In a few months i am taking a high performance engines and chassis fabrication course at my school. I am going to be building a intake manifold and i just wanted to get some input on my first design. its simalar to a ITB's set up, but with only one large throttle body, i attached a crude ms paint diagram for people to get a better idea of the set up. Im running two pieces of tubing just after the throttle body right to peripherial ported intake ports. Anyone seen a set up such as this? Any ideas for improvement? I am running a 61mm sound performance turbo and i think a 85mm or so throttle body should be sufficient, anyone think other wise? Any in input would be great! thanks! Damn, i cant shrink the ms paint diagram down enough to post it, if anyone is interested in seeing exactly what im talking about ill draw it out and photograph it.

 

Take a look at this:

https://www.rx7club.com/forum/showthread.php?t=498432

 

2a+RoNs build.
https://www.rx7club.com/single-turbo-rx-7s-23/intake-manifold-pics-my-single-fd-project-518205/

 

I know there is a lot of benefit to be had with aftermarket intake manifolds on a piston engine. You can get like 20+ HP just by changing the intake manifold on some 4 cylinder engines, I've seen dyno proof.

On a rotary it's different though. The power curve is a lot different. If you put a short running intake on a rotary you might kill your bottom end, but gain top end only. It seems that you would have to very carefuly plan it because the rotary is such a dynamic engine.

 

eastcoast.. don't copy this.. flow to 1 & 4 runner will be poor , flow dynamics into all the ports to the runners is poor without a smooth transition into the runner you will end up with a huge boundry layer, reducing the internal diameter of the runner by a considerable percentage. Adding a bell mouth or some form of smoothing of the transition point for improved laminar flow in the runner

 

Yes, as I mentioned in the thread it would be nice to have a longer plenum and small velocity stacks. That would take care of any turbulence around the inlets of the runners.

Physical space in the engine bay limited the plenum size though.

 

that's odd, mine worked out just fine with a smoothed transition internally to the plenum, a well volumed Plenum and tuned lenght runners.. with loads of room to work with room above, below and on both sides of the intake manifold

 

doridori-rx7 do you have pictures of yours?

 

yes but because I'm not a site sponsor, you'll have to PM me for the pics.. I'd hate to be seen as ' self promoting my business...' on here.

 

Post the pictures...Unless you are actually trying to sell your products as part of a business on this forum then you're not a vendor and there's no problem with posting something your shop has done...

If the rear end of my plenum was expanded beyond what it currently is, then there would not be any more room for the vacuum nipples or temp sensor. Of course those could just be relocated but that didn't occurr to me at the time. A much better spot would have been on the throttle mounting area.

That's likely what I'll be doing on the next one. The little velocity stacks are fairly easy to make as well with a press and a mandrel (or a big vice!). The intake shown in the thread above was a prototype and what I learned from that will go into the next one. Also direct flow bench comparisons between the prototype, stock and improved intakes...

 

While I agree that a smooth transition to runner is important, flow to runners 1 and 4 will not be poor. First of all the bend the airflow needs to make into them isn't that bad. What you need to remember that while there are 4 runners, there are only 2 rotors. Air will flow quite evenly to each end along with the corresponding center ports. If this were a piston engine where there were 4 separate runners feeding 4 separate pistons, that would be a little different but still not as bad as you think. In this case since each pair of runners is always feeding the same rotor, the pressure in each runner will always equalize with the other one. This will cause a flow stability between them which will even out flow to the end runners. It won't be a problem. If the throttlebody was at 1 end of the plenum on the end, then you'd have a problem with flow. For a rotary, this design is fine. Yes it can be improved a little bit but by absolutely no means is it bad.

 

I love threads like this so much info. Aaron BTW that is a very nice setup.

 

it still is a good idea to keep the runners a tunable length, just some food for thought.