LT5 Ignition Systems Question??? - Page 5 - ZR-1 Net Registry Forums

mike100 · 03-10-2011

do the ign modules have different part numbers for different years, or are they all the same? I want to know if I can keep a spare from a 90 for use on my 91.

zr1don · 03-10-2011

For LT5 Ignition: My LT5 continues to run w/two spark plug wires pulled. I inadvertantly left #'s 1 & 3 off and failed to plug them back in when I started it. It ran rough, but continued to run in that condition.

A26B · 03-10-2011

Quote:

Originally Posted by mike100

do the ign modules have different part numbers for different years, or are they all the same? I want to know if I can keep a spare from a 90 for use on my 91.

Depends on which 90 DIS module. The first 500 90 models used PN 1103737.

LT5 Ignition · 03-10-2011

ZR1don,
thanks for the info on the secondary wires. The IM does not sense or control the high voltage side of the coil (transformer). Therefore it should continue to operate all the coils with secondary wires off ( Be careful with the loose wire 40,000 volts !!)
XfireZ51,
If all 4 coils stop working it is more likely that the IM is the cause of them not working since it is the source of their power. In addition to checking the resistance of coil windings, you can connect a spark plug across the secondary towers and momentarily touch 12 volts across the primary. You should see a nice blue spark.

LT5 Ignition · 03-10-2011

XfireZ51 ref. post #35,
There are 3 operating points to challenge an ignition design.
1 idle requires higher energy ( longer, fatter spark ) to ignite the poorer mixture due to low air velocity across the injector. LT5 has high velocity across the primary injector at idle because the secondary runners are closed.
2 Peak torque has the highest cylinder pressure to ignite so you need the most secondary voltage to jump the gap. After the initial arc not much energy is required because the dense gas contains a lot of energy from heat and compression.
3 at high speed you start to run out of time to charge the coil or coils. Big problem with distributors on an 8 cylinder. 4 coil DIS helps because two coils can charge at a time.
I know the system has some margin for more power. but I have not tested it beyond stock power. I would be interested if some Forum members have.

carter200 · 03-10-2011

Quote:

Originally Posted by A26B

Depends on which 90 DIS module. The first 500 90 models used PN 1103737.

Jerry,
Do you have a number for a 95?

tomtom72 · 03-10-2011

Hi Ron, I think that all the larger displacement LT5's, like the 368, 400, 415 and the 441 and 427's which range in hp from 500+ rwhp to past 650 rwhp still use the OEM DIS ignition.

I would hasten to add that I am not fluent in making any of these bigger inch LT5's...it's just that the ignition system is never mentioned as having been supplanted by another system other than the OEM system on these motors.

Tom

XfireZ51 · 03-10-2011

LT5-Ignition,

If you were responding to my question of all 4 coils. not working, I was posing that condition where rather than grounding the coil, that ground signal was used as a trigger for the LSx coil. I believe the IM fires the appropriate coil by grounding that coil. Now what if the IM was grounding the coil was simply converted to an ~.4v trigger signal sent to the corresponding LSx coil pairs.
There would be very little load to the IM. And now that happens for all coils. Also, what is the dwell set for the LT-5 coils and where is it controlled? CN it be adjusted?

I hope that I am being clear and would be happy to try to clarify further if I can. But think of it as the IM being converted to simply a sequencer for the LSx coils. And using what was originally the trigger ground for the LT-5 coils and converting that into a compatible trigger signal recognized by the LSx coils instead. Much less voltage. As I see it, GM took the ignition module functions and divided those functions between the coils themselves and the ECM thereby eliminating the need for the IM.

-=Jeff=- · 03-10-2011

F.A.S.T. use to (might still) make an eDIST. it would eliminate a distributor and would sequence LS Coils.. it needs a Crank and Cam Sensor.. cam for position and Crnak for firing, but the Crank sensor had 4 notches not 9..

I would think that connected to our ECM might work, but the main challenge would be the Crank sensor

-=Jeff=- · 03-10-2011

eDIST threads I found:

http://www.thirdgen.org/techboard/di...on-system.html

http://www.turbobuick.com/forums/per...-ignition.html

03-10-2011	#41
mike100 Join Date: Feb 2011 Location: San Marcos CA Posts: 1,802	Re: LT5 Ignition Systems Question??? do the ign modules have different part numbers for different years, or are they all the same? I want to know if I can keep a spare from a 90 for use on my 91.

