LT1 EFI and ECU

[antwanray]

I am in the very early planning stages of my Z conversion, and I would like my LT1 to have electronic fuel injection but I had a quick question about it. First off, please forgive me if my question is elementary, but we're all still learning, Right?

 

I can't remember the original thread, but it was talking about having to

reprogram the ECU. I read up on how EFI works at www.howstuffworks.com and I don't understand why that is neccessary. It is the same engine same fuel

injectors. The only thing I could think of is the exhaust system. So,

I guess my question would be What in the swap causes the ECU to be reprogramed? Is reprogramming the ECU avoidable? How?

[jbc3]

I'll try and make it simple...

The LT1 PCM controls many things and after the conversion, some things may be deleted or altered. The computer must be reprogrammed. A few that come to mind... (nowhere near a complete list)

 

Rear gear ratio

CAGS (for the M6)

canister purge

EGR

fans

rear O2's for the OBD2's

 

There are ways to get around some of the above things (resistor in the CAGS plug or rear O2 sims) but in general, there will likely be a need to reprogram.

All that being said.... the reprogramming is the LEAST of your worries in a conversion. There are many people that can/will do a reprogram for you... there aren't many that will do the motor swap for you (and all the other things that come with a conversion)

 

Jody

[Dan Juday]

Jody is right. Don't worry about reprogramming now.

 

If you get all the wires hooked up to the right places the motor will run. It will run with open headers and no O2 sensors and no knock sensor. Ask me how I know. It runs a whole lot better with those sensors though. You don't even have to reprogram if you don't want to and it will run just like it did in the car it came out of. Reprogramming makes some things easier, like deleteing the VATS so you don't have to wire in the VATS modual or add the resistor to simulate the key pellet. It also allows you to get a little more power out of the engine by massageing the AFR maps and raising the fuel cut off (rev limiter) a few hundred rpms.

 

Spend some time in the archives here and you will find lots of valuable info on the LT1 swap, like chosing the '95 f-body motor for your Z.

 

Good luck, and welcome to Hybrid.

[240Z28]

Another option to using the factory ECU is to purchase an aftermarket fuel injection system. I bought an Accel digital 6 fuel injection(DFI) controller which replaces the factory ECU and wiring harness. These units are getting cheap these days as serious LT1 racers are upgrading to the digital 7 system. This system allows you to adjust the fuel and ignition at all rpms by programming with a laptop. Check them out at the Accel website. Just another option if you have the cash.

[wheelman]

Another option to using the factory ECU is to purchase an aftermarket fuel injection system. I bought an Accel digital 6 fuel injection(DFI) controller which replaces the factory ECU and wiring harness. These units are getting cheap these days as serious LT1 racers are upgrading to the digital 7 system. This system allows you to adjust the fuel and ignition at all rpms by programming with a laptop. Check them out at the Accel website. Just another option if you have the cash.

 

You can make the same adjustments with the stock PCM from a 1994 or 1995 LT1. The 94/95 models had the OBD1 and flashable roms so it's programmable with a laptop. That's why Dan mentioned getting an LT1 from a 1995 F-Body.

I picked up a retired Montana highway patrol car that had an LT1. These things are plentiful and relatively cheap, their only drawback (if you want to call it that) is that they have iron heads rather than aluminum.

So its very easy to program and if you get the car then all the electronics is there for the taking. Rebuilding the stock harness is not all that hard, just tedious so it's a very good alternative to spending $$$ on an aftermarket system.

 

BTW: The iron LT1 heads are supposed to flow 20% better than the aluminum.

 

Wheelman