Thread: Disabling VVL at rev limit?

Since I have an aftermarket ECU, I have various methods of engaging / disengaging VVL. This got me wondering if there is any danger in disengaging VVL at or above the RPM hard cut.

The idea behind setting it up in the first place is so that if I miss a shift, it potentially reduces the risk of piston/valve contact from valve float, as the low lobe has much smaller lift (SR20VE cams) and there will be less rocker inertia.

Are there potential risks in doing this? Is the VVL activation pin likely to fail as a result of being disengaged (and then subsequently re-engaged as the RPM drops) at high RPM? Is the low lobe's ramp angle high enough to negate the lower lift?

This is a very interesting idea. I do like where your head is at but I do think it could potentially have an issue at that high an RPM dissengaging so fast. My in fact do the exact opposite of what you want and the valves could still hit pistons. What I am saying is that valve train is moving so fast at that RPM limit that the Rocker Arms sudden disengagement could be to much free play for a fraction of a second. Really is hard to say though. I can see why no one else has posted yet. This thread you have created requires you to think. Unfortunately the only real way to know is to experiment. If I was you I would start trying it but at a lower rpm say 6500 and then work your way up in increments and see. That is the safest way to be sure and go about it I fell. Lets keep this thread going. Could be the first of its kind.

Don't see the problem in doing this, does the VVl not disengage as soon as you realese the throttle. That would be the same procedure.

Dre was telling me the other day that he had a costumer who destroyed a VE head by doing this. I hope he can chime in on this.

Personally I don't think it is a good idea. I am too tired to go into a deep explaination right now, but I will list the reasons if someone doesn't chime in before tomorrow. The best thing to do is become better at shifting. If this were not so much of a shock on the valvetrain, stock ecu's would be doing this as a safety measure. Hope someone chimes in with a more technical and detailed description on why this would be such a shock to the valvetrain. Good Night, way too much thinking this late for more than that....sorry

I ran the low lobes past 7500rpm before with no consequence. but I agree that having the VVL engage and disengage at high rpm could have ill effects. Perhaps disengaging them until a lower rev is reached until allowing the VVL to engage again may work.

Hit the VVL cut at 8K, then don't have the VVL engage again until revs drop below 5K. Maybe this would work, and wouldn't shock the valvetrain as much.

Never mind I don't want to be responsible LOL

ya, totally. I don't wanna be responsible either. So uh, do so at your own risk.

you'll blow your motor

Do we know this for sure as in someone has done this?