air fuel ratio on the dyno

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Diablo
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A dyno is just a tool. Its not a cure all. The big difference between setting up on the dyno and setting up on the road for me at least is time-it saves you lots of it.
Its also really good for fine tuning and for showing what works and what doesn't.
A combination of your mates experience and him interpreting what he sees on the dyno would probably see you take a step forward simply because lots of set ups can be tried in a short space of time.
MattsDad
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I've been to various dyno where they've been way out under load. I wasn't trying to lead but do you agree the bike should be road set up first and then tweaked slightly under dyno, given the road experience?
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Speed Demon
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If you are into racing and have a mate who can jet for you like that then you are very lucky in terms of both friends and a venue. If you are after the last percent of performance then a dyno will only get you so far because 100% optimum jetting can only be achieved when you take into account changing weather conditions at the time you are running.

What a dyno (with an air/fuel meter) can do is provide a window to see more clearly what the engine is doing at different rpm and different throttle positions - you still need someone with an ear for an engine to interpret that information and to make the right decisions on what to change to improve things. That in itself is a skill that not everyone who runs a dyno possesses, and that's what you are paying the money for if you take it to someone who has got a clue.

In defence of "blew up on the way home" dyno operators though - you could jet a scooter pretty well on a few short dyno runs, but if it has a partly-blocked fuel tap it will still hole a piston on the way home. Is that the fault of the dyno operator, or the owner? Certainly if you use a dyno where they road test the scooter properly to check their settings then it's more likely to get picked up on.
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MattsDad
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Certainly agree that some operators are better than others and thats why I go to dyno to see what its doing at different revs, hp etc.

Wanted to ask then opinion on this re A/F as a couple of years ago I bought an NGK AFX monitor, never used it but still have it; got the instructions in front of me now:

'The AFX is designed for 4 stroke cycle engines, and will not accurately perform in a 2-stroke engine. Due to scavenging of 2 stroke engines, the true AFR reading becomes distorted. the nature of 2 strokes is inherently one that is not compatible with exhaust gas sensors.'

Its a good read anyway and is on page 7.

http://www.ngksparkplugs.com/pdf/AFX_Tu ... REV_06.pdf
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tony
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Eden you have picked up on something here.

My own experience started quite a while ago with mappable ignitions on a dynojet. An inertia dyno.
I was tweaking the settings to give me the widest spread and peak for my race bike. I'd do a static run... then another... and another... each time the graph shifted up.... so I thought great.. i can stick in some more low down advance,, 20 secs later another run... the graph moves up again... another run... the same again.. I couldnt understand at that time what was happening. I'm adding advance low down and the graph is still moving up.. this should not be happening. So I carry on as I know at some point the low down power must increase... eventually it does...and I bring in power low down on the graph.. but now I am at silly advance figures.. the comp is correct for the fuel and all the other factors are pretty much right... but there is no way this thing will tolerate 34 degrees of advance. BUT the graph shows otherwise.. its making great power.. the band is good.. carburation is at the right level according to the dyno... so what is happening.... ?
What is happening is that the motor is not under any load and after each run temps are climbing.. Then 'm trying to hold it at 5000 rpm and the motor is yawning at me. All its doing is spinning a drum thats already spinning under its own inertia. So what does this say about the graph and figures? How can I set up mid-range? (this is really important for you road guys as this is where you engine lives on rally duty) .The engine is not working in the 'real world'.. so how can it A: show real world figures or B: help you set up the engine? The answer is it cant really.. Each time you do an inertia run you build more and more heat into it all..its not consistent. Its only working on acceleration load and things are changing very quickly here.. The inertia dyno is designed for a power run after you have set it up. Its not really ideal for a set up tool. As al said .. 'the motor is not under any load' .. hence why he does a road test after.
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MattsDad
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That was hard work Tony :), but I think I do the same, road set up first then dyno to see power/torque changes after whatever you've done differently. I gave up on AF/ignition set up on dyno as I always had to change in real conditions. Ended my season on an on the edge lean plug colour, went to dyno a few weeks ago for HP, same set up and practically black!
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OzOAP
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Looking forward to a trip to Al's at the weekend.
Changed a few things on one of me bikes, let him spend some time on the dyno and round his test route :baddevil:
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Interesting all this.

There is a place not two miles down the round from me that have offered dyno services for 35$ a pop. This helps to tell them what I would be needing. I know of at least one shop here that bench tests thier motors, but never road tests. I keep telling the owner he needs to put a load on to show real world conditions, same as what you lot are trying to do with the dyno.
Trying to dial in a Malossi or anything else very peaky by the seat of your pants is a bit more hair raising as you get older.

Mind if I cut and paste some of the info here to give to the dyno operator I am going to use?
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Diablo
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Tend to agree with some of what you say Tony. As I said a dyno is just a tool and is certainly not the only thing we use here to set up bikes.
The most important tool I use when setting up scooters is over 25 years experience of attending rallys all over the country and Europe in all weather conditions on lots of different types of scooter. So when load is talked about I think things like 1/4 throttle openings while sat behind a lorry your mate on his p2 can't get past play a part. Knowing how a scooter behaves on part throttle openings on the motorway especially riding with scooters slower than yourself is something no dyno can replicate. Being then able to blast off for a thrash without blowing it up also comes into it :D
This is often the real world of mid range rally riding Tony. Try replicating the drag of that lorry on any dyno loaded or not.
The most realistic load conditions I can think of are the ones on the actual road. This does give you an ear for an engine especially when your scooter has taught you another harsh lesson and your sat by the road freezing your nads off waiting for the AA again. When bikes come in for dyno in August I've got to also jet them for cold winter mornings in Febuary. There has to be a big factor of safety. At the same time the bike has to be ridable not some spluttery mess spouting fuel every where. This is completely different to setting a bike up with optimium settings for the track. I agree a braked dyno will probably give more accurate results.
It could also be conversley argued that braked dynos introduce an unnatural amount of heat into the engine and will actually run hotter on the dyno than they would on the move.
At the end of the day the AFR graphs are a graph which need to be interpretted. I disagree they are not useful with 2 stroke engines.
Setting up aircooled 2 strokes especially ones with race pipes ridden on the road can be difficult. Peoples expectations and also choice of parts also doesn't help.
I keep hearing Adam being asked for a touring pipe for an RB. How daft is that? I really can't see what the point of buying a RB kit with the port timings it has then fitting a pipe totally at odds with the cylinder. Then I'm expected to jet it and set it up on the dyno?
The big problem is people want a cure all. Often a complete miss match of parts is expected to have a magic wand waved over it by the dyno operator and hey presto a well set up bike with a cast iron garuntee it will never blow up or breakdown again.
We can all pull stuff off the internet that suits our arguments one way or the other. For the most part what is written on the internet is not verified with indisputable fact and much of it is written with one bias or another including this thread and everything on this forum.
What I will say is if you are thinking of having your bike dynoed speak to others who have had their bikes dynoed at the same place and simply ask the question-"was it better after it left and was it worth the money?"
If the answer is yes phone the dyno centre and have a chat about your expectations and go from there.
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C*NTSPEED
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Diablo wrote:What I will say is if you are thinking of having your bike dynoed speak to others who have had their bikes dynoed at the same place and simply ask the question-"was it better after it left and was it worth the money?"
If the answer is yes phone the dyno centre and have a chat about your expectations and go from there.

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