LS2/LS3 Coils to Gen 3 411 PCM

[STR8BALLN]

If I swap LS2/LS3 coils to 411 pcm 2002 gen 3 harness. I know the connectors work, but do I need to change the dwell time or any PCM mods?

Or can you just plug and go and it should work without needing to change anything?

[STR8BALLN]

I got the motor running with the stock(square coil) data with the LS2/LS3 coils. But I have read that guys have switched the dwell times to match LS3 dwell times. The other thing I noticed is the 2002 pcm has cranking modifier and power up tables that the LS3 does not have. Thoughts?

[Alvin]

I've not done it.. and I've done it.. Never saw a difference either way.

[STR8BALLN]

I've not done it.. and I've done it.. Never saw a difference either way.

thx

[edcmat-l1]

Yep plug em in and go.

[STR8BALLN]

Update: for the guys that will search this in the future.......

We just tested the engine on the dyno. LS2/LS3 coils with dwell settings left at (stock square coil settings) and (stock ls3 dwell settings) saw no gain or lost in power. Both settings produced the same amount of power.

thx to edcmat-l1 and Alvin

[Alvin]

Cool thanks

[Fast4.7]

I have coil dwell times from an unspecified source that were GM race proven to increase the coil output without overheating or damaging them. I know where they came from but not at will to say whom, lets suffice to say retired former GM powertrain engineer that had a large hand in GM OE calibrations. They work very well in high compression and boosted applications. If the stock dwell times are sufficient to ignite the mixture on every cycle in every cylinder, increasing dwell time only adds heat to the coils reducing life and increases drag on the alternator via the increased current draw. On a 12:1 engine running factory GM TSB plug gaps the GM race dwell settings were good for about 13 whp gain. The increased dwell eliminated the need to reduce the plug gap with the greatly elevated cylinder pressure. The plugs also stayed cleaner longer on C16 with the increased spark energy minimizing misfiring. When I get back to the shop I will post a tune that has the GM engineered dwell settings in it. My $0.02 the less dwell you can run and still have adequate spark output the better.

[STR8BALLN]

I have coil dwell times from an unspecified source that were GM race proven to increase the coil output without overheating or damaging them. I know where they came from but not at will to say whom, lets suffice to say retired former GM powertrain engineer that had a large hand in GM OE calibrations. They work very well in high compression and boosted applications. If the stock dwell times are sufficient to ignite the mixture on every cycle in every cylinder, increasing dwell time only adds heat to the coils reducing life and increases drag on the alternator via the increased current draw. On a 12:1 engine running factory GM TSB plug gaps the GM race dwell settings were good for about 13 whp gain. The increased dwell eliminated the need to reduce the plug gap with the greatly elevated cylinder pressure. The plugs also stayed cleaner longer on C16 with the increased spark energy minimizing misfiring. When I get back to the shop I will post a tune that has the GM engineered dwell settings in it. My $0.02 the less dwell you can run and still have adequate spark output the better.

Cool

I noticed that the Ls2/ls3 coils dwells were less than the stock 02 square coil dwells. So basically you are suggesting that the lesser dwell would help preserve coil life?

[Fast4.7]

Cool

I noticed that the Ls2/ls3 coils dwells were less than the stock 02 square coil dwells. So basically you are suggesting that the lesser dwell would help preserve coil life?

Not just suggesting it, it is a fact that the coil windings will experience less heat with the reduced dwell time. The less time the power is running through them, the less heat generated and the lower the possibility of heat degredation. The coil windings basically act as reaistors, the more current put into them, the hotter they get.

[SiriusC1024]

Cool

I noticed that the Ls2/ls3 coils dwells were less than the stock 02 square coil dwells. So basically you are suggesting that the lesser dwell would help preserve coil life?

It has more to do with coil operation being optimized for the design. The different types of coils have different B-H curves. Increasing energy input beyond saturation turns into heat. Charge/discharge rates differ. Not setting dwell time to match the coil because there is no hp difference is nonsense because that's not what it's about. It's not hard to copy/paste.

[Fast4.7]

It has more to do with coil operation being optimized for the design. The different types of coils have different B-H curves. Increasing energy input beyond saturation turns into heat. Charge/discharge rates differ. Not setting dwell time to match the coil because there is no hp difference is nonsense because that's not what it's about. It's not hard to copy/paste.

