air fuel ratio on the dyno

[MattsDad]

Drivel and its like that is it!

Thats too selective of what I have posted, concessions have been given to experienced dyno operators and to you personally from your explanation of how you set up. That is just a pad out of what we agree on on anyway; as I have stated I still use dynos!

I could conclude but i'll reserve judgement, that you're just an aggrieved / defensive dyno owner who doesn't understand his own kit and can't be bothered to find out.

Although my posts are littered with caution about 'my understanding', not wanting to 'lead' etc, my experiences are this:

1. Every dyno I have been to setting up with a sensor has had to be subsequently changed.
2. Some dyno users do not use the sensor.
3. Not one or two but a number of persons known to me have seized on the way back from dynos recently aquired by an operator or an operator more aquainted with 4 strokes.
4. The NGK engineer I spoke to 2 years ago, got their number off google as well, told me it wouldn't be accurate on a 2 stroke.
5. The karting teams I have spoken to say similar.
6. And if you insist I quote Prof Blair, I can't be bothered; Dan can confirm that for you in the book my mate gave Sean - page 38.

So, if this has made people think before they walk in somewhere and shout I want 14.5:1, thats a good thing and if its enlightened you as to why you use 12:1, maybe you should put a caveat on your graphs that its not really the AFR, its the 'Diablo adjusted figure', 25 years experience don't you know.

Of course I may still be completely wrong and I'll hold my hands up if I am.

[MattsDad]

PM on way to you JIMS.

[drunkmunkey6969]

And if you insist I quote Prof Blair, I can't be bothered; Dan can confirm that for you in the book my mate gave Sean - page 38.

So, if this has made people think before they walk in somewhere and shout I want 14.5:1, thats a good thing and if its enlightened you as to why you use 12:1, maybe you should put a caveat on your graphs that its not really the AFR, its the 'Diablo adjusted figure', 25 years experience don't you know.

Of course I may still be completely wrong and I'll hold my hands up if I am.

IMHO......you are quoting Blair out of context. He does not say that they DONT work, he merely surmises that (at that point - 15 years ago) that 'Much of the instrumentation avalablie had been developed with 4 strokes in mind'. He goes on to say that instruments designed for 4 stroke analysis often cant record subtle changes. And he is talking about this topic in context of emission control for legislative purposes........not keeping a 40 year old Vespa from seizing.

I dont know what the state of play was 15 years ago in terms of AF meters, but we use Bosch wide band, 5-wire lamba sensors, coupled up to expensive electronic equipment, that feeds into computer software to display the information....and this equipment and software was designed specifically by a top guy in motorcyle race tuning, with 2 strokes and scooters in mind. Is that what Blair had in front of him 15 years ago? Is that what Blair was refering to? No....i dont think so.

As far as someone walking in anywhere and asking for 14:1.........ive never heard or seen that happen, and 14:1 is the definative stoich for 4 strokes....so why would they? 12.7:1 is the definative stoich for 2 strokes, but with the anomlies that occur with air/fan cooled vespas, we often pitch on the side of safety and move toward 12:1 for safety. There is no mystery or fudge factor here, its actual hard fact, combined with common sense. So IT IS the AFR that you see......not an adjusted figure??

And this is what happens....i run the scooter up on the dyno, i see the AF chart on screen....it shows me an 'AF curve'. I can repeat that run 10 times over, and it will show me the same curve......i alter the jetting 1 clip....the curve changes. I know from experience how the curve will change, and it does. I can now repeat the dyno run 10 times....and it will give the same curve. These are mappable and repeatable changes, that can be read, made, and seen on screen, consistently over and over.

Imagine a blind person sitting in an unfamiliar room, they have no knowledge of how to get out of that room without falling over all the stuff in their way. However if a person explains to them what the room looks like and gives verbal directions, then the blind person is guided out of the room. The blind man cant see, and the verbal explination doesnt replace a good set of eyes........but it paints a picture to help with the task. The AF meter/electronics/software gives you a mappable and repeatable picture to work with, and as you change the engine/jetting then the picture changes to reflect the work you've done.....or need to do. Its that simple.

I dont think Blairs superficial reference to out of date and underdeveloped technology back in the 90's, that is focussed on emissions testing is a definitive fact that suggests AF ratio equipment 'doesnt work on two stroke'.......because it does. IMHO, it would be fair to say that there are significant differences between working on 4 strokes and 2 strokes when using AFR equipment, but thats common sense and common knowledge. There are actual figures and tech info for both......and anyone working to the 4 stroke figures on a 2 stroke scooter is just a dick, full stop.

