Kind of a long story but didnt want to leave anything out.


The other day I decided to actually drive my car around a bit since I havent for about 2 months. The battery was dead. Not really a surprise, so I throw it on my awesome charger I have. I set it to 50 amps, set the timer to 60 mins and walk away for a while.

I come back out start the car and man this thing is holding an idle really well (charger still hooked up). In fact its idling at 1300 instead of the 900 I have it set to. I let it sit there waiting for it to die because it always does until the temp needle actually moves. It never dies...

So, after a few minutes I figure its safe to get out and unhook the charger. Suddenly the engine is idling slower (900 its set at) and has a tiny brap like normal. I think to myself "hm, thats weird" so I hook the charger back up and low and behold the idle increases and smooths back out.

I think to myself, "oh this must be happening since the batt is still low the alt must be really putting a drain on the engine". Makes sense to me. I drive around a bit (like an hour or so) and come back home and hook the charger back up and exact same thing happens.



So, knowing that my battery is good (tested) and my alt is good (tested) AND that my grounds are good (all new wiring, plus a few extra grounding spots added), what could my problem be? I have S4 70 amp alt. Would I need to upgrade alt feed wiring (from alt to charge batt, currently 8 ga)? Anyone else notice this before? Call me paranoid, but I am thinking that something is wrong and I REALLY hate electrical issues.

-Ian

 

What kind of ignition setup are you using?

It sounds to me like when the charger is hooked up your now getting higher
voltage thru the system and that is translating into a hotter spark in some way.
So you could have some weak ignition components in the mix.

 

I think there is a simple answer here. At idle, the alternator simply isn't able to produce the same level of power that the charger is. Once the alternator spins up, then it should produce enough to supply everything.

When you coming over man? Big event this weekend (hint, hint)




.

 

I think I know what's going on. Try unhooking your alt electrically, starting your car, and check for the 1300 idle. Then hook up the alt while running (yes, kinda dangerous, do at own risk). See if idle drops back down. If it does the charger is causing the alt to not go into charge mode at low RPM/idle. The FC alts put more load/drag on your idle than a stock 50 amp alt would.

Another test is spin an alt with a power drill (gotta fab up an adaptor to hold a socket). Make sure it's hooked up electrically like they do at auto parts stores that test alts and starters. The only difference here is with a power drill you can feel when the alt kicks on. The drill will feel like it just drilled into something really tough. If that's not enough to lower an idle, you're doing it wrong. Nearly ripped the drill out of my hand. It was pretty cool.

 

I need to try that one now. I like hands on tests like that.

Good point about the FC alternator. It seems so obvious once you pointed out.

 

i know this way is kind of lame compared to the drill thing, but you could measure the voltage @ the coils with the charger on and off....

i know back in the day the racers used to run the coils right from the alt, more voltage = quicker charger time = more ignition power

 

I was thinking similar things today at work. I bet the extra voltage plus the extra current going to the batt is causing the alt to not need to be "engaged" and also the extra voltage is maybe bumping up the power to the ignition system.

I am running Blaster 2 coils (2 total) in stock location. I also have some non-mazda type (ford racing) 9mm wires and stock plugs. I rewired my coil main power back in the day when I ran DLIDFIS and upgraded power wires to 12ga instead of the 14 or 16 ga that was stock. I have thought about going back to stock plug wires just to get rid of some excess in the engine bay since the ford wires are a bit longer (and now that Im thinking about it are probably a different resistance value).

 

The only purpose of resistance in plug wires is for noise suppression: Takes the sharp edges off the waveforms, thus dropping harmonic content. From a performance standpoint, lower is better.

 

new NGK's are like 7.5k ohms, the spec for replacement is 16k, it makes a huge difference