Nicholas:

I have been thinking about how I might trick the circuit to get additional advance. At the moment, I don't know how the resistor is used. Right now it is out, so no current is flowing obviously.

I am not sure a zener diode would do anything in the circuit. It would depend on what voltage is driving the circuit, I guess.

But you have suggested to me that I make a couple of tests:

Measure current with stock resistor; measure voltage across terminals with and without resistor. These measurements might shed some light on how the circuit works.

It might be possible to place a small battery in the circuit to cause the electronic ignition to actually advance beyond the normal open-circuit baseline value. Have to be careful here because those EZL ignition controllers are expensive to replace!

I'm looking for some Bosch Manual information on the EZL but have not found any so far. MB manuals don't cover details of operation. I know there is a Bosch ignition manual out there but got out-bid on ebay! Maybe a forum member has a copy??

Thanks for your interest. More to come after some tests.

For your information, a forum member (Jim Villiers) made some acceleration tests in his '87 2.3-16 with/without resistor. Made a difference of 1.5 seconds in acceleration in 3rd gear, 2000-6000 rpm. That's fairly significant. Calculated HP differences were of the order of 20 HP out of about 160 HP! That supports the seat of the pants evaluations the group of us 16-valvers have had.

I have put together a spreadsheet which allows calculation of HP curves from acceleration and deceleration tests made on a vehicle. Process comes from a book published by Chris Jacobs of Jacobs Electronics ignition fame. Interesting book with lots of ideas. Anyone interested can email me.

Best regards,

Tom Elerding