Philip Slate said:
Andy, I have no idea what you just said although it sounds as though all the BMW motronic stuff can be replaced with GM stuff. If this is so, you'll have to write up a tech article to tell us ECU inhanced but electronically challenged folks how to make the swap.
Phil -- I'll take pictures. The only really difficult part is the programming -- but its easier than burning a custom chip for a Motronic set up. I wouldn't say the rest is bolt-on, but its certainly no more difficult than the Motronic conversion using a D-Jet or L-Jet manifold.
x_atlas0 -- No Megasquirt -- I'm modifying a stock GM ECU. I have a Megasquirt I built last year which I may use on something at some point, but I want to try to use the GM ECU first. I like the idea of finding a replacement ECU at any wrecking yard or autoparts store. With the Megasquirt or any other "aftermarket" ECU, I'd never feel comfortable without carrying around a fully-programmed spare in the trunk (sorta how I feel about the D-Jet right now). It could easily be converted to Megasquirt at some point -- the sensors are all interchangeable.
Malc -- The GM stuff is pretty much interchangeable as far as sensors go. Here's a short list of what I'm using:
1227730 ECU from certain late 80s/early 90s GM cars. This is the ECU that is used on the "Tuned Port Injection" 305 and 350 Camaros as well as a number of V6 motors. It uses manifold pressure only and does not need a mass air flow sensor. There are a number of others you could use, but this is the one I picked. Check out
www.tunercat.com for the various parameters that can be modified on supported ECUs.
Map sensor - standard GM for TBI or TPI
Coolant Temp sensor (CTS) - standard GM for just about anything with F.I.
Intake Air Temp sensor (IAT) - again, standard stuff.
Throttle Position sensor - this one can be tricky - I have one I am going to try to adapt to the stock thottle body, but I may need to dig further.
O2 sensor - standard bosch will work.
Injectors -- standard bosch-style will work. I'm using 24# Accel injectors. The ECU will need to be programmed accordingly.
I'm also using a GM idle air control valve to handle idle stabilization. It will go in place of the stock D-Jet slide valve on the driver's side (um, at least in the U.S.). I bought a harness consisting only of pre-marked wires, but no terminations on the ends. I have all of the stock connectors and the right professional crimp tools for "factory" installations on both ends. Its just a matter of threading it all to the right place, then crimping on the proper terminals.
The other tricky part is figuring out the ignition. I'm currently debating between a Bosch distributor with a VR sensor to trigger an MSD ignition box, which in turn will trigger the ECU, or running a crank trigger. If I want to run full ECU ignition control, I already had the front pulley modified so I can use a sensor on that to trigger a GM ignition module for full timing control. I already have all of the parts for either one, but the current plan is the MSD and let the distributor control the timing until I get the fuel stuff working right.
All of this will be somewhat "stealth" and won't be obviously different from stock (like having a big Air Flow Meter), easy to service and fully tunable. I'll take plenty of pictures as this progresses (slowly) and let you guys know the results. The cool part is that once I get the programming figured out, it would be quite easy to duplicate the motor/cam/injection set up for consistent results.
But I do recommend staying away from any alcohol when using angle grinders, air tools, cutting torches, welders, etc. -- they're dangerous enough as is.