Keeping your Protec EFI with a DUI system
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=42357
Printed Date: April-26-2024 at 4:49pm
Topic: Keeping your Protec EFI with a DUI system
Posted By: 2001Sunsport
Subject: Keeping your Protec EFI with a DUI system
Date Posted: January-30-2018 at 5:10pm
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Disclaimer - I no longer have my 1994 Supra Comp with the Pro Boss 351 EFI. It has been replaced by a 1995 Supra Comp with the GT40. The 1994 was still running great, with the full Protec intact, when I sold it last year. And also, I know supposedly "EFI cant be kept without the ignition" My brother and I took a Protec system and did some work identifying what is required from each module for the EFI to function. We hooked it up to an oscilloscope and determined the following. Starting point was the thread on planet nautique containing this info "7) The EFI module and the Pro-Tec module communicate with each other via the green/purple wire connected to terminal "C" of each module. No signal from the Pro-Tec module, then the injectors will NOT operate (check continuity of this wire). " Both the ignition and the EFI module share the signal coming from the trigger connector terminal B. The shared wire is green/purple. This signal is a 4 volt (confirmed not 5 volt) signal that drops to near 0 each time a tooth on the trigger wheel goes past the hall effect sensor. From the oscilloscope we confirmed it's a 4 volt square wave. The trigger wheel has 8 teeth. So, remove the ignition module and all the EFI module should be looking for is this 4 volt square wave. The DUI distributor/coil puts out a 12 volt square wave from it's tachometer wire. This information was obtained from DUI. I don't know how this signal works as I don't have a DUI setup. Does it drop to 0 during each pulse and how many pulses per revolution? I can't find the information but I recall reading somewhere that the EFI is looking for >300 rpm from the trigger to start firing the injectors. It seems to my brother and I that a simple electronic device could be used to create a 4 volt square wave from the 12 volt square wave provided by the DUI. Feed this into the EFI module via terminal C and you should be able to have EFI without Protec ignition. I'm the mechanical engineer and my brother is electrical, so I'll have to wait until my brother gets back to the USA to add what electronic device he had come up with. Just wanted to share what I've learned and get others thoughts. Reference threads - Protec conversion to DUI http://www.correctcraftfan.com/forum/forum_posts.asp?TID=34338&title=protec-ignition-swap - Protec wiring diagram on first page http://www.correctcraftfan.com/forum/forum_posts.asp?TID=33526&PN=1&title=protec-ignition-replacement-question - First thread I started on this topic http://www.correctcraftfan.com/forum/forum_posts.asp?TID=37481&title=pcm-protec-pro-boss-efi |
Replies:
Posted By: 2001Sunsport
Date Posted: January-30-2018 at 5:12pm
| I also created this thread because the previous owner of that 1994 Supra had done the Holley injector upgrade for ~$1000 so I was very interested in keeping EFI while I had the boat. |
Posted By: TRBenj
Date Posted: January-30-2018 at 5:50pm
| 0v would be my expectation from the tach wire in a conventional distributor ignition. You’ll get 8 pulses per revolution of the rotor (4 per revolution of the engine since it’s a 4stroke v8). |
Posted By: KENO
Date Posted: January-30-2018 at 6:33pm
I read this and said to myself that I think you'll have a fluctuating voltage between 0 and 12 at the negative terminal of the coil with a conventional distributor. Since the tach wire hooks up there, it gets the same fluctuating voltage. The boats are in hibernation but the plow truck was readily available for some experimenting and that's what I got was a 0 to 12 volt fluctuation. Checked it on my little distributor machine too. Being homegrown and rather low tech, it doesn't have an oscilloscope so all I could do was watch voltage rise and fall on a digital voltmeter. Like Tm said, a pulse for every firing of a plug. I think your idea sounds good and is worth trying, but it sounds like you don't have a pro tec to try it on any more. |
TRBenj wrote:Posted By: KENO
Date Posted: January-30-2018 at 7:56pm
What does this mean? Or what's it supposed to say? |
Posted By: tryathlete
Date Posted: January-30-2018 at 9:21pm
| You won’t find this on PN |
Posted By: 2001Sunsport
Date Posted: January-30-2018 at 11:16pm
| Sorry, was writing while on the plane, believe it autocorrected. It's supposed to be 300 rpm, I'll correct the other post. |
Posted By: 2001Sunsport
Date Posted: January-30-2018 at 11:20pm
Unfortunately I do not have the boat anymore so I can't test anything on an engine. When I get time I could try to set up some old protec parts on a bench again.
