Duty Cycle Pickup Lead

[pasogrande]

Next to my Bosch distributor there is a blue wire with the end wrapped in electrical tape.

The manual for the US Spec 280i S2 indicates (I think) it is the duty cycle pickup lead. Does it have a purpose? Maybe a predecessor to the OBD2 sensor?

Wilf.

[pasogrande]

V8,

It is the vertical blueish wire maybe two inches in front of the coil.




This pic is not much better. The other end of the wire is through the firewall to the ECU.



Wilf.

[pasogrande]

Mark,

On mine the blue ballast wire ends are on the other side of the engine, near that exhaust manifold. Yes, it may be for the US spec cars only.

Wilf.

[pasogrande]

Mark,

I still have problems getting 12 volts to the coil, despite the new yellow and green wires I used to replace the bad old ones. I cheat by running a wire direct from the battery to that empty connector on the coil. One more thing to sort!

Wilf.

[pasogrande]

Below are two scans from the TVR manual.

The first is parts of two pages, one showing the Lambda Electronic Control Unit (sometimes called an Electronic Control Module); the other a picture of the coil with the duty cycle pickup wire.

The ECU is a similar size to the Electronic Amplifier Module. The main purpose of the ECU is to get information from the oxygen sensor to control emissions (I guess a condom wouldn't work for that!)



The second scan is part of the wiring diagram showing the lead connected to the last terminal.



I have no idea if the lead serves a useful purpose.

Wilf.

[pasogrande]

Thanks for all the comments. I believe the wire is there to be used for some test, or maybe for tuning. Judging from the picture it left the factory unconnected, with electrical tape wrapped around the end.

I wonder if this is the explanation:

https://learn.sparkfun.com/tutorials/pulse-width-m...

We made an LED dimmer using pulse width modulation. Maybe the lead could be used to measure how the duration of the spark.

Wilf.

[pasogrande]

BINGO!!! I've found the answer to my own question - although I don't fully understand it.

Below are scans of two pages from the Emissions section of the manual:

The first explains duty cycle.



The second explains the system, pulse ratios, and using a dwell meter



So that wire just sits there ready for somebody with the right test equipment (and skills)

(And V8, that unused crimp is mine; it is where I connect the +ve terminal of the coil to the battery)

[pasogrande]

V8,

I just spent a few minutes looking at the Berlina Sportive website you referenced. Very interesting.

It looks like an updated version of what I have. I didn't see any mention of the duty cycle pickup lead, but it is an excellent source of information on many other things.

Thanks for sharing it,

Wilf.