LT1 opti to LS1 coil conversion
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
Here is another option that I posted in another thread:
MSD DIS IGNITION SYSTEM
You'd have to do the LT1 distributor hole mod to make this work on an LT1, but it's another $1200 option for those who've had enough with their opti's.
MSD DIS IGNITION SYSTEM
You'd have to do the LT1 distributor hole mod to make this work on an LT1, but it's another $1200 option for those who've had enough with their opti's.
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
And as I posted in another thread, it does not include any provisions to talk to the stock EFI in the car whatsoever, so the CCM would be unhappy (dash), the ABS/ASR would be unhappy and would not be able to retard timing for ASR events, and of course the PCM would be unhappy due to the loss of high resolution and low resolution opti signals, among others.
It could be used as a piggyback, but if you wanted the car's systems to continue working as intended you would need to keep the optispark right where it is. Now all that being said, if MSD wanted to they could have a version of that kit designed for the Gen 2 LT1 and it wouldn't change much about the design in the long run. But as it stands, it's designed for 'normal' small-block engines, not our specific application, and as such will require making some decisions.
It could be used as a piggyback, but if you wanted the car's systems to continue working as intended you would need to keep the optispark right where it is. Now all that being said, if MSD wanted to they could have a version of that kit designed for the Gen 2 LT1 and it wouldn't change much about the design in the long run. But as it stands, it's designed for 'normal' small-block engines, not our specific application, and as such will require making some decisions.
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
I don't agree. Well, I do, but...
Since it runs it's own distributor, You could easily leave the opti in place and the opti harness hooked up...then ditch the coil, wires, ICM...rotor too. The Opti would feed a signal to the ECM and all would function normally....other than the (MSD) ignition would operate isolated/on it's own, w/it's own distributor (crank/cam sensor).
Oh wait....you already said that in your second paragraph.
Sorry.
Since it runs it's own distributor, You could easily leave the opti in place and the opti harness hooked up...then ditch the coil, wires, ICM...rotor too. The Opti would feed a signal to the ECM and all would function normally....other than the (MSD) ignition would operate isolated/on it's own, w/it's own distributor (crank/cam sensor).
Oh wait....you already said that in your second paragraph.
Sorry.
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
Hey, no worries! It's just that as far as actually "getting rid of" the optispark goes, the only available option I'm aware of that actually keeps everything in the car happy is the Torqhead. All other options either require losing various systems (the dash and ABS/ASR, mostly) or keeping the opti on as a sensor for the factory PCM to keep it and everything else happy. Though the MSD solution, as noted, will additionally lose knock feedback and ASR timing retard as it has zero provision for external input save for a coolant temperature sensor. The LTCC and its DIY derivatives accept timing input from the factory PCM to handle advance/retard.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
I did take a look, and it doesn't have any way to make the CCM or ABS/ASR happy, as you can see it's not in a Corvette. But if you don't care about the CCM (digital dash) or ABS/ASR, then yessir, it's yet another option to throw onto the pile. I guess it's basically the DIY version of the Torqhead, minus the niceties they include in their kit that make it a plug-and-play install for C4 Corvettes.
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
I could be wrong, and if I am, I'd love to hear some clarification, but I believe that the crux of the compatibility problem between LTx/Opti and ANY other ignition/engine management system boils down to the resolution. Everyone is using 4x, 8x, 24x or 56(?)x...something like that. The LTx ECM is looking for 360* of resolution...plus the low res, cylinder specific, 4x signal.
With that operating strategy, IDK how you could "feed" the LTx ECM a usable, aftermarket signal from any option -that isn't an "opti" based signal. The only solution that I can fathom would be a dual reluctor wheel affair with one 360 pulse wheel and another, 8 pulse wheel run off the cam, with varying pulse widths or multi pulses for the "low res" signal.
That leaves us with basically two configurations:
1. A system that leaves the opti unit in place to trigger the system
2. a system that abandons that entirely and therefore, looses out on the module to module interfaces.
