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I'm working through some issues on a recently installed 2.5L Frankenmotor (2.2 heads) in an '87 GL Syncro. The numbers on the ECM are: 22611 AB414 JAI 18000 RT8 4910
The VIN of the Subaru donor car is 45(could be S)B3K655057324604
The engine wiring harness was modified by a local mechanic. He used either Small Car or KEP instructions. I have copies of the schematics that apply, but the source isn't marked on the pages.
There's a VSS on the back of the speedo, sourced from GoWesty. I've verified that the read lead is connected to switched 12V, the black to ground, and the gray to the ECM connector B84, pin 57.
In 4th gear at 4000 RPM, which registers about 67 MPH on the speedo, the engine falls flat on it's face until RPMs drop. At that point it will start pulling strongly again. If I just leave my foot flat on the floor on the throttle pedal, RPMs will cut at 4000, then pick up again until it hits 4000 RPM again, and just keep repeating until I? lift my foot a little to stay under the 4000 RPM ceiling. The engine pulls cleanly past 5000 RPM in 1st, 2nd, and 3rd gears.
I hooked up a known good Fluke DVM and measured a signal?on the VSS lead?that fluctuates between 0 and 4.82 volts as the van moves. The leads went between ground and pin 57 of connector B84 to the ECM, so I'm pretty sure that the VSS is doing its job. At speeds over a walking pace, the DVM display averages the readings at about 2.4 volts, but the instantaneous reading bar graph at the bottom of the display shows the signal is still fluctuating.
I'm trying to understand how the rev limiter works, and specifically why it isn't cutting out in the lower gears.?
I'd also like to know how to work around the cut out, or where to check for the cause.
Thanks in advance,
Scot
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Hi Scot, Your problem is caused by the fact that the Syncro speedo turns at 2X the rev rate of the non non syncro. Thisresults in the ECU seeing something over 120 mph - which triggers the Rev limiter.
Tom Burlington ON
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Scot,
? Based on what Tom said, it sounds like you need a divide-by-two type of circuit.
I would think that Small Car or some other supplier would have it available.
Larry A.
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Thanks, Tom. Looks like I need to find a speed sensor that isn't dependent on the speedo. Small Car and Van Cafe offer options that use a Hall sensor and magnets mounted on the transaxle CV flange. Anybody have experience with these?
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There's a company in Canada that sells a Syncro compatible VSS:
Anybody tried it?
Thanks!
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They appear to work well.
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Scot. The cv axle mounted vss units are a popular item amongst the subaruvanagon conversion crowd.? Some vendor supplied earlier models had weak magnets but that problem has long ago been resolved.? Easy to install and wire up.
Best, Brent
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Thanks for that link, Wayne. You must be a Samba search genius! I spent some time over there over the past several days looking into options, and never found that thread. It nicely summarized all the misgivings I had about the CV based sensors, and the only people not complaining had the Fast Forward VSS.?
The GoWesty VSS seems to work fine in my application, though, as far as putting out a nice, clean 0-5V square wave. It's just that the Syncro speedo runs at double speed (thanks for pointing that out, Tom), and that causes the Subaru ECU to throw the rev limiter. From what I saw on their web site, GoWesty is very careful NOT to make any suitability statements with regard to their VSS in situations where an engine conversion is done. That should have been enough of a hint to keep looking.
Anyway, that Samba thread helps me feel a lot more confident about the Fast Forward VSS, which I purchased this morning, *before* reading your post! ;)
I'll post back once I've had a chance to install it and see how well it works.
Scot
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I¡¯ve ordered other items from David at Fast Forward in the past, and his stuff is top notch.? Please post how you mounted his CV sensor. Thanks! ? Stuart ?
