Launch Control...how to?

[towerymt]

MS&S-extra 025v, no daughtercard. I want launch control. From my research, it would appear that I don't need the daughtercard, but that it would make it a little easier.

I've tried to do the research and figure it out on my own, but I don't want to make a wiring mistake and fry the board (several times that has been mentioned regarding the 5v input).

http://www.msefi.com/viewtopic.php?t=11425:

On v2.2 you can find +5v on the JP1 row of holes beside the CPU. 5v is right by the letters JP1, 0v is the next one up.
On v3 +5v and 0v are clearly available on the proto area.

But, if you build it externally, use the TPS +5v supply, pin 26.

Be sure to never connect this input wire to +12v or you will destroy the Megasquirt CPU.

I usually just use the internal pullup and put an inline resistor on the wire connecting the pin to the ground switch.

http://megasquirt.sourceforge.net/extra/pix/LaunchIn.JPG


http://www.msefi.com/viewtopic.php?t=11962

I'm looking for some interpretation and explanation as to how to go about wiring this up the best way. 5v from the TPS pin 26? No problem there. What/where is JP1 pin4? This, I have no idea about. For the clutch switch, I was thinking about instead using a thumb switch, perhaps an M46 shift knob w/button.

[Matt Dupuis]

http://www.bgsoflex.com/v22/Megasquirt_LayoutV2.2.pdf

Page 3, to the right of U1 (the main chip). Basically, you'll be connecting JP1 pin 4 (fourth from the bottom) to the shifter mounted switch, and then the shifter mounted switch goes to ground. JP1 pin 1 is the 5v supply that he's talking about (closest to the lettering "JP1"), which you then run thru a 2.2 kohm pullup resistor and then to the wire between pin 4 and the switch.

Whenever the button is NOT pushed, JP1 pin 4 sees 5 volts and disables launch control. When you push the button, you ground the circuit and the circuit goes low (~0 volts) and launch control engages. The pullup resistor protects the 5v circuit by limiting current while the button is pushed.

AFAIK, there are two ways of selecting launch control: The first way is to "hard program" the rev limiter, so that every time you push the button, it limits revs to the RPM you've preselected. The second way is to rev the engine to the RPM you desire, push the button, and mash the throttle. When you push the button, you load that RPM value into memory and clear the last RPM value. Useful if you're doing some drag racing, 'cause you can select a burnout RPM, then a launch RPM, and then use it to flat shift if you desire. Also lets you tune your launch by adjusting RPM at the line, based on how long your burnout was, how long AGO your burnout was, what the temperature and condition of the track is, etc. If you're hard programming it, it's alright to use a clutch pedal, but then you need an arm-disarm switch to allow you to double clutch and heel-toe. If you're using the other method, it's best to have the switch not connected to the clutch pedal at all...

[towerymt]

derka, derka

http://mason.gmu.edu/~mtowery/konica/PICT1066_jp.jpg

So I guess I'll just run a wire from jp1 pin 4 to the db37 connector and from there to the switch...worth a shot.

[Matt Dupuis]

Um, no. JP1 pin 4 goes thru a resistor to supply +5 volts to JP1 pin 1. When you ground the switch, you're grounding the circuit and because of the resistor, JP1 pin 1 sees ground. That's when launch control engages. Running JP1 pin 4 to the switch and then to ground without the resistor will probably fry the 5V regulator circuit, and even if you add the resistor it won't get you anywhere 'cause it's JP1 pin 1 that triggers launch control.

[towerymt]

Yeah sorry, I know there's a resistor required to protect it. I just didn't mention it when I was thinking outloud.

And I thought jp1 pin 4 was the one that triggers launch control, not jp1 pin 1. The way I read it initially is that I could get 5v from jp1 pin 1 (he said the one nearest the letters "JP1", didn't actually say pin 1, but I assume the numbering starts at the letters and goes up). Or I could just pull 5v off my TPS wire (pin 26 off the DB37). If I do that, jp1 pin 1 shouldn't even be used.

I should run a wire from jp 1 pin 4 to the switch. Just to get this wire outside of the case, I was going to run it through an open pin on the DB37 (I thought that's what was proposed here: http://www.msefi.com/viewtopic.php?t=11962 ) Then I either feed the 5v with inline resistor from inside the case at jp1 pin 1, or from outside the case from pin 26 TPS.

