I have a Ptuning kit, and wired up my fan setup how Ptuning describes in their instructions. When my Spal fan comes on, the initial voltage drop that comes with it is causing my car to stall out. No amount of massaging the battery offset table has helped with this issue. The AEM EMS is reacting too slow to catch the idle when the fan comes on. Even if I make it dump fuel and increase the IGN vs idle RPM table to 12 degrees when the rpms drop.

I'm thinking if I wire in a capacitor to be there when the fan demands all that initial voltage, the fan will take whats stored in the capacitor each time and not show such a large initial drop to my battery/alternator/AEM EMS. After the fan has used the energy in the capacitor for it's initial turn on, the system will then begin to run normally from the battery and alternator.

I'm not the best when it comes to wiring in things, so I'm trying to figure out if this will even work to help solve my problem. I have never been into car audio so I'm not entirly sure how these things work, but I know they hold charge. I'm not sure about what size I'd need either...

Here's something I just drew up to help me visualize this.


Theres a relay in there somewhere too... just didn't draw it in.

I'm not the only one with this issue and I'm not just going to rev my car up every time my fan comes on. I'm going to solve this somehow...

 

Drop the ignition advance at idle and open the throttle idle position slightly to compensate. Then right under the idle rpms add the ignition advance back in.

The advance will catch the engine whilst the IAV takes it's time to adjust.

 

Raise the idle rpm a bit maybe?


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ok, what? I think you're saying lower my average ignition advance during idle, and increase the amount the throttle plate is open. Then go back and add back in the ingition timing...

Maybe clarify a little.


I have raised the idle rpm, currently it's at 1075rpm. It holds perfect and I only see fluctuations of maybe 15rpms either way. Well, until the fan kicks on.

 

ithink he meant to drop the ignition advance at your idle target, and open the throttle idle position slightly to compensate. then under the idle rpms (lower than 1000rpm) add the ignition advance back in

 

copy, thanks.


Anyways, to test my theory, I took the battery out of my friend's s2000 after he came over today and basically made it my (test) capacitor. I connected the power wire for my fan to the positive post on his battery and then made a ground wire for the negative post of his battery to a ground location on my car.

When the fan came on, my car did nothing... but idle 100% correctly. AFRs were in the 14s, idle speed didn't drop or raise, voltage didn't budge. My plan worked flawlessly. The fan didn't seem as powerful, but I attribute that to the fact that the battery (in this case the "capacitor") wasn't being filled back up with voltage by the car's battery and alternator. Once I figure out how big of a capacitor I need and where to put it, I should be good to go.

 

I had the same issue with my civic when I still had it. Spal does make a fan controller (a pwm-3 I think) that has a 2-speed setting based on water temp. And it also has a "soft start" built into the unit. The fan will progressively spin to the lo-temp setting, and the later to the hi-temp (preset to your liking).

Sounds like you have it figured out, but this is another way to approach the problem.

 

Exactly that, we do that on all the racers and they have no trouble catching the idle even with silly cams (alright, different engines, but the same applies), and they tend to be turning 2 x 16 inch fans on, oil cooler fans, + electric PAS pumps, etc.

Generally I aim for running only a couple of degrees of advance at idle with the engine warm when doing that, it does mean you'll use more fuel when idling though!

 

this is awesome info im having the same problem, thank you for tis thread.

 

Neat idea!