I saw an interesting post in a discussion about MXL2 screen configurations about tracking PSM intervention. Wheel speed differences were suggested as a measure of PSM intervention. Any thoughts on how much of a difference is meaningful to identify intervention?

 

If you can get individual brake calliper pressures, that's a clear indication of PSM intervention (unless it's inside rear wheel, which is PTV)

 

@Ubermensch , it’s more a rate of change that indicates activation.

You could build a status variable or a trigger command (take a look at Robinson Shay’s 2-11 video on YouTube on AiMSports LearnFast channels) to log or display this status variable change.

 

Maybe you could expand on your idea? I'm not sure a status variable would do what you want (any different than math channels or alarms) and trigger commands aren't available on the MXL2. The trigger command would be an interesting use as I don't see changing the dash page, requesting a button hit, or resetting an alarm helpful.

 

That would be handy, and the most specific, but I'm not aware of any Porsche vehicles with caliper specific pressure sensors. I'm guessing I could rig something but not sure I'm willing to go to quite that much effort. I was hoping for something using existing sensors like wheel speed.

 

I'll look into the rate of change idea. I can certainly calculate that after the fact but so far the limited math channel capability of the mxl2 had been a bit disappointing for real time calculations. I'm not familiar with the status variable function. I'll check out that video.

Matt, any other suggestions or tips?

Thanks!

 

991.1, 991.2, 981 and 718 cars all have individual brake pressure sensor channels for all current AiM loggers.

The cars have to have this information to actuate the PSM.

 

Ha! You learn something every day! I'll check those out on my 718.

I should have been more specific that My original question was regarding a 987.2.

Thanks for all the replies

 

There is no way to do rate of change in the dash. You could do slip a few different ways (bias is probably easiest) and then set an alarm if it's out of some range. What is the range? I would look at some data and try to figure out where it is. I personally don't have a number to give you that would say the PSM would start intervening.

 

Brake caliper pressure is the way to go; smaller interventions can readily cause less wheel dynamics than you'll experience from just hard driving on track (especially features like curb strikes), so merely looking at wheel speed or wheel accelerations would be an extremely crude measure of activations. You'd almost be better off looking at pump motor activation.

That said, some other options to consider... depending on the project, if the dash warning light is activated from interventions you could consider looking at that on CAN. Though again there can be small interventions that are below calibratable thresholds to even activate the light. If it's not even outright suppressed during sport modes, which is quite common. However, independent of dash lamp activation there may also be signals on the (CAN) bus that straight-up indicate ESC/PSM interventions.

Another one to consider is engine torque reductions, separate from brake interventions. Again, depends on both your project and what mode you're running in, but it may be appropriate to monitor the TCS engine torque reduction request, definitely should be on the bus, since that's how the request is usually communicated to the engine controller...

Hope that helps with some ideas...

 

Thanks for all of the suggestions. Honestly I started down this path thinking it would be fairly easy and modestly interesting. That's a good ratio of cost/reward. From what you guys are saying it's not going to be easy, and frankly I'm not sure I'd do much with the information so I'm going to put this one on hold. PSM is rarely if ever intruding in a way that I notice, but I thought it might be interesting to catch it in the act and understand what's happening in the moment. I'll try looking at my past data and see if I can see any more subtle interventions based on wheel speed, but the point about other things impacting wheel speed is well taken.

Shawn

 

Shawn, agree 100%, this is true for a lot of the more arcane measures.

If you had a later model car (2012/3 on) with individual brake pressures, that would be the easy button.

Realistically, you're trying to validate what you feel with your butt gyro. Then, you can craft exercises to incrementally lessen or even increase the intervention. Then, you can measure again to see if there was improvement. Or not...

But, I will tell you that 99 44/100% of drivers have SO MUCH MORE to work on than this...

Great thread, though.