Oversaturation is bad and builds heat for no gain in spark energy, but not fully saturating the coil is not necessarily a bad thing. If you are not needing the full voltage output of the coil to jump the gap, simply not necessary to fully charge said coil. That is proven by the fact that most OEM tunes reduce the dwell at part throttle and at higher engine temperatures to further reduce heat in the coils. Most tunes ramp up the dwell the highest during transient conditions and it falls off during steady state operation. I agree to start with the correct settings for the coils in use. Turns out upon closer inspection the coil dwell settings I have are very close to the D585 truck application. The exception being in the 12-16 volt range they are a bit higher in dwell time. Simple math shows right at 5% longer through that area compared to the stock D585 settings. Looking at the difference between the D585 truck calibration, the GM Racing calibration and a stock 2002 LS1 Z/28 the LS1 coils have the longest dwell of all. Several individuals tested D585 coils on their LS1s and found as much as a 10 hp gain. I fully believe those guys were over saturating the D585 coils and would have killed them over time. The LS1 dwell settings likely allowed for full output of the D585 coils throughout all engine operation and traded longevity for full output. It is also very possible they saw increased power due to replacing a failing coil rather than increased coil output itself. A new set of LS1 coils may very well have resulted in the same power gain. If the vehicle is seeing full power with less dwell, run less dwell, it is easier on the coils long term.

[edcmat-l1]

I'm trying to resize some scope shots to post here. Maybe some can give me advice on how to get that done. Most of my older scope shots are too big to post here and I'm unable to get them down to size without them coming out too physically small to view. If anyone has any advice on how-to, the files currently are .jpeg already and they're roughly 60 KB in size.

Anyway, all smart coils basically have current limiting built into them. Once they reach a certain amperage they will "pull up" from ground just enough to cap the saturation but not enough to fire the coil. You can see this using a 2 channel scope, one channel monitoring the ground the other monitoring the amperage.

Shortening the dwell time while it will help with coil life it will also reduce the voltage output. All coils need to reach a certain level of saturation to provide XX amount of secondary voltage output.

Lengthening the dwell time can and will increase the saturation and secondary output voltage to a point where the current limiting protection kicks in and just will not allow the coil to over charge itself.

[edcmat-l1]

Coil dwell current limiting.jpg

Coil dwell current limiting. Channel 2 is the trigger voltage channel 1 is the charge amperage.

[04silverado6.0]

I have made my own dwell tables for higher compression engines. Id be curious to see the GM calibration for extended dwell.

[edcmat-l1]

I have made my own dwell tables for higher compression engines. Id be curious to see the GM calibration for extended dwell.

Tightening the gap would be easier and most likely the real fix.

[04silverado6.0]

A combination of gap and dwell i would say is ideal. I do like to gap on the tight side just because i can get a little extra life out of the cheap plugs. I could dyno test dwell on my 11:1 6.0 but im sure it would not be measurable.

[Fast4.7]

I have made my own dwell tables for higher compression engines. Id be curious to see the GM calibration for extended dwell.

It is literally the dwell for D585 coils (2002 6.0L used them) with 5% added from 12-16 volts. I was told it was run with D585 coils.

[Fast4.7]

A combination of gap and dwell i would say is ideal. I do like to gap on the tight side just because i can get a little extra life out of the cheap plugs. I could dyno test dwell on my 11:1 6.0 but im sure it would not be measurable.

It is too bad mine will not be an A to B comparison between a Vortec distributor and D585 coils. Swapping intakes and the cam at the same time I do the 24x swap on my 11:1 383. I am also going from an 80mm TB to a 103mm TB and eliminating the restrictive plastic Vortec 350 air hat over the throttle body that necks my 4" air intake down to 3.5". I have a 4.5" to 4" silicone duct to slide over the 103mm and connect to the 4" MAF where I previously had a 4" to 3.5" duct connected to the plastic air hat.

[Fast4.7]

Holley could send me a SBC High Ram and I would do a good writeup on installing it in a Vortec application (my aluminum heads have ports that would match well to it and a dual drilled)and do some testing on a potent small block 383, lol.