How the hell do you use launch control? - Miata Turbo Forum - Boost cars, acquire cats.

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Old 05-07-2009, 01:18 PM   #1
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Default How the hell do you use launch control?

I just got LC hooked up and enabled. Set to the default 2500 RPM I just waste the tires unless I'm really feathering the clutch. I'm finding it much harder to launch consistently. Is there some sort of trick to this?
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Old 05-07-2009, 01:22 PM   #2
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Is the "Launch" indicator illuminating in MegaTune (at the bottom of the screen) when you're in launch mode?

(also, off to the MegaSquirt section with this thread.)
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Old 05-07-2009, 01:37 PM   #3
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Quote:
Originally Posted by Joe Perez View Post
Is the "Launch" indicator illuminating in MegaTune (at the bottom of the screen) when you're in launch mode?

(also, off to the MegaSquirt section with this thread.)
Seems like he's asking more about proper launching technique rather than how to set it up.
Is it bouncing off your rev limiter at 2500 correctly?
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Old 05-07-2009, 01:38 PM   #4
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Not sure. I wasn't looking at the screen. The functionality of the hardware is not in question, though. It is working. Limiter kicks in at 2500.

I'm just not sure how useful the feature is, considering I have traction problems off the line even without LC.
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Old 05-07-2009, 01:41 PM   #5
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Sounds like you need better tires. LC isn't going to make up for a gross lack of mechanical grip.
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Old 05-07-2009, 01:42 PM   #6
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Azeni RT-615. Thought they were pretty good until now.
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Old 05-07-2009, 01:47 PM   #7
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I guess what I'm asking is: Is burning the hell out of the clutch really the way LC is used? Otherwise I really don't see the usefulness of the feature. Maybe lowering the setpoint to, like 1500rpm?
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Old 05-07-2009, 01:54 PM   #8
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Quote:
Originally Posted by bryanlow View Post
Azeni RT-615. Thought they were pretty good until now.

Not for drag racing.

Untill now meaning hooking up launch control? Or now as in turbo charging your car?

Try throwing some ET radials on and report back on the usefulness of LC.


Keep in mind LC is not traction control. It does one specific thing, which is give you a second rev limiter when you've got the clutch in. It's not going to stop wheel spin if you dump the clutch at 2500RPM where you'd have wheelspin without it at 2500RPM.
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Old 05-07-2009, 01:58 PM   #9
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Quote:
Originally Posted by bryanlow View Post
I guess what I'm asking is: Is burning the hell out of the clutch really the way LC is used?
Yes, that's what launch control is for.

There are basically three ways to launch a car that I'm aware of.

1: Let out the clutch nice-n-easy with minimal (or no) throttle application. Easy on tires, easy on the clutch, slow.

2: Floor the throttle, release the clutch, resulting in wheelspin. Hard on tires, hard on the clutch, slow.

3: Launch control: Floor the throttle and have the computer hold it at a fixed RPM while you release the clutch, such that wheelspin is reduced or eliminated. Hard on the clutch, easy on the tires, fast.

If you're still getting wheelspin with RT-615s (and they're not old and hard) then congratulations- you have a manly engine.

Start by decreasing the ignition timing in launch mode even further. I believe the default is -10 (which is 10 BTDC) so try moving it back to -5, or even 0. If that does not cure it, try reducing the limiter RPM until wheelspin is eliminated. You'll come out at a lower RPM, but the turbo should still be fully spun up.
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Old 05-07-2009, 02:01 PM   #10
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not even good tires and i can dump it just fine with a little spin:

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Old 05-07-2009, 02:03 PM   #11
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Launch control, thats like a wheel chair for someone who can walk.
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Old 05-07-2009, 02:03 PM   #12
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Fastest way off the line when I had LC hooked up was to set the limiter at around 3500, and then engage the clutch enough to get off the line, but not enough to let the LC turn off. Wait a split second while you let the car catch up with the tires at 3500rpm, then step off the clutch, turn off the rev limiter, and let it rev 1st gear out completely.

If you just feather quickly, then step off, it's a great way to lay long stripes to impress your friends. Not fast, though.
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Old 05-07-2009, 02:04 PM   #13
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Originally Posted by Braineack View Post
not even good tires and i can dump it just fine with a little spin:
Slow. You can hear it bog.
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Old 05-07-2009, 02:38 PM   #14
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Quote:
Originally Posted by Savington View Post
Fastest way off the line when I had LC hooked up was to set the limiter at around 3500, and then engage the clutch enough to get off the line, but not enough to let the LC turn off. Wait a split second while you let the car catch up with the tires at 3500rpm, then step off the clutch, turn off the rev limiter, and let it rev 1st gear out completely.
Not sure if I understand this completely but this may be part of the problem: You can engage the clutch w/o turning off LC. I'm using the stock clutch switch which closes long before the engagement point. Therefore I'm sitting on the line at 2500rpm and as soon as I start to pull the clutch, rpms are starting to rise. I'm still having to find the engagement point and feather to prevent wheelspin as if I wasn't using LC at all. Sounds like I need to adjust the switch. Savington, did you pull the LC for a reason? How about flat shift? I'm guessing the most useful part of the LC function is flat shift.
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Old 05-08-2009, 03:47 AM   #15
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Are you using spark cut only or spark and fuel? Spark cut by itself is too aggressive for me regardless of what tires I'm running - it builds too much boost. I switched to spark and fuel cut, and that was the sweet spot for me (6psi).
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Old 05-08-2009, 04:27 AM   #16
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Quote:
Originally Posted by bryanlow View Post
Savington, did you pull the LC for a reason? How about flat shift? I'm guessing the most useful part of the LC function is flat shift.

Track cars dont need flat shifting.

Its more of a "fun, hey look what my car can do" kinda thing to me. I do not ever plan to seriously drag race the car but its fun to crack it open every now and then.

I used my flat shift a few times @ laguna. It doesn't make me any faster. Only fun.
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Old 05-08-2009, 05:32 AM   #17
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I decided the minimal time drop just wasn't worth the added abuse to the drivetrain.
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Old 05-08-2009, 10:46 AM   #18
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I might have something to contribute to this thread if I'd ever sorted out why my launch control doesn't work.

Quote:
Originally Posted by thesnowboarder View Post
I used my flat shift a few times @ laguna. It doesn't make me any faster. Only fun.
You should have seen some of the other workers ducking for cover and questioning the health of the offending car when you'd go by on the front straight and blow shotgun shells out of the exhaust!
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