Autosport Labs

I am enjoying my new MegaJolt/EDIS ignition on my air cooled VW motor. How do I "tune" my motor? I have a spark map loaded up and the motor runs pretty good, but how do i know what the spark map should look like for optimum tune? Can i use the data logger or is it all just a trial and error process changing the map and see how it feels in the seat of my pants?

There are a few solutions to do this with varying risk

Ideally take it to a rolling road where someone experienced with your setup can give you a good map and exploit the potential of your setup in a safe enviroment.

Slightly less risky is to obtain a map from someone with a very similar spec to your engine.

Probably more risky especially for a novice is the seat of the pants aka trial and error. If your going with this solution then do plenty of research and try to get some experience from someone who knows what they are talking about. I believe it would be best to have a friend with you to drive and sit in the passenger seat with the laptop whilst changing your MAP. You need to be really listening to the engine and know what your listening for. I have seen stethoscope like devices attached to engines so tuners can hear the very early stages of pinking. Having a safe MAP on the MAP option switch would be a nice to have should you make a mistake or go to far with the advance and you need to change MAPs quickly or for comparison to changes. A hill and a long straight road is best for this as you can put the engine under strain at WOT to set your max advance.

It's up to you how you would like to approach altering your MAP but spending a little money at a rolling road may save you hours and expense later on.

Personally, me having an inquisitive nature with engines and the enjoyment of DIY I would have a go myself, but then I have seen engines being mapped before so I have a little experience. Although some may say a little knowledge is dangerous, lol

Hope this helps

Thanks for your help Nitropixie. So I want to map in as much advance as it will take without detonating or pinging? I do have a couple air cooled VW maps I've been playing around with. I will keep experimenting. I wasn't sure if there was some way to use the info from the datalogger to help dial it in or not.
I have a 1641cc VW with a Weber DCNF 40 carb and a Engle 110 cam if anybody has a good map for me to try out.
Thanks

Mimic an 009 map for a start, 28 advanced at 3000, starting at 8 or 9 around idle. Make it linear, the Megajolt will extrapolate the advance in between points. You can try retarding the advance too above 5000 rpm to redline. Try 1 degree for every 250 revs, or 4 degrees per 1000. For load, try 5 degrees at light throttle. If it handles that without pinging, up it a couple degrees at a time until it does, then back off. There isn't a whole lot if any extra power between max advance and two degrees to the safe side of max.

I have some maps put up on the site. Mine is a high state of tune 2165 type1 on Weber 44 IDFs.

At the risk of sounding like a smartarse..

"You simply keep changing the settings in a systematic manner until it is running at its best at all rpm/load conditions."

The magic two keys points are "in an systematic manner" and "running at its best"

Systematic manner = following a step-by-step plan designed to hone in on the best curve bit by bit...

eg.
you start off with the full-load points (pedal to the metal) and find the maximum amount of advance the motor will take without pinging at each rpm point, and depending on your motors sensitivity to advance, then you back it off anywhere from 1 to 5 degrees from that point.

Once you have the full noise curve in place and reasonably close, then you start adding advance at progressively lower load levels (to compensate for reduced effective compression when the engine is throttled) across the rpm range, Testing to verify all the way - Drive up hills, down hills, along freeways, take a co-pilot to either drive or fiddle, dont try to do both yourself. Rinse and Repeat - over and over and over again. Chances are you will be well bored of it before you hit the sweet spot, so be prepared to space the process out over days or weeks if you are new at it.

The second magic key-phrase "running at its best" is all up to skill of the tuner.

You need to be experienced and sensitive enough to be able to *feel* the engine feeling lazy or snappy, or lugging or pinging. To be able to detect small changes in throttle response, acceleration and smoothness. Or you need to have instrumentation (stopwatch, marked road, G-Meters, 1/4 Mile) to verify your seat-of-the-pants senses. If you have no way to verify the "running at its best" part, then you are just guessing based on gut-feel.


Or If your patience, skill, time or persistence at sticking to an intricate repetitive plan run out, then you take it to a professional with the right instruments (a dyno) to do it for you (pay $$),

or you copy a curve from someone with a combo (engine, car, carb, gears, cam etc) as close to your own as you can find, throw that at it, and leave it at that. you'll probably still be a fair way ahead of any old mechanical dizzy system.

Having the patience to adjust, test, repeat, and keep fiddling to Find those last few horses or responsiveness is what makes the difference between a pro "tuner" and an amateur..

Unfortunately, no how-to guide on a forum will make an amateur into a pro-tuner.. you need to do the hours testing and develop the feel, or just employ someone who has already done their time to do it for you.

(edit: heh, reading what I just wrote, I realise Mr NitroPixie already said pretty much exactly the same thing, which should give you a hint on the right way to do it )

Thanks for the help! I would have thought by now someone would have a good map for a basic VW motor!!! It does run better than it did on the dizzy, however, I had no idea it would be this challanging to dial in. I will take your suggestions and start playing around with the map.