Holley Fuel Injection ECU replacement options

[Joe Guilbeau]

I am looking to find a replacement for my Holley Analog Electronic Control Unit (ECU)that shipped with the 502-Series Analog Pro-Jection 670 CFM Throttle Body Injection that I put on my SJ in the mid-90's.

Came across a website that involves a Do-it-yourself (DIY) fuel injection controller that you put together yourself, called MegaSquirt.

For about a couple of hundred dollars, it seems that you can build an ECU that can be used to replace the Holley ECU.

Anyone out there heard any pro's or con's on this unit?

[gsmikie]

what is the diff in control between it and the holly ?????

[SpruceMoose]

i was under the impression that you could use the digital ecu in place of the analog one, provided you also install the manifold pressure sensor. give holley a shout, and let us all know what options there are.

sm.

[Joe Guilbeau]

The MegaSquirt is a Motorola based microprocessor based on the 8-MHz Motorola 68HC908GP32 Flash-badsed microcontroller, and a Motorola MPX4250AP MAP sensor.

The open code is written in assembly language along with a free-ware compiler.

Since you build the ECU from schematics and purchase the components and/or the printed circuit board, you are in a much better position to troubleshoot and modify the system for your specific requirements.

The system uses commonly available GM sensors (MAP, coolant temp, manifold air temp, throttle position, oxygen, and tach trigger) and all schematics, software, components are listed for anyone to review.

The system uses pusle width modulation to pulse the injectors and control is via the MC68HC908GP32 and a lap top CPU with a serial port to interface to the pre-programmed processor.

Essentially you purchase the Printed Circuit Board (PCB), the MAP sensor and a Field Effect Transistor (FET) driver in a partial kit. The remaining parts are available from Digi-Key and you purchase them separately with the BOM. Then stuff and solder the PCB and mount in an LMB Heeger case to house the Electronic Control Unit.

Next would be the addition of the MAP sensor and the Oxyden sensor and wire into the system.

Then change out the control lines to the throttle body injectors and away you go.

There have supposedly been around 1000 of these kits purchased.

Holleys options are just as SpruceMoose indicated.

However, that is Holleys solution and they do not give out schematics, nor offer code to folks.

Holley has been less than open about some of the problems that have plauged the Analog units.

Besides, I am an Electronic Technician and am not afraid to get into the details, there is little chance that I cannot use everything that I currently have set up, and just add the MAP and Oxygen sensor and build the ECU from MegaSquirt to replace the Analog unit (which is archaic to say the least). Lots of knob turning to adapt to various situations, new after 10 years of use, I think that I have found a more tunable solution for a few hundred dollars.

[Stolen76]

You can also go with TPIGUY's system. Most of the Holley system is GM stuff anyways and you'd just have a couple of things to add.

[Joe Guilbeau]

Originally posted by Stolen76:
You can also go with TPIGUY's system. Most of the Holley system is GM stuff anyways and you'd just have a couple of things to add.

I hear you, with all of GM's R&D Budjet pouring into the design, that is probably by far the best engineered solution that is easily converted.

I sent an e-mil out to tpiguy, about a electronic fuel pump, but havn't heard back as of yet.

I suppose that I just like to tinker...

[Dive 30]

The Holley ECU is rumored to be based on the GM 747 ECU, I haven't seen one, but am told that the harness connectors are the same. Thus, you could get a 747 ECU and re-program it or buy the Howell ECU that is designed for AMC 360s.

Phil