I tried the resistor removal on three different vehicles (including my former M103 300E) and it did very little to nothing to change the engine performance. On the M103 it made no difference at all, on the M116's it improved low end torque a little bit, but I'd say under 5%

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

...interesting to read that post several years later. Perhaps I did not give enough time to let my SOTP form an impression, but removing the resistor definitely improved the low end torque once I had some experience with it and allowed me to alter my driving style and considerably increase urban driving fuel economy as I stated in my June 9 post.

It's also possible that I screwed up the test.

As I said, I invite everyone else to do the same test.

There are numerous EZL modules, which have different characteristics including both initial advance and different advance-RPM characterisitcs depending on the R16/1 value. I think the details are in the service publications, but for a given EZL module, the only way I know of to alter the advance curve is by using different R16/1 resistances. The initial timing is fixed by the EZL and is not adjustable, but different EZLs may offer different initial timing values.

It's possible that the increase in low end torque is less noticeable on automatics because if you apply significant throttle below converter stall speed the engine will immediately rev to the stall speed. I don't know what the automatic converter stall speed is, but 2000 is typical. You can test yours by firmly applying the brake at a dead stop, then floor the throttle for a couple of seconds and read the tach.

My experience with my five-speed and no R16/1 resistor installed is that I can drop it into fifth gear on a level road at 35 MPH, which is about 1300 revs. If traffic slows to 30 (1100) and then increases back to 35, I don't bother to downshift. With the OE 750K ohm resistor installed fifth was not useable below about 45 MPH.

My major complaint with the M103 was always lack of low end torque, but that's not the case, today. It now has the broad torque bandwidth of my favorite Corvette SHP engines. I call it "half a L-79" - the 327 CID, 350 HP Corvette engine from '65 to '68 that will easily pull from 1000 revs in top gear and make useable power to 6500.

Now if I can find a LSD 3.27:1 axle from the US version 16V, the car will be perfect!

Duke

Be assured that I'm definitely taking out the resistor. The improvement in performance, if any, will show up in the fuel economy.

The t/c has a stall of only 1800.

I found another interesting tidbit last night with it.

The vacuum level at a steady state 60 mph is LOWER than the vacuum level at a steady state 65 mph. The engine climbs about 250 rpm in this speed differential (to about 2300 rpm) and that amount is significant enough to add more than enough torque to compensate for the increased air resistance.

The vehicle might get better fuel economy at 65 mph than it can at 60 mph using the new fourth gear because the rpm at 60 is simply too low.

Highly possible. You have to look at the efficiency map for the engine. The same thing happens with my F350, it gets the same economy at 60 as it does at 70 because 70 in 6th is right in the middle of the efficiency map. At 60 it has to work harder to spool the turbo. On a long, unloaded trip I can crack 20 MPG

-J

What powers your F350? I have that 6.4 in mine.

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'87 300SDL 251k
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As a general rule, engine efficiency is greatest at high load, low revs assuming the spark timing is optimum for the specific operating condition. But low rev spark advance may be limited by detonation considerations, which may account for your observation. At 60 MPH - about 2100 - spark advance may fall off to the point where the engine loses considerably efficiency, so you have to use more throttle than at 65/2300.

Run the same test with the R16/1 resistor removed.

I ran a test on a long grade of about 4-5 percent at 30 MPH in fifth (1100) and fourth (1400). The engine would pull the grade without detonation in fifth, but the coolant temperature increased, which indicated higher EGT due to much less than optimum spark advance. In fourth there was no increase in coolant temperature.

My conclusion is that under these conditions fourth is more efficient. Fifth is okay for level ground down to 30 MPH, but any significant grade at 30-35 calls for fourth gear.

Another trick is to never use WOT unless you plan to rev the engine all the way or near the redline. Half to three-quarter throttle below about 3500 revs will cause manifold vacuum to go to near zero, but it stays in closed loop mode maintaining stoichiometric A/F ratio. When you push the throttle all the way to the floor, the WOT switch on the throttle body tells the KE system to go into open loop, which adds about 10-20 percent excess fuel. Power improves slightly, but not enough to make much difference in acceleration considering the extra fuel being consumed.

I'm constantly scolding my vintage Corvette buddies for driving them around town in second gear all the time. Hey, it's not a '65 911! Even with the huge mechanical lifter camshafts from the sixties, if set up right, these torque shy high revving small blocks will easily cruise along and keep up with traffic in top gear at 1000 revs. A C2 small block weighs about 10 percent more than my 190E 2.6, but has twice the displacement, which means about twice the torque at any engine speed.

