Looking to do a Digital Fuel Adjuster

[Occasionally6]

Originally Posted by racprops

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

Bought as kits or assembled? The instructions in the kits are photocopies of the relevant chapter from "Performance Electronics for Cars", providing the detail on how they work. I don't know what comes/came with the assembled items.

They do not have the DPA any more.

Apologies for my typos - where I typed "DPA" above I meant DFA - Digital Fuel Adjuster. Assuming you meant the same, there is what appears to be an updated version, now called "Voltage Interceptor for Cars with ECUs" for which PCB artwork and software is being made available:

Programmed Micros - Silicon Chip Shop - Silicon Chip Online

I haven't looked to see if there is a full kit form for sale anywhere.

While I don't have immediate access to those issues of SC in which it was described, I can access them if you have questions about that device that you would like answered before spending money on a subscription, the PCB or software.

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...

The engine will draw through the air flow meter the same mass of air for a range of engine loads i.e. inlet manifold pressures. It depends on the engine speed that a particular air flow occurs at.

At low manifold pressures, high rpm, you could safely lean out the air:fuel ratios. At high manifold pressures, low rpm - with the same air flow rate - you may run into detonation with an air:fuel ratio leaned out by the same amount. With a single dimensional interceptor, like DFA, you are unable to make the distinction.

With closed loop fuel control, you will have to go further in order to reach the limits of the closed loop correction. That may result in even leaner air:fuel ratios at high manifold pressures, when you do get into open loop, or a fault code default to an open loop, rich (safe) air:fuel ratio map in place of closed loop control. It depends on what the ECU does to correct against the changes being made and where it sees a fault.

I think the original intention of the DFA was to bring back the air:fuel ratios to something resembling the factory functionality after changes like altered valve timing (cam swaps), larger injectors or air flow meters. It probably works OK to do that.

Here an interceptor, like the Apexi AFC, with two - rpm and TPS - dimensional inputs may be superior. That allows a distinction to be made between low and high manifold pressures i.e. engine load. If I understand it correctly, it overlays an n-alpha mesh over the existing engine management maps and allows the amount of correction to be adjusted independently within each cell (16 load points = 4x4?) of the mesh. Perhaps iveyjh would like to comment on this. You will still have to deal with the closed loop and O2 sensors.

It is the 1 to 5 volt range.

For the O2 sensor? That would be unusual for a narrow band sensor but OK. If it is not narrow band, that changes the whole thing.

I also have devices that will change the O2 response...

Rich

And you have 4 of them right? From experience, it can be tricky to emulate O2 sensor signals. I think it's because the ECU looks for the response to changes it has made and not just a signal that "looks" to be right.

[racprops]

Thanks that is deep think..

I am using a Dutchman Optimizer with has to digital O2 mod and has the good sense to have a timer to delay changing the output for a minute to allow the CPU to do its check and set ups.

And yes I have couple for both front and post O2s.

You are right although I can get the system to 16.5 it will not last and something like 3 to 5 minutes it goes open loop and nuts.

And I can do the same thing using the Optimizer but had some minor connection problems and will retesting it soon, but it looked good and it seemed to be able to change the A/F ratios with out the problems I ran into with changing the MAF...

Will have to watch the fuel trims with this one, The MAF seemed to cause major fuel trim changes ...will watch for them with the O2s.

Rich

[mwilliamshs]

Great thread! What if you use an Innovate LM2 to read actual AFR and modify the O2 signal to the ECU via the LM2's adjustable output so that instead of 14.7:1 in closed loop you were running say 16:1? (Or basically as lean as possible but as rich as necessary)

You'd have the gauge to monitor actual AFR so excessively lean running (and high EGTs) could be avoided and you'd still have the stock power enrichment (open loop) tables to preserve high load needs.

I've been thinking about this for years but never dug into it much. I now have a speed-density vehicle (no measure of airflow on the intake) and think a modified 02 signal would work to improve FE.

[racprops]

As I understood the old Camaro system it would enter into the lean burn mode only under special conductions like a light throttle, and light load, change either of these and it would switch back to normal A/F ratios.

I do not know if there was any other changes like with the timing..

The Jarcar Digital Fuel Adjuster has the ability to be mapped to the settings of the MAF so my idea is to cause the unit to output a signal that tells the PCM the car is coasting like under a light load which should (if I understand the programing) lean out the A/F ratios to the engine, producing a lean burn, any change out of this idea range of light load should put it back to stock.

Also a selector could lock this feature out unless switched on so it would be a user selected use.

Now doing one with the unit I have is OK for me, but I want to offer these to my friends and other thus the need for a replacement system.

[racprops]

I wanted to add I have two Zeitronix Air Fuel ratio meters, so I can both see the cars A/F ratios and with them change the A/F ratios from a round 10 to 1 up to 20:1 ratios, just not easily.

This was how I learned that I can see about 5 more MPG at 16.5:1 ratios.

Rich

[racprops]

Did some MPG Testing today.

Found a few interesting things: A) the 2000 Ford PCM system will NOT allow me to change the Air/Fuel Ratios with the MAF, I would reach 16:1 and for a couple of miles and then the PCM would go open loop and freak out.

So any use of a Digital Fuel Adjuster will be worthless, so a Digital Fuel Adjuster will not work on the car after all, I had thought I had gone a lot deeper with the A/F ratios, but even a little freaks out the PCM.

Second I found that EVEN adding the a control in line of the MAF caused the scan gauge to read much higher MPG like 35/50 MPG when here was no real change as reported correctly by the MPGunio…

And that with a EFI on the back O2s I can change the A/F ratios with the Zientronic Devices to 16:1 and get around 35 MPG with no noticeable power lost, so I reset it to 15.7:1 and will see how it feels.

Rich