Use of a dyno bank

[Tobyjugs]

Hello chaps
                 After reading about Holty's misfortune it got me thinking about the way in which the air/fuel ratio is measured.
I have used two different banks, one dyno bank from a tuner which is mostly used for two strokes, he never measures the air fuel ratio unless you specifically ask him, and the other is in what i call a proper bike shop were if i come with my rd it gets a lot of attention as it is mostly only four stroke that go there. (even the mechanics in the workplace come out for a look)
The bike shop is only two miles away so was handy to go to for the dyno as i specifically wanted to know how the carburation was. The dyno operator had the sensor on a long pipe which he tried to put in the exhaust pipe. The bike has the original exhaust system so i suggested removing the baffle.

On a bike with proper expansion chambers you can just shove the sensor straight in. Is this normal procedure for a two stroke on the dynobank. The reason i ask this question is because the stinger has to be of a certain diameter, if it is too small this could cause overheating of the engine, if you put the sensor in this will reduce the effective diameter of the stinger theoretically causing the engine to over heat. Due to the short burst on the dynobank maybe this is not a problem.

What have your experiance's been on a dynobank in this respect?

[4l04ever]

Yes, this is normal, and it can affect the exhaust stinger size slightly, while the sensor pipe is in the exhaust.

[Tobyjugs]

Do they swap the sensor from pipe to pipe?

[4l04ever]

Yes, so you can check the fuelling on both, as sometimes they need different jetting.

[marsbar350]

Kev at projexs say that there's on oil that shags the sensors in the probe and that's silkolene 3 sensors knackered at £90 a pop

[phil38]

I'm pretty sure measuring air fuel ratio with a lambda sensor does not work very well on a two stroke as the inlet & exhaust are "short circuited" due to scavenging. This means the exhaust has more oxygen in it due to some of the fresh air going straight through, so it's not telling you what the air-fuel ratio is in the cylinder. I think most two stroke tuners (although I have not direct experience) would use a CO sensor and set-up the jetting based on that.

[Tobyjugs]

Mar 30, 2016 12:35:38 GMT 1 phil38 said:

I'm pretty sure measuring air fuel ratio with a lambda sensor does not work very well on a two stroke as the inlet & exhaust are "short circuited" due to scavenging. This means the exhaust has more oxygen in it due to some of the fresh air going straight through, so it's not telling you what the air-fuel ratio is in the cylinder. I think most two stroke tuners (although I have not direct experience) would use a CO sensor and set-up the jetting based on that.

I've got no idea what type of sensor they use but it does sound logical that the unburnt residue can knacker the sensor.
Next time i see Piet the tuner i will ask him why he doesn't measure the air fuel ratio unless asked.