[joeythescooterboy]

This one could go on forever with no definitive resolution, however I think we've gone slightly off topic.............

When carrying out your comparisons are the final figures given in thick Lincolns or skinny chipolatas, and where exactly would a cocktail sausage fit into the equasion?

Merry Xmas

[mark]

cocktail sausages are the midgets of the susage dyno world,so they are simply there to make drunk people laugh

[MattsDad]

I had hoped this would fizzle out but I think that you're probably more naive than arrogant in dismissing Prof Blair so readily! His specialty is 2 strokes, the book is about 2 stroke engine design; he makes reference to four stroke in one sentence about oxygen concentration but conveniently you leave out the sentence directly after! "Thus, in a 2 stroke engine the oxygen concentration is always high (shift 8-10%)"

Thats the science of it and you won't change that. Stoich is a political number to balance performance / emissions; Blair covers that too but its a different subject as was the sensor being blocked up comment. Back to the question of whether Lambda is accurate for 2S or not:

1. Blair says no
2. NGK the spark plug people say similar
3. Cosworth PI Research too
4. AIM Racing Data Power as well

In the Scootering article a couple of years ago it was evident that most of the dynos used are knocking on and have been superceded, so to say because the above comes from 15 years ago is not relevant, well.

Yours is the cheap and cheerful MJP dyno, you say Michael Jansberg had 2 strokes in mind, did he now? His website seems to be all about 4 stroke racing. If yours is indeed thee cutting edge piece of kit then I'll ask you this. Does your dyno have a switch to flick or a setting in the software to differentiate between you putting a 2/4 stroke on? If so then you've bought the right one and I think thats the crux of all this - honest answer please.

If you race 2 strokes, what you'd really like Father Christmas to bring you is the Mycron4 analysis kit. Why is it they say this?

'In general we can say that LAMBDA values lower than 1 indicates a low
presence of oxygen remaining after combustion (rich mixture), while LAMBDA value
higher than 1 indicates that presence of oxygen remaining after combustion is in
excess of the quantity needed to burn the fuel (lean mixture). This is absolutely true
in 4 strokes Otto cycle and Diesel four strokes for street use engines. On the contrary,
it is true but with some corrections in the case of two strokes engines. In two strokes
engines, in fact, there are moments during the cycle when incoming and exhaust
gases ports are open simultaneously. Depending on the type of two strokes engine,
at certain RPM values, part of the incoming gas passes directly to the exhaust gas
pipe without taking part in the combustion. This leads to a false reading of the
quantity of remaining oxygen because its value results from the addition of left
incoming gas and not combusted gas. This means that a reading corresponding to
lean mixture doesn’t always reflect a real situation of lean mixture engine. In the
same way a Lambda value higher than 1 (apparently lean mixture engine) can be
due to the partial combustion of the mixture caused by a weak ignition that cannot
brake the dielectrical between the electrodes of the spark. In fact higher compression
ratio engines need more power to make the plug spark. If the signal is weak a delay
occurs and there is a variation in the ignition advance curve (i.e. the ignition curve is
late). This too leads to a reading of excess in oxygen not consistent with the real
engine carburation'.

Its because the recognise its not accurate and for the Lamda sensor to work in its set up it needs to be coupled / balanced with EGT and fancy software, I think I mentioned that earlier.

[drunkmunkey6969]

I had hoped this would fizzle out but I think that you're probably more naive than arrogant in dismissing Prof Blair so readily!.

Thank you for the lovely compliment, im feeling loved.

In the Scootering article a couple of years ago it was evident that most of the dynos used are knocking on and have been superceded, so to say because the above comes from 15 years ago is not relevant, well..

I didnt have a dyno when that article came out, mine is reletavliy new by comparison, i can only comment on what i know/do and not others. Although im almost certain that at least 2 (if not 3) of the dyno owners have infact updated/replaced their own equipment too since that article. And the article itself was based around power readings, not AF equipment.

Yours is the cheap and cheerful MJP dyno .

Indeed it is, although its the same electrical hardware and almost identical software as the more expensive eddy current/step testing 2200 version, the increase in cost is mostly due to the eddy brake equipment and the larger dyno bed/roller of the 2200 series. So i get the technology benefits without the cost, and a roller size more suited to scooters than superbikes.

you say Michael Jansberg had 2 strokes in mind, did he now? His website seems to be all about 4 stroke racing.

