Speed cut woes.

[2JZR31]

I have done an Aristo conversion on my R31 skyline and I don't even have the main speed sensor hooked up. But the ECU must still be figuring out speed from the other speed sensor and cutting the show at 180. From what I hear, normally the main speed sensor signal goes to the Speedo head then the signal gets modified and comes back to the ECU. This is the signal I don't even have connected at all. (everything works 100% fine though). Now how do these speed cut defenders work? I hear they grab this signal from the Speedo head, divide it then send it back to the ECU? Is this right? Wouldn't this stuff around with auto shift points though?

[CrUZida]

All they do is plateau the speed into to the ecu at about 170kph.
So the ecu thinks you are only doing 170, even thought you are doing much more.

Yes, it does play havoc with the Drive-O/D shift (ie, it won't do it while your foot is flat), but if you back off it will change into O/D and then put the boot back into it.

[2JZR31]

Cool so the frequency is kept as normal up untill 170, then the frequency just stays at that point? And I guess it does not shift into 4th becuase 3rd revs out over 170 which therfore makes the ECU think its not time to go into 4th gear yet? Are sure it does not just divide the signal by a ratio the whole time?

[CrUZida]

3rd revs out to about 200 with a 3.909 diff, 180 with a 4.1, 210 with a 3.727 (etc)

I can't speak for ALL speed cut units, but that is how most work.

[2JZR31]

Cool, so the non shifting into 4th prob is not going to bother me on the quarter mile unless I can run 124mph. Thats all I was worried about. I think I will hit 180 though :D

Do you have to buy a certain type for the car or are these things adjustable?

[CrUZida]

AFAIK they are a generic unit.

Whether its a generic 'toyota' unit, as opposed to a generic 'nissan' unit I dont know.

But one designed for a Soarer/Supra/etc should work on yours.

[wagonist]

I'm waiting for a 2nd hand generic fueltronics one to arrive in the post.
It only has 4 wires. Ign on, earth, SS in, SS out, & a laptop port.
Cut the SS wire & put the box in the middle & wire the rest up.
Go for a drive at a preset speed to program the box via the laptop. Give the speed at which you want the intercept to occur at.
Done.

Not sure about other units though.

[2JZR31]

That sounds pretty cool. How much did that cost?

[wagonist]

It was $120 from another forum.
They run at around $300ish new I think (I haven't needed one for 4 years because the Caldina isn't fitted with one)
I think there may be cheaper one's around, though.

Importers may have some half-cuts fitted with them.

[Mos]

The aristo auto gearbox has a bipolar speed sensor (SP2) for the shift points on the extension housing. If you don't have the main speed sensor hooked up (SPD or SP1 pin) then the ECU must be speed cutting off the SP2 signal.

AFAIK all the speed cut defenders intercept the SPD signal (squarewave). The SP2 signal is generated by an inductive pickup and to my knowledge there isn't anything that intercepts that (but I could be wrong).

You could disconnect the SP2 signal, reinstate the SPD signal, and install the speed cut defender on the SPD signal. (The auto will shift off the SPD signal if the SP2 signal is not available).

Thoughts?

Mos.

[CrUZida]

Sounds feasible.

[2JZR31]

What does the wave form look like from the SP2 2 wire sensor? Isn't it a square wave? If it is I thought I would be able to configure the speed cut device in the same way as normal. I was a bit worried about it though.

The reason I dont have the 3 wire sensor hooked up is becuase the engine is in a skyline and it does not have the signal divider circuit on the speedo head that is needed to correct the signal before it can be hooked back up to the the ECU. ATM the 3 wire sensor just runs my speedo with 2 jaycar speedo correctors. It was a real PITA to get the speedo to work with it as it is. To hook it up, I would need to get the signal divider circuit right, then intercept it with the speed cut defender. I was seriously hopeing to avoid this.

If this the device can't work with the 2 wire sensor I had another idea. Using a jaycar frequency switch to just turn the 2 wire sensors output off totally before the frequency reaches whatever it is at before 180km/h. Not sure what effect this would have though. With anyluck it will stay in 3rd gear and not try and go back to first or second :eek:

[wagonist]

I've got my Fueltronics unit now, but I know where there's another one.
It doesn't do anything with the wave until the interrupt point.
It wouldn't matter whether you hooked this particular unit up before or after your divider circuit because it is laptop programmable.

[2JZR31]

I dont have a divider circuit though. My ECU runs of the 2 wire sensor only and this might be a sine wave not a square wave.

