YOUNG GUNS15

i have been looking around for a shop that can bend the cold pipes for a twin turbo setup and i finally found one. and was curious to what diameter works the best performance, and fit in the engine compartment. i was looking at 4'' cold pipes but i was thinking it was kinda overkill

Brendan

I'm not sure on the exact size, but I do know 4 inches is way to big, I they are 3 inches or a little smaller yet. I would imagine that they would be a similar size to your current intercooler pipes.

BigErksG2

for a daily driver, 3 inch works great because you keep the velocity going. 4 inch would be for more of a competition application. mine are 3 inch and I have no flow problems on the intake side.

RowJ

You want to maintain size, when possible, throughout entire system.
Piping for air filter to the primary turbo will be 4" or 5" depending on which turbo you use for a primary. Pick your air filter to match the size of the primary inlet.
Primary to Secondary will probably be 3" with a flair to 4" at the secondary inlet.
Never create a restriction by using cool piping bigger than inlet size on the turbo it goes to.
You can open it up, at the turbo inlet, if required, but never reduce it.

RJ

Fishin2Deep4U

I like 3.5". It matches up better to the flange sizes and it's just a natural fit. Even the hot pipe I prefer as 3.5".


Intake pipe should match the primarily inlet as mentioned. But 4" is just making you have to fill a bigger void. It will work, but takes longer for the primary to catch up.

Dave

YOUNG GUNS15

thanks! this really helps alot! i am in the process of building twins and the piping is my main hang up both hot and cold... im shure i can build my own hot pipe but the cold pipes are another story.

The primary turbo is going to be a HT3B and the secondary is the stock HX35.

HOHN

I'd match the cold pipe size to the outlet of your big turbo. Do NOT put a transition at the big charger outlet-- do it at the small charger inlet.

3.5" sounds good to me, too.

JMO

BigErksG2

even if the inlet on the 35 is 4 inch, how big is the actual inlet on the turbine? I would rather do a 3 inch (the size of the outlet on a 3b) and keep things moving smoothly. Velocity is very important in street twins.

YOUNG GUNS15

im looking at a do it yourself cold pipe setup from source automotice on ebay, it looks legit, and its a fairly reasonable price! about 180$ i dont know the pipe size but i think im going to go that route

gwhammy

I used 3 inch on mine. On the he inlet I used a 4 inch by 3inch silicone 90 then two 3 inch aluminum 90's welded together to get to the outlet on the 3b. It's more compact than most but I needed to clear the on board aircompressor mounted above the alt. With this only one weld is needed but if you had no access to a welder you could use one more silicone coupler and have no welds.

RowJ

Have seen several of RIP's set ups on 24v's.... using their HX-35 on top. They are very nice.
Make sure the "Air Filter to Primary Turbo" is the right size for your HT3B inlet.
All the ones I've seen were set up for S400's and used straight 5" piping, I believe.

RJ

olddodgetruck

my 35/3b setup uses 3.5. so it only expands to 4'' at the secondary on the cold pipe. but my buddy has 3'' and i think his primary responds better.

12valve

where can i get short bent 90 degree elbows, to weld together?

Fishin2Deep4U

I use J bends. Much easier and far cleaner than all the welds.

Dave

Tate

I got mine from an exhaust shop, 4" radius bends on a 4" pipe.