Hello,

Does anyone here have experience with the EZL (ignition) system on 560 M117.168 engines?

On non-US cars, this resistor is actually a potentiometer or rotary switch. For US cars, the resistance is fixed to 750 ohms.

My understanding is that in our 117.968 (560SEC) engines, the 750 ohm resistor gives us 3-7 degrees advance at idle, and 24-28 degrees at 3500 RPM (which is where our motors produce the most torque). Would there be any gains in torque by advancing the ignition even further? How much tolerance do you think MB programmed in to allow for 91 octane pump gas?

My guess is that a lower resistance would increase/hasten advance, but I can't be certain. Assuming I do try to change this value by substituting a potentiometer, is there a safe way to experiment without "pinging" my engine to pieces? Maybe I should get some octane boosting additive before I try this.


Here's the only reference I see to the R16 resistor in the MB CD-ROM manual (paraphrased):

-vacuum advance is activated at idle speed (not a fixed curve). The reference resistor is also active at this speed (without vacuum).
-when the coolant temperature rises above 95C, certain ignition curves are retarded to prevent engine temperature from rising.

As you can see, the manual is vague about the purpose of this resistor.

I have observed that making the resistance infinite (open circuit) causes the idle to smooth and rise about 75RPM. This is advance, right?

Thanks,
oktane

Someone in Australia has recently emailed me explaining what his mechanic did to better his low end torque:

The mechanic disconnected the R16 resistor altogether, causing an open circuit. He then installed a 1-way vacuum check valve feeding into the EZL unit. The car now apparently has much better low end feel, with the caveat that it needs 98 octane (R+M)/2 gasoline. The engine knocks at lower grades.

My thinking was that the mechanic killed some of the timing advance at idle by disconnecting the resistor, although that's contrary to what I found via experimentation.

The check valve prevents vacuum pressure from disappating, causing maximum advance even under heavily loaded conditions. This boils down to a total advance of 40-44 degrees at 3500+RPM, and 10-14 degrees at idle (probably less), regardless of load.

I'm sorry if that didn't make a whole lot of sense, but it's hard for me to explain this coherently when I have so many questions myself.

I'm very weary of the mod this mechanic did, since the timing advance is so radical. I am having my car dynoed tomorrow (along with 2 other people) and am just curious to see if this might work.

Thanks
-oktane

i have an 85 380 se and would like to know more about this r-16 resister. has any one done this on the 126 cars?

the only reason i want to mod this is for better fuel economy (maybe a little power too)

I can only answer for the 190E-16V, but I am sure things are similar on the other cars of the same vintage.

Increasing the R16 resistance results in less retard (more advance) in the basic ignition timing. In my case, I removed the resistor completely, giving me about 6 degrees more advance. I think this cnange applies across the entire load/rpm range.

I can hear no pinging after making this change. Other 16V owners have also noticed a significant performance improvement by doing this. One member calculated about a 10-15 hp max difference (based on analysis of acceleration times) on a nominal 165 HP engine.

One other comment--and I am not an agent for them--I installed a Jacobs electronic ignition and plug wires. Bottom line there was easier starting, smoother idle, and more horsepower (about 10-15 calculated from decreases in acceleration times). I am usually a skeptic about product claims, especially in the automotive industry. In this case the claims were proved valid.

I think the price of these things is excessive--I bought my unit on ebay for well less than half of the new price. The unit was unused.

Best regards

Tom Elerding

Apparently, the adjustable knob on there for Euro cars is labelled EZL ECE with positions S,2,N,4,5,6,7.

It is MB part # 015 545 07 28.

This is based on information I read on a mailing list.


SWITCH: RESISTANCE: RETARD: OCTANE:
S infinite 0 degrees 98
2 2400 ohms 2 95
N 1300 ohms 4 93
4 750 6 91 (the US setting)
5 470 8 89
6 220 10 87
7 0 12??? ???


When I tried on the "S" setting I noticed the engine revving about 50RPM higher, and accelerating off the line a bit smoother/faster. There was no noticable difference past idle and low RPM speeds. On my dyno run both with the "S" setting I noticed another 5HP and maybe 5 lb-ft torque only at the very start. The rest was exactly the same.[FONT=courier new]

where is the resister located in the US cars ?

anyone!

Brothers of The Benz, that little unplug resistor has surfaced again.
Those I'm familiar with are taped and tiewraped to the suction line of the AC. I imagine that's a free heat sink.
I've run my 124030, 108983, engine both with and with out. I simply remove it tape the connection and go for it.
I must say my fuel economy(mpg)dropped signifigantly; not the resistors doing but my driving habits changed.
These machines that are 10-15 years old, with 200-250,000 miles on the odometer don't come up with new intovations that haven't been tried before; no one has re-invented the wheel. Remember the Spiderman's Dual cold Ram air? Nothing new, the 500's have it, so why not the 300's?
Then there was the thread concerning the K & N Air filter. WOW!
Then there are those of us than would try anything in an attempt to improve performance with out the integrity of the machne.
I think I'll get the shop manuals out and see where the Engineers goofed.
Happy Trails Beep Beep from the Spiderman in Houston!!!

Ok, I am wondering this too. I have a euro car and want to see where mine is set at. Where is the little dial or the resisitor on my car??

__________________
'86 420SE Euro
904 Midnight Blue, Gray Velour
Dad bought it new, now I own it.

"A Mercedes-Benz is like a fine wine, it only gets better with age."

The other day I was looking around on my euro car and found that adjustable ECE EZL switch. The thing that struck me was that it is set on "S". According to this post, S needs 98 octane. Well I am sure that my dad has not touched this switch since the car was new and he said he has run 87 in it and it has never knocked according to him. He knows enough about cars to know what knocking is or if it was happening. And, if it was knocking for 165,000 miles, I am sure something would have happened by now and the car runs just fine. Also, I took it to the dealer for a problem and they messed with my fuel curve and timing (which I will restore b/c I think it was a wrong diagnosis) and anyways it started knocking. I put 91 or 93 in it and that stopped the knocking. So if my switch is set to S, what gives? Just to emphasize, I inspected the switch closely and even took off the little cap and it is in fact set on S, no mistaking.

__________________
'86 420SE Euro
904 Midnight Blue, Gray Velour
Dad bought it new, now I own it.

"A Mercedes-Benz is like a fine wine, it only gets better with age."