A/F/R gauge for tuning

ive got an AEM uego in summary useful as hell...like it.. been in ten years, still like it.

bung in exhaust/ mine is at the junction of the headers, needs to be in the right position
i.e 10* or more north of a horizonatal diameter-line of the pipe cross section. i.e at 10, 11 12, 1, 2 o'clock not 9 not 3 and not anywhere else.
so the thing can't fill up with condensation and burn out.
In some cases the sender and its plug are a calibrated part you can't just stick another sender into the plug the plug had a resistor etched away by a laser as they tuned the sensor during manufacture... this is a feature of some 3 and 4 wire wide band sensors and not a feature of some others. if it looks like 2 plugs, it is.... one of them stays with the sender. AEM will say in the intructions what you got... probably Bosch 4 wire.

They will die quick if you use AVGAS or leaded race fuel.

i agree with what has been said if your tune is miles out the thing will confuse the hell out of you.

sender too close to the head will read rich on overlap at some rpm or other and you risk over heating it or drownng it in fuel.
too far away leads to signal delay and if you have no muffler at all, air can be drawn in and it will read lean at some rpm or other
somewhere between the front foot well and the rear footwell on a car with mufflers works ok. its a compromise its not ideal.

OEMs put them up front closer to the head... but they know what they are doing... its an ecu controlled car and the chances of flames lapping at the sensor due to seroiusly wrong timeing or serious over fueling are low.

misfire/flat spot what caused it? wet plugs too rich the thing reads rich
misfire/flat spot what caused it? too lean, or marginal ignition system/plugs well the thing will read rich bceause you didn't burn any of the charge and it will continue to read rich until you drive through the flat spot. it may or may not go lean after that . It depends on if your mixture is now correct for your current RPM and igntion advance. but you will think its rich and lean it out even though it was a lean flat spot and it will then pig pong between rich and lean like you would not believe over a much wider rpm... :)

you just have to get your ears in tune...... and you nose.....

the wrong heat range of plugs will have you chasing your tail.

the car needs to run and drive for it to be of use

The AEM has an inteface on the back the can outpout a voltage that can be used in place of a lambda sensor output into an ECU of any type that has a user defined or lambda table provided you can customise range. or you can connect it to a data logger thats plumbed into igntion


if you tune to 14.7
your car won't run well at all it might if it was a heart shaped, pent roof 4 valve combsution chamber in an ally headed four pot withn VVT but not a chunky old v8

aim for 12.5 to 13.5 with foot down
no probs if it goes north of 14.7 up to 15-16 or so on cruise or when you lift off. your advance curve or ideally vacuum advance or MAP should cater for that.

a wheel nut off a vintage rover makes a good bung for the exhaust :) robust weldable and same thread but most gauges come with one. :)

set idle then check guage, should be 13.5 13.7 14 or some such
move onto progression WOT then check cruise

any issues you have will probably stem from plugs or ingition curve. an Igntion system that just can't cut it, once the car's tune gets into the good place is often a problem. previously you were running around rich all over putting out the flame slightly as it were

i.e better mixture = more power = faster exhaust gas speed= more extraction effect= bigger inlet charge= higher combustion chamber pressure at some rpm just as it gets on cam = intermittent failure of igntion system in some way, that maybe you can feel or hear or maybe not. but your lambda guage is going suddenly rich for 200-500 rpm

resulting in
Daft lambda gauge readings = doing the wrong thing to fix the problem= having to stop and have a beer and try again tomorrow

I found i suddenly had more valuble information and i was easily lead by the erroneous crap that is also shown..becasue i never knew about it before.

they are a great and a useful tool once you know about the stumbling blocks
and of course the output when used by an ECU is sampled and filtered and processed to cater for anomolous results when everything is badly out of bounds....

your eyes can't do that,

So you tune it as you always did and use this to check results, not the other way around. this is for the last 20% the tweaking. and a useful warning system on track or at dyno.. if the gauge is all red half way through a pull.........ssssssstttttttop before you melt a piston

Dave