DIY LTCC or similar system for LT1s

[spfautsch]

Hey all I wanted to drop in an update on the project status.

As many of you have probably seen over in the 'humidity' thread I've found what I believe to be the sole cause of my driveability problems - a slipped opti hub. My priority at the moment is to get this fixed so a determination can be made as to whether this was everything that was wrong, or just one piece of a larger puzzle.

In the mean time, for anyone still wanting to actively test I'd like to hear your coil PNs so I can prioritize which to purchase for testing. It may be several weeks before I have the funds available to buy test units, and at the moment vilefly is also extremely busy. So unless anyone would want to volunteer to tackle this, all I can offer is hopefully soon one of us will be able to determine specs on the coils mentioned in post #466.

If any of these coils that have been reported to draw several milliamps on the igniter pin will work in the current PCB configuration, it will definitely require replacing all the rc network resistors on the coil driver circuits with 47 or 100 ohm pieces. And in the case of the coils vilefly owns it's seems likely that a separate driver stage will be required.

It was a monumental oversight on my part to have assumed all these coils would have similar igniter circuit requirements. For this I can only apologize. If any of the paying testers would like to abort at this point I'll gladly buy your kits back or refund your $25.

The only good news I have to report is that the 12658183 coils I happened by dumb luck to choose will work with no problems whatsoever. I'm anxious to test one to determine dwell requirements.

[kur4o]

https://www.eevblog.com/forum/projec...il-driver-cct/

Some interesting reading.

I will try to gather a list of all available coils through the years and link them to pcm they were used with.

I also remembered that there were a dwell tables in some of the ls calibrations.
There is 1 main table base dwell time vs rpm vs voltage.
There is coolant temp correction multiplier vs voltage, and map correction multiplier.

So to dublicate the tables you need 4 inputs: map, coolant, rpm and IGN voltage.

I will get you some screenshots of the tables later for reference

[kur4o]

SOme coil reference by years.

The one you have are not available in the catalog, I could only find that they interchange with 12621750. So you got one of newest designs. I will try to dig out a 2014 truck bin to see the dwell tables.

The general consensus is that d585 is the highest output coil, so if you`re shopping look for that one.

[kur4o]

http://www.gearhead-efi.com/Fuel-Inj...7&d=1529720855

A printout of 2015 truck calibration data. Search for dwell.

I hope the coils you have are the same used with this 2015 truck.

[vilefly]

Looks like base dwell @ 14v ranges from 3.10 mS to 2.41@8000rpm.

[spfautsch]

Good info kur4o, thanks!

https://www.eevblog.com/forum/projec...il-driver-cct/

Some interesting reading.

I think I ran across this in some of my initial research and dismissed it as a nothing sandwich. There's no meat between the bread, just anecdotal nonsense that couln't be verified. I've never found anything leading me to believe the early LS (or even the current stuff) had feedback capable coils. If that's the case it opens the doors to a lot of possibilities for future work.

The general consensus is that d585 is the highest output coil, so if you`re shopping look for that one.

They're also the most expensive. I had one saved in my Amazon cart at a relatively decent price, but it was no longer available this morning. :-\ I'm still paying for the recently acquired valvetrain parts - in more ways than one. My wife has been threatening to "roll <censored: the car> out in the driveway and set it on fire".

From what I've been able to gather from RockAuto's parts lookup the 12658183 coils I have were only used on some of the 2014 and newer LT1,LT4 and LT5s and only in the Y-bodies. I've also been unable to find an abbreviated Delco part # (i.e. D514).

Edit: correction - it looks like these were also used on the 6.2 truck engines starting in 2014.

Edit2: Interesting - AutoZone is describing the AC 12674754 a "Capacitive Discharge System".

Looks like base dwell @ 14v ranges from 3.10 mS to 2.41@8000rpm.

I wonder why they're reducing dwell with RPM. It seems like if there is time available to get a fatter spark, why not utilize it? Obviously above 5000 RPM the driver is requesting all the "go" the machine has available.

[kur4o]

In 2014 Gm introduced new Pcm with the Direct injection v8s. The ingition drivers might also get an upgrade and the need of new coils. I saw some interesting tables labelled multi pulse spark dwell. Not clear what they do and is this coil capable of multi spark events. They have the shortest dwell of all of the GM coils. When you factor the 10% coolant reduction you land at 2.16ms dwell at 8000rpm.