Search results

I was talking about richening it up until it 4-strokes under load, that would happen the 10:1 AFR range. A saw will be happy at 12.5 but 13.5 is too lean. My earlier point is to not assume the AFR numbers from the meter are accurate as it's not designed for the high O2 and high HC...

How rich will it go? You should see 10 or lower before it starts 4-stroking.

What numbers are you getting for AFR at the richest and leanest points you're comfortable setting it? Chances are the accuracy with a 2-stroke is going to be off, but if it's repeatable it will be a good tuning tool.

That would be a silly way to calculate power for any dynamometer. Note the (1 - μ) term. Your dt is only due to pump inefficiency, not the amount of work put into the system from the engine. The higher the pump efficiency the smaller the temperature rise would be--if the pump was 100%...

You must have missed the torque arm and scale on this dyno. Change in fluid temperature won't affect the accuracy of the measurement. It will cause difficulty in load control because the viscosity will change and the pressure drop across the regulating valve will drop as the oil heats. This...

There's the problem--in my world scales measure force, not distance.

Try again. If the saw is making 1 lb-ft of torque the scale would measure 1 lb if the torque arm is 1 ft long. It would display 0.1 lb if the arm was 10 ft, and 0.01 lb if the arm was 100 feet long.

A shorter torque arm increases resolution and makes it easier to see small changes in torque.

Why is the torque arm so long? Scale maxes out?

What's the wet weight for an equal run time? If fuel economy improvements are significant the strato saws could be lighter than those with conventional 2-strokes.

I think chadihman had it right the first time. The longer torque arm reduces your resolution. The difference between 1 ft-lb and 1.5 ft-lb as measured by the scale is 0.5 lb for the short arm and 0.1 for the long arm. Longer arm requires a more precise force measurement.

Effectively all the shaft power of the engine is going into heating the oil. Doesn't matter how small the pump is, what the flowrate is, or what speed the pump turns. 3 gallons is not a large reservoir, it's going to get hot. Running a 3 hp saw continuously is the same as putting a 2300 Watt...

Carb part #31 is not a pump, though it's labeled as such. It's an assembly with a tapered pin that is coupled to the throttle shaft through a cam (labeled #10, 'lever slope'). It moves axially in its bore. It only moves with the main throttle; it does not pulsate while the engine is running...

...and EU emission regs are as tight as the US EPA limits. And their vibration standards are higher.

If I remember it was a piece of hollow round gray CI stock purchased from McMaster-Carr or MSC. There was no heat treating on the one I made and no discussion of tempering the ones made by Advanced Sleeve. If you trust Wikipedia as a source it says that grey CI is usually used as cast (no heat...

Nevermind, I now remember it was a moped cylinder with a removable head. The sleeve dropped in from the top and the head clamped it down. A blind cylinder is going to be different beast. Found some old photos; the alignment pin was at the bottom, not the top.

I turned a sleeve from cast iron stock once. I've got no record of tolerances; I used a light shrink fit and a did something with a pin in the cylinder and a notch in the top ring of the sleeve to align it when it dropped in. The hard part was cutting the ports; I used a CNC to cut them before...

I have presented the AFR data for an engine bogged to a speed that can not be reached by a chainsaw and explained that in the text you quoted. I have presented fuel rate and air flow data that shows there is not a velocity squared correlation.* There's no point in discussing this further...

Here are some more plots from the same run to look for a correlation between air velocity and fuel flow.

That run was to characterize the performance of that engine through all normal operating ranges with emphasis on AFR, emissions, and BSFC. Since it seems you are new to reviewing this type of data it's a bit presumptuous to tell me what my goals were when I ran these tests. There's no need...