Tune help needed: Engine running w/ wild surging

[Targa44]

This is carried forward from "Coil Pack" thread because emphasis and direction changed...
MS3 not MS3X
Relay Board in engine compartment
Older 911 3.0 liter air cooled
Intake air sensor, coolant temp (headbolt attached), Orig. Aux Air regulator (bi-metal temp controlled startup air), DIY IGN-6 coilpack w/ign drivers in MS3 box, new AEM 30-4110 wideband. All this is very "Bitz" like for fuel. The only added feature is a Clewett 60-2 cranktrigger.
BillR was kind enough to drop by yesterday and help set up timing and spark and tweak TS a little. Now we're asking for more eyes to look at the MSQ and log.

Goal: Getting it smoothed out enough to drive it to a tuner with dyno (hour away).... who has excellent MS experience on the dyno.

Thank you,

kj

[elutionsdesign]

Look at your log and see where the motor is running in a circle on the VE and ignition tables? Just "flatten" out those areas of the VE and ignition table, set all the cells in that area of the VE to 55 and all the cells in that area of the ignition table to 15, or even better set the ignition timing to "fixed" (top right column of ignition settings) and timing at fixed advance to 15. If it still surges after that you have a big vacuum leak.

[Targa44]

I'm not sure I can read the log myself, but I did see that 'circle' on the VE table when we had it running at my surging idle. But you're right about it going around constantly in an odd trianglish shape. You have good eyes! I'll attempt your suggestions today.

thank you,

kj

[billr]

Are you having any success? I have a few more comments:

My *guess* is that your bank firing of the injectors may give better distribution set for "simultaneous" and "three squirts/per cycle". But, that will give rather short individual squirts (~ 3 msec).

The reqfuel is presently 11 msec, but was about 8.8 msec when I first started fussing with it. That 11 msec is correct, for the injector flow stated and our common E10; but I'm wondering where the lower number came from?

I only glanced at it, but my recollection is that your fuel-pressure gauge was showing up towards 60 psi. That is higher than the common 44 psi (3 bar), so I'm wondering what the flow rate of your injectors really is.

All the above underscore that flowing the injectors for rate and dead-time, before spending the money on a pro tune, would be beneficial.

You should re-scale both your spark and VE tables so that max MAP is about 105 kPa; you are giving away resolution by having them go up to 400 on this NA engine.

Yes, that bi-metallic IAC valve will work, many millions (billions?) of engines have run acceptably with similar. It just won't allow as easy/elegant idle control as possible with an electric-controlled IAC valve. I doubt it will be a problem for you.