Thread: VE intake manifolds

I'm curious. Why is it that SR20's have such relatively large plenums on the IM's and the guys who build custom manifolds go even larger on the plenum? Compared to all the different aftermarket honda manifolds which have very small plenums yet still make good power. All the aftermarket sr plenums are huge.

So why the difference?

most are built for boost. boosted engines like large plenums in general.

Granted, but even the guys building custom plenums for N/A builds make large plenums.

Wondering what's the threory behind IM design, cause I'm about to embark on that route.

And here's a thought. A lot of guys have been running the honda tri-y on their sr20's, so it's got me thinking how something like a skunk2 manifold welded to a sr20 intake flange would perform. Off course with the plenum reversed for the TB to face the right way.

You may be onto something here doctorg.

Make it happen.

Stratton.

I'd love to Stratton but skunk2 for me means importing at 7:1 exchange rate excl. taxes and shipping. Customising it is not that much of a problem. Derm loves this kinda R&D and he's very handy with a welder ;-)

It's just interesting to me that the small plenum design is a common factor amongst all these manifolds of high rpm motors. I'm guessing it has something to do with the tuned length for specific rpm and bouncing the airwaves off the back of the plenum to get more VE. Whilst the SR's don't rev that high (in stock form) and generally have larger stock plenums.

Well doctor g check out some of the higher hp higher reving honda motors like k24s k26s and h series motors. They do run big plenums. Only b series all motors run the smaller skunk 2 type intake manis.

Stratton.

You might want to try the RBC intake plenum from the K20A.

dam good observation:

i asked a friend the other day about the honda plenum

it's more than just plenum though, u have to take runner length size shape etc into consideration

those plenums wre mainly for 1600 and 1800cc motors

maybe the k20 aftermarket intake may be more of a comparison

but lets see...

peace

i would say look at k20 stuff too since they have the same 86x86 bore and stroke. the heads are still different in many ways but at least it has similar dynamics to an sr engine. the b series is 81x87 or up to 84x89 so i would imagine that would require very different harmonics.

An RBC intake manifold with the throttle body position in the center, flipped upside down so the throttle body points up woud probably be pretty sick. Mount the throttle body facing upwards and do a large 90 to some 3.5" piping would be pretty sick and should have no problem fitting under the hood because of the runner and plenum design. The runners have a slight U shape that goes downwards so its got the proper runner length and allows better fitment due to the bend in the runners and the way they shapped the plenum. they put the ports towards the top of the plenum and made the large part of the plenum go downward. That would be very interesting to see done. Shouldnt be too hard to do either. Runners appear to sit fairly close as far as spacing is concerned.