Looking for some help with electronics! - 2jz kickdown switch

[indeecent]

Right, quick background on the car

2jz (jzs147) cressida, auto shift kitted etc

There is no kickdown switch currently hooked up, so once you're over 20km/h (and not still in first) it doesnt often drop into first, which I would imagine puts a hell of a strain on the gearbox, and fails to get any real take off until it winds out a bit

I'm looking to put a voltage switch in wired off the TPS to trigger when it reaches at or near WOT, would this suffice? Universal Voltage Switch - Jaycar Electronics

Also if I recall correctly the kickdown switch from the ecu is a single wire that gets grounded? so all I need to do is configure the switch to ground this wire?

Hopefully it's that simple, if not someone correct me before i break things

Cheers
David

[Supra967]

Does your box have the ECT hooked up? Are you talking about the line pressure soleniod?

[dumbass]

look at yr diags see if theres a "kd" wire
if u have the big 40 and 80 pin plugs then its pin 3 on the 40 pin plug
green/yellow
i know cause im doing one today
wire that wire to a micro switch on the pedal then switch to ground
simple as that

[indeecent]

the wire was already seperated from when the car was wired up, but the previous owner never hooked up the kickdown

i dont think the pedal on the cressida has provision for a switch? placentajuan rigged his tps up with a trigger - so i'm assuming he couldnt get a switch on the pedal

thats why I was looking at a voltage switch to close the circuit to ground when the tps reaches max throttle

[wilbo666]

I'm pretty sure the Jaycar kit will do what you want, but if you have a little bit of electrical smarts what you really need / want is really just a comparator and a potentiometer (to set the trigger level)....

i.e.
Voltage Comparators

You'd want Circuit A in the below image taken from the above website.



I'd power the comparator (say an LM311 from jaycar for $1.75) from the +5V that feeds the TPS etc. You can tap into this (+5V), the TPS signal value, GND and the KD pin at the engine ECU

Not sure if you've seen my wiki, but it details the engine ECU pinouts for 2JZGTE JZS147...
wilbo666 / 2JZ-GTE JZS147 Aristo Engine Wiring

Cheers
Wilbo

[indeecent]

cheers wilbo, as much as i would love to use such a smaller/cheaper bit of kit, I dont even know where to begin with the LM311 (electronics have never been a strong point)

[wilbo666]

That's OK

I'm quite sure the jaycar kit uses a comparator anyway with some extra bits you don't really need like a relay and a voltage regulator.

I had a quick look and wasn't able to find a schematic though


Also worth mentioning that the kick down switch was only for early models (10/1991 to 08/1993, engine ECU part number 89661-30560).

Another thing to bear in mind is in that if you have "Power mode" of the auto selected, and you manually select 2nd gear the auto won't drop down to first, it will hold 2nd.

Cheers
Wilbo

[hosking1991]

Also worth mentioning that the kick down switch was only for early models (10/1991 to 08/1993, engine ECU part number 89661-30560).


Cheers
Wilbo

hey wilbo if this is the case than i guess thats why i couldnt find the kickdown switch on my aristo wreck (1995) lol

so if they dont have this switch how do they recognise when to kick down?

[wilbo666]

hey wilbo if this is the case than i guess thats why i couldnt find the kickdown switch on my aristo wreck (1995) lol

so if they dont have this switch how do they recognise when to kick down?

I'm sure the engine ECU is smart enough to take the voltage from the Throttle Position Sensor and wok out from that when the accel pedal is fully pressed

Personally I don't see why they needed the kick down switch in the first place!

Cheers
Wilbo

[hosking1991]

I see makes sense cheers for that mate,

Cheers luke

[CrUZida]

I've never hooked up the kickdown switch in any of my conversions.
And even in the Celsior I think I activated it once in 5 years of driving.
Not only do you have to put your foot flat, but you have to press extra hard to get the switch to activate, its not a normal thing to do.

Plus, with PWR on, the gbox has normally kicked down well before you've reached full throttle.

[dumbass]

I used to never hook it up too
I think 1 and 2js might not be as bad
but I've had 5 1uzs which would not
kickdown unless u fitted it
but easy way to know I u need it is drive car
an get to about 30 kph then floor it if it doesn't kick down
get the kd wire lengthen it and as u floor it again
touch the kd wire to earth
see if it helps it kickdown