air fuel ratio on the dyno

[MattsDad]

Yes goodwill etc because I'm not wanting to fall out with anybody.

The MJP demo version you provided the link for does indeed show a box to tick for a 2 stroke engine. It is however in the bmep section of the paramaters and of course the 2 stroke figure is half the psi of a 4 stroke so this tick box is to differentiate between that and has nothing to do with the lambda reading.

[Diablo]

Ok I can see your point here MattsDad and theres quite a lot I can agree with you on. But this is my take on it.
If you go back to my first answer to the original question in the thread I did advise to keep as much of the fuel graph running at 12.
I did also say it isn't always possible and I can accept that unburnt gasses are detected by the sensor and show as leaness on the graph.

The sensors job is to detect oxygen which it does accurately whether its unburnt or not. The operators job is to recognise what is happening and differentiate it from actual lean jetting.

One thing that certainly has moved on in 15 years is software. This now allows AFR readings to be measured and plotted in real time. This allows you to compare the fuel graph against the power curve and know that 6000rpm on the fuel graph corresponds with 6000rpm on the power curve.
If you have a sensor that doesn't measure in real time I also accept that it may give a false reading which could be interpreted as leaness.This is possibly why your Sensor is not recommended for 2 strokes.

If you do have a sensor that measures in real time then the rest of the graph,subsequent runs on part throttle openings and comparing the fuel graph to the power curve help you to interpret what has been measured. Road testing, listening to the engine on the dyno and under load when riding also back this up.

[MattsDad]

Thanks Al, thats the post that has made this worthwhile for me and relieved a little stress over this.

My take has always been that you cannot argue with the science of this in terms of the accuracy, the scavenging nature won't allow it. The Lamda sensor I bought was for a car in the belief AF is AF and is readily available for a few hundred quid and I think this is the difference between that and a dyno and also the Mycron technology.

The reference I made early on about my friend who's been road testing 2 strokes for almost 30 years, you just can't buy that. Overlaying of graphs and information is a massive step forward in terms of information and is open to the interpretation of of the experienced operator which I have also mentioned.

The original poster mentioned about taking this to a 4 stroke dyno person, so in an way this is a bit of an advert for you and Dan. Problem is though a financial one as I still believe there be an innacuracy, that in an ideal world you would run a bike on a dyno on this basis and then do half a days road testing to balance the two; expensive so people usually opt for one or the other.

Dan mentioned earlier that anyone going to a 4 stroke person is a 'dick'; thats the real danger over this and I certainly fell into that category previously before looking at it more closley and also a 2 stroke operator that doesn't have an appreciation of the margin within which they work.

I think its been a good read and beneficial but can I throw this one in I think theres some merit and proven software for balancing lambda with EGT as per Mycron. Maybe this could be an add on to the dyno service and fairly inexpensive, no need to boss etc?

I'm pm'ing you a link over this.

[drunkmunkey6969]

It is however in the bmep section of the paramaters....

Fair enough, i have to confess....i've never used the 2200 series software and i was looking for the same tab that the 1100 series has, which is a values page which is a programable for AF outputs, delay rates, and response speeds and the like etc....but i dont see it on the 2200 software (which i presumed would be more advanced). Perhaps this is because the 2200 is more likely to be used on large 4 stroke bikes and the 1100 on small 2 stroke scooters etc which is why i have the seperate tab of programable values....who knows?

Just seen i have a PM from you, will check the link.

Dan

[drunkmunkey6969]

Dan mentioned earlier that anyone going to a 4 stroke person is a 'dick'.

LOL....just to clarify that quote, what i actually said was "....anyone working to the 4 stroke figures on a 2 stroke scooter is just a dick...."

I dont have anything against 4 stroke operators, just the ones setting 2 stroke scooters to 4 stroke AF values.......just wanted to clarify that! lol

[dirtyhandslopez]

Have read and re-read this thread and I am no techy expert by any means, but wouldn't the AF reading change if the amount of two stroke used differed on different dyno sessions, even on the same dyno, same motor?

[MattsDad]

That's a really good point; 4% Lammy mix would give a 0.60 ratio difference to the lean side.