Wouldnt all you need to do to get this to work is to swap the coil and injector wiring so that it fires the right one so that the LT1 would fire in the right order? I would think that you would need to use the same sensors on the LS1 on the LT1 right? Just courious.

Thanks
Jeremy

 

Been thinking about this for a while. The maf sensor uses a differant output I think (I belive the whole unit will interchange though). Your right on having to swap some injecter and coil wires around.
I really haven't been able to find any info on cam or crank signals or what the computer uses as referance instead of the optispark except that it's a reluctor on the cam.
The colors on the wiring are similar from one system to the other.

 

Well doesnt the LS1 a batch fire motor instead on sequental? If so then there would be no need for a cam or crank sensor. That was the other thing I forgot to ask, I know that the LS1 uses a cam sensor, but how is it wired up? I have never really looked at one before, so I someone has pics that would really help.

 

LS1 uses sequential injection. Cam position sensor is a single-notched reluctor wheel on the back of the camshaft, and the pickup plugs in from the top of the engine.

The PCM can actually synch correctly even if the CMP signal is not present. On startup, it fires the plug based on crank position signal (CKP) and then looks at the MAF sensor. If air flow suddenly increases after the initial attempt to synch/fire, it assumes it has synched correctly, and continues to run. If air flow does not increase, it assumes it made a bad guess, and resynchs the system by one crank revolution.

 

Hmmmmm
wouldn’t this be a cheaper long-term alternative to getting rid of the dreaded opti?
The only major thing would be in setting up a crank trigger (I am sure that a MSD crank trigger system can be adapted) what do you guys think?

 

Mr Injuneer, is the crank position signal the same from an lt1?

 

There is no CKP on an LT1, at least not for ignition purposes. The 96/97's added a CKP for misfire detection only.

The LT1 CMP is essentially the low resolution pulse pattern from the Opti wheel. There are 8 slots in the inner diameter of the optical wheel, and there is a unique number of degrees for four of the cylinders, and they alternate with 4 equal length slots for the other four cylinders. By knowing the length of the pulse in degrees (it can compare the low res pulse to the 360 individual pulse from the high res/outer portion of the wheel) it knows exactly which cylinder is approaching TDC on the compression stroke.

The exact pulse pattern is 2deg(#1)-7deg(#8)-2deg(#4)-12deg(#3)-2deg(#6)-17deg(#5)-2deg(#7)-22deg(#2).

Just comparing the wiring diagrams for the LT1 PCM to the LS1 PCM (I only have the LS1 diagrams for the C5), it is hard to see how you would just swap computers. But the C5 diagrams are complicated by the real time damping system, pitch/yaw control, dual knock sensors, dual fuel tanks, etc. Maybe the F-Body wiring diagrams would be more similar.

I think all someone needs to do is duplicate the Electromotive Opti-Eliminator chip, and incorporate a "synch" input... something like the cam sensor NEDyno is using. Or, if MSD ever actually produces the "CPC" distributor "plug" cam position sensor, build a chip that synthesizes the Opti pulse pattern from the "plug" output pulse signal. I wouldn't think it would be that difficult.

 

Sorry, now that I look at my original post I didnt specifiy enough. What I meant was not just swaping the PCM, but the PCM wiring harness and the sensors, where needed. The only real problem I see is possible with the cam sensor so the computer knows where the pistons are. How did they get the PCM to work on the TPI engines? Did they use the HEI as a type of cam position sensor or was it just batch fire?

 

The distributor on the TPI engines is the de facto cam position sensor for ignition timing.... it fires the next plug in the sequence. The ECM didn't need to know the cam position, since the TPI injectors are batch fire.

If you want to run an LT1 without the Opti, all you need to do is start with a 93 ECM (batch fire) and use the Opti-Eliminator chip, which synthesizes the low res pulse from a 60-tooth crank wheel. Not sure where you would find one, but I know my old O-E/SDI setup is still floating around out there......

 

That's the one i was talking about . Any idea if the signal from this is compatible with what the ls1 uses?

I don't think it would be "plug and play". An adapter harness could be used, wiring harness swapped or rewire the plug at the computer.

Some of the benefits would be retaining obd2, access to newer technology (livev5/diablo/ect), coil per cylinder,....

 

IF you could get this to work, would LS1 Edit work on an LT1???

justin

 

Yes, and you'd pretty much HAVE to have that or the PCM reprogrammed to adjust spark timing, fuel tables, etc. to work with the LT1.

 

Wouldn't it create a problem with the firing order (unless you can program the firing order) It seems the cam would be opening the wrong valves for the computer...


Jason

 

Correcting the LS1 computer firing order to the LT1 engine firing order should be as simple as hooking up the injector wires in the correct order, and hooking the individual coils to the correct plug. Where you might get into problems would be in the misfire detection, where the PCM is looking for a specific pattern in the irregularities of the crank.

Somehow, it would seem easier to keep the LT1 PCM and develop a means to generate the Opti low res pulse pattern from a cam sprocket or distrubutor "plug" type sensor. It appears people are having some problem locating/mounting the magnet in the LT1 cam sprocket, at least from Jimlab's experience, but I have seen a do-it-yourself magnet mounted in a cam sprocket on a Ford engine, that pushes a Pro 5.0 car to 7.0-seconds.

Once you have that signal, all you need is a chip that produces the low res pulse pattern each time the chip is triggered by the crank sensor. Then you need to correct the timing of the pulse pattern based on comparing the pulse signal to a crank trigger signal, to keep them in synch.

The E'motive chip synthesizes the low res pulse pattern from a crank trigger, so it would seem that something similar could be done along the lines of what I outlined.

Just throwing some thoughts out... not a lot of in-depth thinking behind them, just random thoughts.

 

Would the tooth learn error mode take care of this and do the obd2 lt1 computers have this mode?