Launch Control setup options

[Beams AE82]

Hi all.

Firstly, big ups to all the assistance you guys have provided me with over the last few weeks. I am progressively building on my tune, logging real time and using Mixture map almost exclusively now for the fuel tuning. My injector duty cycle has peaked at 80% during yesterdays tuning session indicating I'm probably close to my initial target 150kW. (Spec is 1987 Toyota Corolla EE80 FWD, 3SGE Gen4 and C60 6sp gearbox with LSD).

Onto todays topic of discussion. I'd like to setup an effective launch control. Despite running an LSD, there is no way I can put the power down on hard pull aways. Traction or lack thereof is a very real problem for me.

My Launch control is currently activated as follows;

Dash mount enable switch made, clutch switch made for 1,5sec, >90% TPS and it then launch control function limits engine speed to 4000rpm. As soon as I drop the clutch all hell breaks loose and traction is again lost. Not a good solution..

I have some thoughts to improve the setup, as follows ;

1) Add a timer which will hold launch control active for a set period after I release the clutch. This would enable me to get moving before releasing the full RPM range of the engine. This could work all be it a rather rudimentary solution. I'm not sure how I will add a timer as I still need to look for a method in the software.

2) Though not necessarily a quick easy solution would be to add a wheel speed sensor to a rear non-driven wheel. I could then run a varied RPM limiter against wheel/road speed input. Activate via dash enable switch, >90% TPS and look for non-driven wheel speed input between 0-60km/hr speed range for example. After 60km/hr I'd be into 2nd gear where lack of traction is less of a problem and "Launch Control" would no longer be active.

3) Another option would be to run a basic version of "traction control" by % slip calculation (between front and rear wheels). This would necessitate the addition of at least 1 front and 1 rear wheel speed sensor. Then span % slip against a "soft" rpm limit. As traction is found the "limiter" would not longer be in place.

Another query, is there a preferred type of wheel speed sensor that I should source and what is the recommended frequency range I should aim at? At a very enthusiastic and safely over estimated top speed (rpm limit) in top gear (8200 rpm, 250km/hr in 6th gear), my wheel speed will be 2301rpm.

Please share your thoughts on the above. All suggestions are welcome and will be greatly appreciated.

[Adamw]

1. The timer setup will likely work better than your present setup without any extra hardware needed.  So if you want to give that a go I can help you set up the timer if you cant work it out yourself.
2. For tarmac standing starts, option 2 is by far the best and is what most professional circuit cars would use as a start line strategy.  Usually you set it up to initially spin enough to prevent it bogging then quickly pull RPM down to allow the tyres to "catch up" before slowly ramping it back in.  Usually you dont even need an enable switch - it will just be active anytime speed drops below say 50km/h.
3. Wheel Slip based control strategies typically arent good options for standing starts.  You actually need more slip than you would imagine for a good launch.

For a wheel speed sensor I would suggest 4-12teeth and use a hall effect sensor (so it works down to near 0KM/h).  Almost any will work. The GS1005, GS1007 or GS1012 from ZF would be my suggestions.  

[Beams AE82]

Hello Adam.

Thank you for your response.

Ok, so we'll eliminate option 3 then. I'd like to play around as an interim measure and to learn the timer functionality with option 1. I'd like to follow the following sequence of activation events, thereafter, maybe you can guide me through the timer setup.

1. Dash mount enable switch made.
2. Clutch mount enable switch (in series with Dash switch) made - clutch depressed.
3. TPS >90%
4. RPM limit activated.
5. When I release the clutch -clutch switch input will be broken, I want the timer to start and run for "X" time period, extending the launch control rpm limit turn off point by that period. Effectively I guess this acts as a delay timer in industrial automation terms. Please guide me through this setup process.

For Option 2, I will source and install an appropriate Hall effect sensor on one of the non-driven wheels. I'm running drum brakes on these wheels so space/fitment might be an issue but I will make a plan. Ideally, the sensor should pick up from a bladed wheel or even from an array of evenly spaced bolt heads I guess. If I drilled say 4 evenly spaced holes into the rim of the brake drum, would we be able to configure the brake in the signal as the "gap/hole" passes the sensor as our input?

Could you possibly share some setup guidelines to configure this concept in VTS? I'd still like a digital enable switch for the function, in my case the Dash mount toggle.

What sort of a control table would I set up for this? 2D with Road speed on 1 axis and RPM limit as the variable input data as per simple example below or would there be benefit to adding TPS as another axis against road speed in a 3D table?

