LS computer for non-LS engine
06-13-2014, 07:55 AM
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LS computer for non-LS engine OK, I am a newbie here and I am trying to help a buddy convert his 1973 Cadillac 500cid engine to EFI. He wants to use the GM LS-type control system, in particular, the 411 PCM. I did some research and I agree that this PCM has a lot of capabilities and there are several sources for programming software to program and tune it. However, this PCM is looking for a 24x VRS crank signal and a 1x VRS cam signal from the engine. On LS engines these sensors are built into the engine. So on the Cadillac 500cid engine, how can I get the required crank and cam signals?
I have looked for aftermarket Distributors, but all I have found is the Accel Dual sync with uses hall sensor. I could make the cam sensor work but the crank sensor data rate and profile is 8X. I could make a distributor the provide the cam signal pretty easily, but what to do for the 24x crank signal?
Anyone every done anything like this?
P.S. I have made a 1970 Cad 472 engine run with Ford EFI, using a 1990 SEFI-MA EEC IV system from a 5.0L Mustang. The key to that was making a TFI distributor to fit in the Cad motor to get the cam and crank signals. So I am familiar with the Cad engines and with EFI systems in general.
I have looked for aftermarket Distributors, but all I have found is the Accel Dual sync with uses hall sensor. I could make the cam sensor work but the crank sensor data rate and profile is 8X. I could make a distributor the provide the cam signal pretty easily, but what to do for the 24x crank signal?
Anyone every done anything like this?
P.S. I have made a 1970 Cad 472 engine run with Ford EFI, using a 1990 SEFI-MA EEC IV system from a 5.0L Mustang. The key to that was making a TFI distributor to fit in the Cad motor to get the cam and crank signals. So I am familiar with the Cad engines and with EFI systems in general.
06-13-2014, 10:07 AM
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Have you been to Thirdgen.org
There are a lot of hacks for the GM ECM.
http://www.thirdgen.org/
Have you looked at MegaSquirt?
They support about any ignition pattern imaginable.
http://www.msextra.com/forums/index....112a6a1c5d28ad
This is how I set up a 36-1 trigger wheel for a traditional Pontiac engine.
Trigger wheel is bolted to the back side of the crank dampener.
There are a lot of hacks for the GM ECM.
http://www.thirdgen.org/
Have you looked at MegaSquirt?
They support about any ignition pattern imaginable.
http://www.msextra.com/forums/index....112a6a1c5d28ad
This is how I set up a 36-1 trigger wheel for a traditional Pontiac engine.
Trigger wheel is bolted to the back side of the crank dampener.
Last edited by Ollie8974; 06-13-2014 at 10:23 AM.
06-13-2014, 10:16 AM
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Ollie,
Thanks. Yes I have looked at Thirdgen.org and did not really find any good info their on this concern. Yes, MegaSquirt does support just about any sensor inputs but the owner wants to use a production GM EFI system PCM as the basis for his system.
The 24x and 58x GM controllers can do just about anything you could want including FBW features with integrated speed control etc.etc.. To use on of these systems, what we really need is a way to provide the 24x or 58x VRS crank sensor input signals. I think we are going to need to fab up a wheel and sensor mount for the front of his 500cid engine. Unless someone here has a better suggestion.
Thanks. Yes I have looked at Thirdgen.org and did not really find any good info their on this concern. Yes, MegaSquirt does support just about any sensor inputs but the owner wants to use a production GM EFI system PCM as the basis for his system.
The 24x and 58x GM controllers can do just about anything you could want including FBW features with integrated speed control etc.etc.. To use on of these systems, what we really need is a way to provide the 24x or 58x VRS crank sensor input signals. I think we are going to need to fab up a wheel and sensor mount for the front of his 500cid engine. Unless someone here has a better suggestion.
06-13-2014, 11:27 AM
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Ollie,
Thanks. I wonder if the GM PCM uses the timing between events on the crank trigger as information as well as the provide shape. I know that Ford does use this info and thus when you make their 36-1 wheel you need to keep it the exact size and profile as that Ford uses in production. Luckily, Ford uses a pretty large wheel and they put it on the front damper. The GM 24x and 58x factory reluctance wheels are a smaller diameter that the Cadillac 500cid engine front damper. Looks like we will need to do some designing to get it packaged to that it works correctly without our sensor hitting the Damper or missing signals.
Any other suggestions anyone?
Thanks. I wonder if the GM PCM uses the timing between events on the crank trigger as information as well as the provide shape. I know that Ford does use this info and thus when you make their 36-1 wheel you need to keep it the exact size and profile as that Ford uses in production. Luckily, Ford uses a pretty large wheel and they put it on the front damper. The GM 24x and 58x factory reluctance wheels are a smaller diameter that the Cadillac 500cid engine front damper. Looks like we will need to do some designing to get it packaged to that it works correctly without our sensor hitting the Damper or missing signals.
Any other suggestions anyone?
06-17-2014, 06:59 AM
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Well, looks like we have decided to back-up and use a lower data rate GM PCM system.
Plan now is to use the 12200411 PCM with the 2002 Chevy Savanna van 5.7L V8 Vortec operating system. This system needs only a 4x crank signal which we can get by using the Accel Dual Sync distributor for both crank and cam signals.
It is a lower data rate, but it should still work just fine to get this old Cad motor up to modern SEFI-MA performance.
Plan now is to use the 12200411 PCM with the 2002 Chevy Savanna van 5.7L V8 Vortec operating system. This system needs only a 4x crank signal which we can get by using the Accel Dual Sync distributor for both crank and cam signals.
It is a lower data rate, but it should still work just fine to get this old Cad motor up to modern SEFI-MA performance.