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From: subaruvanagon@... Sent: Wednesday, October 10, 2018 10:29 AM To: subaruvanagon@... Subject: [subaruvanagon] Re: Rev Limiter Issue? ? ? Thanks for that link, Wayne. You must be a Samba search genius! I spent some time over there over the past several days looking into options, and never found that thread. It nicely summarized all the misgivings I had about the CV based sensors, and the only people not complaining had the Fast Forward VSS.? The GoWesty VSS seems to work fine in my application, though, as far as putting out a nice, clean 0-5V square wave. It's just that the Syncro speedo runs at double speed (thanks for pointing that out, Tom), and that causes the Subaru ECU to throw the rev limiter. From what I saw on their web site, GoWesty is very careful NOT to make any suitability statements with regard to their VSS in situations where an engine conversion is done. That should have been enough of a hint to keep looking. Anyway, that Samba thread helps me feel a lot more confident about the Fast Forward VSS, which I purchased this morning, *before* reading your post! ;) I'll post back once I've had a chance to install it and see how well it works.
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Thanks for sharing your positive experience with David and Fast Forward, Stuart.
Just to clarify, though, the VSS I ordered mounts to the back of the Syncro speedo.
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Won¡¯t that give you the same problem with the 2x rotation? ? Stuart ?
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From: subaruvanagon@... Sent: Wednesday, October 10, 2018 10:46 AM To: subaruvanagon@... Subject: [subaruvanagon] Re: Rev Limiter Issue? ? ? Thanks for sharing your positive experience with David and Fast Forward, Stuart. Just to clarify, though, the VSS I ordered mounts to the back of the Syncro speedo.
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Not according to the Fast Forward website:
The SpeedPuls VSS is offered in both a 4 and 8 pulse/revolution version, the 4P being appropriate for the Syncro speedo.
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That sounds like something David would come up with! ? Stuart ?
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From: subaruvanagon@... <subaruvanagon@...> Sent: Wednesday, October 10, 2018 11:09 AM To: subaruvanagon@... Subject: [subaruvanagon] Re: Rev Limiter Issue? ? ? Not according to the Fast Forward website: The SpeedPuls VSS is offered in both a 4 and 8 pulse/revolution version, the 4P being appropriate for the Syncro speedo.
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Here's an update on the rev limit problem. I installed a 4 pulse/revolution VSS from FastForward and verified that it does indeed generate four pulses for each turn of the speedometer cable. Unfortunately, the rev limiter still triggers a slow down at about 67 MPH. Yesterday I hooked a new code reader up to the OBD II port and read 111 MPH on the OBD II speedometer parameter when the van was actually doing 67 MPH according to the dash speedometer. Apperantly the Subaru speedometer generates fewer pulses per revolution than the four that the FastForward VSS generates. Fastforward also sells the Hasenwerk VSS Korrekt Speed Signal Calibrator that allows the pulse frequency to be adjusted. It's listed about 2/3 of the way down this page:
Has anyone here installed the Speed Signal Calibrator, and did it fix the problem?
Am I correct in thinking that the issue is in the way the VW VSS pulse train differs from what the Subaru EMU expects to see?
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??? ??? TeC Scot
??? 1st posted this back in Mar 2011 ~ Hope it might help >
??? ??? To the VSS interested folks
??? I have a 2k1 EJ25 in my 90Westy VDubaru & ran it the 1st 2kMiles without a "working" VSS. I had a VSS installed (back of speedo type)
but due to my lack of experience with a Subi converted Vanagon & therefore lack of knowledge of how things should be working, I assumed it
was working. During that 1st 2kMiles I was going through a break in routine on a "fresh" short block & I never pushed it beyond 4kRPM so I
don't know if the RPM limit that a lot of people talk about would have shut me down. My 1st sign that something was wrong was on the 1st
high speed hi-way test drive I took it on when after about 10.5Mis @ 75mph/3750rpm it lost power, just throttled down giving me the impression
at 1st that it had shut down completely but as I coasted to a spot where I could pull over safely I realized that it was still running but not responding
to the gas peddle. Having had computers in my life for close to 20yrs I decided to try the - turn it off, wait 30secs & turn it back on trick & voila,
it was running just fine. I spent a couple of min's arguing with myself about whether to go home or press on & the press on won. Another 10.5Mis
of 75mph & it happened again @ which point I turned around & headed for home. It happened twice more on the way home @ about 10.5Mi of 75mph
?intervals. I found out during those last two events that there was no need to pull over, just put in the clutch turn the key off & back on, release the
clutch & proceed.
