I don't know if anyone else has a problem with an e-fan killing the idle on their car, but I know I did, even with an underdrive pulley, which raises other concerns, but anyway. Back to the topic at hand. My RX-7 for some reason would loose about 150rpm off the idle by turning on my e-fan. I found a solution for this. For those of you that have removed the rats nest, you should already have the part on hand if you didn't toss it in the garbage. If you did throw out a very usefull little part, then you'll have to find one. But the part I'm talking about are those little vacuum solenoids that control various things in the emissions system.

Basically, these solenoids work just like a standard air bypass valve. When power is put to the solenoid, it allows air to be sucked through the little filter on the one end. This essentially creates a vacuum leak if you have this hooked up to one of the vacuum nipples. We all know a vacuum leak raises idle, so when used right, one of these solenoids can be used to raise the idle when a small load is put on the engine at idle, such as the a/c or an e-fan.

So, all you really have to do, is hook one of these solenoids with a small section of vacuum hose up to a manifold vacuum source, and turn the solenoid on whenever there may be a load put on the engine at idle, from the e-fan. Hook one terminal from the solenoid to the relay switched power that goes to your e-fan, and hook the other terminal to a good chassis or engine ground. Then, for your vacuum lines, just run a vacuum line from the proper port on the solenoid to your manifold vacuum source. This may change depending on which solenoid you choose, and to tell you the truth, I'm not sure which one I used for sure. I'll leave it up to you to determine the right port on the solenoid to use.

To sum it up, before I installed the solenoid, turning on the e-fan lowered my idle speed by about 150rpm. After the solenoid, I don't loose any engine speed, keeping my alternator in a good range to keep charging the battery.

Mabey this is old news, I don't know for sure. But I don't know of any threads on the subject to date. I'll update this thread with pics as I get my install finished and looking good.

 

Damn that makes a lot of sense! I might just have to steal you idea... my idle drops like crazy when the lights are on, this might just take care of that....

 

No problem stealing the idea, thats why I posted this up. I'm sure a lot of people haven't thought of this.

As a little addition, incase it wasn't apparent in the first post, this can be used with anything that is turned on with some sort of electrical signal. Headlights, e-fan, air conditioning, fuel pump if it draws a lot of current, various other high draw items that are used at idle. The overall aim of this is to keep the rpm's up to help with keeping a charge in the battery under high draw conditions.

 

Rather than allow it have a vacuum leak, why not hook the solenoid up the the throttle opener for the A/C? It's adjustable to get whatever idle speed you need.
My A/C wiring was all outta whack, so I re-wired it to an aftermarket relay. When there's power going to clutch, it also sends power to the A/C solenoid, which in turn, opens the throttle.
Neat thing is, all cars have the throttle opener, and it's useless without the A/C solenoid hooked up.

 

But for those of us with aftermarket carbs, its easier to do it with the "vacuum leak" than rig up some sort of throttle opener. It also has no real adverse effect on the A/F ratio either. Can't say why exactly, but my wideband reports no change in A/F ratio at all with the solenoid open.

 

Where are you drawing the power for the fan from? I draw mine from the battery, rather than the alternator or fuse box, and haven't experienced any problems with idle shifting. I believe that the battery works as a buffer to prevent that from happening...

 

I draw everything off the battery through the FC fuse block I have. In the end, it doesn't really matter where you draw the power from, its all connected in a circuit, even though the connection is closer to the battery, doesn't mean it only draws from the battery. It might be that my battery is a little older too so it puts more draw on the alternator to keep the charge up.

 

Yeah, that's what I was talking about. If you draw from any point between the alternator and the battery, then the alternator will "feel" it immediately. However, if you draw straight from the positive post on the battery, then the battery will help to absorb the load a bit. Either way, it sounds like you've come up with your own solution to this.