[Mos]

What does the wave form look like from the SP2 2 wire sensor? Isn't it a square wave? If it is I thought I would be able to configure the speed cut device in the same way as normal. I was a bit worried about it though.
It's a waveform typical of an inductive sensor - I'll try to describe it.
When the rotor approches the pickup, the voltage rises up to a peak, then as the edge of the rotor passes by the pickup the voltage sharply drops, crosses zero and goes negative to the same peak as the positive. Then as the rotor moves away from the pickup the voltage returns to zero. The waveform is diagonally symetric.

Try this:
http://www.picotech.com/auto/waveforms/distributor_inductive_running.html

The reason I dont have the 3 wire sensor hooked up is becuase the engine is in a skyline and it does not have the signal divider circuit on the speedo head that is needed to correct the signal before it can be hooked back up to the the ECU. ATM the 3 wire sensor just runs my speedo with 2 jaycar speedo correctors. It was a real PITA to get the speedo to work with it as it is. To hook it up, I would need to get the signal divider circuit right, then intercept it with the speed cut defender. I was seriously hopeing to avoid this.
You don't need the divider. The speed sensor on the aristo spits out 4 pulses per revolution of speedo output, which is the same as what the ECU needs, so you can hook it up directly to the SPD input.
Older engines, such as 1G-GTEs etc out of G/MZ20 soarers used a speed sensor that generated a 20 pulse per rev of speedo output, needing a division by 5 to generate the 4 ppr needed by the ECU.

If this the device can't work with the 2 wire sensor I had another idea. Using a jaycar frequency switch to just turn the 2 wire sensors output off totally before the frequency reaches whatever it is at before 180km/h. Not sure what effect this would have though. With anyluck it will stay in 3rd gear and not try and go back to first or second :eek:
Yeah, I had a similar idea (to disconnect all available speed signals) - for about a microsecond ;)
Taking into account that it won't change out of first if it has no speed signal present, it can be expected that it will try to change back to first...
Not something I would like to try :)

Mos.

[CrUZida]

Mine changed from 1st to 2nd when I had no speed signal, but then would drop into drive, then neutral, then drive, then neutral etc.

I had to leave the shifter in 2nd to drive the car.

[Mos]

Mine changed from 1st to 2nd when I had no speed signal, but then would drop into drive, then neutral, then drive, then neutral etc.

Was that (1->2) with solenoids and all connected? Admittedly I never went to redline in 1st, but it didn't seem to want to shift, and the speed signal was a connector away :)
But the D->N->D->N sounds strange.
Mos.

[CrUZida]

Yeah, everything else was working (except the shift quality solenoid - A341E).

I can't explain the D/N thing either.

But I changed the dash over to a different one (both had the 4p/rev working when tested with multimeter), and she shifted correctly again (it gave me an SPD error code for a split second when it wasn't shifting correctly)

Then got the SP2 working properly (Crown box set up for hall effect needed to work with Soarer's reluctance sensor), and all errors disappear.

[2JZR31]

Thanks guys. Great info there Mos. So can just hook the 3 wire straight up to the ECU with the speed cut defender eh? No need for signal modification first?

Yeah, I had a similar idea (to disconnect all available speed signals) - for about a microsecond
Taking into account that it won't change out of first if it has no speed signal present, it can be expected that it will try to change back to first...
Not something I would like to try

My idea was to only turn the sensor off at about 170 with a frequency switch so it would behave as normal under 170. I realize it would not work if I just disabled it permenently. That wave form you posted would probably still be recognised by something that would recognise a square wave. I believe it just needs a high and a low to trigger, but I could be wrong. But all this means moot if I can just hook the other sensor up.

[Mos]

What I was saying was that: If no speed signal = 1st gear
Then the implication is that: Disconnecting speed signal at 170km/h = transmission will try to change back to 1st

It's something you could maybe try with a signal generator (at idle) and some visualisation on the solenoids, run the freq up to 170km/h, then disconnect sig gen while observing the solenoids' function.

I wouldn't expect the inductive sensor to be correctly picked up by a squarewave input but you could be lucky if it's sensitive enough. I think the amplitude of the inductive signal is very small, while the squarewave is 12V.

For SPD, yes, you can just connect the aristo vehicle speed sensor signal output directly to the ECU SPD pin.

Mos.

[wagonist]

This is also why the speed cut defenders aren't that cheap. They need to calculate the signal produced at 170 or whatever its set at & then reproduce it to send to the ECU to trick it into thinking the car's still travelling at 170.

[2JZR31]

I hear you Mos. Thats what I was a bit worried about too!

Doesnt matter though if I can just hook it straight up. I will try that with the speed cut defender and let you know how it goes :) Does the same apply for the 1JZ soarer speed input?

I got my pivot for $50 so it sounds like a got a good deal then.

[Mos]

If it's JZZ30 it should be the same.
Mos.