Keeping your Protec EFI with a DUI system

I’m using a 680 ohm and a 330 ohm in a voltage dividing circuit. 680 between the tach and ecu and 330 between the ecu and ground. 

With a throttle body injection, the timing of the fuel injectors is based on the amount of air coming in and not based on the ignition.

The Dui unit has a mechanical advance for ignition timing. So everything is good.


Also as an update, I’ve put 30 hours (probably 25 of them pulling skier, boarders, and tubes) on the boat since I put in the Dui unit and it’s still working well. I appreciate the help from everyone here.

KENO wrote: KENO wrote: So................does this thread ever get a good finish like a writeup,of just what was done, and a diagram for somebody to follow if they're trying to do the same thing? So will the good finish ever happen so that the next guy that wants to do this has something useful to work with?

Thanks, now we have the good finish

I emailed you my wiring diagram. It’s the green/ purple wire on the ecu you connect to.

I will happily send someone a picture of my wiring diagram to post, but I don’t have a computer to post it myself.

So................does this thread ever get a good finish like a writeup,of just what was done, and a diagram for somebody to follow if they're trying to do the same thing?

Mikewolf wrote: I just tested it out. Ran an indicated 48 mph. With the failing protec ignition I couldn’t get it above 35 mph. Thanks everyone for all the help and info posted. Need to go out for a ski now.

Sweet!! Big thanks to @Dreaming and @malcolm2 for providing old Pro-Tec parts for me to bench test. Really excited we were able to figure this out!

I just tested it out. Ran an indicated 48 mph. With the failing protec ignition I couldn’t get it above 35 mph. Thanks everyone for all the help and info posted. Need to go out for a ski now.

Mikewolf wrote: I tried 10k and 5k and also 8.2 and 4.7 ohm With the 10k and 5k, there was no signal getting to the ecu. With the 8.2 and 4.7 ohm, the ecu was getting signal, but the distributor was being grounded out.

It sounds like the tach wire has a limit as to how much current it can source (this could vary under load) and the EFI module has a minimum current requirement. Depending on what those numbers are you may not have much margin. Given what you have found out the ideal situation would be to use the tach wire to drive a circuit that connects to the EFI module (just like the Protec unit did) so they are isolated from each other and wouldn't limit current.   You may have been able to use the old Protec unit to supply the signal. Just connect power/ground/tach wire and the EFI module wire.

Hopefully it runs well as is.   Good job to all!

Way to go getting it running.

To post a picture, hit the post reply button and a new window pops up. Use the button at the tops of the page with a tree and an arrow. Navigate to your picture on your computer and select it. It will upload to the site and insert a link. You can use the Preview button to see what it will look like.

Before you upload you might need to lower the resolution so it is under the file size limit.

From a smartphone or tablet, you have to use a photo sharing site and I haven’t messed with those.

2001Sunsport wrote: Glad we could prove PCM otherwise. They were the first ones to tell me this would be impossible.

My experience too, but in their defense we are talking about long out of production engines. Would be nice if they and their parent company could help a little........

What resistors were you using when it didn't run?

I’m using a 680 ohm and a 330 ohm in a voltage dividing circuit. 680 between the tach and ecu and 330 between the ecu and ground.

Anyone know an easy way to post pics? Without photobucket, I don’t have a place to host them anymore.