Porsche 928 ECU Conversion Project

I'm converting the OEM Bosch L-Jet ECU on my 1984 Porsche 928 4.7 liter V8 to run with a GM 1227749 ECU. As part of the process I've adapted the intake plenum to accept a throttle body from a Camaro LT1.

Throttle body adaptor plate on 928 intake spider. I wasn't done with the polishing at this point.

Intake, throttle body & boot. This will be mounted backwards on the engine, so the throttle body and boot will face the rear.

The '749 controls the spark timing so we defeated the distributor's advance by welding the plate in place.

'749 ECU and adaptor pigtail to attach to 928 wiring harness. This EFI control system is from a Cyclone/Typhoon truck, GM 1227749, and it knows all about positive manifold pressure. There is an electronic wastegate control so the computer can set the max boost level, electronic spark timing with knock detection retard, and of course injector pulse width control. I've replaced the injector drivers so that it can drive the 8 low impedance drivers in pulse & hold mode.

Here's a shot early in the install, with the old intake removed.

The wiring is coming out pretty neat. Most of the connections were made through the existing 928 wiring harness with a minimum of cutting and splicing.

Here we've got the laptop connected and we're checking out the sensors.

I'm using FreeScan as one of my tuning tools. It's a good package with data logging capabilities and this neat dashboard display. (And the price is right! ;-) Thanks Andy!

The new intake is installed and most of the plumbing is in place. The new MAP sensor is visible in the top right corner (black body, green plug), bolted to the fuel rail.

I'm starting the supercharger install. A catch tank has been added (blue, under the radiator hose) for the oil separator and a fuel pressure guage on the end of the fuel rail. Things are kind of tight behind the Vortech. I'll have to move some hoses to make room for the drive belt. Note the new electric fan in the bottom left corner of the picture.

We had to make a hybrid power steering pump pulley. I just couldn't see any way to make the ribbed pulley work as designed as-is, so we cut the center out of the stock pulley and machined the ribbed pulley to accept the stock hub. It took a bit of fiddling to get it to run true, but is woriking OK now.

This shot shows the oil return lines (blue pipes). We hooked it all up and ran it for a while to verify the oil supply was OK before we put the SC belt on (note the empty space on the crank pulley).

The oil feed line (-3 AN stainless braided hose to SC) is via a sandwich adaptor at the filter. The basic install is completed now. We're seeing about 5 pounds of boost, it gets to red line quite a bit faster than before :-) It's not quite done though, there's still more tweaking to go.

Last updated: May 4, 2004