28 replies to this topic

[klivins]

Yes it is

[ACDodd]

If you just revved the engine without driving the car post back the readings at 2000, 3000, 4000, and 5000rpm.

Is is fluctuating during this test? It should be rock steady.

What’s the idle reading? Does it fluctuate?

Ac

Edited by ACDodd, 16 April 2021 - 08:44 PM.

[klivins]

AC, I didn't want to rev it much, as it is fresh rebuild. I will check all of the suggestions next week.

[klivins]

coming back with answers

At idle the AFR are steady-ish ar about 13.5

At 'cruise' the AFR readings are not steady. See for yourselves https://youtu.be/N6ZPJYGwpVU from 0:40 

at about 2000 rpm - 14 - 15.8 afr

3000:  13.5 - 15

4000:   13 - 14

and from that on more steady-ish

5000:   12.5

6000:   12.5

 

Any pointers to what could be the cause?

Edited by klivins, 20 April 2021 - 08:35 AM.

[klivins]

after closer look there was a small leak in the exaust just before the sensor, where parts of the exaust are connected with the clamp. I rectified this, and got more stable readings, but I cant say they are 'rock solid'. The readings now are a bit richer overall.

Run out of time for today, will continue to tweak the needle on Friday. 

[ACDodd]

Have you tried another sensor?

Sensors can go down especially if they have been running very rich.

If it’s still fluctuating with a new sensor and no air leaks it can only be the carb is unable to
Control the fueling.

Ac

[klivins]

Thanks. It is a new sensor and only been run for 100 kms. Can it go bad in so short time? I will continue on Friday with this.

[ACDodd]

I have had them go in less than 20mins!


Your fueling is too rich at part throttle up to 4000rpm 14:1 no richer, 5000rpm 13.5:1, you only need 12.5:1 when you go for full power.

Road engines only need enough fuel to avoid misfire on part throttle, any more simply adds ring wear.

Ac

Edited by ACDodd, 20 April 2021 - 06:07 PM.

[PoolGuy]

Does your afr gauge have a ‘sensor health’ readout?

[Spider]

Thanks. It is a new sensor and only been run for 100 kms. Can it go bad in so short time? I will continue on Friday with this.

 

Yes, they can become choked in a less than a minute, but many have heaters in them to help clear this - to a point. They are designed for vehicles that have electronic injection that rarely stray too far off centre line.

[Maccmike8]

Where is the sensor fitted?

[klivins]

Thanks all for your input. 

I dont think the gauge has a 'health readout' as such. All I can is switch between AFR and one another mode, I think, oxigen level?. 

The sensor itself is just after all the manifold parts meet in the exaust, just before the gear selection mechanism. It is at a slight angle upwards, as per instructions. 

[Maccmike8]

I dug the instructions out of my Innovate kit (that I havent fitted yet) and that says to fit it 24" after the collector, or turbo if fitted.

On a Mini I appreciate thats quite far back but may be worth welding in another bung and seeing if it effects your readings?

 

 

Thanks all for your input. 

I dont think the gauge has a 'health readout' as such. All I can is switch between AFR and one another mode, I think, oxigen level?. 

The sensor itself is just after all the manifold parts meet in the exaust, just before the gear selection mechanism. It is at a slight angle upwards, as per instructions. 

[klivins]

An update. I do believe erratic AFR readings were because of the leak in exaust joint - in top of it, where I missed it in the first place. Even after my first attempt to sort it oit there was a leak. Now I got the radings stable, (but I wouldnt call them rock solid) got the car thru its MOT, and will attempt to fine-tune the needle next. As I only have couple of evenings per week for this, it might take time:)