Was talking about this in a different thread - every once in a while, my car will rev hang - not the little float between shifting, but literally after WOT, I throw it in neutral (like coming off an autox course) the car will very slowly float from 5k rpm or whatever back down to idle.

It's almost as if the car is still in gear and I'm slowing down via braking only, except not that fast, very gentle float. Both my Evos have done this pulling off an autox course. I'm not sure what it is, but I'm curious if it happens while I'm in gear, or if there's any indication I could see whether or not that happens - and if it DOES happen, is this trying to keep the engine spinning enough to go against braking, which is forcing the RPMs down very quickly?

Probably nothing, just wanted to check.

 

I get a rev hang as well, very similar to what you described

Dont think it would affect braking, as being in gear would pull the engine speed down IMO. Whatever its doing, I would like it corrected

 

Have had this happen to me as well. In for answers.

 

well being in gear pulls the engine speed down because the wheels are slowing down - wheels slow down via braking. in an extreme example if you were WOT & braking, they would be fighting each other. wondering if the float, if it happens in gear, is causing any fight against the braking. I'm assuming marginal if any, but it is bizarre when I pull out of 2nd after WOT to see it float down like that

 

My car does not do that. But I would think it could have a marginal effect on braking. I would consult your tuner.

 

You would lose the brake assist from brake booster. Anticipate to press the brakes harder to compensate for the difference until you fix the problem.

 

this could make sense. no matter how hard I slam the brakes at autox I'm never able to get into ABS, which is bizarre.

 

try slamming brakes on gravel to see if your ABS is still working. If it works, then your sticky tires overpowers your brakes. Then you should look for better pads that is softer and can handle the heat of autox or upgrade brakes ($$$$). GL!

 

I def can/have recently engaged ABS. just doesn't at autox, so maybe it is the tires. regardless I'd think the car could brake harder.. i'll ping my tuner and see what he says about it

 

Rev hang shouldn't effect the brakes technically as there is still vacuum in the plenum.

Either way this has been discussed in the ecuflash forums, and there are fixes. Quick search in there will hook you right up.

 

thanks - i don't know much about the intricacies of how things work - do you think there's any "fight" the rev hang is putting up if it's happening in gear & i'm braking? just from the engine trying to spin?

 

It will remove the engine braking effect, which def will prevent the car from slowing as quickly.

 

not having engine braking makes complete sense - and i think it plays a bigger role than people realize. i drove a friends car a couple weekends ago and the passenger's side axle broke just before/during braking - the driver's side locked up, and the passenger's side, with no engine braking & only brake-braking, hardly felt like it was slowing the car at all.

i guess the alternative solution would be to get even stronger brakes, to the point that they could kick in abs - but i'll always be braking harder than if i had engine braking assisting me.

im not 100% sure this is the case, but it does kind of feel like it. having the tuner take a look, hopefully he can get rid of it, because it definitely does rev hang, at least in neutral from time to time right after a WOT pull. happens most frequently right after crossing the finish lights at autox and throwing the car in neutral

 

Kyoo, On your next track day, try plugging the line to your intake and put a check valve on the brake booster and pull the biggest vacuum you can with a manual pump. Then test your power assist out to see if that will give you the extra clamping power to kick on your ABS.
By the way, you may want to check your brake booster line for leaks (this could be why your engine is hanging)

 

I hardly understand what that means, but I feel like I'd be experiencing other symptoms if there was something wrong with the vac lines themselves. I don't think my tune has been adjusted for revhang so i'll check that first. my racing is pretty infrequent as of late due to school on Saturdays but i'll check the car over a little when I get another chance