I'm in the process of fitting a BW EFR6258 to my 1.8 built 1999 Miata. The plan is to reach 320 whp maybe more.

Now I can either go log, short tubular with collector or full ramhorn style manifold.

What's the concensus on which is the best compromise for spool and top end?

Anyone tried both log and ramhorn on the EFR6258 have some comments?

 

I chose to go ramhorn with the shortest runners I could do while still having a good collector and equalish length. Having a good collector is the whole trick with exhaust manifolds. I also chose to go with 1.25" sch40 rather than the normal 1.5" because IMO 1.25" is fine for the amount of power the 6758 or 6258 can put out, it might slightly choke the 6758 running ALLOFIT but thats like the difference between making 430hp on e85 rather than 450hp. Packaging the EFR on a true log could also be difficult since the compressor cover is closer to the manifold than the turbine flange by like half an inch.

Mine sticks the turbo as low as it can reasonably go. If I was going to make it again, I'd move the turbo just a smidge higher in the engine bay. Then I'd be confident that it would fit on every miata, right now its super close to everything.

 

Ok nice setup

Have you got any spool data available?

Lloyd

 

No, havent gotten around to it. But it will make 2 psi at 2200rpm in 5th.

 

I cannot answer your question directly but this may give you a data point.
I made a top mount tubular with 1.5" runners to be able to keep AC PS and it is making 314hp at 21PSI.
I would go with 1.25 runners if I was doing it again.
Good luck with your project.

 

I make 12psi at 2000rpm in 5th. Come at me bro.

 

F2T FTW

 

I think it should reach 320 either way, so the question is - what do you prefer?
Think packaging, think response, think total torque and power output.

 

Oh, i wasn't talking about the F2T. That does that in 2nd gear.

 

The tubular manifold will shine up top. It will add a little spool time but usually its negligible.

At your power levels a tubular manifold would be a wise investment. Beyond that you need to determine the number you will honestly be happy with.

The suggestion on pipe size above is a good one but if you want to make much more power than you have mentioned (and be happy with, even just for a dyno run) you will likely need the larger pipe size. Think of it as a larger a/r turbine housing, but for your manifold. Slightly reduced spool for high end flow. Again, that comment is for pipe size, not manifold type.

 

In theory a tubular manifold with a good collector should spool faster than a log manifold. 1.25" sch40 shouldnt start to choke off till ~400-450whp worth of exhaust gas flow. So it really should be the choice for every T25 flanged tubular manifold beside one for an EFR7163.

 

https://www.miataturbo.net/build-thr...-thread-59615/
this is my manifold and I love it lots.

 

I had Abe (ARTech) make me a top mount for my EFR6258. It looks like this with Swaintech coating.



I didn't notice any lack of spool even running 8.5 compression and a slightly ported hear (both of which are theoretically not good for spool speed). Boost comes on nice and early and STRONG.

 

The collector will make a difference in top end, but the volume of the small log manifold will flood to the turbo quickly because it has nowhere to go. I should note, when I say spool I mean the time it takes from when you hit the gas to when the system goes from vacuum to 0psi as well as starting to build boost. Not hitting a target boost. Everything becomes constantly variable when trying to hit a target boost- all drawing back to operating load and the limiting factors in each persons setup.

Theoretically with horsepower vs pipe sizes you mention, you are correct.... But remember your thread where we said that theory doesn't always work out in reality? I have some different numbers, but yes a t2 housing can get to be a restriction as well around there.



Nice manifold. Your running small diameter pipe. You would have had slightly slower boost response than if you compared to a log, but again its not really noticeable when your driving. It would be less than 200rpm's difference. I reiterate: when I say spool I mean the time it takes from when you hit the gas to when the system goes from vacuum to 0psi as well as starting to build boost. Not hitting a target boost.

 

All manifolds posted look good

Although I'm leaning towards Soviets but with longer cylinder 1 & 4 tubes going into a standard 4 pipe T25 collector like Absurd flow use

Is there any data to directly compare Soviet's tubular short pipe to say the ramhorns ?

Lloyd

 

Kind of, do the math on the volume difference of the 1.5" sch40 log manifold and a 1.25" sch40 tubular with 12" long runners, and then figure out the mass flow on an N/A miata engine and see if its even worth caring about.

 

****

So what do we call Soviet's?

A flow directed log?
Or a short tubular?

 

Show me yours

 

Soviets is a shorty unequal length tubular. I misstaed once that it was a "flowly log" manifold and got my pee pee slapped. For reference a flowly log below.



Ben has a 2554R, not an EFR.

 

It's not an EFR, so it's not actually relevant to your discussion. I just like stalking Leafy. Sorry for shitting up your thread.