Battery voltage relation to spark quality? - PeachParts Mercedes-Benz Forum

whunter · #1 10-05-2010, 09:54 PM

Quote:

Originally Posted by PanzerSD

In Drive? Really??

With my car, if I had the loaded idle that high it'd want to get away from me...Set right now, to what I think is too high, is a 1000 rpm unloaded idle (2000 cold) and in drive, I judge the needle to be at about 600, and it's trying to go..

But at any rate, I was COMPLETELY on the wrong path with the alternator. I had it tested and the alternator is fine, I was kind of disappointed to hear that it makes 80 A and 14.2 V.

It seems, that the pulley, and the belt engineering is somewhat sub standard, as having the alternator driven by too big of a pulley. I noticed that the pulley on my alternator was a 2 piece pulley, and I thought about it, and I took the pulley off, put a washer in between and in distancing the two plates, it makes the pulley smaller. I gained 2.5 volts at idle, however with headlamps, fog, radio, heater, and wipers it still drops to 11.9, but does increase, albeit slowly to 12. I still think I should have maybe a minimum 13 V with all loads..

It sounds like you are on the right path.
If the pulley is to large = low alternator RPM.
At 11.9 you may want another spacer, or need to find a smaller pulley.
With the correct pulley you can lower the idle to your comfort level.

Idle speed is a very personal question for many people.
I have several local diesel owners demanding 450 - 500 RPM idle speed, difficult/impossible to get smooth idle + correct alternator charge that slow.

PanzerSD · #2 10-06-2010, 12:44 AM

Quote:

Originally Posted by whunter

It sounds like you are on the right path.
If the pulley is to large = low alternator RPM.
At 11.9 you may want another spacer, or need to find a smaller pulley.
With the correct pulley you can lower the idle to your comfort level.

Idle speed is a very personal question for many people.
I have several local diesel owners demanding 450 - 500 RPM idle speed, difficult/impossible to get smooth idle + correct alternator charge that slow.

I agree, I've always set my idle speed as low as possible. Actually, the adjustment procedure describes it as just low enough for the engine to overcome the friction and drag of ancillary equipment. Another previous hunch I had a few weeks ago. Perhaps my tach has some discrepancies..I should really be using a diagnostic tachometer to measure RPM I'll just bet that my dash tach is off by at least 50-75 RPM.
I've had her running smoothly, hot at an even 500~550rpm in D, Oil pressure was .75 bar, it was awesome..That's another thing I use to determine my idle speeds, Oil pressure.

I was looking at the pulley system earlier today, and I noticed that the water pump\fan is being driven by two belts (M117.986) The Water pump pulley is quite a bit smaller than the crank pulley, but is exactly 1 inch to the rear of the alternator belt path. I have a gap of approximately 2" from the face of the fan and my radiator. I think I can re-route the outboard water pump belt over to the alternator if I space the fan pulley out 1" with a solid machined spacer and longer bolts. I know the risks involved in adding length to a spinning body, so I'll demo it without the fan. if it works, and I can maintain at LEAST 12V at hot loaded idle, with partial loads then I've succeeded, and I'll use the E-fan from my SD.

If it doesn't work, at least the entire thing is reversible, and I guess I start looking for a AL129X