Launch/traction control

Dimbit · Post by **Dimbit** » Thu Jan 17, 2008 8:32 am

Seems like the logical next step. Has anyone tried this yet?
I'm just starting to think about building an mjlj and rev limiter, but already thinking about how it could be done.
I already have a speed sensor on a front wheel (mountain bike speedo used while my speedo cable's been broken) that will produce road speed dependent pulses. I reckon that coupled with the tach out from the MJ and a simple PIC should let you work out if you're spinning up (in 1st gear at least) and cut spark. With rpm info from each wheel (or a front wheel and prop flange) full-on traction control should be trivial. Anyone laughing at me yet??

Post by **brentp** » Thu Jan 17, 2008 8:47 am

Hello, and welcome!

Yes- Launch control is something I've given some thought to, and would be an interesting capability. I think there are a few ways to do it; measuring the speed of a non-driven wheel is certainly one option.

I've been mostly thinking of a an effective way to do it *without* using any wheel/speed sensors at all- but I'm not sure if it would be practical or effective.

Dimbit · Post by **Dimbit** » Thu Jan 17, 2008 5:28 pm

Hi, and thanks.
I considered that. The only method I can see would come down to measuring rpm/sec and comparing that to realistic max acceleration, but that's never going to be as reliable as you'd like. Once you move away from peak power it seems near impossible to implement to me.
Any other way needs at least 2 wheel sensors, or one speed and one "what gear am I in" sensor. I had a think about the PIC code today (first time I've even looked at anything like it) and it looks like comparing 2 speeds and sending an output high is pretty easy. Wheel speed sensors are easy to install on cars like mine (7 replicas) so that's the way I'll hopefully go in a few weeks/months, when/if I ever get around to it. Maybe one day I'll have some useful experience...

Anyway, I need to build a MJLJ and set up a rev limiter before this even becomes feasible for me. I'll be off to the scrapyards this weekend for edis parts, and searching for a p channel power mosfet that I can get 1 of in the UK...

Edit: Just noticed there's already another thread about this so sorry for the duplicate

Dimbit · Post by **Dimbit** » Thu Jan 17, 2008 7:45 pm

Ooh, just had another thought. Instead of cutting spark when the wheels spin, you could use the PIC to first switch the MJ to a less aggressive map using the option switch input. Would that work on the fly? Can you switch maps while giving it full beans without upsetting the MJ?

Post by **brentp** » Sun Jan 20, 2008 7:58 pm

It's certainly possible! Yes, the map can be changed on the fly, it was specifically designed to do this.

However, you may consider modifying the actual MJLJ firmware to add the features you seek, that way you have full control over the whole system, in one unit.

Oliver Sedlacek · Post by **Oliver Sedlacek** » Wed Jan 23, 2008 6:57 am

Some spark boxes over a "rate of rpm rise" limit, which can be adjusted with switch inputs. The switches are connected to the gear stick, so that the "rate of rpm rise" changes according to which gear you are in. This is useful in race classes where traction control is banned, although it clearly achieves a similar goal.

Humpty · Post by **Humpty** » Wed Nov 21, 2012 2:34 am

Bringing back a very old thread..... Has anyone had any success with this idea?