VQ Swap Speedo

[Pharaohabq]

So I was reading... The Speedo looks like it's run from signalling through the ABS system which has signals from all 4 wheels. If the wheel signals all match even pulses then the ABS knows nothing is slipping and keeps feeding pulses to the ACAmp then to the Speedo.

 

So I was thinking the easiest way to run the speedo is to tie the signals from the wheel sensors together and pulse that off the driveshaft, in appropo pulses. If you had the stock z33 cluster mounted, but I guess you'd need the ABS and Electrics and the wheel sensors to try this. I don't know what the wheel sensors read to get their signal, so I don't know the signal, the manual doesn't say, I'd have to find someone with a 350z who'd let us hook a meter up to the wheel sensor, then turn the wheel jacked up, to recreate the signal. Tho the Manual does say it sends 8 pulses to the speedo. (combi meter)

 

I found someone who has a junked up 07 I'm going to get some parts from, and maybe we'll see how this part works.

 

Phar

[240hoke]

You can do the same things with a cheap proximity sensor on the DS flange bolts, provided you use a aftermarket tach. I did this but was pretty stupid in underestimating the movement of the diff even when double poly mounted. Im making a new one to bolt to the diff and move with it next time Im under there. All you need is a 5v output, I think that sounds like a big PITA. You need alot more wiring to run the dash too.

[Jared]

I agree, much easier to just run a hall sensor off one of the axles, the driveshaft or something. To pull off the stock cluster, you would need the abs control unit from the 350Z(which also includes the hydraulics), the front and rear sensors, the front wheel bearings(because they included the sensor rings), and the rear axles.

[Pharaohabq]

Jared, Hey sounds like you know a bit about this. The front bearings have the sensor rings. Do you know how many pulses per revolution?

 

The Wheel sensors may not actually be needed, in that if I can reproduce the signals they feed the ABS, then the ABS will tell the ACAmp what to send to to the Speedo for a reading. I was figuring the wheel sensors could be either tied together, or multiplexed digitally to all recieve the same pulses from a single pickup off a proximity sensor like you both were talking. though it would have to be adapted for gear ratio, and number of pulses per revolution.

 

I wonder if the ABS unit requires the hydraulics to function, or just to have fluid in place. the Hydraulic ports could concievably be plugged and I'm not sure the unit would know the difference, and if all 4 wheel sensors always read the same, then the ABS would always figure no wheel slippage and never pulse.

 

Phar

 

 

I know it's going to take a little more figuring to get the dash to run. but since I'm pulling the stock 07 harnesses and such hopefully I'll be able to get it figured.

[Jared]

I'm not sure how many pulses per revolution that the stock sensors output. I will take a look and see if we have one in stock that I can look at. Also, I'm not sure if tying them together would work. The Z33 has different sized wheels front to rear stock and compensates for that, so bare minimum you would need one front and one rear. I don't think the ABS control unit requires the hydraulic section to function. Even though they aren't available seperately, you can unbolt the control unit from the hydraulic section. No fluid exists between the two, the hyraulic section is self contained and the electromagnets in the actuator/electrical side move the valves in the hydralic side. This would need a little more work than just guessing though. If you were to continually get enough minor wheel speed differences to very frequently actuate the abs unit, eventually it will burn out the control unit and shut down.

[Pharaohabq]

Yeah, Jared, If you could find out the pulses per rotation that would really be helpful in figuring the speed signals. I would really be grateful. once I get all my parts, I'll have to hook things to a signal generator to see if I can fool the speedo. that would be fun. Do you know if consultIII has a speedo test? I'm sure it does.

 

Phar

[Pharaohabq]

Okay, I was looking around and I saw this:

 

 

You'll note the rear Wheel sensors are on the diff, on this 350z AT. If I count right there's about 48 teeth on that wheel. You can see these are also Alum teeth, so that would tell me it's a hall effect reader. though I had another Nissan tech tell me the signal was +5v to ground. So I'd assume the front wheels have a similar # of teeth.

 

This is good, since if I was going to drive these sensors off the driveshaft I'd only need a 15 or 16 tooth wheel. (48/3.3 gear ratio) I still may need to build a box to multiplex the lines, but now I at least know how these sensors are read. A box would allow me to fine tune what the ABS Pump, AC AMP & BCM read for the Speedo.

 

on the down side, I need to find a new HR Speedo cluster, I think I broke mine...

 

Phar

[Pharaohabq]

I read a little about the slippage notation in the 350z system. it seems if any two opposing wheels turn more than 45 degrees, apart from it's opposite wheel, it'll flag a slip and the system would try to compensate. Running these all off the same Hall rotor, it shouldn't be a problem. The 350z system apparently does NOT track changes between front and rear wheel speeds. I guess Nissan expects people to peel out now and then

 

Phar