RPM bounce after sequential gear change

[tricky1024]

hi all, hope we are all well,

have an issue with gear change with sequential paddle shift, gear changes up and down and working really well with an exception, i am getting rpm smoothing bounce after the gear change, happens both up and down but you can really feel it on an up change. you can also see ignition following the bounce. i would like to know how i could track down what might be causing it, i have attached a snippet from the log so you can see.

just wondering what i can actually log to see what is doing that.

[stevieturbo]

log as much as you can, as fast as you can.

Although pretty sure I see the same thing on a sequential with a manual flat shift.

Let's face it, a flat sequential shift of any kind as these boxes do is a pretty aggressive thing

Not sure why it would appear the way it does though.

[tricky1024]

thanks for the reply, i will log as much as possible as you suggest, i will play with the cut and ramp in as i currently dont cut any fuel so i might add in some fuel cut too.

[stevieturbo]

I doubt it is anything to do with cuts really, as all cuts will have stopped very early, and the rpm variations continuing long after.

Whether it's something of a concern, some sort of wind up in the drivetrain etc....no idea.

[littlefella]

Lots to check here, your lambda after shift, your ignition after shift, gear pot voltage, cut active etc etc, log at very high rate, 500hz min. you can sometimes dampen this with Ign retard on shift and then feed the ign back in at a slower rate. Def a problem.. Check your vehicle speed (logged at least 100hz) for a dip in speed on or after shift. I am guessing you are running full closed loop to gear voltage.. If it is a turbo engine check your MAP and your wastegate PIDs

[stevieturbo]

After viewing a log from another car, another ecu, regular manual low powered car.....it has a lot of wobbles.

Probably concerning over nothing really. ( and just to add, i bought the car with this ecu, I utterly despise AEM's software, and anything it is derived from !!! It will be going Syvecs soon )

aemlog wobble.jpg (586.38 KiB) Viewed 25015 times

[littlefella]

This is more what it should look like.. Paddle shift. probably a bit of overcut on the shift. Note no significant drop in wheel speed after shift

[stevieturbo]

So exactly what is the bounce, given I see it just on a regular manual car ? And from the nasty AEM log, not even always during a gearchange ?

I think it's a OE 60-2 trigger on this car.

[littlefella]

Steve, on the Syvecs log as it is long delta and for long period after shift I would say it is wastegate if the car is turbo's, otherwise possibly lambda corrections or if is is a car with a "rubber doughnut" type universal in the driveshaft and big power maybe the doughnut is beyond it's torque limit or if it is a spring type (Standard clutch) the springs may be beyond the torque limit, clutch centre will fall out soon if that is the case. No vehicle speed, MAP or Lambda in the log so difficult to say.
AEM, sorry but who knows and who cares, mystery pack on a good day

[tricky1024]

Just looking back over my logs for this issue and i just accepted that it happens, my speed increase is nice and smooth the wobbles in rpm are clear, i like the idea that is could be wastegate or lambda, i have a mega clutch in mine, twin plate carbon ceramic (switch lol) i still run the evo AYC rear diff but that is leaving soon for an LSD.

Mine could easily be trans or drive component as you can see it also occurring on the downshift.

How could we test to see if its the wastegate bouncing?

Screenshot 2023-06-26 142010.jpg (161.59 KiB) Viewed 24874 times

Screenshot 2023-06-26 143154.jpg (58.73 KiB) Viewed 24874 times