Hey I'm looking for some info about the Megasquirt vs converting to a LS PCM. I've beat the stock LT1 2 bar open loop to death and while it runs perfect I want more control over winter/summer AFR changes, the last and final limiting factor ends up being the IAT sensor if you can believe that. The IAT settings in Tunercat do not directly affect the result of the fueling, there is some other unknown setting that IAT feeds info to that we cannot control in Tunercat. if it did then winter/summer temp AFR changes could be tuned, but varying IAT temps while data logging shows inconsistent (but safe) changes in injector pulse width, just enough to annoy and realize it would be perfect if we could use it directly to control fuel adjustments.

So, has anyone piggybacked a Megasquirt to the stock PCM to control fuel only? Specifically all I need to do is figure out how to get the opti signal to the Megasquirt since I can piggyback MAP and add a Coolant sensor since it's an RTD. The IAT sensor I can steal since the Lt1 only uses it for fuel.

 

yes I am intrested to if this is possible

 

I had my 93 vette fuel only for a short time years ago on an MS1. You can feed the MS just the low resolution wire from the opti-spark. I didn't have this very long and I put a 60-2 tooth wheel on it and 4 coils for wasted spark ignition.

I left the stock ecm in just to run the gauges. Between being able to tune while it is running and having software that is so much better, It is so much faster and easier to tune the MegaSquirt than the stock ecm.

 

HOW DID YOU RUN THE 60-2 WHEEL (my problem is i run a blower on the car so the blower pulley might be a problem) thx

 

I had 2 different setups for the 60-2 on the LT1 (now it has a 555 BBC).
1st I had spacers that held the trigger wheel out in front of the damper / pulley. this is the way Electromotive did it with the old Opti-Spark Eliminator.

Then a bit later I put switched to a regular sbc damper and pulley, so then I sandwiched it between the damper and pulley. This setup is a lot more straight forward and the pulley from an L98 and standard sbc damper does still line up with the other accessories.
The trouble with the later setup is that you need to have the Opti-spark gone completely. Actually at that point I was using a double roller timing chain and electric water pump.

 

would you happen to have pictures of your old set up some place?

 

You can see the pulley and wheel in these pics, this is with the later setup where I had gone to the standard damper and L98 pulley:
http://www.myphotosonline.biz/albums...Nov+17%2C+2002

The previous setup, I can't find any pics. A search for Electromotive Opti-Spark Eliminator might turn something up. But they haven't made those in about 10 years.

 

I got this running with MS3+MS3X in batch fire mode since I'm using an MSD Pro Billet Opti that DOES NOT work in sequential mode. The stock opti works fine in full sequential mode, tested it up to 12,000rpm. Pretty amazing stuff.

I stole the gauge coolant temp for the MS3 and IAT temp, and left the stock computer there to control spark for knock purposes... as soon as I find a reliable knock detector I'll take spark into the MS3 as well.

Amazing software!

 

That is kind of surprising, while the MegaSquirt stuff is cheapest, the software is way beyond even the highest dollar units. But i might be bias.

 

Ha! Now I see why Well yea it is good stuff. I come from the stock PCM and wow will I never go back.

Hey since your here, is there a way to add a timer option to keep a second fuel pump on for say 3 seconds after it's enabled? Im using the bank 1 Injector output since I have MS3X running the actual injectors.

I have a manual trans and I want to keep the second fuel pump on under boost between shifts, the way it's setup now is it responds pretty quick to falling MAP or TPS and shuts off then comes back on and I want to avoid upsetting the regualtor or pressure in the rails.. maybe I could use RPM to keep it on (say over 3700rpm?).

 

That takes a firmware change, so you will need James too. I'm trying to think of a simple way to do it now....

What are you using to activate the pump now, generic port set up to activate with TPS > x or MAP > X, then driving V3 inj1 port?
What if you add a second condition of Or RPM > Y?

A relatively simple circuit could add the hysteresis, but a delay in the firmware would probably be useful in other conditions too.

 

Well I just hooked up the second pump, havent started it yet but have it triggering like you say pretty much, but am using the TPS at greater than 20%, and it reacts so very fast. I may try RPM trick and see how it goes, that might be all I need. I'll ask James about a timer and see what he thinks, but I've been bothering him with the MSD opti for a week or two now... ha. Thanks!