Plenum box with two inlets and one outlet

[ptuomov]

We've got a turbo conversion project with intercoolers in front fenders and the intake manifold fed from behind. This will naturally give raise to a somewhat torturous path for the compressed air pipes. The whole journey culminates at the point where the two pipes need to merge into the single inlet to the intake manifold. What complicates the issue is that the intake manifold is fed thru a (blow-thru) MAF housing that is very close to the hoodline. Therefore, any sort of usual 90-degree Y-merge either doesn't fit or has the risk of producing very inconsistent air flow into the MAF sensor. A further consideration is that the forces acting on any large surface areas will end up being very large.

Here's a solution that John Kuhn who's designing this stuff came up with. Comments appreciated!

Here's the drawing:

Box1.jpg

Box2.jpg

Here's where it needs to sit:

Box4.jpg

[ptuomov]

Here's what the fabricated box looks like:

AB1.jpg

AB2.jpg

AB7.jpg

There are multiple vanes/diffusers inside the box to help the air first slow down smoothly and then to make the turn into the MAF housing.

[ptuomov]

Side view:

AB5.jpg

How the pipes will ultimately feed the box:

Feed1.jpg

[ptuomov]

The pipe size is stepped up with a very gradual, conical diffuser before the 90-degree turn into the plenum box. We figured out that anything that helps slow down the air speed before the 90-degree turn and the expansion into the plenum box. Because the pipe has to reenter the engine compartment from the fenders, we can't go with the biggest pipe for the entire duration of the path.

BoostPipe1.jpg

BoostPipe2.jpg

I think that two of these are going to flow a lot of air mass at say 25 psi boost, don't you think?

BoostPipe3.jpg

The plenum box is aluminum but these pipes are stainless steel. The space constraints are so extreme at some spots the the better wall thickness is more important than the weight penalty! Mild steel would have been cheaper, but the insides of the boost pipes will look nicer after use with SS. In case someone opens it up and looks!

[midnightbluS10]

Whatever happened with this? Did you guys end up using the box? How did it work? Anything done after that as far as modifying the box or making an entirely new one based on results gathered from this one?

[ptuomov]

Whatever happened with this? Did you guys end up using the box? How did it work? Anything done after that as far as modifying the box or making an entirely new one based on results gathered from this one?

The box worked, but we relocated the MAF (and went to dual MAFs) so now there's a y-pipe there.

[BLSTIC]

I was going to say that a blow through maf sounds like a lot of trouble. But so does blending two maf signals, I don't know of many ECU's thay could handle that and I'd doubt the accuracy of using only one maf in a twin system. The Z32 was twin everything except airflow meter

[midnightbluS10]

Whatever happened with this? Did you guys end up using the box? How did it work? Anything done after that as far as modifying the box or making an entirely new one based on results gathered from this one?

The box worked, but we relocated the MAF (and went to dual MAFs) so now there's a y-pipe there.

Thank you! I was curious after coming across this in the 'similar threads' list on another thread.

[ptuomov]

I was going to say that a blow through maf sounds like a lot of trouble. But so does blending two maf signals, I don't know of many ECU's thay could handle that and I'd doubt the accuracy of using only one maf in a twin system. The Z32 was twin everything except airflow meter

The box worked great. The MAF also worked great until it went outside the spec range. In terms of air flow, the old system worked well, but MAF out of range isn't ideal in metering fuel and adjusting spark for a turbo car.

The new system with dual blow-thru MAFs works even better, and has a tiny bit lower pressure drop than the earlier box. It makes much more power, but 99% because fuel and spark are now under control.

Neither system had any asymmetry or air flowing in the wrong direction. We were able to test this by running all three MAFs the same time. Air only flew exactly as John intended it.