As with world GP racing, 2 strokes out outlawed and a diminishing interest for many, where his business future lies now is 4 strokes, where his heritage, knowledge and interest started was two strokes. I have spoken many times with Michael and Hans from MJP and i know it was designed for smaller application 2 strokes, as that is what they told me directly.

If yours is indeed thee cutting edge piece of kit then I'll ask you this. Does your dyno have a switch to flick or a setting in the software to differentiate between you putting a 2/4 stroke on? If so then you've bought the right one and I think thats the crux of all this - honest answer please..

Mine doesnt have the 'switch' although the 2200 series software does. Mine is manually re-programable on the AF settings/perameters page. You can download the 2200 series 'old' software demo version (newer versions are now available) and see on the parameters page that there is a tick box for 2 strokes: http://www.mjpdyno.com/software.htm the MJP software (in my opinion) is quite good and has many flexible settings for the operator to choose from.

The sensor i use is the Bosh 5-wire, wide band lamba sensor, this is coupled to an innovate LC-1 lambda cable, which then goes into the MJP lamba sensor electronic box of tricks, which then goes into the computer and hooks up to the programmable software. The theoretical stoich for 4 strokes is 14.7:1, this means 14.7 pounds of air for every pound of fuel. Diferent values are as follows:

Gasoline 4 stroke: 14.7
Gasoline 2 stroke: 12.7
LPG (propane): 15.5
Methanol: 6.4
Ethanol: 9.0
CNG: 17.2
Diesel: 14.6

There are many lambda/AFR displays on the market, most are essentially volt meters for a voltage between 0v & 1v and measure the analogue voltage of a narrow band oxygen sensor. Some are true analogue instruments, whilst others provide LED bar. Because of the limited range of narrow band sensors, they are essentially useless as true AFR meters. Our Innovate LC-1 and Bosch 5-wire wide band lambda combo, combined with the MJP electronic box of tricks andprogrammable software give us a true remote AFR meter. Our setup measures oxygen, burned and unburned fuel in the exhaust gasses, we can alter linear outputs, delay rates, and response speeds, and we can program our software for a linear output between 0v and 5v, (AFR of 7.35 to 22.39) which gives us more than ample information to re-jet a Vespa or Lambretta scooter.

At the end of this post, all i can say is......my dyno gives me readings that i can interpret and use to re-jet scooters safely and effectivly......and if other people feel/think/say that AF fuel info isnt relevant or the equipment doesnt 'work' properly then thats up to them. You asked a question (quite a few actually) and i have tried to answer them. You disagree with me, i disagree with you.....or at least we just misunderstand each other. No major shakes, no worries....everyone is entitled to their opinion, im not trying to convert you, was just trying to offer input and opinions that differ from yours.

Peace and goodwill to all men.........game of football anyone?

[J1MS]

Mattsdad has raised a good point with regards to how the AFR's are taken knowing how a four stroke fills the cylinder with very little valve overlap on a fourstroke
whereas a two stroke has no check valve to seperate the incoming air/fuel from the exhaust gasses, with an exhaust system designed to supercharge the cylinder using efficient expansion chambers designed to draw fuel/air into the chamber then reverse that fuel with positive pressure waves plugging the port & adding extra charge at certain revs to the cylinder.
It must be possible for unburnt gasses to pass to the sensor how would the sensor know when unburnt gasses were being analysed along with the burnt gasses. Are the new sensors a new breed are the software programmes calibrated for this?

I think Mattsdad has put his point well. And no one has to agree, but an explaination that carries factual information why he's wrong maybe.

Even if some from this forum give the answers in sausages.

Can someone explain how and why the sensors and software could only ever give the correct AFR's

Thanks. Mark....

[drunkmunkey6969]

AFR meter shoot out has some good info: http://www.innovatemotorsports.com/reso ... ootout.pdf

As does the innovate page: http://www.innovatemotorsports.com/products/lc1.php

Bosch & NTK lamba info from MJP: http://www.mjpdyno.com/lambda.htm

[drunkmunkey6969]

It must be possible for unburnt gasses to pass to the sensor how would the sensor know when unburnt gasses were being analysed along with the burnt gasses. Are the new sensors a new breed are the software programmes calibrated for this?

I believe the answer is yes, they can sense burnt and unburrned gasses......i dont have the technical knowledge to explain how, but thtas what it says on the tin.....or at least what Innovate say in their blurb they provided me with.