??? I put a call into my harness guy Hans @ Vanaru & while waiting for a response from him decided to call our favorite Guru & Wizard Mr TShiels & he
promptly informed me that I probably had a VSS problem & sure enough he was correct, I had a bad one. Now that I have a good, properly functioning
VSS it runs pretty darn fine no matter how fast or how far I choose to go.
??? At this point, even though the ECU is not getting the correct number of Pulses/Mile & so, therefore, does not accurately know how fast it is going,
I am not experiencing any limitations due to high RPM or MPH, although I have not yet tried to go any faster than 96mph. I am considering putting one
of the DakotaDigi SGI-5 U'S'I's on it like Rich' Jones has done, just so I can know for sure that the ECU is getting all the right signals.
??? ??? ??? ??? ??? ??? ??? ORR ~ DeanB
??? In Apr 2011 I did install the Dak'Digi' SGI-5 & to this day am still quite pleased with the results ~ But even before the SGI-5, I had no problem,
as mentioned above, pushing VDubaru to 96MPH (with plenty of peddle left > just ran out of confidence in My front Tires) ~
??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ORR ~ DeanB
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Those symptoms aren't exactly the same as the ones I'm experiencing. In my case, the EMU is doing something to slow the RPMs (retard timing, throttle down fuel, or ???), and once the RPMs drop below about 3700, power returns. I can leave the accelerator pedal flat on the floor and experience a repeated cycle of normal power -> cut power -> RPM drop -> normal power all day long and don't have to turn the key off at all. I would be very grateful to learn just what triggers the various power reducing modes in the EJ22 and EJ 25 Subaru motors, or pointers to where I could look to find them. Nothing quite like the feeling in the pit of your stomach the first time one encounters one of these power reduction modes, is there?
And here's another data point: Yesterday I had the tachometer out to replace the 16 uF capacitor in the temperature gauge (trying to remedy a flashing LED in that gauge) and noticed that the header that Fast Forward Automotive used on the back of its VSS looked strange. When I disconnected it, I found strands of copper wire hanging out of the connector, and some were long enough to touch similar strands in the adjacent lead. I stuffed the strands back up into the connector, then used tape to build an insulating barrier between the wires. I'm not sure it was causing a problem because the FF VSS also has an LED that flashes each time a pulse is detected, and this VSS was flashing. But it could have meant trouble in the future.
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??? ??? TeC Scot
??? Retold that whole story just to show why I have the Dakota Digital SGI-5 adjusting VSS signal to ECU ~ It does sound as if You are
experiencing the Subi OverSpeed Limiter ~ What Year is Your Eng' Harness > Do You get OBD2 Data ~
??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ORR ~ DeanB
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Fuel pressure? Coolant temp sender?
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Just to update this thread.
Last year I installed the Fast Forward Automotive? Hasenwerk VSS Korrekt Speed Signal Calibrator that can convert the frequency of one pulse train to another:
http://fastforward.ca/signalprocessors/ (about 2/3 of the way down the page). I installed it, and went for a series of short drives, each time adjusting the converter so that the speedo reading coinsicded with the GPS reading and the OBDII reading. It took two or three tries. That fixed the overspeed cutout problem with the Subaru EMU.
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On Feb 15, 2023, at 10:32 AM, BlacknWhite via groups.io <general@...> wrote:
?Just to update this thread.
Last year I installed the Fast Forward Automotive? Hasenwerk VSS Korrekt Speed Signal Calibrator that can convert the frequency of one pulse train to another:
http://fastforward.ca/signalprocessors/ (about 2/3 of the way down the page). I installed it, and went for a series of short drives, each time adjusting the converter so that the speedo reading coinsicded with the GPS reading and the OBDII reading. It took
two or three tries. That fixed the overspeed cutout problem with the Subaru EMU.
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Brent Weide
OlRivrRat DeanB
Dr Mark