Hi I was searching for timing tips for my 1983 230E when I came across your thread.

In analog circuits zener diodes are often used to provide a fixed reference voltage (zener diodes are available in many set voltages). This essentially accomplishes the same thing as a resistor (increasing your resistance lowers your reference voltage.) A zener diode is superior as the output will remain steady even with slight input variation thus providing a more stable reference voltage. You could adjust your timing by substituting a different voltage zener.

Hope this helps.

...Nicholas

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Almost mint 1983 230E eurospec.
Honda civic for those not so mint moments.

Not an expert, but we use diodes to cut battery voltages in R/C aircraft applications.
About 1/2 volt drop in a series circuit. So there may be a simularity ....

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

they must be biased (typically 5 to 10ma depending on wattage) in order to act as a 'zener'.

In my DI module there is NO bias so it would not be possible to use one even if you wanted to! Also the zener impedance is low and does not equate to a resistor's impedance.

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Regards . . . . JimF
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'94 S500 Cpe

Visit my Mercedes Web Page

Tom and Jim:

How are you testing your diodes? To my knowledge zeners are biased until the potential difference across the terminals exceeds the zener voltage, at this point they breakdown and loose their bias. Zener voltages typically range from 2 to 200V so unless you were testing at a low voltage, say 1v (more than the 0.6V internal resistance) it would appear unbiased as JimF stated.

What is the voltage that you get between terminals without a diode in place? Is it steady or intermittent?

Your ignitions are more recent than mine (I have the euro-adjuster plug) so I have a couple of other questions toward an alternate solution.

Does your ignition measure crank position with a hall effect (sensor) at the crank(or flywheel, or balancer) or, does it sense it in the distributor (usually below the rotor)?

Does your distributor still incorporate vacuum advance/retard?

There is a Bosch parts distributor near my house I know he sells fuel injection data/testing/troubleshooting books I will inquire about EZL ignition books.

Purely out of curiosity what plug gap are you using?

...Nicholas

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Almost mint 1983 230E eurospec.
Honda civic for those not so mint moments.

I simply got a hold of a parts yard in the UK and had them pull the adjustable resistance knob from a 190E and ship it to me. I installed it in place of the R16 resistor module and now I can change the retard or advance on the timing when ever and to what ever I want. it works just fine and and I paid about $20 for the part and the shipping. I can change the timing in my 2.3-16v according to my driving style and the fuel octane I am using.

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Christopher Henkel
1990 190E 2.6 - Arctic white SOLD
1986 190E-16v - Blauswartze
1993 300CE - SOLD
2003 W208 CLK 320 Cabriolet - Magma Red

Tom,
How were your results running without resistor?
Did you have it completely removed or did you installed a wire in place of it?
Thank you
Tony.

Hello All,
I have a 1988 260E M103 2.6. I have had this car for almost three years and love it. Except for one problem. It is extremely slow on take off.

It is so slow that I will often turn right out of my subdivision and drive 3 additional miles to avoid having to turn left across traffic and into traffic (USA) because I might not be able to get out of the way in time.

I had read on this site and others that the R16 mod is nonsense. But after reading this thread and seeing the values of the resistors and what they do I decided to give it a try and remove it.

There is in my case anyway, a very noticeable improvement. While not a rocket ship by any means, it will get up to speed quicker.

I think the spark being advanced allows just enough torque to get the RPM's up faster and into the power band. I don't think I found any additional HP but I feel I moved it into the lower RPM's a bit where it is beneficial.

Thanks for all the information.