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M1tch

Need a quick hand with launch control

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Hi all,

Just in the process of trying to get launch control sorted for my car, digital input 1 is the speed signal, 1 hz is about 1 mph, think it over-reads slightly, basically I can't use it as a wheel speed as the ECU can't use the signal as given (the signal is from the ABS ECU so is already converted to a MPH pulse). Anyway, I think I can still use it to flag when the car is stationary vs moving as the driven speed goes from 0kph to 360kph for 1hz on the signal - basically trying to set the limiter to say 3k RPM for launch, then unlock to the full RPM limiter as soon as I am moving. Eg '0kph driven = 3k limit, more than 0kph driven = full 7k rpm limit'.

I have attached both the current mapping file and a recent log from earlier today (with the CLL off), looks like I need to tidy up - basically around 3,100rpm and 40KPa is steady cruise at 70 - think its running at around 13.8:1 so need to lean that out slightly.

Can anyone help me and add in launch control? I have tried before but the car just revs past the RPM limiter all the times I have tried.

Thanks in advance!

feb.pclr Log 2019-02-21 1;50;59 pm.llg

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You'll need to amend the "Calibration DI #1" value to the correct number of pulses per 100m

You can try to calculate it, or just try giving it a big change, such as to 100, 200, 300 etc until it gets closer to the correct speed, then make smaller changes to dial it in.

For reference, I've got calibration values of  236 and 906 for my front and rear speed sensors, but these are reading from the diff-prop mounts, and the back of the hub on the 4 bolts holding the brake disk on, so I don't know if these values will be anywhere near for you, but to show that there is quite an applicable range for the Calibration value!

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1 hour ago, Confused said:

You'll need to amend the "Calibration DI #1" value to the correct number of pulses per 100m

You can try to calculate it, or just try giving it a big change, such as to 100, 200, 300 etc until it gets closer to the correct speed, then make smaller changes to dial it in.

For reference, I've got calibration values of  236 and 906 for my front and rear speed sensors, but these are reading from the diff-prop mounts, and the back of the hub on the 4 bolts holding the brake disk on, so I don't know if these values will be anywhere near for you, but to show that there is quite an applicable range for the Calibration value!

The ABS sensor signals go into a separate ABS ECU, the ABS ECU then sends a signal to the ECU which the DI#1 is taking a signal from. All of the calculations are done in the ABS ECU to output the MPH figure rather than the larger number of pulses from the actual ABS reluctor rings (although I will need to tap into the ABS sensors directly to sort out traction control in the future as I need driven and non driven speeds).

1 pulse from DI#1 = 1mph

1 mph = 1.609 kph = 1609 metres per hour

Guessing if I chop that value down by 100 I guess my starting calibration would be 161?

The alternative calculation if I were to tap into an ABS sensor would be to use the teeth count, I believe my car runs a 48 tooth ring, using the help file it would be:

(48/1.88468)*31.83 = 810

I can't use that figure as its above the maximum of 500?

Looking at the log of the last drive it shows the DI#1 value at 1hz with a speed of 360kph - I guess I could also try 360 as a calibration figure to start with?

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From what youve said about that log being approx 70mph, try 224 as your calibration number for DI1. should put you in the ballpark.

Then grab a gps/phone and a straight road or dyno  and a friend, hold the speed steady on the GPS, then have your friend bump the number up/down until it matches.

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3 hours ago, cj said:

From what youve said about that log being approx 70mph, try 224 as your calibration number for DI1. should put you in the ballpark.

Then grab a gps/phone and a straight road or dyno  and a friend, hold the speed steady on the GPS, then have your friend bump the number up/down until it matches.

Thank you, will check to see how close that figure is, hopefully then I can work out launch control!

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On 2/23/2019 at 6:14 AM, cj said:

From what youve said about that log being approx 70mph, try 224 as your calibration number for DI1. should put you in the ballpark.

Then grab a gps/phone and a straight road or dyno  and a friend, hold the speed steady on the GPS, then have your friend bump the number up/down until it matches.

Just wanted to thank you for your help on this, that calibration figure seems to be about right! Also looks like the ECU has worked out the gear number as well which is great :)

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