air fuel ratio on the dyno
Do you think it's worth welding a lamda boss onto my exhaust pipe so I can have a air/ fuel ratio meter and lamda sensor on my bike to help keep an eye on what the engine is doing ?
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joeythescooterboy
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So on a Polini 208 with PM and 30mm delly how many sausages should I be pushing out and and are we talking skinny chipolatas or thick juicy ones?
Nemo saltat sorbius, nisi infanus est.
Mine runs lovely with 18 herby snags and a chipolata with 12 bacon rashers on the side 
sarsijes.......MMMMMMM. i"m away for me tea. anybody got any broon sarce?
Been away, man flu etc!Speed Demon wrote:Last post because talking to brick walls is a waste of time.MattsDad wrote:
Find it bemusing that these long winded posts as to whether the AFR reading on your dynos is an accurate reflection of what goes bang in the barrels you place on them!?
Clogging up the sensor, thats not even the same subject
If you went to a dyno that only measured in units of 'sausages' and it said your 20hp Vespa read 100 'sausages', but you made some adjustments and it came away reading 110 'sausages' is that improvement invalid because the dyno is inaccurate? The units or 'perceived accuracy' are irrelevant because the readings are just numbers - the comparison is the point. If you went back and got 120 sausages out if it then that is a result. As long as the dyno is consistent then the units don't matter.
Clogging up the sensor is relevant - the point I was making is that the readings are consistent across several sensors and many different 2-strokes. The readings themselves don't have to be 'perceived accurate' (I'm not saying that they aren't before you jump in) as long as they are consistent and you know how the readings relate to jetting on the road. If the meter was scaled in 'bacon' and 20 'bacons' was rich and 10 'bacons' was lean, and you knew from experience on the road by plug chops that the optimum setting was 15 bacons then as long as it is consistent that's all you need to know.
Thank you so very much for that, its all so very clear now! You need to read the earlier posts and perhaps threads on this forum which openly concede that not all dynos are the same and to maintain a degree of consistency in what you're doing, you should stick with the same dyno butcher for your particular bike.
The inconsistencies were shown in the 'Scootering' article a couple of years, a least you should remember that!
Pointless playing tennis with this because my intention was an honest debate about whether there is an innacuracy in the AFR graphs given out (2 stoke). Regardless of the margins operators may work within to compensate for this, knowingly or otherwise, this is a valid point for discussion.
I'm thick skinned and you've already named my race bike for next season and for the purposes of discussion - are dyno AFR readings 100% accurate for a 2 stroke? Whenever I've been dyno I've been given a printout, so I'd very much like you to answer that honestly and within your understanding!
COCKSPEED TUNING
Actually Mattsdad if you read the post again I think you'll find that Sticky did indeed just say that using the same dyno is a must for comparison.
"I'm thick skinned and you've already named my race bike for next season and for the purposes of discussion - are dyno AFR readings 100% accurate for a 2 stroke? Whenever I've been dyno I've been given a printout, so I'd very much like you to answer that honestly and within your understanding!"
I think if you go back to the start of the thread and read it that isn't at all what you were asking.
Your asking it now because you didn't like the answers to your original questions.
I have repeatedly told you that the AFR reading is not considered to be the be all and end all of setting up the bike. Whether that is because the sensor is inaccurate and not compatable for 2 strokes is for people brainier than me to decide and inncedently a quick search on the net finds many that think the readings relevent.
What I can and have said is that they are consistant, they can be manipulated in a predicted way by changes to the jetting and they can be interpreted and related to how the bike will behave on the road. I
Just yesterday I changed a main jet as a result of how the bike ran on the road rather than simply blind trusting the AFR. It was only one jet size though and very much based on what I heards from the engine during a varied road test.
You say this is a debate. When people debate one side argues from one side and provides details and facts to illustrate it then the other side returns with a counter argument.
What we have here is me and Sticky explaining how the AFR is used as a set up tool. If you want I can show you some different fueling graphs as hard data on real machines that run on and are still running on real roads.
What you are saying is that AFRs are inaccurate for 2 strokes. Ok fair enough but lets have some real world evidence of this. Back it up with something tangible. Even in your opening statements you said....
"I only ask this because you hear of such and such saying I went to this dyno and it seized up on the way home etc etc."
Such and such is who? etc etc?-what does that mean?
