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I'm trying to get all the knowledge I need to tune my d16z6 turbo build on my own and find that VTEC engines are the exception to a number of rules anyone have some guidance for tuning the high speed vs low speed cam, seeing both ignition maps and what load cells I should be using? Or any other guidance I may need? Thanks
initially tune with the VTEC switched off. tune the full range, then get the cam to switch over as early as possible and tune that map fully, after that all that will need tuned is the transition between cams
Chris's advice is sound however I'll elaborate slightly.
When you're setting the Vtec changeover, I initially do a very rough tune on the engine - Don't waste time trying to get it all perfect but rather just enough that you can do a ramp run at WOT from 2000-6000 rpm or thereabouts. Once you've done this on low cam only, run the engine from about 3500-6000 on high cam only again just making enough changes to get the engine to run through. The point where your torque and power graphs cross is where the Vtec point should be. Once you've gone through and fine tuned the fuel and ignition tables, you can move the Vtec point up and down 200-500 rpm to fine tune it.
If you want to get fussy then you may find that the optimum Vtec point will be different at lower load than it is at WOT. If you want to spend the extra time, you can set up a Vtec window based on throttle position and rpm. If you do it this way I typically set up dual fuel and ignition maps and use the Vtec window to switch between them. In all honesty it's probably not worth the additional effort.
One last point - Make sure you have a hysteresis of about 50 rpm or the Vtec will shuttle if you happen to sit at the switchover rpm.