R16 resistor
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Joined: Mar 2003
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From: Hedgesville, WV
1990 300E 2.6
R16 resistor
I was reading an older thread on www.mercedesshop.com about removing or modifying the 750 ohm resistor found in the ignition system, on 201/124 USA cars. The info is 1-2 years old but was interesting. Said that the factory resistor of 750 ohms resulted in a -6 degree retard to compensate for our lower octane gas in the US. By removing the resistor altogether you get 0 degree retard and by substituting one of 1.3K ohm, you get a -3 degree retard.
Is there any truth to this? Article said there could be a slight performance gain, slightly less heat generated and I guess a slight increase in gas mileage. I have found said resistor in the area just behind the antilock brake pump on my car. It is marked with large "24 81" numbers, and above these "000 540". Below is the number "09 3659 24". Part numbers given in the thread for various resistors do not match any numbers on mine, including one for the 750 ohm standard resistor.
Any ideas? I have a 1990 300E 2.6.
Thanks,
OliverB
Is there any truth to this? Article said there could be a slight performance gain, slightly less heat generated and I guess a slight increase in gas mileage. I have found said resistor in the area just behind the antilock brake pump on my car. It is marked with large "24 81" numbers, and above these "000 540". Below is the number "09 3659 24". Part numbers given in the thread for various resistors do not match any numbers on mine, including one for the 750 ohm standard resistor.
Any ideas? I have a 1990 300E 2.6.
Thanks,
OliverB
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Joined: Dec 2002
Posts: 516
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From: Iowa
'03 G500, '11 S550 4Matic, '12 SL63 AMG, '13 ML350, '16 AMG GTS Ed. 1
I also followed that thread from the beginning and removed that resistor from my 87 260E, 90 300E and 88 300TE. The engine seemed to have a little more zip and better throttle response, but absolutely no facts to back this up. Just how the engine felt. It was most notable on my 260, it also had the most mileage. I would have thought it to be more noticeable on a newer, less mileage, engine.
Give it a try and let us know what you think.
Give it a try and let us know what you think.
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Joined: Aug 2002
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From: Germany
'00 S320 W220, '98 A160 W168/ sold in 2005 '86 260 E W124 '90 260E W124
Hi,
the original thought from MB having this adjustment was to adapt to different qualities of gas in the international and national markets. It was generated during the later 80's when in Germany there was still leaded gasoline available and several non leaded qualities. Both was not 100% covering the country. SO MB had this resitor plug to adapt to the quality of gas when traveling and the better qualitiy was not to get. Always was a temporary solution and not necessarily meant for "performance gains". My personal view is not fiddle with that to gain a few split seconds in performance and risk the engine's health.
the original thought from MB having this adjustment was to adapt to different qualities of gas in the international and national markets. It was generated during the later 80's when in Germany there was still leaded gasoline available and several non leaded qualities. Both was not 100% covering the country. SO MB had this resitor plug to adapt to the quality of gas when traveling and the better qualitiy was not to get. Always was a temporary solution and not necessarily meant for "performance gains". My personal view is not fiddle with that to gain a few split seconds in performance and risk the engine's health.
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Joined: Dec 2002
Posts: 516
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From: Iowa
'03 G500, '11 S550 4Matic, '12 SL63 AMG, '13 ML350, '16 AMG GTS Ed. 1
This will become obvious, but I will preface my questions by stating: I have very little mechanical knowledge!
Is it "unhealthy" for the car to have no advance? Or is there an advantage to having the six degree advance provided by the resistor? I was under the assumption, however poor, that the engine is "more pure" without the resistor and would run as intended from the factory. In otherwords, if you run higher octane gas and remove the resistor, required to import to the US?, you are running the engine as the engineers intended.
Am I way off?
Is it "unhealthy" for the car to have no advance? Or is there an advantage to having the six degree advance provided by the resistor? I was under the assumption, however poor, that the engine is "more pure" without the resistor and would run as intended from the factory. In otherwords, if you run higher octane gas and remove the resistor, required to import to the US?, you are running the engine as the engineers intended.
Am I way off?
Thread Starter
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Joined: Mar 2003
Posts: 76
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From: Hedgesville, WV
1990 300E 2.6
Reason for retarding spark
It was common practice for engineers to retard the spark advance on an engine to "de-tune" it, allowing it to run better, w/o pinging, on lower octane gasolines - especially when unleaded replaced leaded gasoline. Retarding spark at idle also reduced pollution, allowing engines to better meet pollution standards. In the past, many people would" advance" the spark a couple of degrees on their engines to achieve better performance and gas mileage, makig certain that they kept the advance below the level producing ping.
What I don't know about the MB setup on the 103/104 engines with the fixed resistor, is how the spark advance curve built into the distributor is set up. If our engine has a resistor that electronically retards the spark 6 degrees and we remove the resistor or replace it with ones producing a -2 or -4 degree retard, are we still keeping our engines within the safe range for spark advance at higher RPMs? I use 93 octane premium in my 1990 2.6. If I stick with this gas, I could probably safely subsitiute a resistor - say -2 degree retard - w/o damage to the engine. I would like to hear from someone who has technical expertise in this area for this engine.
What I don't know about the MB setup on the 103/104 engines with the fixed resistor, is how the spark advance curve built into the distributor is set up. If our engine has a resistor that electronically retards the spark 6 degrees and we remove the resistor or replace it with ones producing a -2 or -4 degree retard, are we still keeping our engines within the safe range for spark advance at higher RPMs? I use 93 octane premium in my 1990 2.6. If I stick with this gas, I could probably safely subsitiute a resistor - say -2 degree retard - w/o damage to the engine. I would like to hear from someone who has technical expertise in this area for this engine.
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Joined: Aug 2002
Posts: 1,005
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From: Germany
'00 S320 W220, '98 A160 W168/ sold in 2005 '86 260 E W124 '90 260E W124
A few months ago some in this forum had described the functions and the values and the "curves" for this topic very clearly, but I have no clue how to find this again.
But I still repeat my statement. For a split second of quicker response I would not risk anything concerning the engine life. And PINGING is the worst you can do to the engines, and PNGING is a matter of premature ignition, and this what is avoided by the right values of resitors.
But I still repeat my statement. For a split second of quicker response I would not risk anything concerning the engine life. And PINGING is the worst you can do to the engines, and PNGING is a matter of premature ignition, and this what is avoided by the right values of resitors.
