wideband AFR advice.
Turbo Mini Forums

14.7 is stochiometrich, the chemicaly ideal fuel to air ratio, you want it around this at idle.

15.75 ish is supsedly best for fuel economy so you want it in the 15's at cruise.

under throttle boost it should be 12-12.5 for max power, if it starts going higher you are going to run the risk of meting things.

well, ive been learning about these over the last year or so (mainly for na purposes though), and beginning to get my head around whats good and whats bad, in short:

At idle, it doesnt really matter what AFR your running, most people reccommend to just get the engine happy and leave it at that (although for MOT's etc you might find you have to tweak it a little :) ) usually, ive found that will probably be anywhere between 12:1 and 17:1, so quite a scope!

Heres a chart that gives rough equivalents so if you know what CO readings you need at MOT, you can use your wideband to tweak the AFR and get you in the right region:



(btw you can set the AEM to read off the AFRs or the Lambda, so set it to whatever you understand best)

12.5:1 (a bit rich) is regarded as the best afr for full power, but obviously all engines are a bit different

14.7:1 (stoic) is the most efficient afr, as the fuel should be entirely burnt, and is referred to as Lambda 1, and people aim for this for this under cruise conditions, but my stg 1 1275 mini cruises at 70mph at 17:1 with no problems at all, and i imagine im saving a fair bit of gas too, so again theres scope here too

now with turbo'd engines someone else will have to comment, (i have next to no experience here), but the general jist is the same, but under boost its imperative not to let the engine run too lean as (correct me if im wrong) lean engines run hotter, leading to all sorts of complications like melted pistons, det etc, which can cause broken ringlands and holes in pistons etc

Im sure theres much much more to it than that, but as a quick start do dar, hopefully it will get you on track

have fun!

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

ha, i think about 4 people answered at once lol

better than none i guess haha

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

im going to fly in the face of fashion here and say that id run 12.5 to 13.5 on idle ,12 to 12.5 on boost up to 10 psi ,then 11.5 to 12 above 10 psi ,and as lean as itll run on cruise ,around 16 to 17 :1.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Why so rich on idle Robert?

I knw Matty used to run all fueling around 12.5:1 no matter what the operating condition

ATM I have a fuelling problem -as soon as I accelerate from lowish revs the AFR goes off the rich end of the scale at 10 and the car is v.slow to pick up, quite naturally, As the revs come up to ,say 2500 or so, the mixture leans out to 12 -12.5 and stays there until the boost comes on at 3000rpm+ and then stays at around 11.5 t0 12.0,with boost up to a ridiculous 18psi(to be attended to)

Its just annoying that the reason for the slow pick up seems to be down to just over richness.
Fuel pressure checked and OK.Various oils tried in the carb to no good effect so it looks like a weaker needle and start all over again to get it right.

May try dropping the needle in the piston a fraction to see if it will have any beneficial effect.

Thanks for all the info boys..give me a nice base to go by ...looks like it might be worth me buying a new needle in preperation for what i knows going to be fueling all over the place :) but we'll cross that bridge when we come to it.

sorry to hear about your running problems, hopefully itll be an easy fix, and just needs alittle tweaking

Minivanless, but reluctantly happy living with the decision. There'll be another one day.
http://www.youtube.com/profile?user=minimadmotorman#p/u

Many thanks Richard I am looking forward to meeting you and comparing noted further - I will try the lean off pipe idea soon.

I am meeting with Robert on Sunday to try his mini -wish me luck !

Maybe he will have some more suggestions.

The MJ has certainly cleaned up the fuelling a good deal - stronger spark/more advance ?

glad the threads proving uselfull to more than just myself at this rate we'll all have working minis and wont have anything to talk about haha ok maybe not :)
the wideband turned up yesterday and is a very nice bit of kit, i tried to keep the jumping around like a school kid down to a minimum..hoping to get he gauge fitted and wired in today but might have to wait until during the week until i can get the sensor mounted as i dont have a welder/cant weld ..yet! so need ot take it somewhere to get the bung fitted

Drop it over to me Ben, I'll weld it for you.

Richard.

Minivanless, but reluctantly happy living with the decision. There'll be another one day.
http://www.youtube.com/profile?user=minimadmotorman#p/u

In the mean time if you have a gas soldering iron or a blowtorch you can wave that near the sensor to get a reading

nice one rich ill drop you a txt about that, i got the dash cut, gauge fitted etc so itll be wired in tomorrow morning