Rpm runaway?

Does anyone else have this "problem" with their car? I'm not actually sure if it is a problem or why it happens but in between shifts the rpms seem to keep going until I get in the next gear. No I am not power shifting I let off the gas completely in between shifts. In this log I was shifting around 75-7900 but my max rpms on first and second gear were 8500 and third gear was around 8200! it seems the rpm jumps about 500. I don't think the car has a rev limiter tbh can that be the problem? Any ideas on why this happens it seems to high for comfort.

Clutch is slightly slipping.

Rev hang

Wheel spin when you shift

Same thing happens in my car, I'm pretty sure for that split second maybe the motor is unloaded and shoots up in RPM

As I understand it, the car maintains the high RPMs to make the shift smoother, AKA rev hang. Mine has done it since the day I bought it.

2017GBGTPP said:

As I understand it, the car maintains the high RPMs to make the shift smoother, AKA rev hang. Mine has done it since the day I bought it.

Click to expand...

Rpm Hang would make the engine stay at the same RPM, Not shoot up like the OP is saying. But yes these cars also do have rpm hang.

thanks for the many replies. I know what rev hang is I experienced it on my stock ecoboost and after I tuned it. I also experienced it on my stock gt and after the pp3 installed. But this is not the same as rev hang. The tune actually has basically zero rev hang as is my tuners style, which I don't mind just takes some getting used to shifting faster to be smooth.

It only happens when I'm really revving the car high that I have notice. like over 7k rpm shifts. I was told it's normal and the rpm don't drop as fast as I think it should but it just seems off to me. I don't think he can tune it out. I'm glad someone experienced the same thing at least.

It happened to me with my initial tune from Lund. Sent him a request for a revision and in a few hours it was PERFECT for what I was after. I HATE rev hang! And it would increase in rpm when I engaged the clutch to shift gears. Really annoying

The stock clutch diaphragm just doesn't have enough clamping pressure at that high of rpm. I honestly think it's clutch slippage. You could tell real quick if you log vehicle speed with the data you already provided. If vehicle speed went up during this rpm event in question, then you are spinning the tires ever so slightly. If vehicle speed doesn't increase, then it's your clutch slipping.

Here is an example log of mine. Stock clutch on a sticky bias ply. Blue line is rpm, orange is rear wheel/vehicle speed. The rpm peaks are shifts into 2nd, but most importantly 3rd, then 4th. Notice the spike in revs but the vehicle speed stays at a linear rate? My clutch is slipping...

here is a log with rpm, speed, torque source, and throttle angle. By comparing rpms to the torque source and throttle angle it looks like I'm off throttle and switching gears while its still increasing revs. I notice the throttle angle doesn't drop down to 0 in between shifts it will sit at 30% even though I am completely off throttle is that normal?

Firstly I'm not sure what "torque source" means?

In the last graph, first shift it looks like you've pushed the clutch in before letting off the throttle. Not much, but slightly. That plus the throttle not closing instantly (nor closing completely) might lead to the 350rpm increase?

You can see once power comes back on and clutch engaged that wheel speed spikes (wheelspin) as the rpms are dropping (from the load of the clutch coming back on and throttle going back up).

Seems like the throttle not closing 100% would be contributing. Not sure if that is a driver assistance feature (for shifting), an environmental measure, or an anti-choke / starve measure at higher rpms to prevent the intake charge "drying out" at high rpm.

Definitely on the second shift it looks like wheel speed drops before throttle is let go, leading to free-revving. Doesn't really seem to be a big concern, except that rev limiter should be stopping it from going too high, which you mentioned in the first post.

when its in torque souce 0 driver demand I'm on throttle. then it goes into torque source 16 dashpot torque source 9 target N inbetween shifts. it also looks like it went into torque source 4 tip in limit inbetween the 2-3 shift not sure why that happened but I think it shuts the throttle for an instant maybe due to wheelspin. But mainly I included it in the graph to help show when I let off the throttle. I could be slightly still on gas when clutching in but I never had this with any other tune and my driving style hasn't changed. what do you mean by free reving is that something that normally happens?

Free-revving is revving the engine in neutral (clutch in is effectively the same thing).

I also wasn't considering the disconnect between throttle and your foot (being throttle angle and torque source). I'm not familiar with ("new fangled") systems with various torque sources. Seems like you're getting those coming in when you're off the throttle, when maybe they shouldn't be? Or at least they might not need to be requesting as much if they should be coming in.

I'm also finding the start where torque source (aqua) and throttle angle (orange) a little confusing. It get 99.9% throttle open before it switches to torque source 0.


EDIT: I'm guessing torque source is the "most demanding" source for requesting torque from the engine. I think having throttle position on the graph would be better, in that regard, but it does seem like there's some other (non-driver) request for more from the engine. Seemingly invalid request at those RPMs too. It's a doozey, seems tune-related, but not just basic AFR / load stuff.