fabricating a VSS?

[thecheese429]

I have been thinking about how I would like to be able to make a modification and see, instantly, how much of a difference it makes. Having a non-OBDII vehicle, ScanguageII is out. MPGuino seems like a viable option, with one exception. I don't have a VSS.

My 1986 model is the first to offer TBI, and its electronic control may have more sensors than it knows what to do with, but it is still fairly basic. It has a cable-driven speedometer.

After a bit of digging, it would seem that the biggest problem with installing an MPGuino is finding the VSS wire. Well, my problem would be completely making a VSS.

How would I go about getting a VSS from another car and hooking it up? It could be a possibility to put a contact on the magnet housing behind the speedometer, but that would connect it to ground, not 12V. who knows, I may take the darned thing apart and put some contacts in there from a distributor

Does anyone have experience making this kind of situation work?

[zhillz]

My VSS is on my tranny, are there any transmission that you can swap in that would have one already to wire up too?

[thecheese429]

Do you mean that I might find a VSS on the same model transmission? If this is the case, I will look the next time I go to the pick-and-pull place. I wasn't planning on a tranny swap, if that is what you were suggesting.

Besides, I want to swap the rear axle first (seriously, to get a better ratio these gears are TALL)(or I just have a weak engine)

[Old Mechanic]

Maybe a magnet and pickup on the front of the propeller shaft, or, if FWD on the inside of the half shaft just outside of the axle seal.

regards
Mech

[thecheese429]

Old mechanic, what kind of pickup are you thinking of? I don't honestly know if a reed switch could activate that fast (I figured that my driveshaft will be spinning at about 50 rev/sec, so the switch would need to be able to handle 50HZ.

Or, could I pull one off of some other car that would switch 12v with a passing magnet?

[Old Mechanic]

ABS sensors use a gear like wheel with a magnetic pickup. Similar thing is used for OBD 2 cylinder balance counting 105 flywheel gear teeth per engine revolution on a 1995 Nissan Sentra, for passive cylinder balance calculations while engine is running without disabling any spark plugs.

Old tech cruise controls used a simple magnet on the prop shaft that gave a single impulse signal per revolution of the shaft. Differential ratio would tell you wheel speed relative to prop shaft speed.

Not necessary on front wheel drive, since half shaft speed is same as wheel speed.

Don't think a reed switch would hold up long.

regards
Mech

[thecheese429]

When you say "prop shaft" do you mean the drive shaft? I am not exactly an expert on the drivetrain. My jeep is RWD, by the way. 2WD, to boot.

Thanks for the info

[MetroMPG]

You could buy a $9 bicycle computer which comes with the plastic encased magnet (that you would mount to a driveshaft or axle) and the pickup & wires. There's your signal. Now you just have to possibly amplify & calibrate to the Guino.

The aftermarket cruise control kit I put in my car came with similar parts for making your own VSS if the car wasn't equipped with one.

[Old Mechanic]

Originally Posted by thecheese429

When you say "prop shaft" do you mean the drive shaft? I am not exactly an expert on the drivetrain. My jeep is RWD, by the way. 2WD, to boot.

Thanks for the info

Propeller shaft=drive shaft.

Right where it comes out of the transmission.

Metro is thinking about the same thing with the bicycle speedometer.

regards
Mech

[thecheese429]

How well would this work?
1990-1993 Honda Vehicle Speed Sensor

I imagine that this works with a magnet that passes by. What I am wondering is how to pick a VSS that puts out 0-12V.