There's no point wasting fuel when your slogging around town in traffic. Then when you get a clean shot at a freeway on-ramp - bounce it off the rev limiter!

Duke

Will do. In fact, I'm going out to pull it today.

I'm well aware of the WOT fuel dump. Total waste. In fact, it never sees WOT unless the cruise control causes it on a fairly steep highway upgrade. I now know these upgrades and perform a 3-4 downshift prior to the arrival at the bottom of the grade. I am betting that it is more efficient in 3rd at 3100 than it is in 4th at 2250 when it takes WOT to hold it at 2250.

That extra torque is likely why the V8 is still competitve in fuel economy when driven gently, lately I have been seeing about 17-18 city driving *normally* (under 3k rpm). I can easily accelerate in 4th gear at low speeds (1500-2000rpm) with the M116 without even touching the red/losing manifold vaccuum. And even on hills it never comes close to the red to maintain speed unless the A/C is on. That extra 1.2 liters of displacement and 2 cylinders makes the difference.

Realistically, older gassers are going to become obsolete soon with their thirsty behavior...when gas is $5+ it will make no sense to own/regularly drive vehicles averaging anywhere under 30mpg.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

R16/1 removed.

There is absolutely no doubt that it has more torque at low rpm. In fact, starting in second gear is not an issue under just about any circumstance, despite the 2.47. It quickly climbs in revs and the manifold vacuum stays consistently higher.

Filled the tank for the new test without the resistor.

487 miles on 20.37 gallons.

Back up to: 23.91 combined city/highway.


Without the resistor, I fully expect it to hit 25 combined. We'll see.

See if the 420 will ever reach that...........

I have never seen 25 in mine (high of 23-24 or so)....but my dad has seen 26 going 70 on cruise over a long distance. No A/C....and full flow exhaust. (only the rear muffler)

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

6.0, now featuring the optional flow-through head gaskets!

-J

I'm at 430 miles at the exact 1/4 mark.

Fairly sure that it will go 525 miles to the reserve and take about 21 gallons.

So, the removal of the resistor definitely has a benefit.

I've also increased the highway speed to 65 mph because of the annoyance of driving it at 62. The increase in available torque is noticeable.

I recall you are using 89 PON fuel. Have you detected any detonation?

I use 87 in my '88 190E 2.6 five-speed. I get a little transient detonation on upshifts, shifting at about 2000 if the ambient temperature is over about 70F and the coolant is 80C or higher or if I "second gear" a stop sign - brake until I'm nearly stopped and engine revs are down to idle speed or less, then accelerate if the intersection is clear.

Detonation is less likely with an automatic since the torque converter will will allow revs to increase to stall speed if you load it up below that speed.

Duke

Absolutely nothing at any rpm or load with the 89 fuel at the present time. Tells that it needs more timing...........

Did the 2.6 originally call for 91 as well?

Yes, Mercedes recommended premium fuel, which is 91 PON here in California.

Back when I drove the car daily (and it still had the OE 750K R16/1) it would sometimes detonate on hot days when the coolant temp was over 90 and the A/C was on, so their recommendation was probably correct.

Now I only drive it a few times a month during the winter and spring months when ambient temp is usually no more than 70, and I rarely use the A/C, so 87 is okay.

Detonation is really senstive to inlet air and coolant temperature, but a little transient detonation, which is what I get sometimes, means the spark advance is near ideal.

If both the air temperature and coolant temperature are high I can get around any detonation by shifting at higher revs and easing into the throttle. It's strictly a low rev transient phenomenom. The EZL may be a little slow to back off the vacuum advance on upshifts.

If you're not experiencing any detonation on 89 try 87, and if it doesn't exhibit significant detonation on 87 you can continue to use it. If my car had an auto I doubt if I could detect any detonation because it only happens at below about 1500 at high load, which is not an operating condition a torque converter will allow.

It's really difficult to determine the ideal spark advance map unless you can change it easily and use a high octane fuel on a chassis dyno to determine the optimum advance for all operating conditions. Often it's near the detonation point if you have marginal octane for the specific CR and combustion chamber design, but given the improvement in both low end torque and fuel economy with the R16/1 removed plus the occasional transient detonation, I think the advance is pretty close to ideal in a design that doesn't have a detonation sensor that will tend to keep the advance right on the ragged edge of detonation for all operating conditions. That's how most modern engines are set up.

Duke