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lilpusher

how do i mimic a VSS?

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I just put a 2.2L out of 98 legacy into my 92 loyale. problem is the obd2 ecu needs a Vehicle Speed Sensor signal and the loyale has a cable driven speedo. Any ideas? anyone?:confused:

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Yeah.... was your 92 loyale spfi, mpfi, or turbo?

 

In all 3 cases, you have a VSS. Its built into the gauge cluster. Find the wiring going to the old (loyal) ecu, and tap in there for new legacy ecu.

 

baddabing!

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^ what he said. many early '90s EJ cars have cable speedos (including some OBD II ones). doesn't mean there isn't a VSS signal.

 

wiring diagrams refer to them as a "reed switch".

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I have no idea what the signal requirements are for either systems. You may be able to adapt the old one to the new one with some sort of mod but I can't tell you what you would need to do without knowing more about the signals they generate.

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Yeah, the VSS on the older cars (the SPFI loyales and justys at least) comes from up in the guage cluster, even though it has the mechanical speedo cable. I don't know if it's the same signal as the EJ22 ECU is expecting, but I know the older ECU will also through a VSS code if the mechanical cable goes out.

 

Z

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Some Subarus have a VSS that goes on the front diff, where the cable goes, and then the cable attaches to the top of the sensor, you may be able to use one of those.

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It is a yellow/red stripe wire. You should be able to look up the pin at the ECU if you have an FSM. Or search here.

 

The signal should be the same. 4 pulse per revolution. Just hook up the loyale wire up to the 2.2 ECU

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Didnt older soobies with a spedo cable have a split cable? the cables would join up with a VSS sensor for the cruise control?

 

No - the VSS is part of the speedo head inside the cluster on all older Subaru's. The wire is a yellow/red stripe comming out of the gauge cluster (going to FI, CC, nothing, etc).

 

GD

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The signal should be the same. 4 pulse per revolution. Just hook up the loyale wire up to the 2.2 ECU

 

Even if it weren't the same pulse width it wouldn't matter. The ECU is only looking at whether you are moving or not moving. It doesn't care what the actual speed is. It's only real function is to increase the idle slightly when the car is moving to lengthen clutch life. Anything that generates a square wave at the correct voltage peak works - as it happens both use the same voltage and pulse width making them fully and completely compatible without any modifications.

 

GD

Edited by GeneralDisorder

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Yeah, I'm swapping a '97 EJ22 into a '78 and the '78 never had a VSS hookup.  

The speedo cable is completely covered the entire way or I could hook up some sort of reader.  

My choices are either to trick the ECU into thinking it's always moving, hook up some sort of hall effect sensor on the drive shaft or front axle, or try to cut away some of the speedo cable housing and hook up maybe an optical sensor...

This is a bit above my pay grade.

 

Looks like the VW swap guys usually buy adapter kits that either bolt to a bracket on the stock vanagon speedo or bolt to a CV flange.  

The airplane guys seem to prefer to trick it with homemade pulse generating chips.

American made swap guys seem to usually do a driveshaft hall effect / reed sensor deal.

Edited by julianco

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You can buy senders that will screw into where the cable fits into the gearbox, & then you screw the original cable into the other side of the sender.

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Those look like far and away the best choice, and I've found some online but only from Aussie sites!  Where do I get one of those in the states?

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You could try installingan EA81 speedohead unit (just the guts) into the old EA71 dash.  The reed switch is built into it might have to solder on a wire and give it a ground at the other side.   But even EA81s with carbs after 83 have the VSS reed switch built in.

 

Would require disassembly of the dash but could work they are pretty similar size/ construction.

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On the Loyales, etc, it's that "brass" one hanging out to the left. On those cars that don't need the VSS, Subaru just didn't install the screw that connects the circuit board to that. Not sure if this is the same for the earlier EA81 models.

 

BTW, don't fully believe the statements above about all signals being the same.

In my PM to you, I said I'm installing a 2004 model 2L Hyundai Elantra engine into my 98 Hyundai Excel (Accent) X3. The Excel has a cable driven speedo with a VSS wire from the spoeedo head to the ECU.

The Elantra has an electronic speedo with a sender screwed into the gearbox instead.

These 2 produce different type of waves (I think 1 is square & the other is a sin wave), along with different peaks, so the signals are not compatible.

 

I'm not saying that this is the case for Subaru, but it may be worthwhile checking further which signal your EJ ECU needs.

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Yeah, so far what I've found is that the signal needs to be square and between 0-5v.  4 readings per rotation of the speedo cable.  

I've isolated the reed switch from the GL speedo.  It sits right behind the disk on the backside.  

Now can I just take this little pickup guy and put it behind the same part on the '78 speedo?  Or is there something on the spinning disks/magnetic dealy that is necessary for the reed switch to work?

In the assembly:

PhotoDec0950436PM.jpg

And pulled out:

PhotoDec0950453PM.jpg

 

Lead on the left is + and on the right is ground ... right?

Edited by julianco

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Some old dodges used a 3way speedo spliter to make cruise work haven't seen one in a while speedo went to this unit and two cables came out one to cruise unit and one to spedo head think you could just plug a legacy speed senser into one side of something like that

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Yeah, so far what I've found is that the signal needs to be square and between 0-5v.  4 readings per rotation of the speedo cable.  

I've isolated the reed switch from the GL speedo.  It sits right behind the disk on the backside.  

Now can I just take this little pickup guy and put it behind the same part on the '78 speedo?  Or is there something on the spinning disks/magnetic dealy that is necessary for the reed switch to work?

In the assembly:

PhotoDec0950436PM.jpg

And pulled out:

PhotoDec0950453PM.jpg

 

Lead on the left is + and on the right is ground ... right?

 

One side is the signal wire from the ECU.  Your VSS wire.  Ground the other side.  Done.

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