I was making a concerted effort to try to catch 3rd gear at several corners. This was my last run yesterday, and the purpose of this video was to determine if I am over revving the engine on downshifts. Here it is mostly in Turns 1, 7 & 8, although earlier in the day I was also downshifting into Turn 11 onto the main straight and I'm sure I did it coming into the Bus Stop on occasion.

The question is whether I should be worrying that this amount of downshift over rev is going to damage the engine. Car is bone stock, AP-2 with 8,000 rpm redline. HPDE 2 run group. Primarily a street car with only a few days per year on track.

Sorry for the poor lighting and the big helmet. Seems I am quite busy rolling around in the cockpit with stock seat and belt.

 

If you want to see what you're revving it to exactly, get an OBDLink MX or MX+ (or similar) and use an app like RaceChrono or Harry's with it. (I'd recommend also picking up a bluetooth GPS, fwiw.)

The AP2 redline can safely be raised up to 8600 or so, so if you're not going over that it's definitely fine. I've also read around here that the occasional overrev up to 9500 should be fine (not that you should do it intentionally). Beyond that and you could be damaging valve retainers.

 

If you exceed the "red line" (8200rpm rev limiter) you should get fuel cutoff. You getting this?

What's your VTEC engagement point?

-- Chuck

 

He is looking at mechanical over rev. Fuel cutoff does not prevent that.

I stopped watching when I saw that you cant see the tach well enough to see what is going on, so was not sure what I was supposed to be looking for in the video other than some cool track video.

 

Fuel cutoff does not prevent mechanical over rev but it should occur and cut engine power. I can't see the tach either.

-- Chuck

 

I just figure that he is downshifting into a corner, so is not on throttle when it happens and by the time he would be on throttle he would be below redline, so likely would never notice fuel cutoff.

I do agree though that a logger of some sort is the best way to tell.

 

In this case it seems this would be a minor mechanical over-rev condition but that's akin to "a little bit pregnant" . I'm confident 8400rpm is fine with the AP2 engine and have my car set for this.

Lowering VTEC won't change the rev limits but will provide more power below 6000rpm in the higher gear perhaps making a shift down to 3d at maximum rpm unnecessary but still available depending on conditions.

-- Chuck

 

Thanks for the comments and sorry about the lighting. You almost have to watch on a computer full screen, and even then it is tough. Maybe you can see it at 0:43, 1:05, 2:00 and 3:39.

Initially, I was worried about mechanical over rev on downshift. But in reality, I think I'm blipping the engine into redline and getting a throttle over rev. and then probably a mechanical over rev as I let out the clutch. Only lasts an instant, except in the toe of the boot when the mechanical over rev might be a bit longer, maybe 2 seconds. I do not feel a fuel cutoff while downshifting, although I certainly do feel it if I otherwise hit redline.

Car is bone stock street car, so whatever the VTec engagement point is, it has not been changed.

I like the idea of trying to get a data logger and getting a clearer picture. To me there is little room for error if I'm trying to stay below 8,400 or 8,600 rpm max.

 

That rev limit will always be there with this engine. You can, however, increase the mid-range power (below 6000rpm) of this engine by lowering the VTEC engagement point and perhaps taking this corner in 4th rather than 3d. And that may be one or two less gear shifts in the corner which is faster. Pure speculation on my my part that this will be faster but if you gotta take it in 3d gear you've maxed out your speed there based purely on engine speed limitations.

-- Chuck

 

Lowering VTEC engagement does no always equal more power at lower RPM. As a matter of fact I think many have found it causes quite a power dip below 6000 rpm without the right supporting mods. My tune lowers VTEC to 4000 rpm, but without a HFC it SUCKS from 3k to about 6k and has less power than stock in that range. There is a reason it is set to engage higher on a stock setup. Granted, there is more to my tune than just lower VTEC, but I dont think you can say lowering VTEC = more power at lower RPMs. But I will say that even with the proper mods and my tune, while there is a bit more low end grunt down low I dont know how big of an impact it would have in regards to downshifting or not for a particular corner on a track. But have never tried to compare that.