Electronics help with TPS circuit.

[brett_celicacoupe]

so the kickdown microswitch grounds at WOT?


sorry for all the questions; trying to device a suitable circuit for you

[PlacentaJuan]

yea it grounds at wot.

i will drive it aroudn a bit with the cd (or tps defender) and maybe suss out the rev limiter thing later, at least i can take the car to the drags now without hitting rev limiter.

[brett_celicacoupe]

cool ........

[PlacentaJuan]

yes but any voltage from the tps that is above 3.2v will make the rev limiter activate!

its so fucking frustrating!

[brett_celicacoupe]

you would have to make take the TPS voltage signal before your fancy clamping circuit.


but it really doesnt matter what the signal TPS voltage is, you can adjust the trigger voltage. you can use a kickdown trigger of 3.0V if you want! 1.0V even


ill explain how the above circuit works.

the voltage divider between R1 and R2 gives a voltage close to the desired threshold output of the TPS. this voltage divider produces a fixed voltage. now when the TPS voltage is higher than this voltage, current will flow from right to left on the resistor3.


essentially, if the current flows from left to right, the transistor opens. if the current flows the other way, the tranny wont open

so you just have to adjust the voltage divider close to the desired trigger voltage. only needs to be close because it can be fine tuned with a trim pot.


make sense?

[PlacentaJuan]

nah sorry brett i still don't understand.

the kickdown switch is mechanically actuated, and will earth a dedicated wire to the ecu, it doesn't care about voltage, as long as its earthed.

the tps signal to the ecu has the voltage which tells the ecu how open the throttle is.

for some reason when the throttle is open so that the signal is above 3.2v (and WOT is 4.3v) the rev limiter activates, regardless of revs.

my clamping circuit works fine in preventing rev limiter, but at only 3.2v the ecu wont 'accept' the kickdown switch input.



how about a circuit that disables the tps wire for 5-10 seconds whenever the kickdown switch is activated (after a delay of maybe 0.5 seconds)

that way the tps will be working as normal during everyday driving, but once floored (wheather in traffic or at the drags) the tps is disabled to allow the engine to rev out.

the delay would enable the kickdown switch to still work while i am driving.

[brett_celicacoupe]

the circuit i posted will switch to ground when a voltage from the TPS reaches a predefined voltage (4.0V if you like).

this makes the system entirely reliant on the voltage output of the TPS.

this method wont require a mechanical switch, the switching is done by the circuit.

adding a pot to the above circuit will change the TPS threshold voltage for the 'grounding switch' to close

[wilbo666]

Did MOS's cressida suffer from this?

I imagine that stock aristos didn't suffer from this problem...what, if anything is wired up differently!

Cheers
Wilbo

[Mos]

I'm pretty sure mine did not hit the rev limiter based on throttle position. I'm pretty sure mine shifted down a gear, accelerating violently and genuinely hitting the rev limiter (tacho needle does not keep up with the actual revs).

I imagine that stock Aristos are heavier, not accelerating as fast, consequently having time to shift up a gear before reaching the rev limiter.

As an aside, mine did not have a kick down switch (as in the donor vehicle and ECU did not have the kickdown switch).

Mos.

[PlacentaJuan]

yea but why does removing the tps alltogether 'solve' this problem.

thanks brett i will msn you when i am not at work.

[PlacentaJuan]

just an update in case anyone else comes across this problem;

i have wired in the fuel cut defender circuit that i posted earlier to solve this problem, voltage is set at about 2.7volts, which is low enough for the car to accelerate properly and will even kick down 1 gear with acceleration.

unfortunately it wont kick down anymore and the kickdown switch is also disabled. this is not what i want when cruising or freeway driving so i have wired in a switch in the cabin that will switch between unaltered tps signal, and voltage-clamped tps signal.

switch goes to clamped if i know i am going to floor the car from standing (like a tthe drags) and if i am quick enough, i switch it to voltage clamp when i floor it while driving, after the kickdown switch activates.

if i get no other solution then i will keep it like this, and maybe build some kind of 555 timer circuit that will turn the clamping circuit on and off via a signal from the kicdown switch or something.

[ProjectSleeper]

Mos, Yours definitely acts the same - when I was last driving with Adam he was suffering this..

Mine does it to

The white one I drove about 5 weeks ago Also suffered from this..

I will get a pic of my resistor thingy so you can probably work out it's value..

I am happy enough with mine as it is, If I NEED to drop back to first gear, I just drop the selector back to first and then back into 2nd or Drive and let the ECU control the upshifts. it's perfect from a standing start (12.83 sec with no stalling up) if left in Drive now that I had the Trans rebuilt and can be made to fry tyres on the change into second gear if that is what you prefer..

pic to follow..

[Mos]

Mos, Yours definitely acts the same - when I was last driving with Adam he was suffering this..

Guess it's a function of the driver then

Mos.

[ProjectSleeper]

Ha ha ha - that may well be

Adam's would not shift back to 1st gear - even from a 35km rolling start

As for hitting the revlimiter - yeah, well, it spent more time ON the limiter than off - LOL

[BMWTurbo]

Any further with this?

Not 100% keen on the stuffing around chanigng levels etc. Do std Aristo's behave this way?


I was wondering whether it might be an interface style issue with where the kickdown switch is activated?

I have found I need to hold roughly 80-85% throttle in order for this not to happen. Holding the kick down switch to drop, then backing off enoguh for the switch to dissengage wouldn't work either.