LT5 Ignition Systems Question??? - ZR-1 Net Registry Forums

LT5 Ignition · 03-15-2011

I can now appreciate the concern with the IM availability. Also, I apoligize I got my dates mixed up on LS introductions in post 56. It was the Gen 2 small block LT1 in 1992 (ABITS). The Gen3 LS ~ '97 and Gen 4 ~ '05. I agree that if you can keep the IM module from sinking the primary current it will run cooler.
Now, if someone can come up with a way of turning the 9x VR signal into into a 4x logic signal and also take the single EST signal from the ECM and steer it to the 4 coil pairs in firing order it seems the IM can be eliminated. For sure the LS systems have dwell overlap starting around 4000 RPM. Perhaps the Lt5 does too. In the run mode the IM could have been designed to follow the falling 4x EST signal from the ECM for end of dwell spark timing but control the start of dwell ahead of the rising EST pulse. I can not remember if it actually was. Would it be worthwhile to put a couple of current probes and a scope on the coil primaries to see if the dwell overlaps on a LT5 at higher speed? I wish I had one!!

03-15-2011	#24
LT5 Ignition Join Date: Feb 2011 Location: Sterling Heights, MI Posts: 11	Re: LT5 Ignition Systems Question??? I can now appreciate the concern with the IM availability. Also, I apoligize I got my dates mixed up on LS introductions in post 56. It was the Gen 2 small block LT1 in 1992 (ABITS). The Gen3 LS ~ '97 and Gen 4 ~ '05. I agree that if you can keep the IM module from sinking the primary current it will run cooler. Now, if someone can come up with a way of turning the 9x VR signal into into a 4x logic signal and also take the single EST signal from the ECM and steer it to the 4 coil pairs in firing order it seems the IM can be eliminated. For sure the LS systems have dwell overlap starting around 4000 RPM. Perhaps the Lt5 does too. In the run mode the IM could have been designed to follow the falling 4x EST signal from the ECM for end of dwell spark timing but control the start of dwell ahead of the rising EST pulse. I can not remember if it actually was. Would it be worthwhile to put a couple of current probes and a scope on the coil primaries to see if the dwell overlaps on a LT5 at higher speed? I wish I had one!!