Electical Draw ? Lowers RPM ? 914 and 912E, Pull light switch and drops RPMs? Options

[thompson-mfr]

Hi All,

Finally got my car running better 74 914 2L FI. Thanks to all for suggestions. It turns out it was most likely the main power wires loose to my battery (fixed). Fuel was on and off.

I noticed something else when setting my idle.

When I turn on my headlights my RPM's drop. I recently acquired a 912E and it does the same thing, though not quite as much. I attached some pictures, just because I like threads with pictures better.

A. Could this be my Battery?
B. Grounds?
C. All the above?
D. Other_________?

[JamesM]

So, might help to better understand what is actually causing the RPM drop in order to find a solution, I am not entirely sure it is just load on the engine from the alternator.


D-jet sort of leaves you totally blind when it comes to diagnosing issues but on my megasquirt equip car I was seeing the same RPM change when I kicked on the headlights. Its pretty obvious when looking at the megasquirt dashboard what was happening as when the headlights went on 2 related things happened.

1. system voltage dropped slightly
2. mixture leaned out slightly

In my case the RPM change was due to the mixture change, which in turn was due to having a slightly shorter injection pulse, which was due to reduced system voltage. Thankfully Megasquirt has a setting to compensate for this exact thing, but if this is the case for you i think your only option with d-jet would be try and reduce the voltage drop as much as possible.


If you have a wideband sensor, see what is happening to your mixture with the headlights on, and/or see if the system voltage at the relay board drops when the headlights are on.