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CJD
Yoda
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Dave, I'm still not seeing a problem here.
The little 4 banger was not designed for the heavy draw of an electric fan, so the RPM will always drop when that many amps kicks in. You are increasing the load on the motor without re-adjusting the idle...so it will necessarily drop. Most carbureted cars that had heavy draws, like fans/AC/etc. used a solenoid to bump up the idle speed when the heavy hitters came on line. Without that a drop in idle speed is inevitable.
I grew up with only carbureted cars, and I do not ever remember having one that would idle as long as yours does without clearing the carbon with a rev every several minutes. Remember that modern FI cars run closed loop, reading the O2 levels and constantly adjusting for variations in load and they even vary the air bleed for a rock steady idle. Carburetors do not have a feedback loop. You set it for a speed, and that's what you get. No temp or altitude adjustment is inherent in the carb. Thus, if you let it idle for extremely long periods...which 15 minutes is extremely long for a carbureted car...it is natural for it to load up or lean out.
When a load comes on a carburetor, the idle slows, lowering the vacuum. Lower vacuum will not draw the same fuel as it did with a free idle. Well...I could go on, but bottom line...if I have a carbureted car that will idle for 15+ minutes before it loads up, I am happy. Altering the basic design to add heavy draw fans, and your idle is absolutely incredibly stable.
The little 4 banger was not designed for the heavy draw of an electric fan, so the RPM will always drop when that many amps kicks in. You are increasing the load on the motor without re-adjusting the idle...so it will necessarily drop. Most carbureted cars that had heavy draws, like fans/AC/etc. used a solenoid to bump up the idle speed when the heavy hitters came on line. Without that a drop in idle speed is inevitable.
I grew up with only carbureted cars, and I do not ever remember having one that would idle as long as yours does without clearing the carbon with a rev every several minutes. Remember that modern FI cars run closed loop, reading the O2 levels and constantly adjusting for variations in load and they even vary the air bleed for a rock steady idle. Carburetors do not have a feedback loop. You set it for a speed, and that's what you get. No temp or altitude adjustment is inherent in the carb. Thus, if you let it idle for extremely long periods...which 15 minutes is extremely long for a carbureted car...it is natural for it to load up or lean out.
When a load comes on a carburetor, the idle slows, lowering the vacuum. Lower vacuum will not draw the same fuel as it did with a free idle. Well...I could go on, but bottom line...if I have a carbureted car that will idle for 15+ minutes before it loads up, I am happy. Altering the basic design to add heavy draw fans, and your idle is absolutely incredibly stable.
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