Corvette TBI, Help with Ignition Spike during AE

[Thainglo]

I'm starting to dial in my conversion to fuel injection on my C3 Corvette. While logging some runs to test AE, I started seeing these ignition spikes in the 23,000 advance range. I double checked my tables to make sure I hadn't fat-fingered anything.

Only seems to be happening when I'm goosing the accelerator for Acceleration Enrichment.

Should add some details:
Running 16197427 with the $0D mask from here.
Distributor is set 12* BTDC. That is also recorded in the BIN.

Here is my BIN, ADX, and log. This is my first time posting this kind of info, is there any additional info that could help?

Any ideas?

Thanks!
Matt

[Thainglo]

Would help if I gave a window where to look for the spikes in the log. Right around 21s, then 26s, 34s, 50s. Few more after that.

[dave w]

Usually huge spikes in a data log are caused by the data stream being interrupted with noise. The noise source can vary. I'd first check the grounds to the ECM and ALDL connector, then I'd check the ALDL connector wiring to the ECM. Sometimes wiring with "Butt" splice connectors can cause noise. I recommend solder splicing all EFI wires. Sometimes using an AC inverter to power a Laptop will cause noise in the data log.

dave w

[Thainglo]

Thanks Dave! I'm with you, only solder and heat shrink throughout. The couple of spots with thicker wires that required butt splices still got crimped then soldered.

I'll doublecheck all the wiring in that area. Just seemed to pop up after I put everything into the rear compartment to tidy up the car. Maybe the autoprom in there with close proximity to the wiring harness picking up something?

At least it isn't affecting the engine operation, correct?

[dave w]

The timing spikes should not be affecting the engine.

It can be very challenging to figure out what is causing the spikes. Below is a list if things I would try.
Data log with a different laptop.
Data log with a different ALDL cable.
Data log with a different ECM.


dave w

[Thainglo]

Good tips, Dave. Thanks! I'm also going back and trying older BINs in case one of my adjustments caused it. I only get the erratic reading when stepping on the gas and triggering AE. Like clockwork...

[delcowizzid]

It could have tip in or bump spark that retards with sudden tps movement and its going negative advance and the adx is freaking out from a bad equation that doesn't allow negative values

[Thainglo]

Update: I started over with an original bin that had only been modified to account for manual trans and a few other flags. Had some of the same problems after I adjusted the initial spark advance to the 12* I had the distributor set at. I'd wanted to do that because it was where I had the dizzy set in the carb application and I figured it would run better in LHM with the slight advance.

After returning the dizzy back to 0* and making changes in the initial spark advance scalar and the xdf file, everything started running better. No big when in AE mode. Watching the dashboard I'd made to track, I think the spark was going negative in the program and screwing everything up. Maybe if I'd set a higher bias? Going to leave as is and build up from here.

Back to dialing in fuel, then work on the spark advance.

[B-Lazer]

Thanks for the update!
I just narrowed mine timing doing the same thing around AE and PE events. Mine is set at 9.8° initial mechanically and in the Main Spark Bias scalar.
My timing was actually going through the roof; I felt the power drop, had hundreds if not thousands of knocks logged during the spikes, and the timing was logged as trying to retard 48°.
I will try setting back to 0° tomorrow and see what happens.

1993 Chevy Blazer
5.7L with Summit aluminum heads, chevy performance roller cam, bored tbi, shorty headers to single flowmaster