[Matt Dupuis]

Shoot, sorry - got my pins mixed up. Pin 4 is to trigger launch control, pin 1 is +5v, resistor required. Other than that, you're on the right track. You can't just connect pin 4 to ground 'cause it won't do anything - you need the pullup resistor to supply some volts to the signal when the button is open, so that Megasquirt knows when you close the circuit and ground the switch.

You could use the TPS if you like, but it's easier to use it inside the case, IMHO. Just a 2k2 resistor bent over to bridge JP1 pins 1 and 4, and then solder the wire from the DB37 to the pin 4 side of the resistor.

[towerymt]

Sounds good. Got the resistor tonight, might have it operational tomorrow...

[Matt Dupuis]

Make sure you let us know how it works, Michael. I couldn't use it 'cause I had EDIS and can't drop sparks, and when I tried retarding it as far as it would go (-10) it wasn't enough to really hold back my engine.

[tmyrewot]

problem...hooked it up on rob's, hit the switch, and it flashes "knock" lit in red on the lower right on the megatune screen. right next to it is the "launch" box that should be lighting up, but it's not. so somewhere we've got an output set incorrectly or something. been sifting through MS pages trying to find something, but no such luck.

[Volvorules]

Well, we got it to work. Apparently on my board (not sure about others), the JP1 pin 4 is not actually the 4th pin from the bottom, but it is the 5th one. After installing the switch, the KNOCKING indicator would come on when the switch was flipped. So we knew something was up. I checked out the wiring schematics, and decided to try moving the resistor one pin away, to pin 3. Hooked it up, and now the NOS light came on, but not Launch control. Damn, wrong way. So hooked it to pin 5, and sucess. Verified the settings under the launch control menu, and tested it - voila! It works!!! Makes some loud ass popping and lots of black smoke :) I still have a catalytic converter hooked up, now time to make a test pipe and see if I can get some flames.

I'm glad Michael and I were able to figure it out, especially without frying the MS :)

[Poik]

We need video. That's awesome that you got it working though, I can't wait to do the same on mine :)

[towerymt]

We need video. That's awesome that you got it working though, I can't wait to do the same on mine :)
I'll get some compressed .mov vid on my still camera tomorrow. Might have to drop the cat/muffler off so it will (hopefully) shoot fire. For now it's just loud and kind of smokey. And loud.

[Poik]

Aww but I want it now.. It's dark there now eh? I bet the flames would show up better.. :)

[towerymt]

Aww but I want it now.. It's dark there now eh? I bet the flames would show up better.. :)
There were no flames. So you'll have to wait...if you want flames that is. I bet mine will dump flames when we drop the catback. :-D

[Matt Dupuis]

Hum, shoulda thought of that too. Glad you got it figured out, glad it works, glad you didn't blow up your exhaust by being irresponsible and doing it with a cat in place for too long.

[towerymt]

So perhaps that first pin is 0, then 1, 2, 3, 4, .....? I couldn't find a good diagram.

[towerymt]

http://mason.gmu.edu/~mtowery/konica/PICT0343_launch_.jpg

[the poi]

The square pad is pin1. You're pulling the 5v from jp1-8.

[Volvorules]

Well, that would explain it then...damn, I figured it would count upwards. Never really realized which was 1 :)

Thanks, now there's a reason for it working!!!

[Poik]

Haha, oh **** that's funny. Lucky you didn't fry something :)

I just got my daughterboard kit parts so tonight I'll be soldering up all those options, sweeet :)

[towerymt]

Haha, oh **** that's funny. Lucky you didn't fry something :)

I just got my daughterboard kit parts so tonight I'll be soldering up all those options, sweeet :)
I was there to protect things from frying. I figured that if he moved to another pin, leave the switch closed so that it's just grounding whatever pin is triggered. That way if we find a pin that's already grounded, no frying. If it's an active pin, it will be triggered and show us something is activated (which is what happened, just the wrong function, so moved it again, and it was right).

