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OK lets say I set lower and upper VTEC at 3500 RPM and the "engagement window" is set at 750 Mbar at the same RPM, does the logic mean that VTEC will only engage once both those conditions are met?

The reason I ask this question is because at cruising RPM around 3800 RPM I can see the VTS Light turn on indicating that VTEC is ON even in cruising RPM at a low load condition (under 750 Mbar). I'm only at around 300-350 Mbar @ 65MPH 15-17% TPS and VTEC is ON!

If lower and upper are set to the same thing it will always engage at that RPM because you've eliminated the need for a window.

OK so If I set the VTEC lower RPM at 2500 with an engagement window set at 750 Mbar, theoretically the VTEC (VTS light) should be OFF while cruising at 3500 RPM under 750 Mbar correct?

No, below 750 you'll use the upper engagement and above 750 you'll use the lower engagement. The point of this is to stay on the lower cam profile longer when just cruising to save on fuel economy.

so how do I know what to set it at in order to only have VTEC engage at say 4000 rpm at basically wot , but at 5000 in any other driving?

See the help topic for this!
http://ktuner.com/KTunerHelp/vtec_engagement_window.htm

KTuner wrote:See the help topic for this!
http://ktuner.com/KTunerHelp/vtec_engagement_window.htm

I tried searching this on multiple forums but have come up short. Does the bolt-on OTS tune (the only other preinstalled tune other than stock) adjust the VTEC engagement window at all? I know it's possible to do separately, I'm just curious if any adjustments are already made in the OTS tune on the KTuner.
Thanks!

Depends on the platform. Feel free to check the factory file vs the tuned file settings.

KTuner wrote: ↑Sun Dec 20, 2015 4:56 pm No, below 750 you'll use the upper engagement and above 750 you'll use the lower engagement. The point of this is to stay on the lower cam profile longer when just cruising to save on fuel economy.

in light of your quoted response, can you give an example by filling in the options in VTEC settings
Lower engage ?
Lower disengage ?
Upper engage ?
upper disengage ?

against below query.

RABOOST wrote: ↑Sun Dec 20, 2015 4:52 pm OK so If I set the VTEC lower RPM at 2500 with an engagement window set at 750 Mbar, theoretically the VTEC (VTS light) should be OFF while cruising at 3500 RPM under 750 Mbar correct?

would really appreciate your response.
Confused about using upper engagement below 750mbar and vice versa.

In light of your questioning I did mention watching datalogging to get a handle on the logic for your application. This advice is correct for standard VTEC applications. I've update the advice on the help page to be clearer.