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

[lapuwali]

I'd use something with less teeth than 36-1. With the 8-bit processor (i.e., not MSII), the interrupt load gets pretty nasty with too many teeth. An Electromotive 60-2, for example, is way too much. By the time the interrupt code completes one round, the next tooth is already triggering another one at high revs. The 16-bit processor in the MSII can cope, but the 8-bit processor has a hard time, and is operating pretty close to the limit as it is. Later extra code revisions may make it impossible to use that many teeth.

You also don't really need the resolution the 36-1 wheel gives you. Subaru themselves use under 10 teeth (it's an odd wheel, and I can't remember the exact number of teeth), and I know of plenty of very high rev bike ignitions that use (for example) 8-1 or even 6-1 successfully. Hell, Suzuki used to only have one tooth on their ignition wheels. With only one tooth, your maximum error at 8000rpm is 2.5 degrees, which is still going to beat the average distributor. With a 4-1 wheel, you're under one degree in max error at the kinds of revs a Subaru will see.

EDIS uses discrete components or an ASIC in their ignition box, and it probably uses 36-1 because it made their implementation easier, and EDIS takes all the load off the MS processor for the precise triggering of the spark. I know fiid is using EDIS to trigger his car (turbo Soob 914) quite successfully, and it's a lot simpler than a COP setup.

So, if you haven't already made the wheel, try an 8-1 or a 4-1 wheel instead of a 36-1 wheel, and the code will be a lot more stable. Alternatively, using the EDIS setup and your 36-1 wheel is proven and stable.

As for doing both, you don't really have an option on the later Subaru engines, as there's no distributor.