air fuel ratio on the dyno

[Speed Demon]

Well Sticky, ....If you run an inertia dyno as its supposed to be used from a standing start it has load.. of course... but how to you hold it in midrange and replicate load it has in the real world without a load device?
All I am saying is that this is the way to go for tuning in the scooter world.. you know this is true already.
I've seen how little load is on a motor on an inertia dyno once the drum is spinning and how little effect it has when mapping ignitions.
I was only trying to be constructive and give out some of my findings and things I've learnt over the years.

I think it's just a matter of using different tools to get as close as you can with no particular system being perfect. A braked dyno does give you more options to check static outputs, which I'm sure you'll learn more about as Charlie gets to learn his new Factory Pro.

However a braked dyno in the hands of an idiot is a dangerous tool. I've heard some very bad things about the use of brake dynos grenading two-strokes, but that's possibly down to a lack of cooling in the facility and maybe a lack of understanding on the part of the operators.

I'd rather trust a clever operator like Charlie with an inertia dyno than a plonker with a braked dyno. As ever, getting results from a dyno is the easy bit. Interpreting them is the hard bit, and that's what you pay the money for.

[OzOAP]

However a braked dyno in the hands of an idiot is a dangerous tool.

[drunkmunkey6969]

PMSL.....

[Speed Demon]

An idiot with a large photo library is no less dangerous

[tony]

I did my mapping tests back in 98 . It was then I found the points I tried to make above.
I'll ask charley to see if he is happy to tell me a bit about step testing to post up.

[MattsDad]

I did wonder when the responses would come in and quite typically from those who have been watching and own or have part shares in dynos! PMSL.

I'd like to make myself fairly clear if I can; dynos have a purpose and that is why I use them and others market them. The 2nd before last dyno I went to, who's judgement I trust implicitly, didn't even stick the AFR up its arse! He sat on and said nope, that's not right, then we spent an hour tweaking. He was happy because he wasn't getting cold on a test run (which would took u half a day to achieve what we wanted) and so was I because i was having my input.

This debate has been covered a million times before and I really don't like the charlatan comment!!! People who invest in a dyno do so to complement their business and in lets say some cases, have an understanding of scooters and set their customers up best to suit rally requirements.


Why is there a defensive air in the above posts, I asked for opinion; I know you have businesses to defend but my understanding if I'm correct is that AFR FOR A 2 STROKE ON A DYNO IS INNACURATE and the skill in using one lies with the operator!?

Non dyno owners comments also welcome.

Edit and ps. Just read some of the above back and 'read' was in there again; do you really think anyone / racer goes to dyno and says 'thats all right then'; few less jobs in them F1 trucks if that were the case. Just to throw this one in as well as I've had different experiences - how about the fans dyno operators use to cool whilst testing, it goes on and on!

[Speed Demon]

Why is there a defensive air in the above posts, I asked for opinion; I know you have businesses to defend but my understanding if I'm correct is that AFR FOR A 2 STROKE ON A DYNO IS INNACURATE and the skill in using one lies with the operator!?

Non dyno owners comments also welcome.

I don't have a dyno business, so not defending on that basis. Defending on the basis that I don't think you are right.

AFR INNACURATE ON 2-STROKES? - When Dynostar sold me the dyno they said that you should expect oil to eventually clog the Bosch sensors and I'd have to change them. As a result I bought lots of spare sensors when they were going cheap. So far though we haven't needed to change a single one, though we have occasionally swapped an old one out to see if it still reads the same as a new-un. Guess what - still the same readings from sensor to sensor over 2-years later. So how does that make them innacurate?

As for asking people who don't have dynos what their views on AFR sensors are - is there a point to that? It's like asking me what it's like to give birth. Like you - I don't have a f@@king clue because it not something I've ever had to deal with. Perhaps I could look up an answer on the internet and just portray that answer as definitive fact (especially if I wrote that bit in CAPITALS). Any women who were reading and might have some actual experience would possibly have different opinion. They could therefore be excused for thinking I was another keyboard warrior...

[Diablo]

Its funny because for some time after we had our dyno we didn't have the available software to run the AFR meter.
So they were set up as you've just described by ear and interpreting the power curves and by road testing.
When we got the AFR meter running it was nice to put some of our own bikes on that we had jetted this way and check them against the AFR readings. By and large we were happy with the work we had done despite the AFR meter being so hideously innaccurate. It was ok though because it fell pretty much in line with our previously inaccurate work without it.
What the meter allowed us to do was fine tune and experiment.
It has given us a greater understanding(and equal amounts of confoundment) of what happens when you add bellmouths,different types of filters, lengthening of inlet tracts etc etc.
It showed us how different exhuast port heights effect fueling in fact how just about anything can effect fueling.
Its all innaccurate of course but hey we still like to play.

The thing is its all very well coming on and telling us how stuff isn't relevent and the work somebody makes their living from is innaccurate but thats all your really saying. Anecdotes of people who are always someone other than yourself doing it better by ear are basically telling us nothing. I can set bikes up by ear as well and still do. But its a plain fact that I can see the difference a larger pilot jet makes across the whole fuelling curve using the AFR. I can produce graphs that show it. I find it incredibly useful and that part of the tool saves me time and money. When I test the adjustment in the real world it works so how please tell me is it innaccurate????

[MattsDad]

When you add 2 + 2 and come up with 5 you are inncurate. If you then add another 2 and come up with 7, you've convinced yourself correct because your working on an earlier flawed basis. Thats my point and hence the earlier statement about setting up rich to compensate.

Find it bemusing that these long winded posts won't answer the very simple question with a yes or a no as to whether the AFR reading on your dynos is an accurate reflection of what goes bang in the barrels you place on them!?

I'm not really having a problem with what you're saying Diablo, I get the picture of the way you do things which I think is fine. Clogging up the sensor, thats not even the same subject and analogies of childbirth for fecks sake. Forum users that post links up and quote / plagiarise are nobs which is why I don't; weekend warrior, do you really think so?

Go on, yes or no?

[Speed Demon]

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

Last post because talking to brick walls is a waste of time.

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.