KenRudd

I am testing my WOT switch operation at the LH and the EZF 25 pin connectors. Testing with both connectors off their respective ECU's

On the EZF, I have expected behavior: From throttle closed to about 3/4's open, it is an open circuit from Pin 17 to ground, infinite resistance. At about 3/4's throttle, the circuit at Pin 17 closes to ground and resistance drops to essentially zero. I also then have continuity from Pin 17 to Pin B on the test port under the hood. So far, so good.

However, on the LH side: From throttle closed to about 3/4's open, the circuit at pin 12 shows ~1600 ohm to ground,. At about 3/4's throttle, the circuit at Pin 12 drop to ~400 ohms to ground.

So why is the EZF working properly but the LH showing unexpected resistance values? The WOT switch clearly changes the resistance for LH, but not from infinity to 0.


Throttle closed

Throttle wide open


I am basing my testing on these two threads, plus others I found:
https://rennlist.com/forums/928-foru...ht-to-you.html
https://rennlist.com/forums/928-foru...lh-system.html

KenRudd

I _think_ I figured this out. First of all, based on the wiring diagram, Pin 12 on LH and Pin 17 on EZF should be electrically identical, follow the green line:

KenRudd

However, I have a Porken WOT POT installed ( http://liftbars.com/docs/WOTpot.pdf )and that inserts a potentiometer into Pin 12 on the LH:





From Porken's WOT POT Instructions;

"Check resistance between terminals 12 and 25 ( engine ground) as shown with throttle depressed fully, or a jumper inserted between B and C at the engine test port. Range is 0 to 900 ohms in 15 or 22 turns. Stops can be felt. Clockwise richens. Initial setting should be 300 ohms. Approx. 30 ohms is the minimum adjustment. Below approx. 30 ohms the default WOT addition is applied! If the WOT switch is not closed, reading will be 1200 ohms plus the WOTpot resistance. (EZF WOT input has a 1200 ohm connection to ground.)"

Case closed.

PorKen

Could not have said it better myself.

dr bob

Either Ken:

Does the potentiometer mod only work with the Porken chipset?

I obviously haven't been paying enough attention in the past...

PorKen

Only with my chipset via custom coding. The WOT input on S2/S3 LH 2.2 is variable (could accept a true Throttle Position Sensor). The EZ-F is binary, IIRC.

S4-up LH 2.3 and EZ-K, both idle and WOT inputs are variable resistance (2K?).

KenRudd

The funny thing is that this was a self inflicted wound. Installed WOT POT a while ago, and totally forgot it's role in the circuit until my troubleshooting lead me back to it. I wish I could say this was the first time that something I did came back around to surprise me.