Starting to build my hot side and wonders about the merge. I'm using 2.25 pipe on crossover. The flange is a T4. Should I just merge both at the flange or merge to a 3 in pipe and go 3in into flange. I think it would be easier to make a 3in pipe fit the flange then two 2.25. I read that having a straight section before the turbo cuts down on turbulence. Street car with a single 70mm.

 

I think a short straight section of tubing before the turbo is best IF it has a undivided turbine housing. If it has a split port turbo I would not merge them before the flange.

 

Yes undivided flange. It just think it would be easier to form a 3in pipe to a rectangle to match the T4 flange

Thanks

 

Yes it is.. if you look at the first few pictures in my build thread you can see how I accomplished the same thing. I used a manufactured merge, but then beat the 3" tube square.

 

Exhaust velocity at the flange will effect spool. For better transient response keep the 2.25 all the way to the flange. Let the round tube feed the square turbine housing, a couple of inches beyond the the turbine housing flange it is round again. I use a single 2.5" tube to feed a Gt47-88 with a t-6 flange. I had a 3" feeding the turbo and went to a 2.5" and it made a huge difference in spool time.

 

So gen1 ur saying to run my 2.25 all the way to flange merge the two right at flange?

 

I merge my 2x2.5 about 8" from the flange into a single 2.5". The angle on the pic is poor the merge is not that aggressive...but you get the idea.
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2-1 2.25" merge collector, with a 3.0" outlet, square off the corners to mate with the T4 flange. This way you maintain exhaust velocity all the way to the turbine inlet.

 

Not what I am saying. Maintain velocity with a single 2.25 after the merge. Why open up the 2.25 to a single 3" just to loose velocity then allow the turbine housing neck it down even smaller than 2.25 before the turbine wheel. Keep the velocity up and keep the tubing simple. No the tube feeding the turbine housing wont match but the gas only flows in one direction and the more velocity you have the better the system will respond. On my first kit I thought it would work better with a single 3" expanding to a 3.5" just before the t-6 flange. There is a reason I run a single 2.5" to feed the t-6 flange, hint the turbine wheel is still the restriction.

 

^^^This. All you need to do is look into any turbine housing and see how small it is. I'm not sure how big of a turbo you'd need to match the cross section of a 2.25" pipe, but I bet it would be big.

If I were to build a kit today, I'd drill a hole in the flange material the size of the pipe OD, slip the pipe through until it touches the inside of the housing, pull it back maybe 1/8" and tack it.

 

Do this, exactly.

 

My plan is to merge the two 2.25 pipes right at flange. Make each pipe 1.50 so the total will be 3 in round. Squeeze it down to match the flange

 

You were given border line trade secrets above,(a few years ago the pros started extending the pipe into the turbine housing). If you want a better response for spool, Do not match the piping to the flange. If you want it to look good but not run as well match the pipe to the flange.

 

Maybe I worded that wrong. I'm going to make the two pipes fit inside the flange. My flange already has the rectangle hole in it.

I'd have a bunch to fill in if I just brought the 2.25 pipe into flange. Do they sell a solid flange I could drill my own hole in ?

 

That may work well, but don't be afraid to make the area of the pipes feeding the turbine flange smaller than the turbine flange. What you are saying is to make the merge and lower the t-4 flange as far over the merge as possible then cutting as much that is needed to create clearance for the turbine housing?

 

You could just make your own flange using a gasket as a pattern. Then you could make the inlet how ever you want.

 

Or how about this. Merge both pipes together so I end up with a single 2.25 round pipe. Put this in flange maybe past flange then plate the bottom to fill gap.

 

Lol three people in this thread already told you to do that. Don't run it just past the flange, run it as far as it will go. Do like purple87lx said and make your own flange.

 

Lol. I'm a little slow. This is my first turbo venture. I've always been a nitrous guy. Im in the process of reading the 42 page YB turbo thread.

 

Anyone have a picture what this looks like?

I'm assuming that's only for an undivided housing, I would suspect that wouldn't work as well with a divided housing, but having a hard time imagining what would work best there...