n/a afr readings?
Turbo Mini Forums

Hi

I fitted a aem afr gauge to my mini recently.

When I'm cruising at part throttle the numbers go to 17 and off the scale?
as soon as I plant my foot it goes to 12-13.
It's been set up on a rolling road so it should be ok.
Just wondered if there's something wrong with it.

I'm running shell v power and castrol valvemaster plus. Could this be up setting the readings maybe?


Thanks
josh

My build thread..

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=542985

Should of said. It's a naturally asperated 1380 with 11.2:1 cr.

It doesn't seem to be running bad. Seems responsive and good in fact!

My build thread..

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=542985

Sounds pretty ideal to me.

Max power is usually somewhere around 12.5:1

Cruise you want it as lean as the motor will take without stuttering or stumbling for economy reasons.

Sounds like whoever set it up has got it spot on really.

However I would have thought the Castrol additive will kill the wideband sensor pretty quickly.

If it's running nice and feels good under foot, responsive etc I wouldnt worry too much.

I'd say at cruise it does sound lean but if it feels ok to you then not really an issue. part throttle etc would be more interesting.

Full throttle, high 12's touching 13 seem to be what people say is best for n/a

Valvemaster etc doesnt contain lead or any nasties ? So dont think it should affect the sensor at all.

We arent allowed any nice nasties for our cars anymore lol

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Yea I had no doubt in the setting up as he's very well respected. Just wondered if the gauge was telling porkys lol.
like I said it doesn't have any flat spots or anything.

Just piece of mind :)

My build thread..

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=542985

As the gents state above JT, your rolling road guru got this spot on.

I've got an AFR meter in my n/a mini too. In case of cruise / part throttle the AFR is above 15,5, I always experienced this was a matter of misfire. When one cilinder is not working under that condition, the unburnt (thus plenty oxygene in exhaust) mixture causes high numbers at the AFR meter.

be carefull with 'diagnosing' misfires based on AFR, its not quite as simple as black and white
you should by no means be misfiring at 15.5 afr anyway,
if yours is i would be looking to upgrade the ignition system

Yes i moved to the darkside

Instagram @jdm_brett

Any non fire event will show a leaner reading. But too lean can cause a misfire...which in turn can show even leaner.

But even when rich with a misfire...it could show lean spikes. So as above, lean doesnt always mean lean as such. Widebands only give a small insight and what they tell you needs treated with caution and can only be considered accurate as far as AFR's etc go as long as the engine is running well.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

The castrol additive uses phosphorous to replace the lead.
The other common ones use manganese or sodium.

I don't know the effects of manganese or sodium but phosphorous is known to be bad for the sensors, normally it contaminates the exhaust if an engine uses too much oil (phosphorous is one of many additives in engine oil).

So deliberately putting it directly in the fuel must be even worse.

See part way down this Bosch article.

https://www.boschautoparts.com/auto/oxygen-...-oxygen-sensors


EDIT - and there are a few other reasons a wideband can read wrong apart from the ones already mentioned, especially if they are at the extreme ends of their range.

EDIT 2 - probably worth adding that anyone who uses the engine oils that are high in ZDDP (like Millers) or if you add ZDDP to the oil, the P is phosphate so you need to be even more careful you don't burn excessive amounts.....

Edited by Rod S on 5th Apr, 2015.

Schrödinger's cat - so which one am I ???

We seem to be having a problem with wideband accuracy, when taken to southam the wideband readings were literally miles off what their own afr readings were. The controller is an innovate LC-2 and I've tried recalibrating the sensor to no avail, it's probably been installed for around 6-8months. The lead replacement additive for the 12g295 is added to the tank, we've used various types, millers, carlube, redline and have used most recently redex lead replacement stuff picked up at shell. Is there a way of fixing the miles off wideband readings short of a new sensor? And peoples opinions of the least damaging additive?

What is southam and what wideband or AFR monitoring setup do they use ?

Innovate do have a very high rate of sensor failures, but generally when they work they should be quite reasonable.
When they arent working, sensor errors of various kinds are very common.

If in doubt just replace the sensor though

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Sotham mini and metro centre, i couldn't tell you what machine they use for using the rolling road there

Schrödinger's cat - so which one am I ???

I never did understand why people keep calibrating a used sensor. It makes no sense. The sensor is dirty.

The wideband gauge i use, uses the cal resistor, job done (As do all oem systems). The Ecu i use uses a calibration value that directly represents the cal resitor, and it is stressed that sensor calibration should really only be done with a new sensor.

We've had this debate before and it always ends up back at calibration gasses.

OK, this is going slightly O/T (don't these threads always) but I couldn't agree more.

Bosch put the laser etched resistor in at the factory to exactly match the sensors calibration against a factory gas around slightly rich.

And then virtually everyone re-calibrates on plain air....

How many of your engines actually run on plain air without any fuel ???

It's just calibrating the sensor way off scale and completely over-riding what Bosch did for you.

Yet most of the aftermarket vendors suggest you do this.

Avoid any aftermarket vendor that encourages you to calibrate in free air.

It usually means they went cheap on the controller hardware and/or software/ or even the cable so don't even know the value of the calibration resistor.

Schrödinger's cat - so which one am I ???

So really there's not a lot of point of having one on a carbed mini that uses leaded substitute?

My build thread..

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=542985

Schrödinger's cat - so which one am I ???

I'll have a look.
I like the castrol one though as it was set up with it and it has octane booster in it :)

My build thread..

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=542985

Valvemaster is phosphor based, so upon that it's not much good for a wideband, millers seemed okay, can't find any info on redex

I doubt your readings are way out yet due to the castrol additive, it's a bit too soon.

All I linked to is Bosch saying phosphor (or silicone) does long term damage.

There are many other reasons for widebands not reading right.

Or, more particularly, not reading the same as someone elses.

Pressure and temperature of where they are located will be the most obvious reason but the "free air calibaration" probably the most mis-understood as I doubt anyone actually does it in "free air" and even if they do it is so far off the controllers scale (does any controller claim to read >23 ???) that it becomes worthless.

Bosch didn't put that laser etched resistor in the plug for no reason.

It's just that a lot of the aftermarket companies don't actually use it, only the OEM car makers know what it's for and a very few of the after market wideband controllers.

Rant over.

Schrödinger's cat - so which one am I ???

If I understand correctly, a contaminated sensor just gets sluggish to respond. Any drift in the AFR would mean something else?

If you need to use lead replacement additives and don't use your sensor for closed loop control, I think it would make sense to remove the sensor except for tuning, logging and diagnostics. IIRC, you don't need to put lead replacement in every tank, so could use it sparingly while the sensor is in place.

If you're worried about detonation, a knock sensor and warning light /buzzer may be more useful. After all, you could have perfect AFR, but still induce knock with hot inlet temps, bad fuel, actuator pipe leak, bad timing, etc etc.

I have a couple of innovate wideband sensors, and i think they are bosch. As Rod S says the positioning of the AFR plug makes a difference particularly at idle. ( more of that plain air getting around the place). Also check the readings trend on long periods of WOT.. as dynos sometimes don't do prolonged pulls.... i found a leaning off after about 20seconds... that i wouldn't have guessed at nor necessarily found otherwise