Anyone know what the approx AFR value for a given O2 voltage should be. Standard sensor on a 00MY UK car.

So 10:1 =
11:1 =
12:1 = etc etc.

Trying to set-up the Apexi turbo timer / AFR meter.....

Cheers!

 

It's not so straight forward with the stock narrow band sensor I'm afraid. They are not designed to output a specific voltage at a specific AFR, more to change voltage around Stoich (14.7:1).

It can be used to guesstimate AFR's using a lambdalink, and once it's been on the car a while you'll know what's normal and what's not. Even assuming a healthy sensor (which it may not be!), then you also need to factor in that it under-reads once it gets very hot (ie; on a power run, by the time you're into top gear it'll be reading leaner than in 2nd).

For setting/checking AFR's you're better off getting someone with a wideband to confirm everything.

Richard

 

Dowser,

Aware of all the above, however the sensor will have a set voltage when it goes rich and lean either side of stoich.....know what these voltages are? IT appears to be around 0.2v and 0.65v.......

For example WOT is typically ( and reasonably consistently) 0.85v, is this (approx) 10:1, 11:1, 12:1 etc.........

 

If wot is 0.85 and the sensor is ok you are way too lean.

bob

 

Bob,

So 0.85 would be equivalent of ?????????

Cheers!

 

around 13:1/14:1


Skassa

 

I`ve had a couple of comments about AFR in my application.....

Have run AFR of around 12.2:1 on steady boost, with around 10:1 during spool (on WB sensor) with unichip, as set-up by PS. Been running like this for over 2 years now and 50K miles. VF30, headers, FMIC, FSE, etc etc, running around 320-330PS(on PS rollers), 290lbft, at 1.3bar 1.15bar at 7000rpm. As far as I know running std timing(!!).

Have run like this at 40Deg ambient at 2000m altitude. Have cruised at 120-130MPH for long periods (trips to Europe!) , had the filter changed without filling it, without turning the engine over before firing, loads of track days inc the ring, gets driven very hard (alot!) and the car has never missed a beat!

Given some of the stories you get on here (been hanging around for 5-6years) you`d think you only have to look at the car funny for it to throw a piston........

Must be lucky......!!!!!!

Having checked O2 voltage on WOT, it is actually more like 0.8 - 0.81v, so I guess this ties in with 12.2ish AFR on WB?

The only thing I have never been able to do is run more than 1.3bar. Anything more and I get a `boost-cut` effect (although using FCD). Thought about changing coil for high output one, but hey the car is b****dy fast as is!!!!

Mind you I suppose the g`box failure rate has been the only downside (on my 3rd one!) Car now has 68K on it and still feels tight (famous last words!!!!!!).