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Discussion Starter #1
K24a2 swap into a Toyota Supra chassis. Running Megasquirt EVO. Dyno is a Dynapack using no correction factor. Uncorrected dyno numbers are 180hp/135tq.
Cam timing is spot on. Injectors were cleaned. New spark plugs. Good compression.
50 degree VTC gear with 40* Tractuff limiting pin
70mm Throttle body on a Miata intake
VTEC crossover set at 4000rpm
3" CAI
2.5" exhaust off stock header

Typical torque curves for this engine on the same brand dyno don't have a dip in the middle, just a steady rise from 2k-6krpm. This engine made 50+ pulls on the dyno during tuning and the AFRs are great across the map. The VTC and VTEC are functioning as designed. I think something is wrong but I'm at a loss to figure it out.



 

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Discussion Starter #3
I'll see if I can dig those out of the tune file. I believe that the VTC starts at 15 degrees just before the VTEC crossover, then goes to 30 right at the crossover. Before that I thinks it's at 0 degrees. My tuner tried more angle and said that it made no change.

I'll get the tables posted Sunday when I return home.
 

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Discussion Starter #4
After doing some more digging I found that the VTC is also supposed to advance the intake on the low cam also. My VTC table has 0 degrees of advance until 4000rpm (VTEC crossover).

Any theories how this might affect performance? My guess is that we're giving up significant torque from 2-4000rpm by having no advance.
 

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You'll generally find best performance with the intake fully advanced at low speeds, and then retarding back to zero advance at higher speeds. At the switch over point it's a balancing act of what cam advance doesn't give up too much no the low cam and the high cam.

About a third the way through this presentation there's some good info on how cam timing impacts torque:

Also check this out:
 

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Discussion Starter #7 (Edited)
I found those exact links about 2 weeks ago and started building a cam advance map based on Hondata's optimized tables. The graphs of tq and HP at different cam angle are eye-opening. The Megasquirt table only has 8 columns for RPM so it's going to be a little tricky at the VTEC crossover.

Here's my best guess within the limitations of the MS3 software. There are no command values over 40 because I have a Tractuf 40 degree pin. VTEC is set at 4000rpm. Only some more dyno time will confirm my theory.

 
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