Speed Cut JZZ30

[NeoNasty]

Does anyone know how the Speed cut works in a Soarer/Supra?

I presumed that it was a variable frequency signal sent from a sensor to the Ecu. Is it a seperate one from the dash signal? From a seperate sensor?

I dont particually want an apexi RSM and I am able to build a kit to alter the frequency. I could easily set it to once F = x alter the signal to make the car think its doing less.

But if this will effect the speedo, then I would rather not.

Thanks
-Shaun

[wilbo666]

The ECU does have a SPD input that comes from the dash (from the dash -> ECU), I think that they are both the same signal…

I'd trace back the wire from the ECU (JZZ30 ECU pin outs are around), and isolate it such that you don't change the dash signal if you go playing with it. That was the dash will read as expected.

What the exact uses of the ECU SPD input is I'm not 100% sure. I currently don't have my ECU's speed input wired up with no apparent ill effects....(I'd be very interested to hear exactly what the SPD line does, the thread about it recently was still a little vague for me )

Cheers
Wilbo

[NeoNasty]

I just got a handy pin out of the ECU.

There are a few speed retated inputs.

SP2-, SP2+ = Speed sensors (located on transmission)
NCO-, NCO+ = Speed Sensor (Over drive on Lockup Clutch)
and
SP1 = Speed sensor

Id be inclined to think that SP1 would be the speed cut line in. I could pull apart the Ecu and trace some lines but I would really rather not as if I screw it up no more ECU.

The Apexi RSM removes the speed cut without cutting any lines on the board. This makes me think that perhaps the speedometer uses a different line. If I am able to get this to work I may have found a cheaper alternative if people just want the cut removed.

I'll investigate it further when the cars on the road.

[EldarO]

I just got a handy pin out of the ECU.

There are a few speed retated inputs.

SP2-, SP2+ = Speed sensors (located on transmission)
NCO-, NCO+ = Speed Sensor (Over drive on Lockup Clutch)
and
SP1 = Speed sensor

Id be inclined to think that SP1 would be the speed cut line in. I could pull apart the Ecu and trace some lines but I would really rather not as if I screw it up no more ECU.

The Apexi RSM removes the speed cut without cutting any lines on the board. This makes me think that perhaps the speedometer uses a different line. If I am able to get this to work I may have found a cheaper alternative if people just want the cut removed.

I'll investigate it further when the cars on the road.

we pulled the cover off my mates Jap spec 4age ECU, to have a look at the lines printed on the board, we had it off for quite some time, and it all still functions normally

the main thing is, as is the case with Computer parts and the like, to not touch the components, in case you discharge a bit of static into it, and r00t it beyond fixability.

if your really concerned, jaycar + dick smith etc. sell anti stiatic wrist straps that will guarentee you safe working conditions

if your just going to open it up and have a look, not mess with anything, id say go ahead, you shouldnt run into any problems

Eldar.O.

[NeoNasty]

Nah I know what Im doing working with ICs and the like. Its more that to seperate the sp1 line from the dash ecu and the speed cut ecu, I would have to slice a track or two.

The last thing I want to do it to then have other problems ie. no ABS no Cruise control.

[EldarO]

i gathered that you had a fair bit of knowledge from what you said, but for anyone else thinking of doing the same, its good to have that extra bit of info

i dont think you'll run into any problems experimenting, even if you just twitch the wires together temporarily, the part where people run into problems is when they rush things etc.

i would go through and put an inline switch in, on any wires that interest you, that way you can mess around with them and not have to worry about wires going missing, or shorting anything out, at the end of the day, all it is, is wiring, simple if you do your homework

Eldar.O.

[Shifty]

Do you anticipate you'll be using it on the track at all? If you'll only be using it on the road, then leave it alone as you'll remove the temptation to do a run to 200km/h, or a top speed run.

[The Witzl]

You are best to keep the signal there. Trust me this topic has come up a NUMBER of times on these forums

[CrUZida]

SPD is dash signal, 4 pulse per rev of the speedo gear.
SP2 is gbox signal, usually 4 pulse per rev of the output shaft.

AFAIK it uses SP2 to determine speed cut, as SPD varies depending on diff ratio.