Jump to content
Ultimate Subaru Message Board
lilpusher

how do i mimic a VSS?

Recommended Posts

That's what I wanted to hear.  Thank you Gloyale.

I was just wondering if there was anything in the circuit that helped shape/clean the wave form.  But since it's just getting 5v power from the ECU and grounding when the magnet comes by..

I'll be testing in the next few days and will update.

Share this post


Link to post
Share on other sites

Call me struggles.  This is what I've been trying, but I can't get the switch close. I've bought a few different reed switches new and still no dice.  Giving up and turning back other, more expensive ideas.  Toying with the idea of getting a full custom dash as there is no tach in the '78 dash, the temp gauge is not compatible with the new ECU and would need the '78 temp sensor wired in with either a custom bung or some other way... And then I could just buy a speedo with a built in VSS. Though it's probably the most expensive of routes, something I would probably have to pay someone to do for me, it would clear up a few problems all at once.

PhotoDec1094019PM.jpg

This is the '78 speedo with the new reed switched placed in the same place as the GL speedo's. Doesn't work and not sure why.

Share this post


Link to post
Share on other sites

temp gauge can be corrected to match EA/EJ stuff by adding a 270 ohm resitor parallel to the sender to ground at the engine.  This corrects the gauge very closely.  It's a whole seperate signal  from ECU temp sender.

 

 

For the reed switch I was more suggesting utilizing the whole speedo unit from the EA81.  There is probably a magnet on the shaft of that one that triggers the reed switch.  At very least will need that shaft.

Share this post


Link to post
Share on other sites

Yeah, that is what I was hoping to do for the speedo, but the guts don't match up to well...

 

Thanks for the tips on the temp gauge, I'll check into that... 

So there is a straight from temp sender to gauge wire?

Edited by julianco

Share this post


Link to post
Share on other sites

robm - I thought about adding a magnet to the internals of the speedo, but was afraid that it would throw off the function of the speedo itself.

 

I'm about to order a hall effect sensor from smallcar - this one http://www.smallcar.com/index.php?dispatch=products.view&product_id=29880

They will sell the sensor without the kit for $16 (since it's made to match a vanagon hub).  Plan is to set that up with magnets probably on the drive shaft since it's more out of the way than an axle.  Now i need to figure out how many magnets.  Signal is supposed to be 4000 pulses per mile.  I think that's 5 pulses per wheel rotation... so how many pulses per drive shaft rotation?

Share this post


Link to post
Share on other sites

Well it needs to be 1/16" away from the passing magnets, so drive shaft probably won't work unless I can mount it really close to one of the ends.  Otherwise it will have to be on the axle right next to the tranny and I'll fabricate some kind of bracket to attach to the tranny and position the sensor.

Share this post


Link to post
Share on other sites

Yeah, I was wondering the same.  The small car kit uses 5 pulses per rotation of the wheel (of course that's a vanagon size wheel).  I've been told both that it is very important and not important at all to get that exactly right...

The guy who just sold me the sensor says that it will work even with only 1 pulse per revolution - the ECU just needs to know whether or not the car is moving - he says.

Share this post


Link to post
Share on other sites

You didn't jack it just revived it.  Which is good, it means you where searching for your answer before just repeating the same question over and over like sometimes happens.

 

I think he probably solved it back in 2009 when it was posted.  His swap was easy Loyales have VSS built in/wired up already just gotta splice in the EJ wire.

Share this post


Link to post
Share on other sites

So I've been too busy for a while but had some time yesterday to mount the improvised VSS.  Since the axles move too much for a regular gap between the magnets and the sensor, I decided to mount on the drive shaft where it enters the transmission (sensor on the tranny and magnets on the driveshaft).

The magnets that came with the small car auto kit were long thin cylinders and they have to be sensed at the end so they wouldn't work to attach to the driveshaft. So I ordered some of these little guys http://www.kjmagnetics.com/proddetail.asp?prod=D21

I cut up an old plastic cutting board for a mounting bracket for the hall effect sensor.

PhotoJan2232542PM.jpg

PhotoJan2232611PM.jpg

PhotoJan2232606PM.jpg

 

jb welded the magnets to the driveshaft

PhotoJan2242528PM.jpg

 

And put them together.

