1998 6.5TD exhaust options?

[joe bleaux]

Do people remove the cross over pipe and make their trucks into dual exhaust? If so, are they using mufflers for the new exhaust or removing the standard mufflers and going straight exhaust pipe?

I love the sound of power but don't want to get tickets.

Thank you.

Joe

[DmaxMaverick]

I'm not sure what exactly what you're asking. If you remove the crossover, how do you intend to get both banks through the turbo? Unless you add a second turbo, the crossover is necessary, as it is or in another configuration. Dual exhaust is fine, but it'll have to be after the downpipe.

Noise output is dependent on your state/local laws and tolerance. Straight pipes can be very loud, and not lawful in many places. Many states with vehicle exhaust system requirement laws consider the turbo to be a "baffle" of sorts, so the equipment requirement may be met w/o a muffler. Check your local laws before you do something that'll cause you legal grief (and fines).

[joe bleaux]

Dumb me! I looked and didn't thing.

Do you think that I would see an appreciable power increase with dual exhausts? How about dual exhausts straight through, too?

Thank for your help.

Joe


I'm not sure what exactly what you're asking. If you remove the crossover, how do you intend to get both banks through the turbo? Unless you add a second turbo, the crossover is necessary, as it is or in another configuration. Dual exhaust is fine, but it'll have to be after the downpipe.

Noise output is dependent on your state/local laws and tolerance. Straight pipes can be very loud, and not lawful in many places. Many states with vehicle exhaust system requirement laws consider the turbo to be a "baffle" of sorts, so the equipment requirement may be met w/o a muffler. Check your local laws before you do something that'll cause you legal grief (and fines).

[damork]

If you search the history on this site I think you'll find that you approach the point of diminishing returns when you go over 3.5". There doesn't seem to be much reason to go with a 4" exhaust. With respect to dual exhaust, I really don't see any reason for it beyond looks. It all comes down to a reduction in backpressure behind the turbo and you don't need duals to do that.

I ran a short experiment with my chipped 6.5 TD where I installed a 3.5" system, all except the downpipe was 3.5". The throttle was more responsive and there was a noticeable improvement in acceleration, EGT was down, but no MPG improvement. I've talked to several with the same experience.

[DmaxMaverick]

Dual exhaust has no real function, except appearance, and they sound really cool.

An ideal exhaust system for a TD has as few bends and restrictions as possible. Restrictions include bends, crimp bends, mufflers, splits/Y's, etc. A dual system will have more bends, plus a Y. Fancy tips (shaped or turned) can be a restriction, too. The best option for performance is a single, large diameter (according to the flow you need) exhaust with mandrel bends and as straight as possible. Back pressure is of absolutely no use with a turbo, so forget the old argument of losing low end power w/o restriction. That only applies to N/A engines with certain exhaust configurations.

[joe bleaux]

Okay, damork.

I wonder what pipe I have on this '98 Silverado. Btw, what is a Silverado as compared to a 2500?

How do I get the backpressure down behind the turbo?

I sure have a lot to learn about this truck and engine.

Thanks

Joe


If you search the history on this site I think you'll find that you approach the point of diminishing returns when you go over 3.5". There doesn't seem to be much reason to go with a 4" exhaust. With respect to dual exhaust, I really don't see any reason for it beyond looks. It all comes down to a reduction in backpressure behind the turbo and you don't need duals to do that.

I ran a short experiment with my chipped 6.5 TD where I installed a 3.5" system, all except the downpipe was 3.5". The throttle was more responsive and there was a noticeable improvement in acceleration, EGT was down, but no MPG improvement. I've talked to several with the same experience.

[a5150nut]

Okay, damork.

I wonder what pipe I have on this '98 Silverado. Btw, what is a Silverado as compared to a 2500?

How do I get the backpressure down behind the turbo?

I sure have a lot to learn about this truck and engine.

Thanks

Joe

Silverado is a trim designation. 1500 = 1/2 ton 6 lug wheels 2500 = 3/4 ton 8 lug wheels 3500 = 1 ton with 8 or 10 lug wheels depending on weight rating.

[joe bleaux]

a5150nut, got it. Mine is a 3/4 ton.

Any answers on the other questions?

Joe




Silverado is a trim designation. 1500 = 1/2 ton 6 lug wheels 2500 = 3/4 ton 8 lug wheels 3500 = 1 ton with 8 or 10 lug wheels depending on weight rating.

[damork]

Several 6.5 TD GM diesels came from the factory with crushed turbo downpipes, that is the first place I would look for making an improvement. Mine was noticeably crushed and I replaced it with a Pinnacle Performance bolt in replacement. It was very well constructed and was the second unit I tried as some of the suppliers had not figured out how to bend to clear the frame correctly. A 3" is all you can get into the downpipe space provided unless someone has figured out how to fit a 3.5" or 4" downpipe with an oval section that clears the frame - only way I could see to add more cross sectional area.

Once you've done whatever you can with the downpipe, free up the restrictions all the way to the tailpipe. There are several options to choose from when going this route such as 3.5 or 4 inch pipe.

The 1500 & 2500 models shared the same diameter pipes from the factory, just some different lengths and bends. It doesn't matter if it is a Silverado, Sierra, Tahoe, Yukon, etc. Mine was a Yukon which is a bit of a challenge for aftermarket exhausts due to the short wheelbase which requires a very tight bend up and over the axle right behind the muffler. You shouldn't have much trouble finding aftermarket tubes for yours. The different vendors advertising hear should accommodate most anything you need.

[joe bleaux]

damork, thanks.

That clears things up quite a bit for me. I wonder if some of these muffler shops can fabricate a larger pipe. I will call them tomorrow.

I can weld but don't have an hydraulic bender.

Joe


Several 6.5 TD GM diesels came from the factory with crushed turbo downpipes, that is the first place I would look for making an improvement. Mine was noticeably crushed and I replaced it with a Pinnacle Performance bolt in replacement. It was very well constructed and was the second unit I tried as some of the suppliers had not figured out how to bend to clear the frame correctly. A 3" is all you can get into the downpipe space provided unless someone has figured out how to fit a 3.5" or 4" downpipe with an oval section that clears the frame - only way I could see to add more cross sectional area.

Once you've done whatever you can with the downpipe, free up the restrictions all the way to the tailpipe. There are several options to choose from when going this route such as 3.5 or 4 inch pipe.

The 1500 & 2500 models shared the same diameter pipes from the factory, just some different lengths and bends. It doesn't matter if it is a Silverado, Sierra, Tahoe, Yukon, etc. Mine was a Yukon which is a bit of a challenge for aftermarket exhausts due to the short wheelbase which requires a very tight bend up and over the axle right behind the muffler. You shouldn't have much trouble finding aftermarket tubes for yours. The different vendors advertising hear should accommodate most anything you need.