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Old 06-16-2016, 05:58 PM   #1
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Default Launch control with SPST switch

Wired up my launch control with a SPST switch lastnight but have some issues with it. Wondering if I have installed something incorrectly and get some general input on my method for control of the circuit.

I want to run Launch control and flat-shift but, I want to be able to engage/disengage it with a switch. It was easy enough to wire in my DIYPNP by going from pin V1 to ADC1 and enabling in the software but I can't seem to get it to disengage when I turn the switch to the off position. I am not near as confident in my ability to understand the electrical side of engine modification as I am in the mechanical side of things. So I drew out how I went about wiring it in. Is this a valid way of controlling the LC/FS circuit or am I doing it incorrectly? This is on my 1990 base Miata.
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Launch control with SPST switch-90-93-launch-control-spst..jpg  
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Old 06-16-2016, 06:07 PM   #2
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If you interrupt the megasquirt's signal to ground it will not be able to tell the clutch switch is pressed and launch control will not work. A switch is kinda pointless though, just use something like 80-90% TPS for launch and it won't bother even the roughest rev matching.

If I had to guess your switch isn't interrupting the signal line like you think it is, or you tied the switch to ground. Without a dead short in the switch I'm not sure how one of the two positions isn't killing it though...

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Old 06-16-2016, 07:16 PM   #3
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Originally Posted by deezums View Post
If you interrupt the megasquirt's signal to ground it will not be able to tell the clutch switch is pressed and launch control will not work. A switch is kinda pointless though, just use something like 80-90% TPS for launch and it won't bother even the roughest rev matching.

If I had to guess your switch isn't interrupting the signal line like you think it is, or you tied the switch to ground. Without a dead short in the switch I'm not sure how one of the two positions isn't killing it though...
I was reading some posts earlier about setting TPS way up in the 80-90%. I am just not sure how much throttle I want to give the car during a launch, so I figure with a switch I can be pretty conservative with TPS iinput and still get the benefits of launch control. I'll be testing it tomorrow at our local 1/8th mile strip. As for the switch issues I am going to chalk it up to a faulty switch and try another SPST switch today. Just making sure my logic wasn't bad when building the circuit, thanks for the helpful reply.
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Old 06-16-2016, 08:11 PM   #4
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Quote:
Originally Posted by 90civichhb View Post
I was reading some posts earlier about setting TPS way up in the 80-90%. I am just not sure how much throttle I want to give the car during a launch, so I figure with a switch I can be pretty conservative with TPS iinput and still get the benefits of launch control. I'll be testing it tomorrow at our local 1/8th mile strip. As for the switch issues I am going to chalk it up to a faulty switch and try another SPST switch today. Just making sure my logic wasn't bad when building the circuit, thanks for the helpful reply.
You always launch at WOT. That's like, the whole point. lol. Use timing retard to control wheel spin.
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Old 06-16-2016, 08:51 PM   #5
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Originally Posted by Schuyler View Post
You always launch at WOT. That's like, the whole point. lol. Use timing retard to control wheel spin.
Yeah, after just trying it out this is the best option. It's crazy being able to launch in boost.



So the issue I am having is the that launch control is never disengaging. In other words, when I launch the car (MS set to launch only) the car pulls hard for a split second and then it's like launch control activates again and cuts spark. I even tried to just drive it around and regardless of the RPM I am at, once I high target TPS it cuts spark. This is stock wiring configuration, no switch installed.

Last edited by 90civichhb; 06-16-2016 at 09:27 PM.
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Old 06-16-2016, 09:01 PM   #6
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Quote:
Originally Posted by 90civichhb View Post
Yeah, after just trying it out this is the best option. It's crazy being able to launch in boost.



So the issue I am having is the that launch control is never disengaging. In other words, when I launch the car (MS set to launch only) the car pulls hard for a split second and then it's like launch control activates again and cuts spark. I even tried to just drive it around and regardless of the RPM I am at once I high target TPS it cuts spark. This is stock wiring configuration, no switch installed.
Sounds like you have no speed signal.
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Old 06-16-2016, 09:05 PM   #7
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Originally Posted by Schuyler View Post
Sounds like you have no speed signal.
So from the research I have done are you referring to a VSS signal? I have read that is not an issue for the 90-93 cars.

Although others have tried it.

https://www.miataturbo.net/aem-59/la...rol-you-48648/

Last edited by 90civichhb; 06-16-2016 at 09:24 PM.
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Old 06-16-2016, 10:28 PM   #8
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Wow, this is getting pretty crazy now. I just took this video of what launch control is doing on my car. I would love some input from anyone that has had an issue like this, which, I fear is probably no one.

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