Anyone done it? I'm trying to picture it, but damn it is tight with the turbo sitting up high!

 

the pipes are different sizes for a reason (velocity).

 

What?

 

2 different schools of thought. I have a large bellmouth style downpipe on my Subaru and I love it.

 

I run 3" directly off the turbo and am quite happy.

The best turbo exhaust is no exhaust...

 

With a BEGI or FM manifold and T2 series turbo?

 

Oh i just meant I run 3"... my manifold is custom. I've run 3" on this and my old turbo civic... straight off the turbo with a welded on 3" vband. I wouldn't do it any other way.

Personal opinion of course.

 

I agree 100%. I run 4" on my Turbo Civic and used to run 3" on my old Miata with a custom ETD manifold. However the BEGI/FM manifold makes the turbo sits high and therefore it looks very tight to fit a 3" downpipe.

 

Paul will be getting a 3" downpipe made by TurboTim soon for his 2554 from Begi. That's on his daily driver, not on the machine. I'm sure one of them can comment on it.

 

For the next downpipe I build I plan to do it full 3" just because it would be easier and cheaper to purchase all 3" components instead of the reducer and all.
3" pipe on a 4" radius would be fine.
Here is mine with 2.5" tubing off the flange going to a 2.5-3.0 transition.

 

Yeah, but the 3" does not fit a GT25 exit flange well.. Once I put a transition piece in (from oval to round) it was about 5" and now too long. As you can see I was playing a little today.

 

If you're going to do a transition anyway you might as well do it like mine to make it easy. The 3" radius 2.5" bend makes fitment simple.

 

Trimming the lip at the firewall will give a bit more room. IIRC it bends around over the steering column and sits right behind where the downpipe transitions down.

Frank

 

Paul will be getting either a 2.5" or 3" depending on how I feel that day. I'm not sure about you. I may force you to buy a manifold/DP combo.

 

But I just ordered my ceramic coated manifold from Begi.

 

I think I might try and form a downpipe for my car which will fit. Kinda like they do on Orange Country Choppers when they build Gastanks. We shall see. I really want 3" versus a 2.5" to 3"

 

just dont do a 3" pipe connected to the outlet flange without some transition. you'll get stagnation and flow eddys.

my dream downpipe (if it would fit) would be about 6" of transition exactly matching the turbine outlet to 3 inches and then 3" the rest of the way. I think Paul's is very close to that.

 

O'rly. I've run it on 2 cars now and it works just fine. 3" vband welded directly to the turbine housing. Welded up inside and out, which might provide some air flow guidance.

Works fine and spools nicely on both cars.

I just believe firmly in providing as much space as possible for expansion after the turbine wheel as quickly as possible. A continuation of the "the best turbo exhaust is no exhaust" theory.

 

But there is an exhaust. So this argument is not valid. If you're going to have an exhaust, you might as well have one that promotes flow.

 

My point is to be as close to 'no exhaust' as possible. Providing as much space for the gases to expand as quickly as they can allows them to get the F outta the turbine wheels way.

Yes there is an exhaust... but the idea still applies in a sense.

Regardless... I've used it on my last 2 setups without issue. Pieces to flare just waste space to me.