03-10-2011	#42
zr1don Join Date: Jan 2006 Location: Temecula, CA Posts: 92	Re: LT5 Ignition Systems Question??? For LT5 Ignition: My LT5 continues to run w/two spark plug wires pulled. I inadvertantly left #'s 1 & 3 off and failed to plug them back in when I started it. It ran rough, but continued to run in that condition.

03-10-2011	#44
LT5 Ignition Join Date: Feb 2011 Location: Sterling Heights, MI Posts: 11	Re: LT5 Ignition Systems Question??? ZR1don, thanks for the info on the secondary wires. The IM does not sense or control the high voltage side of the coil (transformer). Therefore it should continue to operate all the coils with secondary wires off ( Be careful with the loose wire 40,000 volts !!) XfireZ51, If all 4 coils stop working it is more likely that the IM is the cause of them not working since it is the source of their power. In addition to checking the resistance of coil windings, you can connect a spark plug across the secondary towers and momentarily touch 12 volts across the primary. You should see a nice blue spark.

03-10-2011	#45
LT5 Ignition Join Date: Feb 2011 Location: Sterling Heights, MI Posts: 11	Re: LT5 Ignition Systems Question??? XfireZ51 ref. post #35, There are 3 operating points to challenge an ignition design. 1 idle requires higher energy ( longer, fatter spark ) to ignite the poorer mixture due to low air velocity across the injector. LT5 has high velocity across the primary injector at idle because the secondary runners are closed. 2 Peak torque has the highest cylinder pressure to ignite so you need the most secondary voltage to jump the gap. After the initial arc not much energy is required because the dense gas contains a lot of energy from heat and compression. 3 at high speed you start to run out of time to charge the coil or coils. Big problem with distributors on an 8 cylinder. 4 coil DIS helps because two coils can charge at a time. I know the system has some margin for more power. but I have not tested it beyond stock power. I would be interested if some Forum members have.

03-10-2011	#47
tomtom72 Join Date: Dec 2004 Location: Jacksonville, FL USA Posts: 4,645	Re: LT5 Ignition Systems Question??? Hi Ron, I think that all the larger displacement LT5's, like the 368, 400, 415 and the 441 and 427's which range in hp from 500+ rwhp to past 650 rwhp still use the OEM DIS ignition. I would hasten to add that I am not fluent in making any of these bigger inch LT5's...it's just that the ignition system is never mentioned as having been supplanted by another system other than the OEM system on these motors. Tom __________________ 1990 ZR-1, Black/grey, #2233, stock. ZR-1 Net Reg Founding Member #316 & NCM member

03-10-2011	#48
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,696	Re: LT5 Ignition Systems Question??? LT5-Ignition, If you were responding to my question of all 4 coils. not working, I was posing that condition where rather than grounding the coil, that ground signal was used as a trigger for the LSx coil. I believe the IM fires the appropriate coil by grounding that coil. Now what if the IM was grounding the coil was simply converted to an ~.4v trigger signal sent to the corresponding LSx coil pairs. There would be very little load to the IM. And now that happens for all coils. Also, what is the dwell set for the LT-5 coils and where is it controlled? CN it be adjusted? I hope that I am being clear and would be happy to try to clarify further if I can. But think of it as the IM being converted to simply a sequencer for the LSx coils. And using what was originally the trigger ground for the LT-5 coils and converting that into a compatible trigger signal recognized by the LSx coils instead. Much less voltage. As I see it, GM took the ignition module functions and divided those functions between the coils themselves and the ECM thereby eliminating the need for the IM.

03-10-2011	#49
-=Jeff=- Join Date: Jul 2007 Location: Bartlett, IL Posts: 7,150	Re: LT5 Ignition Systems Question??? F.A.S.T. use to (might still) make an eDIST. it would eliminate a distributor and would sequence LS Coils.. it needs a Crank and Cam Sensor.. cam for position and Crnak for firing, but the Crank sensor had 4 notches not 9.. I would think that connected to our ECM might work, but the main challenge would be the Crank sensor __________________ 1990 Corvette ZR-1 #1051 Watson Headers (2" Primary) - Borla Catback Late Model IH - Plenum Coilovers - 4.10s Custom Interior NCM Lifetime Member #978