Watching a video of a McClaren launch and go down the strip with what seem like the ideal amount of wheel spin without losing tire or hooking too har d and bogging I had an idea.
Could you set up a system that only allowed RPMs to raise at a preset rate? IE motor is only allowed to go from 2k to 3k in .2 sec. If traction is broken, it will only keep accelerating at the preset rate. Idea being, that it should never fully break the tires lose to the point they reach the 'spinnings not winning' range where you would have to back off.
I know on some of the newest bikes they have controls that limit rate of slip between rear tire and front tire along with throttle adjustments bases on lean angles. Heck you could add in steering wheel angle to the car and limit acceleration, call it the Mustang feature, to keep cars from spinning while achieving maximum acceleration out of corners without the dramatic power cuts with traditional systems.
Could this be a mega squirt 4.0 feature?
Before I think much about your question, I have to congratulate you on your Mustang Feature.
Now that’s good humor!
AIUI, limiting the maximum rise rate of RPM (dRPM/dt) is what the launch control feature of a lot of aftermarket ECUs do. It doesn't need wheel speed sensors and it works OK for a drag strip where the car is going in a straight line and the behaviour is predictable, but it's not useful in general driving or autox.
Megasquirt has a traction control feature in it that does look at wheel speed sensors, but from what I understand (I haven't used it), it doesn't work all that well. I don't know why -- in principle it's got all of the data it needs, so it should just be a case of writing the software properly. I have a RaceLogic standalone traction control systems in my Miata that works by monitoring the wheel speed sensors and intercepting the fuel pulse signals to cut individual cylinders out, and it works quite well.
What if your car has a really nonlinear power delivery, or if it has weird bumps in the powerband where it accelerates harder through certain spots in the powerband?
Just to give you an idea of what others are doing, Hondata implements traction control using the ABS wheel speed sensors. You can adjust the wheelspin percentage via the ECU or by the little knob that comes with the add-on kit. It's really simple but it seems to work well in what few cars I've been in that have it.
https://www.hondata.com/traction-control-product
former520 said:
Watching a video of a McClaren launch and go down the strip with what seem like the ideal amount of wheel spin without losing tire or hooking too har d and bogging I had an idea.
Could you set up a system that only allowed RPMs to raise at a preset rate? IE motor is only allowed to go from 2k to 3k in .2 sec. If traction is broken, it will only keep accelerating at the preset rate. Idea being, that it should never fully break the tires lose to the point they reach the 'spinnings not winning' range where you would have to back off.
Launch control is generally another way to say power limitation, should be the last resort at the strip where the goal is quicker/faster.
A simple linear engine acceleration rate during launch would be far less than optimum. Cars with a clutch usually launch at an elevated rpm and generally lose engine rpm during the launch phase, their bog/spin problems are often more clutch or gearing related. With automatics engine rpm generally rises to the stall speed and then gains rpm slower from there, nowhere close to linear.
Aftermarket systems usually trigger off driveshaft/wheel rpm. But even using that, a pure linear accel rate leaves quite a bit on the table.
Also launch controls that compare wheel speeds don't work very well when the car lifts the front tires.
Grant
