Ok my thread title probably is'nt the clearist, but I'm talking about porting right behind where the throttle body sits. I was wondering if anyone has ported the stock upper intake manifold to the point where there is no longer 3 seperate holes, but one large plenum. Does this sound confusing?

If you have done this, can you tell me how the dyno/butt dyno responded, or if you had to add more fuel etc. Any thoughts or comments would be cool. Thanks, CJ

 

I haven't seen one that has all three on the intake manifold side, but Chuck at RE has a TB that would work with a ported manifold as you described:

 

I might be wrong ... but isn't the primary runner's seperated from the secondary runners inside the plenumn so if you hogged out the three holes into one then you would have to do the same inside the plenumn area as well which would mean you would have to cut open the plenumn to do all the work then weld it back together..?

 

it should be done just like the pic of the rotary extreme tb, keep the primary separate. i have done it but i did a bunch of mods at the same time so i couldn't tell you if there was a noticable difference. however if you still have the double throttle connected you would obviously have to get rid of it.

 

Double throttle has been removed along time ago. CJ

 

My setup has the plenum open all the 3 holes combined to one open plenum. But I'm not using the stock throttlebody I have an 80mm single throttle blade off an LS1 Corvette. I'm very interested in that setup from rotaryextreme has anyone used it and know what kind of cfm's it flows over the stock.

 

i'm interested in it too, i tried looking on their site but didn't find anything. any info on it attila?

 

That TB would work REALLY well with the 13BRE UIM, since the secondaries are open like that...I think. Just port match it a little more and it'd be perfect IMHO

 

I think they keep them seperate so the airspeed is greater in the primary runners to aid fuel atomization at low engine speeds... I think it would make the engine harder to tune as well sence there would be a very large change in VE at slight throttle changes... But who cares, try it and let us know how it works!

 

If you open the whole TB up, your going to end up with a tuning nightmare. The primary throttle plate opens first, allowing for an easy transition from idle to acceleration. The 2 secondary throttle plates open up when the pedal is farther down. I have no idea how far the pedal has to be down though. The best way to find out is to take the elbow off, and look at the TB while someone is pushing down the gas pedal.

You can run a single TB on an rx7, but if you go to large, you'll never get out of the driveway. It'll have MAJOR issues with surging. Rich (Auto Illusions) is using ~95mm TB (3 rotor) For a street 2 rotor, i'd go with ~80mm for a TB. You can only go larger for a purpose built drag car. They don't drive around at partial throttle, which is where the surging would occur, so they have nothing to worry about. If you don't have a problem with going WOT out of your driveway, then you should be just fine!

Your best bet is to do what's in the picture above. Make the secondary throttle plates one. You can also enlarge the primary throttle plate as well.

-Alex

Edit: Just in case anyone is wondering, this is why our cars don't have a plenum. If they did, the air coming in from the TB would go to both the primary and secondary runners. Of course, they would had to run a single TB also. By doing that, the car wouldn't be near as smooth coming off idle. Like I stated above, you can compensate by running a smaller TB, but it'll never have as nice of a transition as stock.