Homemade downpipe or not?

[Ctallman]

Do you guys think there would be noticable difference if i started my 4 inch exhaust at the end of the downpipe? Vs. cutting off my 3" flange and welding it to a 4" downpipe? just curious

 

[Slim]

Howdy, I did mine from the down pipe back and it worked great, as of yet I've been happy good EGT's. but I'm going to be doeing some more upgrades in the near future and am planning on going from the turbo back, at wich point I can record the EGT's and boost etc. I guess it depends on what you want for power.

 

[Greenleaf]

OK... I read this several times and still don't know what your asking. In YOUR opinion, what is the end of the downpipe? At the turbo OR next to the transmission?



IF you begin the 4" exhaust at the transmission this will eliminate the restriction due to the narrow bends in a three inch system. IF you begin the 4" system at the turbo, this will eliminate the two tight restrictive bends in the 3" down pipe.



IF you are refering to the size of the turbo outlet flange; You will have to consider the size of turob you have. There will be no point in not using the 3" turbo flange of a H1C or HX35 and then increse to the 4".



I guss I don't know what your asking.





-S

 

[Forrest Nearing]

good = starting the 4" under the truck



best = starting the 4" right off the turbo

 

[bgilbert]

Yes cut off your flange, weld it up to a 3-4"piece, 4" elbow then 4" back to tailpipe.

C'mon Scott, gotta read through the lines.

 

[Greenleaf]

I was kinda leaning towards his opinion of using a OEM flange and welding to a "bell" adapter or if he needed a full four inch outlet AT the turbo housing... ... ... ... .



I don't believe that employing a OEM flange INTO a 3" to 4" adapter would be a restriction. Heck, the outlet of the turbo flange on a H1C or 35 is like 2. 75"



I don't see how a 3 to 4 adapter would be any sort of restriction. Maybe THAT was what he is asking?



GL

 

[bgilbert]

I knew what he meant/wanted. He wants it the way you have your downpipe, GL. 4" is better than 3". Looks good too. Sexy is good.

 

[cerberusiam]

It sounds like he is asking if the 4" DP is really needed or if the 3" DP into a 4" exhaust the rest of the way would be sufficient. The answer to that would be: it depends. There is a limit to what can be pushed thru the HX35 hot side before the drive pressures get out of control. If the bottle neck is the turbo then a 4" DP is not going to help much and in fact may cause problems by cooling the exhaust flow too much. "It depends" on the amount power you want which relates to how fuel are you going to throw at it and what turbo you want to use.



Unscientific methods indicate a 3" DP/ 4" exhaust system will be totally adequate, and possibly beter, than 4" DP/ 4" exhaust at certain levels. Where exactly that is also has some variables that are a little tough to gauge. If you intend to stay with your current turbo and keep the power in a reasonable level then stay with the current DP and spend the money elsewhere. Better yet wrap the DP from the turbo down to the 4" entry to promote flow to the bigger system. However, if you are eying those big HP numbers then go to the 4".



My . 02

 

[Ctallman]

Thanks for the information, i picked up acouple 4" fittings today to start my DP, working on getting heat in the garage now!