Setting Pit lane speed limit on M150 for use in Tarmac Rally

I am competing in the GT outright class of Targa High Country and want to set a pit lane speed limit of 200KPH on my Motec M150, as that is the outright speed limit that has now been introtuduced. Can anyone help please?

Sorry, can't help - however it may help if you state if it's a mechanical throttle, which will need a fuel and/or ignition cut, or an electronic which should be able to be backed off at the limit.

Hi Gord,

Thanks, it is a drive by wire throttle on a 2017 Lotus Exige. I am sure it is just a setting on the tune as it has been done to a number of Lotus cars that do Targa.

I have found this screen in my M1 tune software, I don’t have a pit lane switch, but I am guessing i can set my condition 0 maximum speed to 200KPH. I just need to make sure of any other settings i need to make. It was in race functions, tab 6 vehicle speed limit.

[img="blob:https://www.hpacademy.com/7d8bd4ae-eab6-4d4d-8673-9d05082a6a3c" alt="" ]

The link doesn't work, perhaps if you edited it and confirmed it's actually working? They can be a little tricky, sometimes, with some links not playing nice.

Hi Darryl, for an outright vehicle speed limit you don't need to use the 'pit limit' function. You'll see at the top of the screen shot you shared that there is a 'vehicle speed maximum' parameter. Set this to your desired max speed and test to see what you're actually achieving. You may find you need to tweak the set value to get a true 200 kmh.

Alternatively you can use the pit limit strategy but you need to be mindful that there are also parameters for the margin and range that will affect the limiting strategy and result in a slightly different actual speed. For example in our own car I have a pit limit value of 36 kmh/to achieve a true 39.5-39.8 kmh to stay under our 40 kmh pit speed limit.

thanks Andre, I assume this comes off the wheel speed sensor speed and not the gps speed, i have the motec gps module fitted as well.

You vehicle speed can come from one on multiple sources, hence the Vehicle speed state channel.

Priority goes to Wheel speed, which will depend the brake state and your vehicle drive type as to which wheel speeds are used.

Second in the list of sources is from the output shaft speed sensor. This is used if no wheel speed sensors are configured, or certain diagnostic errors are present, or the wheel speeds remain zero, and you meet the vehicle moving conditions for the delay period, and your GPS reads higher than 10km/h

GPS is the third priority which will be used if none of the above are configured or have errors.

After that is estimate, which requires certain values to be present, such as tyre diameter and gear ratios, and it will calculate a speed from the engine speed, and assume no slip.

In regards to vehicle speed limiting, the vehicle speed maximum and pit limiters have different control strategies:

Vehicle Speed limit works by throttle limiting, which also requires the Vehicle speed limit control mode to be turned on and calibrated.

Pit limiting on the other hand can use engine speed limiting strategies (fuel and ignition), throttle strategies, or a combination of both.

If you bring up the help (Press F1) on the vehicle speed limit channel, it covers in quite a bit of detail everything you need to know.

For speed limiting I would not use GPS, especially with a Targa car as the signal is too slow on the update (a 10hz update rate has you travelling 5.4m between updates at 200kph, assuming that it is updating that fast) and is prone to dropping out as the overhangs block the signal.

As Andre said, use the Vehicle Speed Maximum and set it to a speed just under 200kph (to allow for limiter operation) and configure the method of speed limiting used. I would start with the throttle, and then introduce some Ignition control. Make sure that the Vehicle Speed inputs are correctly calibrated, as well as the Gear and Wheel circumference values, as these are used as part of the calculations for the required Engine Speed Limit to control the speed.

Also remember that the limiter only prevents the M1 from accelerating the vehicle to a speed greater than the Maximum set once it has control. If you are accelerating into the limiter then it is possible for momentum to carry over the limit, even if the M1 is throttling back and/or cutting/retarding Ignition and fuel. It also cannot prevent the vehicle from exceeding the limit on downhill runs.

Thanks to both Nathan and Stephen, I am sure i can sort it with all this help