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Just having my mind meandering on the 4th of July. If anyone has done a swap to CnP, have u found any appreciable difference in the spark latency now that the ECM/PCM is signaling the LSx type coils?
You don't swap to an individual coil ignition system to try to decrease spark latency. There are tables that, to an extent, can fix spark latency times to what your engine needs. You switch to a newer style ignition scheme because you want a more durable/dependable system, more stable ignition delivery, better dwell times, etc,. It's also not a simple, quick and inexpensive solution.
I totally agree. My question, and its more curiosity, has to do w how much of a variance is there in spark latency between an ignition system using an ignition module and ECM vs CnP w ECM/PCM. I am using the definition of Spark Latency as the lag time between the ECM initiating plug firing and the actual firing of the plug.
So my question is whether anyone who has converted to CnP ignition has found a material difference in the latency values in a stock bin vs what they actually found when using CnP.
There are going to be several variables that are in play. Is the ecm the same, is the spark plug wire length the same, etc. If we're talking LS ecm with the coils on the valve covers vs typical SBC with a single remote coil than yeah I'd think the LS style could use slightly less latency.
Currently, a system is in test that substitutes a orogrammable ICM for the current LT-5 ignition module. The programmable ICM supports the use of CnP LSx style coils. Plug wires are similar length, ECM is the same. It thinks it is comm’d w the stock ICM. There may be additional wire length between the new ICM and ECM given that the new ICM mounts inboard of the cabin whereas the stock ICM was mounted under the plenum.
So the question still remains for those that have made the conversion as to whether they encountered a material difference in needed in spark latency or was the variance insignificant.
Again, same ECM, similar plug wire lengths, different harness wiring lengths between ECM and ICM due to ICM location.
For my LS style ignition I'm using the same spark latency table as I did for my distributor based setup and everything is running fine. I have not noticed any RPM or advance drift. I only know of myself and three other guys on these boards that have switched to individual coil ignitions. Everybody on these boards just swaps engines to the LS family. If you want a large consensus and an in-depth debate on Spark Latency you need to wander over to the MegaSquirt forums.
Is that from someone using the new CnP LT5 interface?
RBob.
Yes it is RBob, but its unfortunately not me altho it is a good friend, and someone who frequents this board at times. I believe u know about this. Working well but still working on some very minor quirks. Engine runs and idles smoothly using the stock LT-5 reluctor and crank sensor.
super late to this thread but any links to the lt-5 icm? if I remember right from the Northstar stuff, that was the eazy way to go dis. only needed a simple trigger wheel like the 4 an v6's use. be nice to see someone make a replacement one..
as for the lag time, it's deep in the old Northstar thread but if I'm remembering right, the bin file from dis cars had a much shorter lag time setting then the dizzy car bin's. someone did the math in degs different. so we plugged the dis settings into the v8 bin once we got the lt1 running off the Northstar coil pack. I would think the ls type coil near plug would be even shorter time wise.
07-04-2019, 11:13 PM
Here’s a pic of LS being used in an LT-5. These are PN 12573190. 
