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Discussion Starter #1
I was looking at some old dyno charts from when my car had only I/H/E and I noticed a dip in torque that started about 200 rpm before the IAB opened and ended at slightly after 5750 rpm when the IAB opened. I recently did some butt dyno tests comparing IAB functioning to IAB not functioning and it seems to me that the car would pull better if the IAB point was about 300 rpm lower. My butt dyno is not good enough to be sure however. Does anyone have any dyno experience concerning this.
 

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the problem is without ECU reprogramming, how are you going to change the vacuum parameter for it to open earlier?

If you have a trick for that, I'd love to hear it.

Of note, Erick Aguilar's GSR IM on his 10.59 sec et all motor 2.1L B18C1? it's not stock INSIDE. Heavily ported. My question is (and we will never be able to get the answer) : did Erick alter the IAB point to change the resonance tuning (as you suggest) or did he remove the butterfly valves altogether ?

If you look at the AEBS R&D B18C, their single stage, single plenum IM has no resonance tuning. The walls on the plenum are nonparallel and tapered like the Jun single plenum, single stage IM. This suggests to me that resonance runner length tuning is less important to these guys since their powerband is way up...whereas we need a broader torque band starting at a lower rpm.
 

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All the ECU does to open the secondary runners is to
de-energize a solenoid at 5750 rpm and dump the vacuum that was holding the butterflies shut, so a RPM switch would work. I would rather reprogram the ECU to do this, but that costs money and last time I talked to Hondata even they didn't do this - I think for any GSR - might just have been for my OBDII ECU.

Resonance tuning (I prefer inertia tuning - makes more sense to me) is complicated like everything else when one gets into it, which we seem to do. I will have to refresh myself on the theory before I start any detailed discussions, and I am certainly no expert.

I read the article in SCC about the AEBS engine and remember that they stated the reason they had the two big throttle bodies was to avoid ANY resonance which I thought odd. I have no idea about Erick Aguilar's engine. I find it strange that he is running a GSR manifold since my understanding is that for a race application with a narrow powerband only a single stage manifold would be necessary. Staged intake manifolds are used to tune an engine over a broad rpm range. Since he is using it, I would assume he is using both sets of runners. I don't know why he would use it without using both sets of runners. If the whole thing is ported that alone would change the resonance tuning. Interesting. Does Erick's motor have the IAB vacuum motor?
 
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