Originally Posted by some_other_dave (Post 459046)

How do you define "better"? A quick Google search shows that the Jaycar unit works by fiddling the air-flow signal (primary load measurement) going to the fuel injection, telling the car that less fuel is going in than actually is. That makes the engine run lean, producing less power and using less fuel.

If you run lean enough for long enough, you can damage your engine. Combustion temps will generally go up, and hot spots can form on head or piston. Those can eventually fail, leading to a loss of compression, and extra metal parts bouncing around inside the engine. Not exactly what you want.

I have found my Ford can run 16.5:1 which is not all that lean...

So what kind of "better" unit are you looking for? One that works on a different principle? One that has more manual control? Less manual control? One that gives you more range of adjustment? Something else?

All of the above: JayCar no longer offers these units so I will need to recreat a new one, I was thinking a less complex board and chip set might be out there.

I suspect that for most of those, you'll have to design and/or build them yourself.

Also note that lean mixtures produce high NOx, and may be bad for your catalyst in the long term.

-soD

Originally Posted by iveyjh (Post 459055)

Apexi AFC is what I use. It's a load based air fuel controller. Can go lean or rich. You can find them on craig's list or ebay. Craig's List is usually cheaper, you don't need a later model, an older one works just fine. I get mine from $60 - $100.

Originally Posted by mechman600 (Post 459089)

A 30% improvement would break all the laws of thermodynamics.
I would guess maybe a 5-10% improvement at most.

Originally Posted by Occasionally6 (Post 459780)

The following might be useful:

The Jaycar DFA is one of three similar units.

A Digital Pulse Adjuster - PWM signal in, altered PWM signal out with the PWM input frequency the same as the output.

An Independent Electronic Boost Controller - PWM signal in (intended to be injector pulse width), programmable PWM signal out with the PWM output frequency fixed at a constant, programmable, value.

The DPA - voltage in, altered voltage out with 0-1V, 0-5V and 0-12V ranges.

I have two of each of these, I don't have the boost Controller..

All three units require a Hand Controller unit to program them so the cost of that will have to be factored in. (One unit can do all three.)

I have two of these.

They are listed in Jaycar's back catalogue so should still be available, from Australia at least.

They do not have the DPA any more.

The kits were developed in conjunction with Silicon Chip magazine and descriptions of them - complete with how they work, circuit diagrams, full scale PCB images, schematics and assembly instructions - are available in book form in "Performance Electronics for Cars". (There are a number of other interesting/useful kits in that publication similarly described.)

Silicon Chip makes available, accessible from a link on the company's website, programmable PICs for projects that are described in the magazine. It's possible that the programmed PICs for these units are available that way i.e. it's possible the kits can be duplicated.

You won't be able to use the DPA to alter air:fuel ratios at part load by altering an air flow meter signal. That is because you can have high or low engine loads at less than full air flow and can't distinguish between them. You should be able to use an altered MAP signal voltage to do so, if you have speed-density based engine management. (I think the Ford 4.6 does not.)

The Ford has a voltage changing MAF. Range is 1 to 5 volts.

Here I would like more info..That is what they said it was for and I can seemly cause the A/F Ratios to change BUT the fuel trims seem to correct for it by adding fuel YET the A/F ratios stay lean...

Using the DPA for introducing lean burn with an air flow meter, you would use the 0-1V range on the adjuster to change the O2 sensor voltage the ECU sees. That would only affect closed loop - by definition light load - air:fuel mixtures, so should be safe. Be careful though because the air:fuel ratios learned in closed loop may be extrapolated into high load open loop. You will also be limited to changes within the fault code error parameters of the ECU self learning.

It is the 1 to 5 volt range.

Consider that when used to alter the O2 sensor signal it is only the air:fuel ratio that can be altered, not the ignition timing. Altering a MAP or air flow meter signal will alter the ignition timing because it moves the engine load:rpm point on both ignition timing and fuel maps.