Hello all. I am fabricating an upper plenum on a 13brew upper manifold. Right now the plenum area is around 1.8L. I know on piston engines like 1L-1L ratio. But since we have a 2 stroke engine what is the best sizing for my application?

There aren't many people with experience in this field so I was wondering if any experienced rotary guys could chime in and help.

A little more info on the set up. I will be using a 75mm mustang throttlebody, T72-Q trim turbo. Want to run 25 psi of boost. Big street port REW engine (went up 1/4" and went 11.5mm from the inner coolant seal groove keeping the stock shape). Exhaust port has the bevelled edge completely ported out (not ported up, ported down and the sides of the exhaust port are also ported. Exhaust ports are flush with the exhaust sleeves.

Engine made 440 RWHP and 358 RWTQ at 20 psi on a 62-1 as it sits now. Its in a 84 FB with ford 8.8 rear with 4.88's.

Any help would be greatly appreciated!

Bryan Nickell
BNR Supercars LLC

 

forced induction application you dont really need to worry that much. you still running a stock lower ? ground zero will help you there..

 

Here are pictures of the manifold right now. It hasn't been cleaned up yet, but it will give you an idea of what I am doing. If I have to cut down on area, I can. But right now I am waiting on the throttlebody to show and I will have it completed. I was going to cut the plenum down to 1.5-1.6L just to be on the safe side. Hopefully Chris Anderson aka Crispeed will chime in .

I also will add I would like to turn 9-10K RPM.

 

FYI, RotaryGod has a few really good posts on this exact topic in various places on this forum.

 

After media blast

 

ya rotarygod might know a few things or two, smart fellow.

 

Hm, I think I want one

 

A higher useful redline would be somewhat beneficial for autocrossing... no?

 

probably not as much as having more low end torque

 

Good point. What would an effective way be to do that? retain stock manifold?

 

Alright, well I just put the manifold together and hopefully everything will be okay . I am sure it will all be okay as soon as 7K RPM hits but I wanted to just cut down on R&D process. I am sure the way the manifold is the engine won't lose much bottom end. The throttle body points in the direction of the primary runners. There should be decent air speed moving through to keep the engine somewhat responsive on the bottom.

 

Very cool. Bring on the dyno sheets!

 

I would love to make some good numbers, but you know those wankels. If they aren't 100% right, you blow em! Well most of the time lol. I will try the tuning it here in the next few months. I have a lot of changes. 1000cc pris, added pump, methenol inj, Billet 71/Q trim turbo, this intake manifold and a different exhaust manifold and down pipe....

Just a lot of huge changes that really will require a totally different fuel curve.

 

Autocrossing is for sissies anyway