Perhaps if you was to quantify your statements a bit better and actually give some actual facts instead of hearsay and supposition it may actually feel like a debate.
So do AFRs acurately measure oxygen in 2 stroke exhaust gas?
My honest opinion is that there are times in the rev range it is probably accurate and there are times when it is not so accurate. So my answer is that no they aren't 100% accurate. If that makes you happy to hear that great but it means nothing.
They are capable of giving consistant and repeatable results. They are sensitive enough to show spots in the rev range as being rich which compares exactly to the cough you hear from the bike as you wind the throttle on. They show jetting changes in a way thats predictable and quantifiable.So please tell me how that isn't relevent?
They are a fantastic comparison tool which if interpreted correctly and backed up with road testing are invaluable. They also save huge amounts of time and keep you warm and dry so I'll keep using mine if thats ok.
What gets me with you is that you have bought a gas tester and because of some blurb put on to cover the manufacturers you haven't even been curious enough to try it? Again this would feel much more like a debate if you actually tried stuff instead of dismissing someone elses way of doing things because of what you've read.
So there you are my side of the debate-lets hear it from you with some actual personal experience. Why are AFR meters innaccurate and not useful for 2 stroke dyno testing and what evidence do you have to back this up?
"I'm thick skinned and you've already named my race bike for next season and for the purposes of discussion - are dyno AFR readings 100% accurate for a 2 stroke? Whenever I've been dyno I've been given a printout, so I'd very much like you to answer that honestly and within your understanding!"
I think if you go back to the start of the thread and read it that isn't at all what you were asking.
Your asking it now because you didn't like the answers to your original questions.
I have repeatedly told you that the AFR reading is not considered to be the be all and end all of setting up the bike. Whether that is because the sensor is inaccurate and not compatable for 2 strokes is for people brainier than me to decide and inncedently a quick search on the net finds many that think the readings relevent.
What I can and have said is that they are consistant, they can be manipulated in a predicted way by changes to the jetting and they can be interpreted and related to how the bike will behave on the road. I
Just yesterday I changed a main jet as a result of how the bike ran on the road rather than simply blind trusting the AFR. It was only one jet size though and very much based on what I heards from the engine during a varied road test.
You say this is a debate. When people debate one side argues from one side and provides details and facts to illustrate it then the other side returns with a counter argument.
What we have here is me and Sticky explaining how the AFR is used as a set up tool. If you want I can show you some different fueling graphs as hard data on real machines that run on and are still running on real roads.
What you are saying is that AFRs are inaccurate for 2 strokes. Ok fair enough but lets have some real world evidence of this. Back it up with something tangible. Even in your opening statements you said....
"I only ask this because you hear of such and such saying I went to this dyno and it seized up on the way home etc etc."
Such and such is who? etc etc?-what does that mean?
Perhaps if you was to quantify your statements a bit better and actually give some actual facts instead of hearsay and supposition it may actually feel like a debate.
So do AFRs acurately measure oxygen in 2 stroke exhaust gas?
My honest opinion is that there are times in the rev range it is probably accurate and there are times when it is not so accurate. So my answer is that no they aren't 100% accurate. If that makes you happy to hear that great but it means nothing.
They are capable of giving consistant and repeatable results. They are sensitive enough to show spots in the rev range as being rich which compares exactly to the cough you hear from the bike as you wind the throttle on. They show jetting changes in a way thats predictable and quantifiable.So please tell me how that isn't relevent?
They are a fantastic comparison tool which if interpreted correctly and backed up with road testing are invaluable. They also save huge amounts of time and keep you warm and dry so I'll keep using mine if thats ok.
What gets me with you is that you have bought a gas tester and because of some blurb put on to cover the manufacturers you haven't even been curious enough to try it? Again this would feel much more like a debate if you actually tried stuff instead of dismissing someone elses way of doing things because of what you've read.
So there you are my side of the debate-lets hear it from you with some actual personal experience. Why are AFR meters innaccurate and not useful for 2 stroke dyno testing and what evidence do you have to back this up?
quote Mattsdad...
"true AFR reading becomes distorted. the nature of 2 strokes is inherently one that is not compatible with exhaust gas sensors"
Please could you explain how and why.
Thanks
"true AFR reading becomes distorted. the nature of 2 strokes is inherently one that is not compatible with exhaust gas sensors"
Please could you explain how and why.
Thanks