While surfing the internet for "high gas mileage" I came across a company that says they've found a way to eke out a couple extra mpg -Dixie Caps

What it amounts to is inserting a capacitor into the the electrical hook-ups of each fuel injector. Basically, a capacitor is like a battery, so it stores a little juice for the next signal coming from the computer, which allows the injector to give a more precise firing pattern.

Rather than pay $10 a piece for their Dixie Caps, it seems like you might be able to go to Radio Shack and pick up a set for the same as they charge for one or two. Unfortunately, I don't know what kind of capacitor you'll need.

Perhaps, some here will have some ideas?

 

Hate to be a naysayer, but I see scant little evidence to support their claims. The injector pin is either open or closed and the amount of voltage normally supplied is more than sufficient to operate the injector. Increased voltage has no effect whatsoever on the injector pattern ("...more precise pattern"). The pattern is affected by fuel pressure flucuation, duration of energization or injector contamination, but a Dixie cap has no influence on these factors.

Bottom line, save your money. Automakers are always looking for ways to improve their fleet CAFE figures and is something this simple would actually work, they would have been providing it long ago.

 

<i>Hate to be a naysayer...</i><P>

Sheesh, you're a whiny one, aren't you?

Considering your naive view of automakers, I think I'll pass on your prognostication.

The price of a set of capacitors at Radio Shack and a few minutes inserting them into the fuel injectors isn't enough to keep some of us from trying.

 

The whole point of EFI is the injector pulsing at a known rate. Putting an extra capacitor in the circuit is going to change that. I can envision a lot of very precisely engineered control strategies going straight out the window.

Given the Feds mandate for CAFE if the thing worked as claimed and didn't increase emissions, it would already be in place from the factory. The manufacturers aren't as venal or as stupid as the conspiracy theorists would have you believe. Save your money.

 

The computer switches the GROUND side of the injectors, so a cap on the switched side won't store any useable energy. If you put them on the ground side, they MIGHT make the injectors open more slowly by effectively increasing the resistance to ground (actually increasing the current that the computer has to pull to get them open). If you put the caps on the hot side of the injectors, you MIGHT get them to open a little faster by effectively REDUCING the resistance to the battery (providing a "battery" closer to the injectors), but I can't imagine it would be appreciable under any circumstances other than SERIOUS problems in the truck's wiring. If you just have to try, put a big honkin' 12-18V cap between the red wire (that goes from the EEC relay to all the injectors) and ground, but be prepared for unpredictable behavior when you turn the key off.

 

Steve83,

Thanks for your reply. As you might've surmised, I'm not going to be deterred by negative prognostication - I'm going to give it a try. I had hoped that this forum would be more conducive to discussion, rather than boo-hooing.

Too bad that Ken Payne has turned off the html, otherwise you could've easily clicked on the link I provided to Dixie Caps and seen that they simply insert the capacitor leads into both wires going to the injectors. In fact, they don't even cut the wires.

The purpose of my post was to fish for some guidlines on the type of capacitor I should try. Your reply has come the closest in answering that, but I wonder if there are other specs to consider:

Amps, ohms of the injector/capicitor?

 

A capacitor across the injector coil will delay the injector opening
slightly, but delay the injector closing a lot! This is due to the
open collector driver in the PCM being able to sink more current
than the injector takes when the coil is energized.

The capacitor will add an additional current spike to the driver
in the PCM, due to the current required to charge the capacitor.
This will stress the PCM driver more......

Bottom line, it is a STUPID idea!!!!!!!!

 

Don't cry to me - tell them.

http://www.fuel-economy-tune-up.com/index.html

 

I'm just warning you that you could damage your PCM, which
is very expensive.....Another problem is a capacitor, and
inductor (injector coil) in parallel creates a resonate circuit,
creating the possibility of oscillating......

I have given you technical sound reasons for NOT putting caps
across your injectors........If you still want to risk damaging
your PCM...go for it!!!

I'm sure manufacturers of Splitfire spark plugs, and intake Tornados are still in business, but these products are TOTAL
Hoaxes!!!!!!

 

From the picture on the Dixie website, the capacitor is in parallel with the injector. Electrically, there should be no additional load on the circuit, because a capacitor doesn't have any current passing through it; the voltage merely produces a charge on the plates of the capacitor. This is an RC circuit like I'm studying in physics right now at NC State.


S1 is the switch that fires the injector; the capacitor is the 5microF in the middle; the injector would be where the 4 ohm resistor is in this diagram, and switch 2 is always closed.

When voltage is turned off, the capacitor discharges its charge through the injector keeping it open for a few more milliseconds after the computer cuts off the circuit. I don't understand the point of doing this though. Theoretically it works, but practically, it's not worth $9.99 each for a capacitor that injects slightly more fuel into the engine. And depending on how big the capacitor is and how long the fire pulse is from the computer, the capacitor might not even have time to fully charge before the circuit was closed and it was discharging again. I wouldn't waste my money on this, as I fail to see how it would improve gas mileage. Ford designed the fuel injection system to work properly; if they thought this would have been better, then they would have designed it with capacitors to start with. And besides, there are probably capacitors in the computer already used to fire the injectors, and this extra capacitor would just discharge the other capacitor faster, and end up firing the injector for the same amount of time as factory, or possibly shorter (this last sentence is speculation, I don't know how the computer fires the injectors, but it is possible/probable). From the "Dixie Cap" website, the whole concept looks like a bunch of b.s. Everything on there is a big load of crock. Hope this clears some stuff up.

Just a curiosity question here regarding the previous post: injectors are inductors? I thought they would be a solonoid type of device. Or are you saying that's what the complete circuit is, like the ignition coil and plugs? I'm just asking because I don't know.

 

The switch S1 in your diagram is an open collector driver in the
PCM. So, when the injector fires, the open collector driver will
see a current spike from the initial charge of the capacitor.

One other point, when the engine is at operating temperature,
the O2 sensors are going to detect a over rich condition from the
wider pulse with, making the pulse width narrower that the
capacitor screwed up........

Definite HOAX!!!!!!!


P.S. If you are an Engineering student at NC State, this should be
real obvious to you......

 

Yes it is obvious...these things are nothing but a big waste of money, and I would never buy any of them. But theoretically the capacitor should be fully discharged by the time the computer fires the injector, depending on how much time there is between injection pulses. If this time is short enough that the capacitor is not fully discharged, yes it will cause a spike in that circuit, and basically cause the injector to hang open all the time. I agree fully with your argument not to spend a dime on this waste, as I see absolutely no benefit in the use of these caps; everything Mr. Ayers and myself have posted, says that this will be harmful to the computer in one way or another.