Every design is a compromise of some sort. Hogging it out accomplishes the same thing as a large plenum with a single throttlebody. On the stock setup the primary ports are only fed by 1 throttle plate while the secondaries by 2. It doesn't matter what the power level is. Once you max out flow through that plate, you have also maxed out flow through the primary ports. By hogging it out into one plenum you now have all ports being fed by the same amount of air which is what is in the plenum. The plenum in turn is fed by 3 throttle plates. The result, assuming you can tune it, is what is pretty much expected to happen. You lose a bit of low end power but gain top end. Although there are forced inducted engines that use stock manifolds and get very high horsepower numbers, don't assume they couldn't be higher with a bit of playing around.

 

I'm just not sure the benefits outweigh the downfalls. Marco from ForceFed made around 900 whp on a stock S5 LIM/UIM/TB. I would have been interested to see the difference by switching them out, but if this level is possible, why not maintain the low end power of the stock UIM?

 

At that power level, you don't really have any anyways. If you are going for 900 hp on a rotary, you aren't concerned with where the stock manifold is tuned. At least you shouldn't be.

 

Cool! I got the pic from SEAN (A-spec). I ended up doing the same, cutting it down the middle-gutting and cleaning up the runners- then rewelded back together. I have been very happy with it. I used the RE LIM also and port matched the runners to the irons.. The RE primary's are WAY larger.

 

i got this LIM big runners, fits FD engine, anybody interested PM

also pix of my 10yrs ago plenum with AI, inside a nice shaped air horn fitted to the tri-shape TB

 

The secondaries are below the runners, incredibly poor placement but was worried would not fit under hood.. Made the flange.

Yes.




I'm planning on building a new manifold and making some changes...

 

hmmm... looks just like mine...'cept i used a half round on the back too.

 

Actually yours looks like mine, lol. Thats a really old pic. Long since sold and gone off the car.
Im running a RXparts.com setup now with a semi pp like the PR race cars.

 

haha nice. Yeah i've only had mine for like a year or so. Im diggin the new setup you have.

 

Welcome to the club Ernie

 

Welcome to the club Ernie!

 

Wow some real nice intakes here is mine.

https://www.rx7club.com/album.php?al...ictureid=23129

 

https://www.rx7club.com/album.php?al...ictureid=23128