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Successfully? maybe......I was able to track my signal quality issues to the GM ignition module being flaky at high frequencies. Grabbed a dual VR board and I was in good shape.
I didn't have a lot of time to tune the traction control strategies before the event but my initial setup seems to be working well. Our current auto-x lot is small, bumpy, and has a very loose surface. It's almost a rally-x course honestly. Combine that with a turbo setup that can easily spin the tires into 2nd gear it was a hot mess. At these low speeds I was able to pretty much stab the throttle and drive the car out of the corners, acceleration would increase as I unwound the wheel and the back end of the car stayed in check. It was a very surreal experience honestly. I would have liked to experiment with increasing the allowable slip angle, if anything it might have been a little conservative. I still need to get some decent data logs to really see how the car reacted but below is a screen shot of my settings and the routine in action on a launch.
The pay off was that I was able to FTD at my regional event. If you listen carefully you can hear the spark cut coming out of the corners.
I'm going to keep tweaking the TC and see if I can make it better. I'll also slap some skinny tires on it or wait for rain to see how it does at higher speeds. I also need to log some tight turns to see if I'm getting the TC engaged prematurely or too early.
I found that I could get it to work at lower power levels and in the rain, but at full power if I got wheel slip it would blow through the spark retard, and spark cut is really violent and cuts boost.
I really want rolling fuel cut like the race logic box
That's strange you were seeing boost loss in spark cut, that's how antilag works, by putting unburned fuel into the exhaust it lights off in the manifold and spins up the turbo. If you watch the video you'll see the boost hang out at 10psi while TC is active and then spike up to my max of 14psi. (Bottom right on tablet) Would you mind posting your settings? Be interested to see how they differ from my setup.
Any thoughts on doing it as a stand alone TCS board? I’d be concerned about pulling spark without the ECU knowing what’s going on, but the risks of a missed injection cycle seem relatively minor. Will a Megasquirt lose it’s mind? Monitoring 4 VR sensors at 100+ and acting on that seems reasonable to put on its own board.
Any thoughts on doing it as a stand alone TCS board? I’d be concerned about pulling spark without the ECU knowing what’s going on, but the risks of a missed injection cycle seem relatively minor. Will a Megasquirt lose it’s mind? Monitoring 4 VR sensors at 100+ and acting on that seems reasonable to put on its own board.
I have that exact setup sitting in my junk drawer. I realized it would be way easier to just mod the firmware of the MS to do it. Still disappointed the latest released firmware doesnt have the source released like 8 months later. But I finished the hardware. 3 VR conditioner chips to get all 4 wheels and crank speed and a spare and 4 normally closed type mosfetts. I wasnt sure how to sync the fuel cuts with the ecu so it didnt cut part of a injection cycle, and then got lazy and busy.
Any thoughts on doing it as a stand alone TCS board? I’d be concerned about pulling spark without the ECU knowing what’s going on, but the risks of a missed injection cycle seem relatively minor. Will a Megasquirt lose it’s mind? Monitoring 4 VR sensors at 100+ and acting on that seems reasonable to put on its own board.
I assumed as much. Wasn’t sure if the race logic box used t feed back to the ECU. Leafy, isn’t it just an and function between spark cut and injector pulse?
Yeah, which is what Leafy and Aiden are talking about wanting. Cutting spark will give you unburnt fuel being dumped into the exhaust, which isn’t awesome. Especially with a turbo.
Cutting fuel is what you want to do. Its much better for the motor and the power delivery. And you want the cylinders cut to roll through the bank. I really think the way forward for all of us is to just use VR converters to get all 4 wheel speed sensors into the MS via digital inputs and run with custom firmware. Its going to be mildly annoying having to be at least 1 revision of the firmware behind and also have to only share our programs via code snippets that need to be copied and pasted into the code and then compiled but its better than any other ecu.
I get that spark cut is hard on hot side parts, but I find it to be smooth on power delivery. It's a progressive strategy that's tunable, the car never felt like it hit a rev limiter. I may be one launch away from burnt valves but it's worked for me.
I used this (very simple) circuit with my Adaptronic to read 2x ABS speed sensors via digital inputs:
I've not got as far as connecting it up to my MS3 to see it the MS will also read it OK though..
As an update to this - with the ABS sensors connected up via the above circuit, I can read speeds on the MS3, with a gotcha:
As soon as VSS1_ms goes over about 87 (raw VSS about 196), then VSS2 craps out. VSS1 is connected to PE2 Flex, VSS2 is connected to Datalog In. Is the sample rate of Datalog In lower, hence the drop outs about a certain number of pulses/second?
Doing some searching, it seems that some inputs are limited to approx 200Hz sample rate...
The other free options I have as digital inputs on the ECU are PT2, Tableswitch, Nitrous In, or a few of the ADC inputs, but I can't find out if these have higher sample rates or not. PT4 seems to be the one that a lot of people use, but I don't think it's built on the MSLabs basic MS3. Annoyingly, it actually has an onboard conditioner for an ABS sensor, but I can't tell what input it is (it's wired direct to one of the pins on the MS3 daughterboard), I can't find the pin list for the MS3 anywhere and Reverent's not answering his mails at the moment...
Send a pic of the board as I don't have any specific notes about which input this custom build used. My guess is that if VSS1 is on PE1, this one will be on PE0.
Rant. It gets slightly irritating when I I answer PMs and email for used units (I count 13 in this case) and the moment I don't answer one message or mail (and with no courtesy of a reminder - "could you please take a look at my previous email and reply when you have the time?"), I get publically called out. /rant.
Did some more testing this morning before the next auto-x tomorrow, man this traction control stuff is neat. I'm pretty happy with the spark cut as the 3rd line of defense. Dumb video I shot to test out the new mic setup and also capture the TC in action. The instances where I'm turning and on the gas I'm just flat footing it and letting the TC keep me out of the ditch. Also flat to the floor on the launch.
04-30-2018, 11:21 PM
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