Revving issue during upshifts

[urbo73]

I noticed that my car will occasionally rev during an upshift. I'm not talking about rev hang, it actually revs up a bit when upshifting, which is bizarre. It usually happens when upshifting at/over 3K RPM from 5th to 6th. Other gears seem to be fine. The first few times I thought I didn't lift off the throttle, but I always do. I do have "REV MATCH" ON, so not sure if it thinks I'm going to go to 4th instead of 6th or what. Anyone else notice this? I think it has happened in other gears, but I can't recall. But from 5th to 6th, I can easily reproduce it. 5th gear on highway, 3K+ RPM, clutch in, shift to 6th, it revs up, then clutch out. It's like doing a blip on the 5-6 upshift. Very strange.

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[Icehawk]

Yep, I guess there is some poor logic for a few of the shifts.

 

[tezzasaurusrex]

I get this on the shift from 1st to 2nd - which is a shift I usually take my time with as I dont want to abuse my 2nd gear synchro. The engine revs will drop naturally as I come off the throttle but the ECU will rev it up again when I finally get into 2nd to match the rpm to the gear. I would say its normal.

Whats not normal is that I occasionally get a missed rev-match on the downshift from 4th to 3rd at Turn 1 at Winton Motor Raceway (in Victoria, Australia) - it doesn't happen anywhere else. I am hard on the brakes going in and with the missed rev-match it results in a very abrupt forward lurch.. not nice. Happened to another FL5 on the day too on the exact same corner..

 

[madbikes]

Unnecessary engine speed increase during upshift is a modern manual transmission car problem. Some are worse out-of-the-box from the factory than the others. You can get a tune, which may fix it or make it not as bad (that depends on the car).

Sadly, any drive-by-cable throttle body manual car will always respond the best.

 

[urbo73]

I get this on the shift from 1st to 2nd - which is a shift I usually take my time with as I dont want to abuse my 2nd gear synchro. The engine revs will drop naturally as I come off the throttle but the ECU will rev it up again when I finally get into 2nd to match the rpm to the gear. I would say its normal.

Whats not normal is that I occasionally get a missed rev-match on the downshift from 4th to 3rd at Turn 1 at Winton Motor Raceway (in Victoria, Australia) - it doesn't happen anywhere else. I am hard on the brakes going in and with the missed rev-match it results in a very abrupt forward lurch.. not nice. Happened to another FL5 on the day too on the exact same corner..

The 1st -> 2nd shift you describe makes sense and is part of the rev-match logic. In my case, I'm shifting fast/normal at high speed from 5th -> 6th, and it revs up before I get to 6th, right when I move the clutch in and move it out of 5th.

The missed rev-match on your downshift sounds like an issue. I think on track, which I haven't taken my car yet, these things are pushed to their limits (the algorithms that is) that weird things can and do happen. I remember when I took my E92 M3 to the track, it would never allow me dow downshift too much under hard braking (DCT transmission) because I think it thought I was braking to crash or something.

I've left rev-match ON because it's my first manual car to have it and was curious to play with it. I'll turn it OFF and see of my issue with 5-6 still happens.

 

[CaryH]

Second or third to fifth?. Well there's your answer. What possible situation that you put yourself in to justify upshifting?

 

[urbo73]

Second or third to fifth?. Well there's your answer. What possible situation that you put yourself in to justify upshifting?

Huh? I said 5-6. Not sure what you're talking about here. And BTW, to answer your own question, you can always upshift from 2-5 or 3-5. Think of accelerating hard onto the highway in 2nd or 3d, at high RPM, and you know you're at the speed where 5th or even 6th is fine to upshift to. Basic stuff really..

 

[urbo73]

So I turned rev-match to OFF and the same thing happens. The only way to avoid it is so shift slower from 5th-6th. Strange it's also happening with rev-match OFF.

 

[Estoril4]

So I turned rev-match to OFF and the same thing happens. The only way to avoid it is so shift slower from 5th-6th. Strange it's also happening with rev-match OFF.

Strange, seems its dependent on throttle application? Ie loping along on highway 5 to 6 it doesn't happen even though there's such a small difference in revs at a steady speed?

 

[tezzasaurusrex]

The 1st -> 2nd shift you describe makes sense and is part of the rev-match logic. In my case, I'm shifting fast/normal at high speed from 5th -> 6th, and it revs up before I get to 6th, right when I move the clutch in and move it out of 5th.

I've left rev-match ON because it's my first manual car to have it and was curious to play with it. I'll turn it OFF and see of my issue with 5-6 still happens.

I see - in that case since its your first manual car I believe what you're experiencing is rev hang. It's something that happens on pretty much all modern drive-by-wire throttle systems for emissions purposes. It can be tuned/programmed out with Hondata or other software.

Try releasing the throttle a bit earlier than you would normally and see how you go.

 

[urbo73]

I see - in that case since its your first manual car I believe what you're experiencing is rev hang. It's something that happens on pretty much all modern drive-by-wire throttle systems for emissions purposes. It can be tuned/programmed out with Hondata or other software.

Try releasing the throttle a bit earlier than you would normally and see how you go.

It’s not my first manual car, just the first to have rev-match. But if you read my last post, it happens with rev-match OFF too. I’ve not had this experience in any of my prior BMW or Porsche manuals. They also weren’t 4 cylinders.

 

[tezzasaurusrex]

It’s not my first manual car, just the first to have rev-match. But if you read my last post, it happens with rev-match OFF too. I’ve not had this experience in any of my prior BMW or Porsche manuals. They also weren’t 4 cylinders.

Like I said in my last post (post #10 in the thread) it sounds like it has nothing to do with the rev-match but caused by rev-hang.

 

[urbo73]

Like I said in my last post (post #10 in the thread) it sounds like it has nothing to do with the rev-match but caused by rev-hang.

Yeah, but rev hang means it drops slower, mine revs up!

 

[tezzasaurusrex]

Yeah, but rev hang means it drops slower, mine revs up!

No my friend - rev hang results in rpm flair as the engine ecu is still injecting fuel when you've lifted off the throttle!

 

[CTR]

It does sound like rev hang to me too. I'm usually fully off throttle in a 5-6 shift so I've never noticed what you are describing exactly.

Also something to keep in mind is unless a transmission is designed for skip shifting it can be harder on the synchros to go from 3-5 or 4-6 quickly.

I do notice rev hang close to redline in lower gears though. I've started to lift a little earlier and don't experience it as much anymore.

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