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drag car traction control

Thread starter #1
I am new to the electronics thing and really can admit I dont know what im talking about. I havnt ever taken on more than a few kits in my time so please bare with me. I am an auto electrician so have a basic knowledge of electrics and electronics. I am trying to make a traction control system to put in a drag car of mine. The theory is I have a speed sensor on the front and rear wheels and when the rear wheels increase over the front wheel speed I need to switch a positive, negative or relay and I can link this back into the engine computer and slightly cut power until wheel speeds become even. I think it should be a pretty simple task. The 2 speed sensors output sine waves. They are identical sensors however different pickup setups and front and rear tires are different diameters. So the inputs need to be adjustable or programmed some how. easiest way would be to drive along at 80 with meters connected to each and adjust a pot or something. The next adjustment I would like would be a way to adjust the sensitivity of the output trigger. basically what differences would be required to in the inputs before the output is triggered.

now the only way I can see to do it is to have a regulator for supply voltage and drop it down to 9vdc? then run 2 separate frequency to voltage convertors with output adjustments via a pot? then i need something to measure the difference in the voltages before triggering my output.
dont know if im anywhere near the rite track so im here for someone to let me know.

if someone could draw me a circuit or point me in the rite direction or any help would be great. Even if you could build it for me and we could sort something out for your time it would be much appreciated. thanks


Well-Known Member
I think your over simplifying this a bit.
Controlling the throttle would do virtually nothing to synchronize the tires, this will not work. In theory if you could control the torque going to each wheel you could synchronize them that way, but that is overly complicated and would be very difficult to implement mechanically for what you want to do all you need is a rear differential that you can manually lock when you're using it as a drag racer then there's no way the rear wheels can get out of sync.
Thread starter #5
thanks for your help guys. I dont want it as complex as what you are saying. the rear wheels are locked together using a locked diff. when the rear wheel speed increases over the front i am obviously getting wheelspin, if i can sense this wheelspin using something like my theory above then i can easily trigger my aftermarket boost controller or engine computer and lower turbo boost or more commonly retard engine ignition timing and make less power/torque until things are under control. during this process i can keep the throttle flat.

i have found this... http://www.circuitstoday.com/frequency-to-voltage-converter-using-lm331
hopefully using something like this with an adjustment for each sensor would get me through step one and i would have a varying voltage equal front and rear
as the car speed increases.
thanks for ur interest guys
Thread starter #6
Think of it like this... at the moment if i accelerate hard the rear wheels spin, I have 2 options here. I take my foot off the throttle and reapply it after wheel-spin is under control and this will get me down the track or road the fastest. or i keep accelerating and hardly increase speed because of the ongoing traction loss. The setup im trying to instal will automatically do the first option for me without lifting off the throttle. and hopefully sense and remove torque from the rear wheels 100 times faster than I can currently. hope this helps.
just a thought, if you have a rev limiter installed, could you not just implement that to also cut the power, it's already there? plus you wouldnt be messing w/ other items?
Thread starter #8
Yeh the rev limiter will cut the power too much, more like a factory system, which are designed to regain traction and put the driver in control no matter what, more for safety than increasing acceleration. An I can currently drive the car and rarely hit limiter. By the time I'm on rev limiter the rear wheels will be going 60miles faster than the front


Well-Known Member
Most Helpful Member
In theory it seems simple. You need 2 of the frequency to voltage converters above. One for the front and one for the rear. Both are fed to a comparitor like the attachment. The front wheel output needs to be set slightly higher than the rear wheel sensor for the same speed. When the rear wheels are faster than the front the comparitor will trip slowing the rear untill the front wheels "appear" faster than the rear.
This seems like a good idea.
Do you already have wheel sensors for anti-lock brakes?
yea, i forgot how my old rev limiter worked, mine killed the engine till i dropped back down to 10500rpms. (didn't have any power). i like ronv's idea. add a pot for adjustments for your main tire runout adj. and even add a fine adj for differing track conditions.

ps. one drawback to this idea would be if your car lifts the front wheels?? if that happens, you would be hindering your times, then a sensor override
in the front suspension would be the next item.
Last edited:
Thread starter #11
sorry for the late reply. thanks ronv! i like your thinking and this is defiantly something i will have a go at now.
thanks again!! will let u know how it turns out!

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