Measuring AFR?

[len_beach]

Following on from another thread. Is there any quick and easy way of measuring AFR?
I had my ecu mapped a while ago which did make a difference but I am now getting a sooty exhaust. Now I wouldn't think a sooty exhaust definately meant I was running rich but I would like to know wether I can match my inlet without a second remap as I know the matching can cause a standard car to run lean.
What should the AFR be on a 172, not that I know what the figures mean.

 

[MarkM]

Reading should be 12.9 for power and 14.7 for economy. The 14.7 reading will be in closed loop control under light load, ie low revs and throttle position. 12.9 will be out of closed loop under high load. The lower the number the richer the mixture.

You need a wideband lambda probe in the exhaust, standard is narrowband, and something to convert the feedback from the probe into an output range a gauge can read. Unfortunately all of this is quite expensive approx £320 for an Innovate setup. BenR did mention someone he knew was designing a system to read AFR may be worth a PM.

 

[16v_jon]

who did your re-map? was it Live map or re-flash? R-sport/grp N programs give you a sooty exhaust as does a de-cat, i have a dynojet wide band commander AFR meter with decat and r-sport it runs within the correct range and mt exhaust is filthy from deposits!

 

[Jones]

Take it to an mot test centre and ask them to bung it on the gas analiser.

You can generally ell when a car is running rich, on my old car i had it running twin 40's and a psychopathic duration cam shaft and it used to coat the back of my car in soot!!!

 

[len_beach]

It was a Pmurray reflash. I also have a Janspeed sports cat which would also account for the sootiness. Normally I would never even associate sootiness with running rich, it was just a thought I had leading from another thread.
I might just take the plunge with a matched manifold. What do you guys reckon?

 

[BenR]

A friend of mine has just finished a plug and play setup which is very neat and tidy and will provide both AFR and EGT information via a gauge on your dash.

Pricing is under £190 for the complete unit, including Wideband sensor, but NOT including the EGT thermocoupling, that is optional extra.

 

[len_beach]

Would the MOT emmissions test be roughly accurate as my MOT is due next month so I could tie it in with that. The simple reason being that I only want to test it once to see wether I have the scope in my map/fuelling to do so and £190/320 is a bit much for just a test.
Many thanks for the input so far though guys.

 

[BenR]

not really as your never testing the AFR under load, which is where i counts.

IN closed loop config, your engine will automcatically be adjusting the AFR to that of 14.7

 

[len_beach]

IN closed loop config, your engine will automcatically be adjusting the AFR to that of 14.7

Even with mods? So where does the need for the remap come in Ben? Please excuse my ignorance.
I am really tempted by one of your manifolds but I really don't want to pay for another remap.

 

[BenR]

All modern cars are set to run a stoichiometric AFR value of 14.7:1, where a complete burn of fuel and O2 occurs, at lower rpms and low load positions. Well, they did, modern cars are now running slightly leaner circa 15.5 for better economy and emissions, and they are running 'lean' upto quite high rpm points for efficient motorway cruising, where older cars used to exit closed loop fueling at about 4000-4500rpm.

Once your at high throttle angles, even at low rpm, the cars run semi open loop off a base map with info from sensors, but no direct feed of AFR. Because of this, the ECU cannot correct for lean conditions at high loads, and you need to remap those areas.

 

[len_beach]

SO if you were to see a copy of my map or some of its values, would you be able to tell wether or not there is enough 'give' to account for the manifold mod?

 

[BenR]

nope, adusting numbers without checking the result just wont work.

It wont be a linear increase requirement, mapping is alwaus all over the shop.