F22A4 and F22A6 exhaust manifold

[masospaghetti]

Hey all, I have a 93 Accord EX, F22A6. I just replaced my stock cast 4-2 manifold with a tubular 4-2 manifold from a F22A4. Has the difference in flow and power ever been definitively shown between the two? Seat of pants is about the same.

Thanks all.

[oni_cb7]

As shown below, the F22A4 vs. the F22A1. The only real difference between the two is the exhaust manifold. This increases the HP rating by 5. Does this definitively show the difference?

F22a1: 125hp
F22a4:130hp
F22a6:140hp


the difference between the motors:

A1: single runner intake manifold. cast iron exhaust maniold


A4: tubular style exhaust manifold. more like after market headers when you look at them.

a6: a more aggressive cam and a dual runner style intake manifold. the a6 intake manifold has 8 runners instead of the a1 and a4's single runner. paired with the PT6 ECU for the A6 the butterfly valves inside of the intake open up at 32ooRPMs i do believe(someone correct me if im wrong) and allow for more airflow.

if you have the f22a1 or a4 get the intake manifold, ECU, and cam out of an F22a6 and you'll get a good increase in power. most say tho they actually felt more of the gain(more OF) from installing the cam. but if you get all three of those and install it on your a1 or a4 you'll get a 15-20hp increase. all from stock parts

[masospaghetti]

Unfortunately not, because the A1 has a different manifold than the A6. Both are cast, but the A6 has the 4-2-1 design, the A1 uses a 4-1 design.

[deevergote]

It is unlikely that Honda would've put an inferior exhaust manifold on the F22A6. Although the F22A6 manifold is cast iron, rather than tubular steel like the F22A4 manifold, it likely flows at roughly the same rate. If there's any difference at all between the two, I doubt it's more than 1hp or so (and it could go either way, honestly.)

[masospaghetti]

From a casual observer that was my impression, the cast manifold actually looks like it has more gradual transitions. No reason it would flow poorly.

[irelandmc]

Cost is one reason Honda might have chosen what would be an inferior flowing cast manifold for the A6 over the tubular manifold of the A4. Surface texture has an impact on flow, so that's one possible drawback of cast over tubular.

I wonder what the weight difference is between the two? Perhaps the swap was one small step towards better weight distribution if not power gains?