Twins piping size???

carcrafter22

carcrafter22

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Oct 24, 2007
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As some of you know I recently threw together a little twin turbo setup for my 3.9L. I have been out of town and had alot of time to think since I am getting so close to the first test drive, I have about a weeks worth of work left on the truck when I get home and should take it for a drive after I get the highly modded pump back on.

I went with an hy35 and hx52 for turbos and should have enough fuel (somewhere around 200cc injection pump and will upgrade injectors later) to spool it. The motor should be capable of 4500rpm but will rarely see the stock 3600rpm limit unless I am just playing around but I dont want to have to rev it very often. I made a custom equal length header mainly to relocate the secondary turbo but to also hopefully help with performance using 1 5/8" ID tubing. I chose 3.5" mandrel bent heavy gauge exhaust pipe for the intermediate piping that goes from turbo to turbo and a 3.5" downpipe and into the exhaust.

What I am wondering is do you guys think I am running too big of a intermediate pipe? Should I have gone 3" to help with spooling?

I chose the 3.5" because it was easier to neck it down from the 4" flange on the hy35 as well as wanting to get as much exhaust flow to the hx52 as I could. I do have ALL the hot piping ceramic coated and wrapped in heat blankets.

So lets hear opinions.

Here is a pic of the pipe in question.





Thanks
Randy
 
lol thanks that would be the equal length header I made.

I am really suprised noone has an opinion on this, I figured it would make for good info.

I have seen talk of 3" intermediate pipes but no talk of whether its good to go with 3" or 3.5" and whether or not there is a gain of any kind either way.

I wonder if 3.5" will hurt spool up over 3". I would imagine it might slow down the spoolup just a little but then the ceramic coating and turbo blankets will bring alot of that back.


I know my hx52 isnt much for a 6 cylinder but its alot of turbo for a 4 banger especially with an hy35.
 
I went with 3" on my twins for the hot pipe. Reason being, is the opening of the turbine inlet is roughly the same area as 3" circle, so instead of expanding, then necking down, keep it as constant as possible. The outlet of my secondary turbo is a HX40 flange, but the actual outlet is about 3" as well, so its pretty consistant throughout.

What flange is on the HX52? Is it a T6? If so, then 3.5" is probably an alright size for it.
 
The hx52 is a t4 flange, I went with mild steel tubing and ceramic coated it inside and out.
 
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