Electronics help with TPS circuit.

[BMWTurbo]

I'd love to, but wouldn't know where to start... Nor do I have access to something that will log enough channels.

[sideshow]

my scanner plugged into my 1uz will give me the basics

its only when u start lookin at obd2 where u can get a shitload of live data

do u know any good mechanics with scanners

a good scanner is only 6000

might be worth it if your goin to spend afew months tryin to fix the prob hehhehheeh

[BMWTurbo]

Or I could jsut fit an SM4 with CDI and MV auto's box and be done with it

[Mos]

Personally I wouldn't touch that particular auto box with anything I considered valuable... sorry..

Mos.

[BMWTurbo]

I D/C the TPS and went for a drive last night, as Placenta said the car reved out in first and changed gears no problems (apart from the car stepping out which caught me by suprise), The car wouldn't go far into second gear before dropping into top though.

[BMWTurbo]

I've managed to get hold of another ARISTO ECU. I'll attach pics, both ECU's have exactly the same part numbers and marking, bar the fact that one was built in 1992 and the other in 1993.

BOTH ECU's exhibit the exact same issue...

[BMWTurbo]

Installed the aforementioned circuit but with a variation last night...

I've changed the design so that under normal conditions the TPS signal will be capped at 2.7Volts... ie will send sensor voltage to the ECU until it hits 2.7V and over, at which voltage it will only send a solid 2.7V (this is adjustable however). I've set this signal along with actual TPS output to a relay with the COM output gongi to the ECU.

Once the KD switch is activated, the realy switches over to actual TPS signal (roughly 3.8V) for approximately 2 seconds to allow KD of the gearbox to take place, and then it reverts back to the 2.7V clamped signal.

I'm suffering an interface issue atm with the mechanical KD switch not sending a clean earth to the switching circuit and hence it's not relliable. Will be inserting another relay at the front of the circuit tonight to create a relliable switched earth from teh KD switchi output to trigger the circuit...

As mentioned earlier in the thread by PlancetJuan when clamped to 2.7V max the Gearbox will kick down a single gear, even two when in O/D but it will NOT kcik back to first in any instance. The car needs to be stopped for it to come back to this gear.

On a happy note, the car will rev out in first, actually touching the limiter before changing into 2nd and stepping out sideways For some reason my gearbox has a very firm change into second, even at part loads.

[Mos]

Try using a 100nF cap in parallel with the kickdown switch - it might stop the signal from bouncing and give you a clean kickdown pulse. Not sure the relay will fix it - they can bounce as well, especially when fed a bouncing signal.
Mos.

[BMWTurbo]

I actually rana couple of diff caps accross it Mos, it helped it run relliably on the bench ( I was getting some bounce etc), but when the KD switch is activated it can see anywhere up to roughly 4ohms resistance accross it, which is enough for it not to work.

I tried the trigger wire with a 10ohm resistor straight to earth and it wouldn't trigger

I'll be grabbing a small relay tonight and dropping the KD switch across it's coil switching to earth.. Hopefully this will sort it out...

[Mos]

Ah okay. Transistor buffer rather than the relay?
Mos.

[BMWTurbo]

I discussed this with my dad last night and he thinks the relay would be the most relliable way to trigger the circuit...

The circuit is turning into a dasiy chain of dribs and drabs atm

I will have a relay driving a 2 second delay which drives a relay, which switchs between TPS actual and a Clamped TPS signal..


I really think I should have gotten into PIC's a while back

[BMWTurbo]

Good news... Relay with a diode accross it works perfectly...

I can floor the car and have it act as it should now.. no rev limits and changes literally on the limit

[sideshow]

i still recon it might be related to speed sensor

doesnt matter what throttle u have it wont kick down after a certain spd

if i trick the 1uzs i canmake it kick down earlier by telling ecu its goin slower than it really is

the kickdown switch on a 1uz doesnt really change much when i did some testing on a sc400 1uz in a hilux

cant see why u wouldget bad kickdown signals too
its either on of off

just an earth trigger

anyway next time i wire up a 2j i might ask to drive it

let u know if yr prob could be wiring related

[wilbo666]

let u know if yr prob could be wiring related

Stock Aristos appear to have the same problem.

Mos's car had the same problem.

I doubt it is wiring

Cheers
Wilbo

[BMWTurbo]

Thanks Sideshow...

I wish it was a wiring issue to be honest, then I could solve the thing instead of bandaiding it...

Well after mucking around with it last night and today, I think I need to shorten the relay clamp time on the switching circuit, it switchs for a fraction too long...

There are a couple of small issues I can't seem to solve... The car will not rev out in second gear when in D no matter what you do, you need to hold it manually and it will do this fine.

Also if you are splatting around and accidentally hit the KD switch when on full noise the early reve limit will come back into play for the amount of time the relay delay goes for...

Aside from that, hold it flat in 1st, change itno 2nd at 5000rpm (jsut clipping the limiter), then you can wind out second (am assuming all the way, didn't get this far), then flick it into 3rd, I guess then until the speed limtier