I know you can convert the LT1 to use a conventional ignition system but is there anyway to keep the opti as your source of ignition and use a carb as your fuel delivery.

I am a bit vague on how the opti senses cylinder location for timing. My car is a 93, I know other years have a crank sensor.

Just wondering if it is a possibility or not. Will the opti loose its high or low res due to no injectors?

 

I'm doing the conversion as we speak. But no I don't think or would you want to keep that damn thing. Just go to the dist. and you won't be sorry.

Kevin

 

It would be more of a temp situation and I know my other options. Eventually it will be a crank trigger and cran dist. Have most of the goods already to do the job just trying to figure some things out combo wise before I switch.

 

The Opti has a pattern of low resolution pulses, eight to be exact, that tells the PCM which cylinder it "next". In effect, it is a cam position sensor.

You need the low res pulse from the Opti if you are going to run your stock PCM for any reason. One reason might be for the speedometer. Without the low res pulse, the Opti also shuts down the fuel pump, but with a carb, you are probably not going to want the stock high pressure FI fuel pump anyway.

If you wanted to keep the "stock" ignition, you need to feed the stock PCM all the data it needs to set the timing. Includes:

-high res Opti pulses
-low res Opti pulses
-MAP
-IAT
-coolant temp

An alternative would be to simply use something like the Electromotive lost spark 4-coil direct fire ignition and avoid the Opti and stock PCM alltogether. If you have to keep the stock PCM, find someone with an E'motive Opti-Eliminator/SDI for sale, and use the chip that comes with it to synthesize the low res pulse. The stock PCM will work fine with the synthesized pulse pattern, since it is using the lost spark ignition, and won't matter if it synchs out of phase with the correct cam position.

Carb and Opti.... certainly the best of both worlds....

 

I am sure the coolant temp is no problem since those sensors will be in their same spots. Is is a possibility to use a resistor of the correct value to mimic the a sensor mainly the IAT if i just want to delete it out of the way. Or else just keep it.

As for MAP what would be the best location on a typical SBC intake to obtain proper readings?

Will the opti still throw out low and high res with the injectors missing. If I place a carb and traditional SBC intake on the block. missing stock items will be the injectors, EGR, MAP, IAC, TPS


Is the ECM going to be searching for the TPS and IAC? Will this pose a problem as well. EGR/AIR is delete already.

 

The IAT contribution to ignition timing appears to be about 3deg advance. You could just put a resistor in the range of 4,400 - 2,500 ohm in the connection. OR you could just leave the sensor connected and stick it outside the engine compartment to pick up ambient air temperature.

MAP need to be connected to a full vacuum port on your intake manifold. The stock sensor has a tit that sticks into the intake manifold. Just attach a vacuum hose to the tit, and the other end of the hose to the full vacuum port on the intake. The shorter the hose the better, or you will be building "delay" into the MAP sensor response.

You will also need to do something about the absence of a knock sensor. You could just screw the stock one into the block drain port, like stock location, and you will be OK.

I'm pretty sure everything will function. I run my stock PCM for the speedo, fuel pump and IAC. Everything else is run off a MoTeC computer. I do have duplicate IAT and CLT temp sensors in the system so I can feed both computers. MAP, TPS and Opti feed both computers in parallel. I get codes for lack of injector connections, knock sensor, absence of any sort of ignition module, and a few others, but the stock PCM still appears to be trying to set ignition timing. But without the KS, it goes into a default knock retard program, with up to 12deg retard.

 

You state the question of the knock sensor.

This will be a LT1 setup still but just with the GMPP intake and carb setup. I am not switching the a GEN 1 setup just yet.

I guess it is still a bit of a gamble to see how the car will actually act once all is converted since it will be looking for items with no response. Might give this a try this summer and see how goes.