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EA-81 Tuning Woes

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Hi there everybody. To give a quick rundown, I've built a standalone Speeduino (like megasquirt with TunerStudio) and small wiring harness for a Subaru Ea81 engine ive turned to TBI for fun. It's my first project and I've had my fair share of issues like syncing and whatnot, but I seem to have gotten then under wraps but my problem is now fueling issues. I've created a base fuel table and started notice that the engine is very difficult to start, runs pig rich most of the time, and the VE table really has somewhat very little effect on the AFR. If I adjust it down enough to be in the ballpark of the 0.95 lambda reading im looking for at idle, (and it floats around between .85 to .95 usually) I have my VE table sitting around 22 and the second something kicks on - Fan usually, lambda readings to wildly lean and the engine dies. From there its exceedingly difficult to start back up again. I have a very basic knowledge of tuner studio but I'm very lost with this one. It's not been at all like the examples shown in the courses and I'm at a loss. I'd like to attach my tunerstudio file just in case somebody can take a peek and notice any glaring red flags, but I thought I had done a decent job of setting everything up as best as I could.


Seems like you need to get out the oscilloscope, and make sure the signals in the Speeduino are rock solid when the transitions to electrical loads happen. Is the ECU loosing sync by missing a crank trigger event, or does it seen an extra one and then the timing is off by one tooth...

What happens to the ECU power & grounds during one of these transitions?

Wildly lean readings on the Lamba usually indicate the lack of combustion (i.e. a mis-fire). Does the ignition timing remain stable / solid? Does the injector duty cycle remain stable?

When you have trouble re-starting -- what happens if you completely power cycle the ECU. Does it then start?

Hey there! Thanks for the response! I suppose the issues could indeed be trigger related, but I thought I had sorted that out for the most part. I've run a composite logger on the signal when the fans kicked on and according to the log, the signal is pretty rock solid. (unfortunately I have no oscope so I'll definitely have to get one) Power cycling the ECU really didn't ever make too much of a difference, but whenever there's a significant string of misses it almost always makes the sync loss counter rise. I've got a 24-1 tooth wheel in the distributor optical sensor and a single tooth cam position ring on that disc. The signals seems reliable and there are a couple things to note. (24-1 tooth wheel trigger angle set at 215* and I set the disty manually at about 20* advance to help the rotor phase)

Playing with it last night I notice it's MUCH easier to start back up when I turn the "skip revolutions" to 0. Sometimes it kicks back at me but not too common. Seems to sync and start much quicker. But power cycling the ECU when it refuses to start really doesn't do too much for me. I've got a 12v signal to the optical sensor, and then 2 5v references from the ECU to the optical sensors and a ground. (all grounds except the fan and fuel pump are mounted on the intake manifold.

Playing with the injector characteristics (ive got almost no info on this stock injector) seemed to help stability of the lambda readings, but increasing the injector open time past 0.9 causes it to want to start a little quicker almost, BUT it makes the VE table almost useless. I know its a low impedance injector mounted in the throttle body, but unfortunately I'm using a resistor to drive it with the saturated drives on the ECU. Otherwise I *believe* its a 800cc injector, but thats relying on information on a Subaru forum. No idea what the injector close angle does for me or where it should be set, but currently that number is 355. Overall when it does idle, it seems to hunt a little bit around the 800rpm range (+-50) depending where the lambda reading is at 26-27 kpa. Drastic changes to the VE table do cause some very minor changes to the lambda reading but it still seems to hunt all over the place there.

I've also set the spark advance table at 18* across the board and according to the timing light on cylinder 1 its pretty solid. (theres not really a timing mark at 18* exactly on the flywheel but its pretty spot on. Whether the rotor is phased correctly, im not entirely sure.)

How many "squirts" per revolution (or cycle) is the single injector providing? I don't see how an injector close angle (the time when it attempts to finish injection) makes sense in a non-sequential non-port injected setup. But perhaps if it's using one squirt per cylinder/cycle, then it could use the close time for that cylinder to decide when the end-of-injection for that "squirt" is.

Are there any cranking or prime tables that could be used to introduce extra fuel just while cranking.

It's set to 4 squirts per cycle. I was sort of assuming that one cycle to tunerstudio was 720* so thats what I set it at. I thought that mightve been my issue with the extremely rich condition the engine was running under so just in case i set it to 2 (in case it meant 360* cycle for some reason) but then it wouldn't start. I don't exactly understand the injector characteristics screen (and most of it is greyed out) so I'm not sure if I could turn off the injector close angle option or not?

I can look for a table that would do something like that. There's a Cranking enrichment table, and a priming pulse-width table but I'm not entirely sure how to set them properly so I left them alone.

First get the engine running with a stable idle. For now, keep a flat ignition timing so that isn't changing while trying to stabilize the idle with fuel.

Use similar values for the low RPMs that you use for idle, just add a bit more fuel (say 10-15% at your lowest RPM - usually 0 or the typical cranking RPM).

Now to improve the starting, just change the Cranking Enrichment -- and try different priming pulses. In general if it's cranking and not firing - add fuel go in pretty big steps initially (20-25%). You might need 2 - 3 x the pulse width used at idle to get the engine to start easily. The colder the engine, the more fuel you will need to add (ie, more enrichment). Often a big prime pulse (10 - 50 ms), followed by only moderate enrichment (say 120% of normal fueling) will get an engine started.

Basically change things -- there are only three results from any change -- It's Better, Worse or the Same.. You just need to figure out what makes it Better!

If you can set the ignition timing when cranking start with something in the 0 - 6 deg advance range.