Lotta fun with Megasquirt, Autotune, tunes while you drive Options

[DNHunt]

I downloaded a newer version of Megasquirt with autotune. It uses a wideband O2 meter to adjust the air fuel mixture to a target while you drive. The targets vary according to RPM and manifold vacuum. I have a high of 14 at cruise and a low of 12.6 at WOT. Megasquit keeps adjusting until the amount of fuel gives the desired voltage from the O2 meter. It speeds up tuning a ton. (IMG:http://www.914world.com/bbs2/html/emoticons/smilie_pokal.gif)

It's cool to see it changing without any key strokes on the computer. There are a couple things to consider (there always are). Tuning is only as good as the O2 meter and the air fuel mixture is just a number pulled out of the air. It will not tune the ignition side of the ECU. So, when I get everything sorted out and the engine well broken in it still goes on a dyno.

Dave

[yarin]

I learned a hell of a lot from this post regarding comparing 914 dizzys to crank fired. Check out this thread, link at the bottom.


QUOTE (Mueller @ Mar 17 2004, 04:53 PM)
I was wondering what the crankfire has over the distributor ignition besides 0 moving parts that can wear out.

Hi Mike! Wow, what a coincidence. Guess what I just did? I just came in from driving my 914 for the first time with crank-fired ignition! I can see it in the papers now "Monkey sucessfully fabricates hall-effect crank possition sensor for 914"

Seriously. Remember a few years ago when I was trying to fab a crank possition sensor with magnets mounted in the rim of the fan pulley? Well the failure of that project has been bugging me for years so tonight I went out to the garage and dug out all the pieces and tried again. It wasn't the physical design that was the problem it was the wiring. This time I shielded the signal leads all the way to the ECU and bridged them to +12v with 1k ohm resistors so that when pulled to ground they would make a nice crisp square wave. It worked! Engine fired right up, I set the timing baseline with the laptop and went for a drive. It was sweet.

If you recall I was previously running a Crane optical sensor in the dizzy. With the optical trigger there was much less spark scatter than with points, but there was still a noticeable amount. I think it's probably because even with a tight dizzy there is gear lash between the dizzy shaft and the crank, not to mention dizzy shaft wobble. I bet at idle speed that dizzy shaft is rattling back and forth across that gear lash. Running off the crank-trigger there is much less spark scatter as viewed with the timing light. The engine definitely idles more smoothly. I don't expect that there is really any more power - maybe a little, or like has been said - the potential now to extract a hair more, but nothing earth-shattering. It definitely seems smoother though, and I like that. It's still firing through the distributor for now (for spark distribution only - not timing or crank possition). I've got the coils for waste-spark but need another compatible ignition amplifier. As soon as I round one up I'll try to go distributorless and see what happens.

-Ben M. (now with new improved crank-fire action)

http://www.914world.com/bbs2/index.php?act=...f=2&t=10134&hl=