downpipe too long for C1500?

[buddy]

Are there different downpipes? I bought a new one and there was no way it wasnt going to hit the frame, and its longer than the Banks one I had. Do the 2wd 1500s sit lower? The Banks downpipe barely cleared the frame when i put it on the ATT, I had to jack it up and the it settled a little above and I put hanger tighter.

The exhaust shop just cut some of it out and basically custom fit it to work in my truck.

I got the SSDS downpipe just because I wanted the 4" output and then I get it and its 4" OD, so I had to buy another coupler to go to the straight pipe I bought locally. No one around here bends or works with 4" so I couldnt get either end spread to 4" ID.

 

[DEERE3594]

Maybe old/bad motor mounts making the motor sit to low? Just thinking out loud..

 

[buddy]

That was a thought too, but my fan aligns perfectly, even with the larger Dmax fan it has even space all around. Could still be the issue I guess. The ATT does make it fit different than stock, but not that much.

I guess it doesnt matter though, because it works awesome now with the 4" to 5" outlet and no cat anymore. I thought the ATT was a dog, but it turns out it just doesnt work well with a cat and 3.5" exhaust. I was getting 5psi max boost and lots of smoke. Now I got 12 psi boost easy on acceleration like I needed.

My GM4 performed very well though with the cat and 3.5", although I did fix one 3/4" rust hole in the downpipe when I installed the ATT

 

[Matt Bachand]

My GM4 performed very well though with the cat and 3.5", although I did fix one 3/4" rust hole in the downpipe when I installed the ATT

Well, glad to hear. Must sound alot better too without that 3/4 hole in the DP!

Might be a case of ol' SSD strikes again....

 

[SmithvilleD]

Opening up the exhaust after the turbine improved the pressure differential across the turbine, thereby gaining back some of the boost response that was otherwise lost going to the larger turbine sectioned turbo.

 

[JMJNet]

Well, the different DP may have different ways to transition to the 4". So if you don't buy a complete set, you have to weld back the transition section (which was cut) and fabricate the mating section to the 4".

IIRC, I mentioned in another thread that there are not too many places in the US that can mandrel bend 4" pipe. Even GM don't have that capability.

 

[packratt]

SSD doesn't make the pipe he sells another companies product. Maybe it was made on a Fri or Mon. and the guy doing the bending wasn't paying attention.

On SSD's exhaust system the intermediate pipe (replaces cat) has a flare which slides over the downpipe IIRC.

 

[bk95td]

SS diesel's exhaust is made by hearthrob exhaust of litchfield mn. 20 miles from my house. I bought mine directly from them. They make custom exhaust for anything. Aluminized or stainless all mandrel bent. I think they can go as big as 5 inch.

 

[chevyCowboy]

i dont remeber when i did mine and dont wanna go out and look but could a 4in dp be squeezed in?

 

[buddy]

Its a real tight fit in mine. 4" would be rubbing in a few areas if it fit at all.

Straight piping has shown me how fast the turbo whistle can come, but its just way too loud. Its incredibly loud.

 

[HighSierra86]

Its a real tight fit in mine. 4" would be rubbing in a few areas if it fit at all.

Straight piping has shown me how fast the turbo whistle can come, but its just way too loud. Its incredibly loud.

From what ive heard, this is due to the fact that you are running the ATT. Ive had mine 4inch straight piped with the GM8 for about 5 years now and it sounds awesome. Loud, leaning on the edge of obnoxious.

But from what everyone has posted on here, the exhaust becomes alot louder with the addition of the ATT. Your exhaust exits behind the rear wheels right?

 

[chevyCowboy]

i betting it has something to do with getting rid of the smashed down pipe connector from the turbin to the exhaust. that is got to be alot of restriction

 

[buddy]

I had a banks exhaust so it was a good downpipe except for being rusted, I had extra flow from the holes in it.

I exited my exhaust in front of the rear wheel, exited 5" pipe from elbow about 8 inches from wheel.

 

[chevyCowboy]

no im talkin bout the cast down 90* elbow off the turbo its like a pancake

 

[SmithvilleD]

Theoretically, the "cobra head" shape is supposed to be the lowest restriction form for such tight bends. Haven't ever seen any flow bench testing though. Soon as the wastegate bypass flapper opens, that's one very turbulent area.

As a generality, the bigger/looser the turbine is, the louder a given engine will be. More sound energy can get thru the bigger passages & out the exhaust before getting cancelled out & turned into heat energy.

 

[Slim Shady]

Theoretically, the "cobra head" shape is supposed to be the lowest restriction form for such tight bends. Haven't ever seen any flow bench testing though. Soon as the wastegate bypass flapper opens, that's one very turbulent area.

As a generality, the bigger/looser the turbine is, the louder a given engine will be. More sound energy can get thru the bigger passages & out the exhaust before getting cancelled out & turned into heat energy.

Looser the turbine is? The housing is not looser: Larger maybe. The clearances on the turbine to the housing are tight. The exhaust is louder because it is less restrictive and flows better than the gm turbine housing.

 

[SmithvilleD]

"looser" meaning less restrictive to a given level of flow. Been using this terminology when dealing with turbo builders for decades. And they claim the noise difference is a function of various soundwaves cancelling one another out to a greater degree, the higher the density of the gas flowing thru - eg. at higher drive pressures the more probability they cancel one another - & that energy converts into a less organized form - heat.