Smallport intake manifold data

[Blof-fan]

Hi guys,

I don't know if anyone ever did some measurements on the 4A-GE Smallport intake manifold before. But I just did to have some data to see if I can use them in designing my own intake manifold for my 4A-GZE.
Figured that some people here might find this usefull information, so here is what I did:

A friend loaned me his Smallport intake manifold to take measurements from. But it was already used and a bit dirty. So I took it apart and thouroughly cleaned it.
I made a gasket and a block-off plate for the runners so I could fill them with water and thus determine what the volume of the runners and the plenum is.











So here are my findings for those of you who find it interessting:

Volume runner cylinder 1: 400cc
Volume runner cylinder 2: 375cc
Volume runner cylinder 3: 375cc
Volume runner cylinder 4: 400cc

Volume plenum: 1300cc

Total volume intake manifold: 2850cc

Lenght of the runners over the biggest radius: 290mm's
Height of the intake port: 27mm's
Width of the intake port: 47mm's

[Rogue-AE95]

Interesting... thanks for sharing this info and doing the research. When I showed a friend of mine (Honda guy) one of my smallport manifolds, he seemed to think it was a terrible design due to the smaller opening for the throttle body and the sudden opening into the plenum. Not sure if that's because he's comparing it to an aftermarket Honda intake, the size of a stock Honda throttle body, or what.

And an aside question, how did you clean that intake so thoroughly inside & out?!

[Blof-fan]

No problem
I have never really looked at a Honda intake manifolds, so I wouldn't really know.
Those Honda manifolds might be better for flow, but the Toyota throttle body is more than large enough to accomodate the needs of the 4A-GE. This manifold had more volume to it than I eventually thought. I know it should be at least 1600cc, but this manifold has almost twice that capacity. So there is more than enough air there for the engine to take a good breath. So up to a certain degree, flow might not even be that much of an issue.
I could imagine that if you have a much smaller manifold with barely the capacity to let the engine breathe, you would need it to flow much better to get the air in there.

I disassembled the entire manifold and chucked it all into a sandblasting cabinet where I worked it all over with some bead blasting
Had to be cleaned out very well afterwards off course to remove all the remaining glass beads.

[Rogue-AE95]

Yeah, I'm not sure about Honda intakes since I only have a stock D series in my del Sol. I've never had it off the engine to get a good look at its design vs a smallport (or the one bigport manifold I have).

I've tried using aircraft stripper to remove gunk and such from my smallport manifold. Seems to work, but that **** is toxic. I wonder if baking soda blasting would also work? A friend of mine has a blast cabinet but right now it's loaded up with sand/grit.

[Blof-fan]

Baking soda? Well, I figure that should work as well. It's not to hard or abrasive so that would probably work with aluminium.

[yoshimitsuspeed]

No problem
I have never really looked at a Honda intake manifolds, so I wouldn't really know.
Those Honda manifolds might be better for flow, but the Toyota throttle body is more than large enough to accomodate the needs of the 4A-GE. This manifold had more volume to it than I eventually thought. I know it should be at least 1600cc, but this manifold has almost twice that capacity. So there is more than enough air there for the engine to take a good breath. So up to a certain degree, flow might not even be that much of an issue.

When calculating volume the important part is the plenum volume.
A pretty common rule of thumb for the plenum on a performance mani is somewhere between 1.5 and 2x the displacement. Another rule of thumb is to err on the smaller side if throttle response is the priority and the larger side if peak power is the priority. I have heard of tests that showed increases above 2x but there quickly becomes a point of diminishing returns and packaging always becomes an issue.

This was my first 4AGE mani for the LP. Unfortunately I never got it on the dyno. My friend rocked it for a good long while and was very happy with it. Without a dyno the most notable thing is that he was very happy with the throttle response even with the big plenum. If I remember right I aimed for around 3 liters.
I chose tubing diameter based off surface area of the port. Although tubing diameter plays some role in a manifolds characteristics one of the biggest concerns is size transitions. I believe that matching the tubing to the port is the way to go.
I went with a long runner and picked the length hoping to grab the second harmonic right around redline. This should also put the third harmonic somewhere around the 3500 RPM range where a lot of cars spend a lot of time cruising and or pulling out of deep corners.