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Posted By: KENO
Date Posted: February-01-2018 at 9:31pm
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I think it's unwritten site rule #7 that says if you bring up something like this and get people interested, you have to do the testing you're talking about So...........get that EE brother of yours involved and see if this will work even if it's only a bench test  How's the new old transplanted Borg Warner treating you? |
Posted By: 2001Sunsport
Date Posted: February-04-2018 at 3:40pm
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Dang, gotta learn the rest of these rules Once he recovers from jet lag and it gets out of the single digits in the garage we'll have to get it set back up. I think we put 30 hours on the Borg so far. Runs great! I'll check shaft alignment again once she's in the water and should be good to go. |
Posted By: rosconole
Date Posted: February-05-2018 at 9:14am
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what kinda of holley injector upgrade was done for efi? is that a SEFI or Batch fire? Im guessing still speed density back then. I would have done FAST efi when I took my protech off but bridge I didn't want to jump off just yet and splice a bunch. ------------- 1989 ski nautique ,1991 barefoot nautique, 1993 Mustang Cobra 1998 5.0 Magazine shootout invitee |
Posted By: Mikewolf
Date Posted: July-10-2018 at 8:09am
| Was hoping this thread would be updated with more results. I have a 94 SN with efi, that is currently experiencing protec ignition problems. I have ordered the Dui distributor and am going to at least try to keep the efi with the disturber. Based on the above info, I need to send it a 4v square wave signal. The Dui tach signal is 12v square wave and has 8 pulses per rotation. I plan to try a voltage divide circuit to get the signal down to 4v. It will be a few days before my Dui shows up. Worst case scenario, I do have a Holley 870cfm from my friends 68 Camaro. I really would prefer to keep the efi though. I’ll let you know how it goes. I’m open to any advice |
Posted By: KENO
Date Posted: July-10-2018 at 9:42am
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One bit of advice might be to do some reading on marine carburetors if you end up going with a carburetor 2001 Sunsport is around fairly often so maybe he'll see this and update it. Otherwise I think it's worth a shot And..............make sure you update with your results
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Posted By: 2001Sunsport
Date Posted: July-11-2018 at 3:26pm
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Hey all, kind of forgot about this while working on my GT40 and skiing. My brother's suggestion was to use a diode to drop the voltage and might need a resistor to sink a little power. PM me and I can get you in touch with him if you want to discuss in more detail. Electrical design is not my forte. I'm pretty confident this project can work and you can keep your EFI. Might take a little tinkering. |
Posted By: Mikewolf
Date Posted: July-11-2018 at 9:05pm
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So today I installed the DUI. I then used a voltage diving circuit (2 resistors one through ground one through the 12v wire) going into the green purple wire going into the efi box. I tried starting it and was getting no spark. I assumed the problem was a lack of 10.5 v at the distributor. I charged up the battery and even ran a second battery with voltage just going to the 12v side of coil. Still no spark. Then I tried unplugging the tach wire from the distributor and the engine started and ran for a few seconds. It turns out the with the tach wire attached, I’m getting the fuel injectors firing, but no spark. When the tach wire is disconnected I get spark, but no fuel. I’m assuming this is because the tach wire is essentially connected to ground with just a resistor between them as that’s how my voltage dividing circuit work. I am not an electrical guy, so I need to figure out if there’s such a thing as a 1 way valve for electrical current. If that’s the case or I figure out a different way to reduce the voltage, I might be in business. |
Posted By: Mikewolf
Date Posted: July-11-2018 at 9:09pm
I just did some googling, a diode is what I might need. I’ll have to wait until tomorrow to go to the electronic store to get one. |
Posted By: KENO
Date Posted: July-11-2018 at 9:42pm
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Well Google didn't lie to ya". That's the function of a diode. There are a large number of different sizes so you should have some idea of the current going through the wire you're going to install it in when you go to get the diode. If in doubt go big
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Posted By: Mikewolf
Date Posted: July-12-2018 at 1:17pm
| Diode didn’t help. At a bit of a standstill as I’m not sure what else to try. I tried a few sizes. I also tried a voltage regulator, but still no spark. |
Posted By: TRBenj
Date Posted: July-12-2018 at 1:28pm
| The diode wasn’t backwards was it (obviously they are directional)? |
Posted By: desertskier
Date Posted: July-12-2018 at 2:12pm
| The white stripe on the diode should be closest to the module (away from the distributor). |
Posted By: Mikewolf
Date Posted: July-12-2018 at 3:05pm
| The diode was the correct direction. |
Posted By: KENO
Date Posted: July-12-2018 at 3:13pm
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How about a hand drawn diagram or a marked up original diagram of what you're doing complete with your voltage reduction circuit and diode shown? |
Posted By: Mikewolf
Date Posted: July-12-2018 at 3:51pm
| It runs! Without a diode and with just some different resistors. I have a hand drawn diagram, just need to figure out how to post pics |
Posted By: desertskier
Date Posted: July-12-2018 at 3:54pm
| What size resistors are you using. Should be fairly large. 10k plus or you could be loading the tach signal down. |
Posted By: tryathlete
Date Posted: July-12-2018 at 3:56pm
CCF, making it possible to keep older boats running, one solution at a time! |
Posted By: Mikewolf
Date Posted: July-12-2018 at 4:17pm
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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. |
Posted By: 2001Sunsport
Date Posted: July-12-2018 at 4:21pm
Awesome!!!  Glad we could prove PCM otherwise. They were the first ones to tell me this would be impossible.
