Hitting rev limiter with supercharger

[CSG Mike]

Originally Posted by xsnapshot

I could see that. There has to be more to this problem. I've contemplated things like

1.) the throttle plate closing causing motor to quickly see a vacuum thus causing a change in the inertia of the system. (doesn't seem like a strong enough effect).

2.) something happening with the decoupling of the drivetrain from the motor

I don't really have a good answer for this.



The way I understand it, mathematically, when you remove the torque from the motor, you would accordingly have zero Jerk and Acceleration. It still has an inherent velocity of course. If you had drag on the system then you would have a deceleration upon removal of the torque. (and whatever corresponding jerk would be due to that drag force)

I can't see any single combustion event raising RPM's as much as you are seeing. That's quite a rise...400 RPM.

According to your data it's happening for 1/10th of a second. At ~7000 RPM that means the motor is accelerating for 11 revolutions beyond the limiter.

What kind of rev limiter do you have in the S2000? A hard rev limit? Ignition cut? Fuel cut? Soft rev limit?

Would you happen to know if a soft rev limiter would fix this problem? I had that NA and on the rare occasion I hit the limiter, it sure seemed a lot "nicer" on everything than the hard limiter.

The S2000 hard cut is an ignition cut. Have no need for a soft limiter on that car, since it's a stock engine with just a tune.

A soft rev limiter can fix this problem, but the peak RPMs seen will still depend on how quickly you are approaching the limiter, and how exactly the limiter is implemented.

[whataboutbob]

Just for reference, I have the Innovate with a 69mm pulley, FF, header, etc, and an AT. I also have a FD change to 4.556. I have not adjusted the redline on my car. When I drive aggressively in full auto the car will hit the rev limiter before making the upshift.

[Ultramaroon]

Originally Posted by CSG Mike

Some more data for you

The hard pivots are from the data being recorded at a slower rate; you're correct in that many channels are 10 and 5 hz. They're the ones I usually don't really need to worry about, so are polled lower.

The data here is mostly at a higher poll rate, but unfortunately it's super old before I started logging everything at 50+ hz. It's from the same data set, but zoomed in more.

What do you think? I'm still under the impression it looks like the engine was unloaded before the throttle had closed enough. The MAP channel seems to support that but I don't think it supports my idea about the latency. Hmmm...

It also looks like you are nice to the clutch - the wheel speeds get a nice bump from engine inertia and then you get back on the gas.

[CSG Mike]

Originally Posted by Ultramaroon

What do you think? I'm still under the impression it looks like the engine was unloaded before the throttle had closed enough. The MAP channel seems to support that but I don't think it supports my idea about the latency. Hmmm...

It also looks like you are nice to the clutch - the wheel speeds get a nice bump from engine inertia and then you get back on the gas.

I don't drive anywhere near as hard or as abusively as people would like to think... You don't get cars to driven if you're breaking them

[Ultramaroon]

Originally Posted by CSG Mike

I don't drive anywhere near as hard or as abusively as people would like to think... You don't get cars to driven if you're breaking them

I never had that impression. You're fast because you know how to drive properly more efficiently than the rest of us. Beating the piss out of it would be the exact opposite.

These data are interesting. I need to break out my Tactrix.

[FRSBRZGT86FAN]

Originally Posted by Freeman

I don't think anyone has cracked or maybe even bothered to crack the computer for the A/T yet. You might look into SSP and their offerings for the A/T.

Yup, no one has even touched the TCM

[TacoTacoBear]

Originally Posted by wise345

Just use manual mode and paddle shift. It's like a manual minus the fun

Kind of curious but wouldn't the general limitation still be the torque converter? I know that was a common problem in my last form when people tried to go FI on auto gearboxes.

Sorry not too well informed on FI, just shooting back on what I've read over the years. Been thinking about picking up a 2nd car with an auto gearbox for stop and go commutes. Driving a stick through Austin was pretty brutal lol.

[wise345]

Originally Posted by TacoTacoBear

Kind of curious but wouldn't the general limitation still be the torque converter? I know that was a common problem in my last form when people tried to go FI on auto gearboxes.

Sorry not too well informed on FI, just shooting back on what I've read over the years. Been thinking about picking up a 2nd car with an auto gearbox for stop and go commutes. Driving a stick through Austin was pretty brutal lol.

hmmm good question maybe someone with an auto FI car could chime in?

[whataboutbob]

The torque converter, when it is healthy, does not slip in 2nd-6th. I've put nearly 94K on mine, boosted since 34K, and it is still doing good. This includes numerous autocross events on r comp tires while being driven in manual mode.