PhotoJan2312924PM.jpg

Share this post


Link to post
Share on other sites

This fixed the problem I had with the car wanting to die at stops - coming down from RPM.  And it seems to run better overall, BUT, now when I hit about 33 mph, it starts to die.  

I've only driven it once, but it seems like I can drive right at the 33ish mark, and the car will run great below and as soon as I go over, start  -I think- cutting spark.  And if I stay over the mark, the engine will die.

 

I put 5 magnets evenly spaced (probably not exactly) on the drive shaft.  I'm thinking it's the wrong number.  

Anybody know how to figure the right number?  

 

For the Vanagon, the axle mounting bracket has 5 readings per rotation.

 

The subie speedo VSS's have 4 readings (which is 4000 pulses per mile) (how many rotations/mile for the driveshaft?)

 

That's about all I know.  I don't know where to start for mathing it, so I might just have to try 4 magnets and see what happens...

Edited by julianco

Share this post


Link to post
Share on other sites

Assuming it is 5 pulses per wheel rotation, and the diff is a 3.9:1 ratio, this would give me 1.28 readings per driveshaft rotation, which is problematic.  

Is it really 5 pulses per wheel rotation though...

So I have a ~22.5" wheel diameter.

* pi = 70.6858 inches

 

a mile is 5280 x 12 for inches is 63360

 

63360/70.6858=47.5343

 

 47.5343 x X = 4000

 

4000/47.5343 = 84.149

 

Then divide this by 3.9 for the driveshaft.....

But 84.149 readings per wheel rotation seems really high, especially when 5 readings per rotation works for the Vanagon guys...

Edited by julianco

Share this post


Link to post
Share on other sites

I dropped the magnet count to 1 per rotation and bought an ultragauge which shows me RPMs and MPH read from the VSS signal.  

The engine runs pretty normal with 1 magenet, though it drops to about 650 RPM after stopping or dropping from higher RPM suddenly.  It never died, but wasn't perfect.  

 

The UltraGauge is reading pretty close to correct MPH, a bit slower, making me think that the 1.28 readings per rotation was fairly close to correct (though obviously unattainable).  So basically, it would probably do better on an axle.

 

ALSO, this made me realize that the '78 speedo is not perfectly compatible with the '89 D/R tranny, reading quite a bit faster than IRL.  That's mostly annoying because the odometer than is not correct either....

 

 

AND, today this happened and I don't know why.  

ED6EEDE3-5F9C-402C-A7CE-8ABFAF2A7352.jpg

CEDE7576-8883-4CDA-9DE9-0980316D8884.jpg

 

So I'm back to square one!

:banghead:  :banghead:  :banghead:  :banghead:  :banghead:

Share this post


Link to post
Share on other sites

It seems like the best way to do this is to use the speedo cable inline style thing (like the Brantz BR4), which is pretty much plug and play, but I haven't been able to find one that fits into the subaru tranny (I think it's a M20x1.5 thread?).

What is the 3 way speedo cable tee ivans imports mentioned above?

Share this post


Link to post
Share on other sites

Just found this in my 4x4 offroad mag Dakota digital speedo adaptors 1-800-852-3228 is for coverting electronic signal to cable signal this one was a ECD-100 these guys I bet would be able to help you

Share this post


Link to post
Share on other sites

Man that thing is 300 bucks!  Also, it requires an electronic output from the tranny, which I don't have.  

I've called those guys before, and they also have some magnetic improvisation kits like this http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=109/category_id=-1/home_id=-1/mode=prod/prd109.htm

 

and a chip that allows you to adjust the input here - so my 1.28 per rotation could be ajusted (but it's good enough)

http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=126/category_id=-1/home_id=-1/mode=prod/prd126.htm

 

and the cream of the crop, a gps speed sensor which creates a pulse in accordance - super dope, but $200.

http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=837/category_id=-1/home_id=-1/mode=prod/prd837.htm

Edited by julianco

Share this post


Link to post
Share on other sites

ivans imports - First of all, thanks for all of your input.  I appreciate the help.  

Have you been able to find those three way speedo splitter deals?  I've been looking and can't seem to find them online.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×