Question about LSx 5.3L truck engine, Dwell and diagnostics

[kingtal0n]

I was hoping somebody could take a look at the coils on this engine here:


And here is why. I have a feeling that the "stock" dwell setting in the MS3 ecu "gold box" of 3.5ms might be too high for these, can anybody confirm? The engine, during cranking, even with 0* btdc timing advance, is "starter knocking" aka engine slowing on the compression stroke as if the spark were occurring too early. If not, then I suspect we have a wiring issue, perhaps a coil is intercepting another coil's command or something. Or a hot-spot type problem (seems to get worse with higher temps... maybe) The motor seems to run fine, but I am scared to push the power output with it doing this.

OH and something else. The owner has installed a very powerful battery, huge, like nothing I have ever seen before. its like some kind of industrial battery, probably weighs 110lbs. Could this be a source of problem, or preignition? I would doubt it, since potential voltage is potential voltage, but when it comes to electronics I've seen some crazy things, and learned that I know nothing... so I thought I would ask.

My first idea is to reduce dwell. 2.8ms for cranking and 3.0ms for running will be my initial adjustment when I see the car again.

OF course, I have verified the timing with a light, using cylinder #1 and I made a white mark, it lines up perfectly with the computer. I was thinking of making 7 more similar marks around the pulley in different colors to ensure that each cylinder is firing when it was supposed to, by disabling all other inj/coil and cranking. I still need to do more testing but my friend isn't available most weeks, so this is an attempt to gain as much advantage as possible before going back and trying more diagnostics. Any ideas, love, appreciated thanks!

[billr]

You only need three more timing marks, not seven, spaced evenly at 90 deg. intervals. Are you using a simple timing light, or a dial-back type? And...

[kingtal0n]

You only need three more timing marks, not seven, spaced evenly at 90 deg. intervals. Are you using a simple timing light, or a dial-back type? And...

I have a dial-back timing light, Ive used for years in a wide variety of applications. I flipped the pickup and found it works better in one direction on most cars. Very consistent when I lock the timing on this engine.

Data-logging is one of the most difficult things for me when using this ECU for some reason. there seems to be three different kinds of logs, and whenever I save them the logger always gives me a bunch of trouble. I will try to get some, but which "logger" should I be using, you want teeth logs or?

And lol at the 3 other marks, I dont know what the #@)( i was thinking lmao

[jsmcortina]

A regular datalog from the Datalogging menu.

James

[kingtal0n]

Here is the latest tune file, and 2 logs taken from a slightly older tune file, on other days (dyno day passes) but very similar (showing same problem etc...)

[LSXCutty]

Now I'm no expert by any means, but I was looking over your data logs and tune file. No Wideband set up? Also on the "WOT" data logs it seems to be only getting 85% throttle on one pass and 124% on the other. Did you calibrate the TPS in the menu?

[nathaninwa]

Cranking dc is low somrunning more dwell is ok. 5 to 6ms works good. Running dwell on the heat sink coils should not go over like 4ms. I run 3.8ms on one car under full power and LS I've been running 3.5ms under power

If you look under the ignition tab, you can setup a dwell table. I run around 2.5ms for idle and cruise and ramp in dwell in power areas

Make sure your plug gaps are good

[kingtal0n]

thank you for inputs, I am aware of the tps issue its been fixed more or less. those logs are from 2 months ago~ ish when the engine was first installed. I felt like there was a timing issue because of the hard starting. I heard some coils pre-fire if the dwell is too high, so I thought to change it first.

What else do you think about the hard starts, the starter knocking, starter slowing? Could it be the starter? Are there some "terrible" LS starters out there that do this sort of thing? It seems to "hang on" to the flywheel once the engine gets going, making me think it isn't aligned correctly or something. When we crank it warm the motor slows and almost stops as if there is 30* of timing being thrown at it. I suppose I just need to get a light on it to rule that out, thanks, just trying to get some ideas before I see the car again. It does the same thing with 10* or 0* of cranking timing. When cold it seems to start pretty easy with 0*, which I also thought was odd? I never tried cranking an engine with 0* before, what are your opinions?

[LSXCutty]

How's the engine grounded.

[jsmcortina]

I suppose I just need to get a light on it to rule that out, thanks, just trying to get some ideas before I see the car again.

Absolutely.

When cold it seems to start pretty easy with 0*, which I also thought was odd? I never tried cranking an engine with 0* before, what are your opinions?

Is it really 0BTDC? Timing light will tell.

James

[billr]

And, yes, most engines will start fine with 0 for cranking advance. It's easier on the starting mechanism, if that is of any benefit to you...