossover pipe. And no tax. They were awesome to work with and everything went in easy.

Flowmaster is not the way to go.

You want a Straight-Thru design muffler.

Original system is 2.75".

Part number from GM for exhaust donut is 88891734.


Where on the Island are you?

I'm in Long Beach.

What's wrong with using a Flowmaster on a diesel? It's just a chamber muffler with a few free flowing baffles, hardly any backpressure.

A straight through design is fine, but I don't want the truck any louder than it already is. The diesel racket is loud enough and my neighbors are pissed at me as it is between the diesel and my Z06's exhaust. So basically, I don't want it much louder than stock, and I don't think a straight through muffler is going to work for that requirement.

2.75" exhaust? What an odd-ball size! Flowmaster doesn't even have a 2.75" muffler, so maybe this is all a moot point. Maybe I'll just look at getting rid of the cat and keep the stock muffler.

I have also heard not to use Flowmaster or chambered muffler with turbo. The amount of air pumped through a turboed engine is much higher than a naturally aspirated engine. Depending on boost pressure of course but I want to say something like 6 times (?) more air volume through a turboed 6.5 than NA one. Any baffle restriction is compounded with the added flowrate. A little backpressure is desired in a gasser the less the better in a turbo diesel.

Going catless will help performance but will increase loudness some too.

For better performance use a turbo muffler doesn't matter if its for a gasser or diesel to my knowledge.

The turbo muffles the sound pretty good. Straight pipe after turbo is nothing like an open header or exhaust manifold. Different pipe thickness, material, diameter, and mufflers will change the tone and resonance as well as the loudness.

You could look at Magnaflow if you have any concern about the baffles. Magnaflows are a straight through design.

Maybe the soot coming out exhaust gets trapped in a chambered muffler more so than a straight through muffler????? I am not sure on that one but sounds reasonable.

I installed a 3" straight through, think it was a Magna flow,
I think Iscrewed up , The muffler has a bunch of slots pointed into the flow
of exhaust, I think they are sooting up as the muffler is getting much quiter,
probably should have installed it backwards....so the slots were no a restriction.

straight pipe it no muffer or cat much cheaper than a exhaust system buy a 10' piece of 3 a 3" 45 a 3 " cuppling a few band claps cut it to size and your done cheap easy slide it in there and brace were nessary i did it do mine best thing you can do

I think chambered mufflers are not good for turbochargers. I have a GMC Typhoon(4.3 turbo) and was told not to use a chambered muffler. Installed straight through muffler and was very happy with the performance and sound

firefighter---how does that goodmark cowl inducted hood work for you? Does it get rid of alot of the under hood heat? How well does it work in a cold climate with snow--also in the summer when it rains?

Thanks Greg Carter Vermont

I think Iscrewed up , The muffler has a bunch of slots pointed into the flow
of exhaust, I think they are sooting up as the muffler is getting much quiter,
probably should have installed it backwards....so the slots were no a restriction.

Qwest,
When I installed mine the paper said the slots should face the rear of the truck or Exhaust should flow over them not into them. However I know of a few people that did it the way you did, and have had no problems. Mine sounds a little quiter, but I think I just use to it now.

firefighter---how does that goodmark cowl inducted hood work for you? Does it get rid of alot of the under hood heat? How well does it work in a cold climate with snow--also in the summer when it rains?

Thanks Greg Carter Vermont

It makes an incredible difference in getting rid of heat and I haven't had any snow or rain issues at all. In hot weather, like high 90's low 100's while pulling my car trailer on the Coquihalla (Sp?) hwy which is nothing but steep hills for miles, the difference before and after the hood was close to 25 deg on the engine temp gauge! Was approaching 230 mark with the stock hood and next trip similar heat with the cowl hood was around 205-210. Only thing I don't like is that it could use some additional bracing around the latch pin. It tends to flex a bit because there is nothing attaching it directly to the hood anymore at this spot due to the cowl profile. I have braced mine a bit now and it is better. Stay away from the fiberglass ones alltogeather! I had a very expensive fiberglass one on my last truck and it was a total PITA POS!Censored