?
With that operating strategy, IDK how you could "feed" the LTx ECM a usable, aftermarket signal from any option -that isn't an "opti" based signal. The only solution that I can fathom would be a dual reluctor wheel affair with one 360 pulse wheel and another, 8 pulse wheel run off the cam, with varying pulse widths or multi pulses for the "low res" signal.
That leaves us with basically two configurations:
1. A system that leaves the opti unit in place to trigger the system
2. a system that abandons that entirely and therefore, looses out on the module to module interfaces.
?
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Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
I could be wrong, and if I am, I'd love to hear some clarification, but I believe that the crux of the compatibility problem between LTx/Opti and ANY other ignition/engine management system boils down to the resolution. Everyone is using 4x, 8x, 24x or 56(?)x...something like that. The LTx ECM is looking for 360* of resolution...plus the low res, cylinder specific, 4x signal.
With that operating strategy, IDK how you could "feed" the LTx ECM a usable, aftermarket signal from any option -that isn't an "opti" based signal. The only solution that I can fathom would be a dual reluctor wheel affair with one 360 pulse wheel and another, 8 pulse wheel run off the cam, with varying pulse widths or multi pulses for the "low res" signal.
That leaves us with basically two configurations:
1. A system that leaves the opti unit in place to trigger the system
2. a system that abandons that entirely and therefore, looses out on the module to module interfaces.
?
With that operating strategy, IDK how you could "feed" the LTx ECM a usable, aftermarket signal from any option -that isn't an "opti" based signal. The only solution that I can fathom would be a dual reluctor wheel affair with one 360 pulse wheel and another, 8 pulse wheel run off the cam, with varying pulse widths or multi pulses for the "low res" signal.
That leaves us with basically two configurations:
1. A system that leaves the opti unit in place to trigger the system
2. a system that abandons that entirely and therefore, looses out on the module to module interfaces.
?
But I mean that's just me. I don't have any experience feeding fake data to control computers and making them happy, no sir, I would never!
Race Director
Joined: Sep 2001
Posts: 14,680
Likes: 752
From: NEwhere Ohio
3. A system that 'emulates' an opti's low and high res signals by fudging them based on its reluctor of choice and feeds that falsified signal back to the PCM to make it and all the rest of the car's systems happy. Additionally have an external input for timing adjustment so that knock feedback and ASR will function correctly.
But I mean that's just me. I don't have any experience feeding fake data to control computers and making them happy, no sir, I would never!
But I mean that's just me. I don't have any experience feeding fake data to control computers and making them happy, no sir, I would never!
you dont have to use the optispark for the ignition (if you believe coil on plug is superior).
im talking using the optispRk for its signal to keep the existing lt1 pcm happy and controlling ASR, etc
whats its cam/ timing cover like?
do the lsx motors use the same cam as an sbc?
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
no
coil-per-plug is superior
but y tho
imaginary
no
imaginary
no
Burning Brakes
Joined: Sep 2016
Posts: 1,133
Likes: 319
From: Ohio
I'm not sure what his fascination is with putting an Opti on an LS but its absolute insanity.
The LS coils are so much more reliable that your Opti will fail 8 times before just 1 of the 8 LS coils fails, not to mention the spark energy increase is SIGNIFICANT.
Also, an MSD coil for an LT1 is rated at 110 mJ of energy.
Each individual LS truck coil is rated at 215 mJ of energy.
The LS coils are so much more reliable that your Opti will fail 8 times before just 1 of the 8 LS coils fails, not to mention the spark energy increase is SIGNIFICANT.
Also, an MSD coil for an LT1 is rated at 110 mJ of energy.
Each individual LS truck coil is rated at 215 mJ of energy.
Last edited by JoeNova; Dec 3, 2020 at 12:25 PM.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Well I believe the optispark has the better resolution from the high resolution waveform trigger. But having and LS reluctor wheel triggered ignition already you have a much more reliable ignition without the mechanical distributor. What you would gain after all the effort to mate the optispark to a distributorless igniton would most likely be unmeasurable. That's my 2 cents here, take it or leave it.
