Help me understand tuning for lower VTEC - AP1 S2000

K-Series Programmable ECU installation questions / support issues
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Joined: Sat Mar 23, 2019 4:43 pm

Help me understand tuning for lower VTEC - AP1 S2000

Post by Juncura1 » Sat Mar 23, 2019 4:49 pm

First, I'd like to say that I'm happy with my tune and this question is for informational purposes only. I'm tuning my car for track use on my own with rented dyno time so I can learn.

My understanding (and the way I've tuned) is to find the cross point between torque curves on the low/high cams. That puts my car right at 5900. I found it interesting that the Spoon ECU actually uses the same engagement point.

Here is my question:
How are people tuning the AP1 for lower VTEC engagement? Every attempt at timing/fuel brings my torque curve intersection to 5800-5900. However, I've seen people claim to have a 4000-4500 engagement point in the AP1.

I'll admit that I tried to lower it to 4100 for a few runs, but it was either too rich or too lean no matter what I did. I was going to try to pull timing on the high cam, but I ended up leaving it. That's what sparked the question. I wasn't sure what kind of timing should be used for the transition. The timing was jumping from about 27° on the low cam to 30° on the high cam and it would just fall on it's face until about 6k. AFR was between 12 and 12.5. I tried richen it up to 11.5, but that didn't help much.
Some more info... I'm at 5280ft. so I had to scale my load tables down since my MAP never goes above 80 kpa.

Current setup:
Stock intake with Mugen filter
Spoon TB
Fujitsubo header
Gernby Exhaust

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