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Posted By: desertskier
Date Posted: July-12-2018 at 4:29pm
| What resistors were you using when it didn't run? |
Posted By: Mikewolf
Date Posted: July-12-2018 at 4:36pm
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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. |
Posted By: Gary S
Date Posted: July-12-2018 at 4:44pm
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........ ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: tryathlete
Date Posted: July-12-2018 at 4:52pm
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I used to work for an electronics supplier and we provided total support for anything we ever made as a matter of good faith. Low volume companies like PCM should be totally responsive for their legacy product, particularly since the Pro Boss system is failing and they don’t have the means to supply out of production components. Perhaps where there’s a will there’s a way is all we have to go on! |
Posted By: MechGaT
Date Posted: July-12-2018 at 4:55pm
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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. ------------- '92 Sport Nautique |
Posted By: KENO
Date Posted: July-12-2018 at 5:01pm
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Before the party starts............make sure it runs under load on the water. Then the celebration can begin |
Posted By: desertskier
Date Posted: July-12-2018 at 5:37pm
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! |
Posted By: 8122pbrainard
Date Posted: July-12-2018 at 5:46pm
Congratulations on proving it could be done. It's sad that the "parent" company could care less about supporting their Protec system. Now if they could only figure out how to stop prop shafts from breaking!!  ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: Mikewolf
Date Posted: July-12-2018 at 6:07pm
| 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. |
Posted By: KENO
Date Posted: July-12-2018 at 6:27pm
Well, let's get this party started Good job |
Posted By: 2001Sunsport
Date Posted: July-12-2018 at 6:47pm
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! |
Posted By: fanofccfan
Date Posted: July-12-2018 at 8:23pm
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The magical powers of the inter web net thingy never cease to amaze me. This thread was so far above me and my skills but sure was a great follow. Good work and happy skiing. ------------- 2004 196 LE Ski 1969 Marauder 19 1978 Ski |
Posted By: KENO
Date Posted: July-15-2018 at 8:33am
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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?
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Posted By: KENO
Date Posted: July-26-2018 at 11:37pm
So will the good finish ever happen so that the next guy that wants to do this has something useful to work with? |
Posted By: Mikewolf
Date Posted: August-09-2018 at 12:01am
| I will happily send someone a picture of my wiring diagram to post, but I don’t have a computer to post it myself. |
Posted By: desertskier
Date Posted: August-10-2018 at 1:04pm
| deleted |
Posted By: Mikewolf
Date Posted: August-13-2018 at 10:38pm
| I emailed you my wiring diagram. It’s the green/ purple wire on the ecu you connect to. |
Posted By: desertskier
Date Posted: August-14-2018 at 5:38pm
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Posted By: KENO
Date Posted: August-14-2018 at 5:49pm
Thanks, now we have the good finish |
Posted By: SNobsessed
Date Posted: August-14-2018 at 8:00pm
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Glad it is working. I am wondering if there is any shift in FI timing, using the DUI pulse as opposed to the OEM signal. If there is, apparently it doesn't affect performance. ------------- “Beer is proof that God loves us and wants us to be happy.” Ben Franklin |
Posted By: Mikewolf
Date Posted: August-15-2018 at 10:51am
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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. |
Posted By: Mikewolf
Date Posted: August-25-2019 at 10:28pm
| One more update. It’s been more than a year and the ignition and injection are still working well. Definitely recommend this for anyone who’s ignition is failing. |
Posted By: darylforman
Date Posted: May-31-2023 at 10:52pm
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Does anyone have the wiring diagram or pics? I have a 94 Ski Nautique with the Protec EFI. This sounds like a good option for my boat! ------------- Daryl |
Posted By: desertskier
Date Posted: June-01-2023 at 9:32am
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I think I have the drawing that Mike sent me somewhere. I'll look for it. It's basically just a voltage divider between the DUI tach output and the EFI input. It reduces the new signal level down to the level of the old signal. ------------- 92 SN - Owned since 93 99 Pro Air 89 SN - Went to live on a lake in Texas 75 Donzi 16 - Sold in 93 |
Posted By: desertskier
Date Posted: June-01-2023 at 11:36am
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I can't find the diagram but these are the statements that Mike posted: It’s the green/ purple wire on the ecu you connect to. ------------- 92 SN - Owned since 93 99 Pro Air 89 SN - Went to live on a lake in Texas 75 Donzi 16 - Sold in 93 |
Posted By: desertskier
Date Posted: June-01-2023 at 11:40am
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So just connect two resistors together, a 680 and 330. The 680 open end goes to the DUI tach output. The 330 open end goes to ground. Connect a wire to the point between the two resistors and connect it to the ecu green/purple wire. ------------- 92 SN - Owned since 93 99 Pro Air 89 SN - Went to live on a lake in Texas 75 Donzi 16 - Sold in 93 |
Posted By: KENO
Date Posted: June-01-2023 at 1:06pm
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Here's the non artist's rendition of Mikewolfs non artist's rendition that disappeared. I scribbled it down back when the thread was new, It matches desertskiers description. Any other info is in the thread. No pictures of the process or description of what components like the proTec module and associated wiring were removed. 
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Posted By: darylforman
Date Posted: June-01-2023 at 11:52pm
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Thank you KENO for the pic you posted. Between that and the info from desertskier I now understand how Mikewolf made it work. I will give it a try and report back when I have some results. ------------- Daryl |