Burning Brakes
Joined: Sep 2016
Posts: 1,133
Likes: 319
From: Ohio
I'd NEVER let it control the ignition.
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
Burning Brakes
Joined: Sep 2016
Posts: 1,133
Likes: 319
From: Ohio
Well I believe the optispark has the better resolution from the high resolution waveform trigger. But having and LS reluctor wheel triggered ignition already you have a much more reliable ignition without the mechanical distributor. What you would gain after all the effort to mate the optispark to a distributorless igniton would most likely be unmeasurable. That's my 2 cents here, take it or leave it.
Sure, the Opti has many counts on the high resolution side. They're all identical, with zero bearing on engine position. They simply track each degree of engine movement.
The accuracy of the 24x/1x wheel combo on the 24x is mechanically limited to 2* per 2500 RPM, but the gen 3 ECU uses timing interpolation to measure the fractions of a millisecond between 2 teeth to time fuel and ignition events down to the fraction of a degree.
Then Gen 4 58x/4x is mechanically limited to 1 degree at 10,000 RPM, with an ECU that can react considerably faster than the Gen 3 stuff.
Does the LT ECU do this, or does it strictly use engine position determined by the 2 sensors? If it relies on the optical sensor alone for engine position, this would likely make the gen 3 ECU more accurate (it can control timing down a 1/10th of a degree).
Burning Brakes
Joined: Sep 2016
Posts: 1,133
Likes: 319
From: Ohio
I just described it in the post you quoted.
A lot of the electronics in the LT powered Corvettes rely on the OEM ECU. Without it, you lose their functionality.
Swapping in a gen 3/4 engine, you'll be able to control the engine just fine, but will not have any way for the ECU to communicate to the car.
If you had a way to keep the Optispark in place on an LS engine, you could tuck away a stock LT ECU and retain full functionality of the car's electronics.
A lot of the electronics in the LT powered Corvettes rely on the OEM ECU. Without it, you lose their functionality.
Swapping in a gen 3/4 engine, you'll be able to control the engine just fine, but will not have any way for the ECU to communicate to the car.
If you had a way to keep the Optispark in place on an LS engine, you could tuck away a stock LT ECU and retain full functionality of the car's electronics.
Race Director
Joined: Sep 2001
Posts: 14,680
Likes: 752
From: NEwhere Ohio
I just described it in the post you quoted.
A lot of the electronics in the LT powered Corvettes rely on the OEM ECU. Without it, you lose their functionality.
Swapping in a gen 3/4 engine, you'll be able to control the engine just fine, but will not have any way for the ECU to communicate to the car.
If you had a way to keep the Optispark in place on an LS engine, you could tuck away a stock LT ECU and retain full functionality of the car's electronics.
A lot of the electronics in the LT powered Corvettes rely on the OEM ECU. Without it, you lose their functionality.
Swapping in a gen 3/4 engine, you'll be able to control the engine just fine, but will not have any way for the ECU to communicate to the car.
If you had a way to keep the Optispark in place on an LS engine, you could tuck away a stock LT ECU and retain full functionality of the car's electronics.
you correctly interpreted what i was asking and avoided ‘making fun of me’ for the question.
Whether others like the optispark or not, it may have a place in lsx based swaps.
Burning Brakes
Joined: Sep 2016
Posts: 1,133
Likes: 319
From: Ohio
I'm not sure if belt driven sensors would be an option or not. You don't exactly need accuracy since they aren't controlling the engine.
I guess the thing to do would be to find exactly which sensors the LT ECU would need to see to keep all OEM functionality inside the car and go from there.
Typical sensors like oil pressure, water temp would be extremely easy to adapt, as the LS engine has multiple ports for these. You're basically stuck with a way to detect RPM.
Minus an RPM signal from the optispark, would everything in the car still operate as normal with the stock LT1 ECU tucked away somewhere under the hood or dash?