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dyno tuning and throttle

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Hello,

I am going to be renting out some dyno time fine tune what I have dialed in so far. My question is, for the dyno, of course the car is in good working condition, fuel tank will be full, oil is fresh, alignment/wheels etc everything is working fine and car is ready for dyno. That's covered.

But, when I'm on the dyno, for example say I'm tuning for VTEC crossover point, loggin the low vtec and high vtec runs, am I to accelerate slowly to full throttle? Or is it partial acceleration through the entire rpm range im measuring, for accuracy? I understand rapid throttle wont give accurate numbers, so I am a bit confused. I am tuning WOT so my assumption is full throttle, just not sure how to go about it. Clarity would be helpful thanks.

Ask the dyno owner for the proper technique to do WOT runs on his dyno.

On my Dynapack, there is a hold RPM and time before the runs starts, so you just accelerate to that RPM and as the dyno holds the RPM, you go to full throttle I normally have a 3 second delay, so I can be smooth getting to full throttle and the dyno will have no issues holding the RPM steady before releasing it for the ramp run (Auto plots in Dynapack lingo).

Thank you for the response.

If you don't mind me asking, in the worked example for vtec crossover tuning, when changing the vtec points (low/high) the Vtec window pressure (kpa/mbar) was not altered, only the vtec points themselves. Can we assume that this can be kept the same?

For crossover tuning, Hondata says to change the vtec window pressure to 80kpa when setting low vtec point, and 40kpa for high vtec point. Currently, my vtec window sits very high at 4311mbar so that it stays in lower engagement all the time. Why would these parameters not be altered in the worked example?

Normally you want to avoid switching the VTEC to the high-lift if you don't have a load (i.e. a higher manifold pressure). I would just set the minimum VTEC MAP to 40kPa (i.e. 400 mbar) and leave it there.

Of course while testing you have two choices to disable the VTEC switch. Either change the minimum MAP, or change the cross-over point. All depends on what you are trying to do.

Sorry I don't have time to re-watch the worked example to see exactly what they are doing there, but I'm sure it's running a WOT pull with lo-cam, and repeating with hi-cam, then seeing the point they cross over and making that the VTEC switching point.

As David said, do two runs, one with the cams in the low position and the other with the cams in the high position and then look for the cross over point/s Sometimes you will see that the high cams work best through the mid range but swapping back to the low cams higher in the rev range can be beneficial, although this applies more to VVT systems than the VTec system that changes the duration and/or lift of the cam.

With a VVT engine I'll do a number of runs advancing the cams in 10 degree increments to see where the gains and losses are with the different angles, and then build my aim table from that. If I want to really build the cam table then I will also do runs at 25%, 50% and 75% throttle to see what the behaviour is are lower mass flows.

Hello as David has stated is the best option for a Honda Vtec system,

generally the cross over point ends up being around 4-4500 rpm on most std vtech engines I have tuned

Regards Ross

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