VTEC Window upper boundary setting

Razathorn · Post by **Razathorn** » Wed Aug 03, 2005 11:26 pm

Okay, so I have a vtec upper and lower boundry... basically one for full throttle, and one for part... got the basic concept. The thing I'm missing / concerned about is what happens at high rpm when you let your foot off. Does vtec disengage at that point, since it is below 24kPa. If so, isn't this very bad since things float at that engine speed?

I can't imagine this is what is happening, I think I would have noticed this in a datalog by now.

Am i understanding the window settings correctly? I am under the impression that when you reach 24kpa, your vtec point is at one setting, then when you reach 90 kpa, your vtec point is at a different setting. I can't imagine vtec doesn't stay engaged at higher rpms if under 24kpa.

Perhaps the behavior is more like the following: Vtec point is at upper boundary starting since you're below 24kPa, then switches to the lower boundry when you hit 90kPa accelerating. Vtec point switches back to the 24kPa setting when the map drops below 24kPa.

In any case, help file wasn't very clear on this. I'm going to load up the seminar dvd and and trainging video files to see if I can find anything on it.

CivicVTi · Post by **CivicVTi** » Thu Aug 04, 2005 2:49 am

Below 24KPa, VTEC is engaged when RPMs are over the upper boundary. ABove 98KPa, VTEC is engaged when RPMs are over the lower boundary. IN between, the ECU interpolates the two values. For example, at 61KPa (mean value), if upper boundary is at 6000rpm and lower boundary at 5000rpm, the VTEC will be engaged if RPMs are over 5500rpm.

Razathorn · Post by **Razathorn** » Thu Aug 04, 2005 12:16 pm

CivicVTi wrote:Below 24KPa, VTEC is engaged when RPMs are over the upper boundary. ABove 98KPa, VTEC is engaged when RPMs are over the lower boundary. IN between, the ECU interpolates the two values. For example, at 61KPa (mean value), if upper boundary is at 6000rpm and lower boundary at 5000rpm, the VTEC will be engaged if RPMs are over 5500rpm.

Awesome -- where did you find this information. I went and watched the 'putting it all together' quicktime movie and it didn't even mention it there other than 'suggested values' of what to use based on cam dyno comparisons.