3D example

	Road speed
TPS	0	10%	20%	30%	40%	50%	60%	70%	80%	90%	100%
	10	0	0	0	0	0	0	5000	4500	3700	3000
	20	0	0	0	0	0	0	5500	4800	3700	3000
	30	0	0	0	0	0	0	6000	5200	4000	3500
	40	0	0	0	0	0	0	7000	6200	5500	5000
	50	0	0	0	0	0	0	8000	7700	7300	7000
	60	0	0	0	0	0	0	8000	8000	8000	8000

2D example

Road speed	0	10	20	30	40	50	60
RPM Limit	0	3000	3000	4000	5000	6500	8000

[Adamw]

Just looking at this now.  Do you have any speed sensor at all connected (even driven wheel/gearbox speed)?  I could do something a bit more effective if you do.

[Beams AE82]

Hello Adam. 

I do not yet have a sensor in place but but i have identified a position where I can mount a hall effect sensor on 1 of the rear non-driven wheels. I will try source a unit this week that will fit in the space available and hopefully fit and wire it in over the weekend. I will assign it to DI1 as ground speed.

 

Please go ahead and share with me your suggestion. 

[Adamw]

Ok, the setup like the "option 1" you originally asked for (with just timer and clutch switch) didnt work out too well as when testing the "arming time" and the timer kind of contradicted each other and you could potentially get a situation where the launch would re activate something like 1 second after each gear change etc.  I could make it work but its going to need 3 virtual auxes and two timers so its going to be pretty hard for anyone to understand or adjust.   If you are happy to fit the non-driven wheel speed then you will have a much better strategy and it will be easier to understand what to adjust.

I would not connect your clutch switch as we dont want it to disable when you let the clutch go, perhaps just connect the dash switch so you can disarm it if it is ever too intrusive, otherwise just leave it active all the time.

Here is an example setup.

[Beams AE82]

Hi Adam. 

I'm glad you were able to simulate option 1 and rule it out of the equation. Thank you. 

The option you've detailed as preferred is Mode 1-2D table. I will install a wheel speed sensor and then revert with feedback once completed and setup. Likely in the course of next week. 

 

Thanks again. 

[Beams AE82]

Hello Adam.

My GS1007 Hall effect sensor arrived today. I've booked some dyno time for tomorrow so will hopefully make up the necessary brackets and fit the sensor after that if I have the time available.

The sensor is a 3 wire unit. One wire will be the voltage supply (I'll wire in a 5V supply from the ECU sensor output), the 2nd wire will be a ground (should this be a sensor ground from the ECU or will a chassis ground be acceptable?) and the 3rd wire will be the signal output to be connected to an assigned Digital input channel. Is it required to install a pull up resistor at all? What will the basic configuration requirements be to accept and read the input signal?

BR,

Robin

[Adamw]

Preferably sensor ground but chassis ground will usually work.  No need to wire a pullup, just turn on the ECU internal one using the settings on the DI.

The only other thing you will need to do is set the DI function to speed and enter a calibration number.  You can either calculate this using the formula below or just use trial and error, bump the cal number up or down until your displayed speed reads about right.

[Beams AE82]

Thanks a mil Adam. This all appears pretty straight forward. I'll have a go at setting it up as soon as I have a spare moment and give you feedback once completed. 

 

Rob

[Beams AE82]

Hi Adam. 

I have fitted the ground speed sensor. All works perfectly. I ran a quick test on your recommended launch control setup and it too works a charm. Next is to spend time configuring optimum rpm limits. 

 

Thanks again for your assistance.

[Beams AE82]

Some quick status update for interest. Yesterday was my little cars first outing to the drag strip. I finished the day with a 13.2 pass at 169km/hr. Am very happy with the result for a non prepared surface with very poor traction. I spent a lot of time optimising the launch control and it definitely has it's place, particularly on a poor traction surface. My problems of poor traction in 1st gear however are now transferred to 2nd gear... I am spinning on the gear change as circled in red in the screen grab  below.

Adam, we spoke of using a slip calculation previously as one of the launch control options. As I have ground speed input, could I set some sort of a slip % limiter but gear based? I'd then utilise the speed based launch control as currently configured (rpm limit in 10km/hr increments phasing out by 50km/hr) for pull away and then apply the slip % limiter only in 2nd gear. The amount of 2nd gear slip was heavily influenced by track temperature. As the day progressed and the track temp dropped from 38degC to 24degC traction improved but the traction problem remains regardless.

Edited November 5, 2017 by Beams AE82
added log screen grab

[Adamw]

This example would control slip between 30-40% in second gear only (assuming this engine didnt have enough torque at 5000RPM to cause slip).  

[Beams AE82]

This looks fantastic, thank you Adam. I'll play around and post further queries as they come up.