The famous R16/1 (Also in Europe???)
 

I know this must be one of the most persistent posts in the forum, but after reading all the posts, I would be very pleased if anyone could clarify this point:
The famous R16/1 resistor seems to be present in some M102 and M103 engines at least. It is said to make wonders to the performance of the engine provided that good fuel is used as it modifies spark timing.
Does anyone know if it exists in W201 (190) european cars or only in american cars? (due to the difference in fuel quality) I have a 1992 190E 2.3 (8v) from Belgium and the only thing I have found is a kind of dial behind the battery with numbers 1 to 7. It must be R17 (that has the function of correcting some warm-up problems, if my information is good). There is also another dial with pos "S" and "N" near the EZL unit. Was R16 resistor substituted by this or they are different things?

If it exists, does anyone know how to locate it in this car? (please, european customers).

Thanks!

The dial is in place of the fixed resistor found on US cars. It is basically a switch that puts one of seven resistors in the circuit. Since I have not actually seen a dial, I don't know which number allows more advance. You will have to research that part on your own.

Good luck,

Looking at the Haynes manual the EZL ignition has a trim pot with 7 postions which you mention, this can be tweaked to suit different fuel grades. However in Europe 95RON is minimum standard as far as I know so changing the trim would be pointless, maybe if you used RON97 "super-unleaded"
you could get more power but I doubt the difference would be noticeable.

The S and N markers should be on the trim plug

info from manual -
3200 rpm/vacume applied/trim plug in S position - 35-39 degrees BTDC
3200 rpm/vacume applied/trim plug in N position - 35-39 degrees BTDC

3200 rpm/no vacume applied/trim plug in S position - 23-27 degrees BTDC
3200 rpm/no vacume applied/trim plug in N position - 17-21 degrees BTDC

I dunno what any of that means!

Mike.

Thanks, but someone once sent me a file where the funcion of R17 (the dial with 7 positions) was explained. It had nothing to do with advance, timing, etc, but seemed something to correct problems with warm-up cycle.

So if that dial is not R16, is the "S"/"N" plug R16? It is strange, as it is near the EZL, when the US guys talk about a resistor near the battery, that is in the opposite side of the engine.

Best regards

The multi-position selector with numbered positions and one position marked S and one marked N is R16. This sets the ignition module (EZL) to look-up different ignition timing maps. Position S is used for premium or super grade fuel whereas N is used for lower octane fuel. S is intended as the default setting whereas when travelling into areas with lower grade fuel N can be used with a resultant slight loss of power. Since MB vehicles delivered to the USA, Australia and a few other markets were intended to operate on fuel of a consistently and known octane rating, they had a fixed resistor fitted (usually tied against the engine wiring harness) for R16 in place of the multi-position selector. In Australia, due to our low octane regular unleaded, this value of R16 corresponded to that for position N.

Many owners in the USA and Australia have experimented with different value resistors (or no resitor fitted) for R16 in conjunction with operation on higher octane fuel. Some claim improvements others do not. I posted a couple of threads on the forums here as well as on other boards with the outcomes of my measured results. Generally speaking, only resistor values corresponding to either position S or N can be guaranteed to give predictable results for a particular model. Position S uses a higher value resistor resulting in greater ignition timing advance than position N. Note that R16 only affects ignition timing under high load. This corresponds to low vacuum (ie. vacuum disconnected) as can be seen in the figures quoted earlier in this thread by Mike65. Therefore any claims of differences under light throttle openings are only imagined. Other values (including resistor removed) may or may not give the expected results. Also note that positions S and N correspond to different numerical positions (ie. resistor values) for different engines. Some falsely believe that a higher resistor value (or R16 removed) gives the greatest ignition advance or that a continuously variable resistor (potentiometer) can be used to dial up whatever you wish. My measurements found that other values for R16 (including R16 removed) gave a "fault condition" of minimum advance (ie. retarded ignition). I operate both my KE-Jetronic engines (M102 & M103) with an R16 value corresponding to position S (originally used a value corresponding to N). I have done this primarily because I prefer to use premium grade fuel which is considered to be of a higher and more consistent quality here in Australia.

Incidently, the other multi-position selector you refer to is R17 which is for the fuel injection ECU and not intended as a user adjustment. If you wish to read my previous threads with my findings see http://www.peachparts.com/shopforum/mercedes-benz-performance-paddock/67773-read-if-you-have-done-free-horsepower-upgrade.html and http://www.peachparts.com/shopforum/tech-help/67772-those-m102-m103-free-power-upgrade-must-read.html

Do you know what are the other positions for?

The plugs all had the same resistor values however S and N positions differed depending upon whether it was an M102 or M103 engine and whether it was KAT or RUF (ie. with or without exhaust catalyst) meaning that different settings were needed in different applications. The owner's manuals generally only suggest operation using either the S or N settings, however if you read all the posts from the previous threads I had links to, it appears that early versions in particular did offer increasing ignition advance at higher resistance settings. My measurements revealed this not to be the case for my M102 and M103 (both 1990) where the resistance values corresponding to the S and N settings were about the only valid settings (the remainder defaulted to maximum retard).