[towerymt]

And now for audio (and some video)

This is the best clip I got I think. ~2.5mb, ~6sec

http://mason.gmu.edu/~mtowery/konica/PICT0358.MOV


This one has some good fire, it's shorter, and less than 1mb.

http://mason.gmu.edu/~mtowery/konica/PICT0360.MOV

[Poik]

SWEEEEET sounds like a damn dragster about to take off! How many RPM is that, and how much timing are you pulling? I can't freaking wait to just do that at a stop light or something hahaha

[towerymt]

I think it was 2800 to start the ign. retard, and 3100 hard cut (the two rpm choices in the launch control window). Then I think the spark drop was 4 of 5. Then I think he changed it later to 3 of 7 or something like that, and it was more stable.

I'm not certain, but I think by spreading the rpm a little, it hits 2800 and starts to slow down from ign. retard, then hits 3100 and drops spark (hard cut). If I'm correct, then that's the hesitation you hear before it starts to pop.

Yesterday in the preliminary testing, I saw 10psi come up VERY quick. Play with the rpm for your launch point, and adjust the the rpm spread, ign. retard, and spark drop controls to fine tune it.

Played with traction control a little bit tonight (it was wet/raining, hence no launch attempts from the turbo car with hard 195/60/15 place holders on the back while it's getting body work done). On my car, we could get it to really hold back the power on a clutch drop in the wet such that it would actually control wheel spin and the car pulled forward pretty well (w/o, it would spin in place easily). But as the rpm climbed, it started cutting power when I would have had traction. Wouldn't be able to rev match downshifts with a purely rpm based traction control system. If I just plant my foot in neutral with a 1000 or 2000 rpm-per-second limiter, it jumps in rpm, bogs, jumps rpm, bogs, jumps rpm, etc. rather quickly, but also harshly. Again, it would take some fine tuning. I might (unlikely) turn it on and play with it at the autocross on sunday if it's wet and I'm on hoosiers. But I predict turning and braking will be far more difficult that throttle control, so I may not mess with it. Just hoping for dry weather.

[Matt Dupuis]

Last time I played with it, traction control was completely unuseable. It's there mostly as a template, AFAIK, so that other coders can play with some other stuff.

Where TC will become a bit more handy is when you hook your speedometer wires to it, and actually give it a VSS input. Then it won't care a whit about the engine RPM climb, but rather limit your rear axle to a maximum acceleration. If you had an ABS front hub, you could double the effectiveness of TC by deriving ACTUAL slip from the rear wheels.

I installed an '85+ axle in my car expressedly for this purpose, but never got around to wiring it. Later on, I planned on using the cruise control sender on my T5 transmission, but now I think I'll be switching EMS anyway.

[towerymt]

To me, it seemed like a bit of a novelty feature. I'll have fun playing with it today in the wet, but probably won't get what I want from it.

I was thinking that it could possibly be useful in autocross. As long as I can pull through first gear w/o it kicking in, get into 2nd gear, I probably won't have to shift again. So if I were a coder, I could put a switch on the shifter and only activate it out of 1st gear, or in 2nd gear. Then I just have to tune it for wheel spin in 2nd, which seems plausible to me. Helps to have a heavy flywheel and slow car I bet...it just doesn't gain rpm quickly in any gear but 1st.

[Poik]

Get a microswitch like a WOT switch for nitrous, and mount it near the shifter so the arm is only touched in first. They have 2 outputs, one to open and one to close the circuit. And then just run that between the clutch switch and MS. You could also wire up a bypass switch so that you could use it in 1st if you want.

[towerymt]

Get a microswitch like a WOT switch for nitrous, and mount it near the shifter so the arm is only touched in first. They have 2 outputs, one to open and one to close the circuit. And then just run that between the clutch switch and MS. You could also wire up a bypass switch so that you could use it in 1st if you want.
Either I'm not sure what you're trying to explain to me, or you've mixed the two systems.

Launch control works (other people say so). Launch uses the clutch switch.

Traction control is just software. If rpm climbs too fast, it cuts spark or retards ignition. In order to turn the traction control off with a WOT switch on the shifter, I think I would need to write code, tell it where to look for the signal, and provide a signal to the board. More than I'm able to do. But like Matt said, the template is there for those who can code.

[the poi]

Actually, phil is running VSS input traction control. i haven't heard much of it other than that it works and not many others have tried it.... i havent looked into it recently though, so i dunno if the inputs necessayr would take up pins for other, more important functions

[Poik]

Ah, yeah, my bad, thought we were still talking about launch control :) Thought you meant you wanted to use it in auto-x for anti-lag in all but 1st gear.