FAST EFI as piggy back with stock PCM
 

I have a FAST EFI setup with a crank trigger setup. I was thinking of taking the spark and fuel away from the stock PCM and let the FAST handle that and let the stock pcm take care of the rest. Has it been done before?

Re: FAST EFI as piggy back with stock PCM
 

Will the FAST accept input from the cam position sensor in the Opti?

Re: FAST EFI as piggy back with stock PCM
 

What is your set up ? I have that on my LT1..

James

Re: FAST EFI as piggy back with stock PCM
 

No, It's an older system.
I'm going to mount a flying magnet wheel on the hub.
Set up? what do you mean?

Re: FAST EFI as piggy back with stock PCM
 

With only a crank position, won't you be limited to batch-fire injection and waste-spark ignition?

Can the FAST run the MAF, or is it speed-density only?

What functions do you want the stock PCM to perform? ....emissions? ...fans? ....speedo? ..... fuel pump? .....tach? Unless you parallel certain sensors to both systems, and with no injectors, ICM, etc. connected the stock PCM is going to be so loaded with codes a lot of subsystems will be disabled.

Re: FAST EFI as piggy back with stock PCM
 

The only sensors it will share with the fast will be the TPS. All others sensors I can add just for the fast.
The fast runs a MSD box and I would be using the stock distributor to point out the cylinders only.The fast is a batch fire system. They work great. I had a street car that ran 5.60's with this system.

Re: FAST EFI as piggy back with stock PCM
 

The only sensors you can "share" are the three wire sensors. The two wire sensors like the CLT, AIT, etc. have to be paralleled. What about MAP? That can be paralleled.

Will the FAST drive a stepper motor IAC?

I run a MoTeC M48 Pro in parallel with my stock PCM. Stocker handles the the speedo, stock tach (which isn't very useful for a 7,000+ RPM application), and the stepper motor IAC. I have dual 2-wire sensors for CLT and IAT.

The MoTeC has the advantage of accepting the incredibly accurate optical cam position signals from the Opti, and using that info for full sequential injection, and an add-on 8-channel ignition driver using the LS1 coils.

Runs speed density, open loop (O2 sensors don't like leaded fuel), no knock sensor (solid roller cam). Speed-density requires development of an accurate VE table..... lot's of time on the dyno, with verification in the field.

Re: FAST EFI as piggy back with stock PCM
 

The only thing I need to share with the stock PCM is the TPS. It wont know its not in control for the most part.