TheSamba.com :: View topic - Megasquirt Plug and Play for 79 Bus

Sun Aug 24, 2014 6:12 pm

So while I had been having some issues with my AFM and other EFI related issues, I decided to pull out my old megasquirt project that I had laying around. After trying to make decisions about all of the wiring etc, I thought "Why not make a plug and play unit?" This is a fuel only install that is designed to literally plug into the stock ECU connector and run megasquirt.

I went to the Junkyard and got an old LH-Jetronic ECU to gut and steal the header from. It was from a mid 80's volvo.

Much to my surprise, the 35 pin header was nicely broken out into a strip that was easy to solder onto a prototype board.

I spent some time with a bentley manual and a multi meter to figure out what to do. Here is the breakdown.

-The Main relay is activated by the ignition key and provides power to the ECU and injectors.
-The TS1 ground is on Pin 27 of the ECU, the Ground is pin 6
-The TSII comes in on pin 13. Ground is system.
-The Injectors are grounded in 2 banks with 1,4 and 2,3 being paired. This is on pins 14,15 and 32,33 of the ECU.
-Ignition comes in on Pin 1.
-The fuel pump is active on cranking and then relies on a contact inside the AFM to close. It has a signal off of pin 36 back to the fuel pump relay, but it also ties to pin 20 of the ECU plug. Megasquirt only provides a ground for the signal, but I needed a 12V to trip the FP relay. I put in a micro-relay to send 12V to the FP relay when megasquirt grounds it.
-The other relay was to provide a current source for the Auxiliary Air Regulator.
I left the CS injector unplugged.

Conspicuously missing is the TPS signal. Currently, I have the throttle switch on ECU pin 3 and 8 to give a 5v signal when at full throttle to allow a flood clear. I hope to use a vanagon TB that has a shaft out the bottom to use a TPS in the future. The other mod I still have to make is removing the stock AFM to see if it makes a power difference. Right now it is simply my intake temp sensor holder. I may someday try to run it with the AFM providing a load signal.

Here is the current wiring setup. I had a couple of 10 pin connectors from my TDI projects that I wired in for ease of connection. This will allow me to build a separate wiring harness in the future if I wish.

The bus started on the second crank!!! It warmed up and idled nicely with minor tweaking. Now the fun part of dialing it all in.

I am still waiting on my wideband controller to arrive and then be able to tune while driving. I will try to post wiring diagrams and a video in the near future.

Sun Aug 24, 2014 7:15 pm

Looks really good. I like the Volvo box....

Sun Aug 24, 2014 8:19 pm

Would seem to me that you would need some kind of load sensor, either airflow (mechanical or hotwire) or manifold pressure, to make this work right. What does your Megasquirt support?

Also: having one of those connectors mounted in a breakout box would make overall system testing trivial...

You could go one further and add a matching connector to the breakout box, such that you could insert the box between the computer and FI harness, allowing you to dynamically monitor system operation...

Just thinking out loud here.

Sun Aug 24, 2014 8:22 pm

The megasquirt uses a MAP sensor plumbed to manifold vacuum. There is code, however, to run it from a mass air flow or vane air flow sensor.
The vacuum connection is the only hookup outside of the stock harness.

Mon Aug 25, 2014 8:55 am

This is cool. My next engine build hopefully involves a stroked type 4 with big valve heads and nickies cylinders. My goal is to implement megasquirt to both control spark using Ford's EDIS system and fuel using some L-Jet parts.

Seen this?
http://www.thesamba.com/vw/forum/viewtopic.php?t=427890&highlight=megasquirt

It's an interesting read.

Mon Aug 25, 2014 9:48 am

Nice! I have never had huge complaints about what I have seen out of MS except early on. Their system and level of research over the years is awesome. However their weak p9ints early on was board vibration control and lack of enclosure.....things the OEM's have a lot of hard-won research into.

The only think I wonder is.....is that metal, screw down serial cable plug simply for plugging into a laptop for tuning....or is it meant to be plugged into the system? The reason I ask is because it is not ideal for automotive use. The terminal type does not handle vibration coupled with heat very well. This is why you dont find them in any oem systems. Ray

Mon Aug 25, 2014 10:16 am

Awesome, I plan on taking on the Megasquirt EFI conversion to my 76' Bus. Currently a single 32/36 DFEV Weber carb conversion. I plan on using Mario for components and support. He specializes in VW aircooled for Megasquirt. Check him out.

http://www.thedubshop.net/

Best of luck with tuning!

Mon Aug 25, 2014 1:00 pm

The plug is a 37 pin DB connector. That is one of the main complaints that people have with the megasquirt, and they have not changed it since 2001. The Microsquirt has a proper automotive grade connector. This is the one that Mario at thedubshop uses.
I have experience in automotive PCB design so, ideally, I would like to use the Microsquirt module, maybe with a wideband controller and design a PCB for the job that could be expanded for ignition control, but I don't have the time for that right now. I think that even a header breakout with terminals could help clean up the wiring inside the ECU box