Any easy/cheap ways of improving the fuel economy of a 4 litre Ford EL Falcon?

[Jaysen]

Theres a kit that you can buy from jaycar that is a mixture tester that hooks up to your oxy sensor. It lights up a row of about 10 or so LEDs and moves up and down them as the mixture changes. It has a varistor incorporated into the circiut so in theory you could exchange these leds for transistors and have each individual transistor hooked up to a different resistance that would run from a + powersource. All you would need to do then is adjust the varistor to what ever mixture you require.

[tandy ass]

Theres a kit that you can buy from jaycar that is a mixture tester that hooks up to your oxy sensor. It lights up a row of about 10 or so LEDs and moves up and down them as the mixture changes. It has a varistor incorporated into the circiut so in theory you could exchange these leds for transistors and have each individual transistor hooked up to a different resistance that would run from a + powersource. All you would need to do then is adjust the varistor to what ever mixture you require.

These things (in my opinion) are as useless as tits on a bull when your car uses a narrowband oxygen sensor. It will only ever read one of two extremes - complete left or complete right.

I believe the ford 4 litre motors use a narrowband sensor so that eliminates the idea.

The narrowband sensor works by putting out either 0 or 1 volt, nothing inbetween. When the gas is perfect stoichometric, it will be random noise between 0-1v, which is rather useless. If the input signal can't be used, you wont have a reliable output signal.

[Peter...]

Just as an addendum to what jmac said, the Falcons tend to run fairly rich as standard, something like 12:1 AFR or close to it. Wind that back a bit and you could find yourself some econ. Seriously though you are getting pretty good econ as it is now.

Just some food for thought. When I had my ED Fairmont, I put a "Stage 2" Crow Cam in it, Pacemaker Extractors (PH4499) and a 2.5 inch Redback Exhaust system on, my economy on highway cruise went from about 600km per tank to around 770-780KM per tank. The exhaust was fairly quiet too, really only changed the note from "air conditioning fan" to "Straight Six". Had one big centre muffler and a rear resonator.

[Charlie]

if you wanted a lean cruise, you'd just need a way of 'switching' the o2 sensor voltage with another voltage source applying say, 0.8v (random guess, would need testing / experimentation no doubt) during cruise conditions.
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[tandy ass]

Charlie, the point i'm trying to argue is the ECU wont use the oxygen signal 'voltage' to determine the A/F ratio. It will merely look at it in two states - is it rich or is it lean? IE is it zero volts or is it one volt. If its at either end, it will attempt to compensate, going into an infinite loop.

That is my understanding on how narrowband oxygen sensor ECU's work.

Correct me if I'm wrong.

[Charlie]

you may well be right. Am not sure, hadn't thought about it like that.
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[jmac]

Is it definitely a case of switching massively richer and leaner to get near max and min voltage alternately, or does it just alternate a touch leaner then richer and keep it within the sensors highest definition range?

If it's the latter, then hypothetically you could alter the signal to always read 0.2 volts different to what it actually is. Then it would be switching between say 15:4 and 15.7 instread of 14.5: 1 and 14.8:1 or similar (the direction and trend is relevant, the specific numbers are just hypothetical)

If it switches massively, then it wouldn't be too hard to log it with some sort of laptop and see the actual frequency it switches at, and duration. Then it wouldn't take a hell of an advanced circuit (and I don't have the knowhow, the last time I did anything remotely like this was the late 80s when I used a 555 timing chip to make my own autofire for the joysticks on my commodore 64) that could intercept the sensor output, then alter it, and provide a modified signal, one 'cycle' later (so it would send the rich signal, albeit showing richer than it actually is, the next time the injectors cycle richer)

I suppose it centres around just how often the ecu trims the fuel and what sort of increment it would alter it by with a modified signal (the gains might take some time to actually show up - depending on how harshly it trims the mixture)

John McKenzie

[TonyJZX]

Wouldn't messing with leaner mixtures be an extremely dangerous exercise for engine safety? Bozz driving what he used to drive, should be well aware of the perils of leaning out.

T.

[tandy ass]

http://www.forparts.com/o-21.htm

http://www.bobblick.com/techref/proj.../o2sensor.html

A rich mixture will produce almost 900 millivolts. A lean mixture produces about 100 millivolts or less. The sensor does not produce in-between voltages with any regularity. I think the material in the sensor is made to match the optimum air-fuel mixture, and the output of the sensor is pretty much on or off(too rich or too lean).

It appears so, I confirmed with an oscilloscope on my taxi that it indeed works this way, also confirming that those oxygen sensor voltage display units are stupid and pointless.

The only way I could foresee getting around it would be to fit a wideband sensor coupled to a control circuit to trick the ECU into the mixture we want by swinging a zero-one volt signal into the original o2 sensor input.

There goes that idea

[tandy ass]

Wouldn't messing with leaner mixtures be an extremely dangerous exercise for engine safety? Bozz driving what he used to drive, should be well aware of the perils of leaning out.

T.

Under very light engine loads, I really dont think so. This idea is only for cruising at under 20%-ish load.

[jmac]

I guess it does hinge on how the ecu reads/trims mixtures.

It'd probably be too good to be true to think something as simple (hypothetically) as a mini amplifier in the wiring to drop the output voltage would do the trick.

I did a little bit of googling, and believe it or not, actually turned up a site that offers something to do exactly that. I haven't used it, obviously, and in theory I can't comment on whether it's ridgy didge. Maybe someone else could look at the link and critique it? I'm not sure whether they are talking about intercepting the signal and modifying it via an algorith to enable the voltage to be displayed as an a/f ratio figure, or whether they mean to use it to modify the signal to the ecu to fool it into running leaner - the wording suggests perhaps the former, but the name (afr modification) suggests the latter.

http://www.perfectpower.com/Products/smt7_features.asp

fwiw, it'd be quite unlikely that you'd ever damage the engine with leaner part throttle a/f ratios. Aside from part throttle lowering VE (sort of) and dropping dynamic compression, they aren't actually near the 'limit' with the a/f ratios. Car manufacturers could (without a doubt) run their engines leaner (and possibly with more part throttle ignition advance) if it was an option, but have to compromise to meet emissions regs.


John McKenzie

[snavy]

my parents EL gets about 12 litres per 100kms city driving, and only driven during peak hour periods.

I once drove to Albury and back in it got around 720 out of a tank!

The EL had a 60 litre tanks doesnt it.

I also heard that chaning the oxygen sensor increase fuel enconony a lot in the 4.0L as well.

[TonyJZX]

I also heard that chaning the oxygen sensor increase fuel enconony a lot in the 4.0L as well.

This is true on older cars.

They rate sensors on a 40,000km cycle.

But some will last up to 100,000km with little signal loss.

I did mine at 80,000km with varying results.

T.

[tandy ass]

The sensor in this car was replaced about a year before I bought it and its still in good nick considering how fast it swings - around once a second at idle and a few times per second under moderate load (in drive with foot on brake and a bit of throttle)

How else can you fool the ECU into running a bit leaner? Play with the engine temp a little and fool it into thinking the engine is warmer than it really is?

[tandy ass]

my parents EL gets about 12 litres per 100kms city driving, and only driven during peak hour periods.

I once drove to Albury and back in it got around 720 out of a tank!

The EL had a 60 litre tanks doesnt it.

I also heard that chaning the oxygen sensor increase fuel enconony a lot in the 4.0L as well.

Thats a fair whack better than mine in peak hour - in peak hour I get around 13.5L/100km.