MT revs upwards when hard driving in between shifts

[Saiahhduhh]

Hi has anyone had this issue? Today when I launched the car at the stop light shift from first to second I clutched in and heard the car rev up as I was shifting to second. I’ve had the happen to me before entering the freeway but thought I was hearing things until today it happened. Anyone know what that could be?

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[djf]

I’ve noticed this a few times, I think between 2-3 mostly. No idea what causes it because I’ve tried recreating it but still havent found a way

 

[Saiahhduhh]

I’ve noticed this a few times, I think between 2-3 mostly. No idea what causes it because I’ve tried recreating it but still havent found a way

Okay thanks. That’s just such a weird thing to happen. Ben driving manuals my whole life and never experienced that.

 

[djf]

Okay thanks. That’s just such a weird thing to happen. Ben driving manuals my whole life and never experienced that.

My guess is that it’s something with the auto rev matching

 

[lucky phil]

Probably just rev hang.



Phil

 

[Saiahhduhh]

Probably just rev hang.



Phil

Man that’s probably the worst rev hang I’ve ever have

 

[ColonelAdama]

Yes I have experienced this multiple times. it is NOT the rev matching or rev hang.

After a hard 1-2 shift and clutch in is when it usually happens. It acts like you put the pedal to the floor in neutral. A bit unnerving.

My guess is that the car is just trying to de-pressurize the charge pipe, but who knows. I thought it was a JB4 quirk tbh ?

I have data logs of it happening. Literally throttle opens and RPMs climb to redline without any pedal input or shifting.

 

[Kujiwara]

Heavy flywheel and slight rev hang will do that, especially if you are used to older cars and non-euro cars. I drove quite a few newer manual euro cars, so sub-consciously I lift off the throttle a little earlier before clutching in, when I drove a MT Supra in the city and spiritly for a day I didn't feel like it was anything different. When I drive older cars i actually have to adjust and speed up the gap between lifting off the gas and clutching in. Try lifting off the gas just 0.2s or so earlier/clutching in 0.2s later after lifting

 

[bk5]

Yeah, I think this is an auto-rev match bug. The trans is probably sending a first gear signal to the ECU, when shfiting, which the ECU then interprets as "rev to 6600rpms". It might be that you "bounced" off second, hitting the first gear gate briefly, triggering the signal, or something like that.

But you're definitely not crazy. I'd let the car break in a little before considering it an issue though. My transmission took a few thousand miles to feel broken in.

I've noticed the auto-rev match feature does not like when you manually rev-match downshift. I've had the same thing happen after driving my other car (w/o rev matching) and accidentally rev matching a shift down to third on the highway.

 

[FuzzyRev]

It's such a love/hate relationship with the i-MT

 

[Saiahhduhh]

Yes I have experienced this multiple times. it is NOT the rev matching or rev hang.

After a hard 1-2 shift and clutch in is when it usually happens. It acts like you put the pedal to the floor in neutral. A bit unnerving.

My guess is that the car is just trying to de-pressurize the charge pipe, but who knows. I thought it was a JB4 quirk tbh ?

I have data logs of it happening. Literally throttle opens and RPMs climb to redline without any pedal input or shifting.

That’s exactly what it was. I’m guessing there’s no way of stopping it

 

[puzzled]

Anyone know what that could be?

Yeah, probably you.

One needs to roll off the throttle even at WOT unless you powershift, or map the throttle for FFS.. not preaching or anything, just fact.

 

[ColonelAdama]

Yeah, probably you.

One needs to roll off the throttle even at WOT unless you powershift, or map the throttle for FFS.. not preaching or anything, just fact.

You really gonna make me dig up the datalog of it happening?? smh?

 

[ColonelAdama]

Yeah, probably you.

One needs to roll off the throttle even at WOT unless you powershift, or map the throttle for FFS.. not preaching or anything, just fact.

Welp, here you go. Conveniently happened on my drive in this AM.

See #1, I lift off the pedal completely after a 2nd gear pull
#2 throttle blips back open briefly
#3 RPM start spiking to redline without any pedal input

I did not even move the shifter, just clutch in.

 

[bk5]

Bringing data like a boss...

So you declutched, and just left it in gear? Then after 2 seconds (?), the engine revs back up?

Kind of makes sense. If you're cruising in second, declutch to come to a stop, but don't move the gear lever, after some amount of time, the car probably assumes you want to be in second then rev matches. I've always gone 2->N->2 in these situations because I assumed the auto rev match wouldn't accommodate for this situation.

I'll try to take mine out today and replicate this. But I think you've uncovered what's going on.

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