Quote:
Originally Posted by jl22996
Thank You
I used a 2 stroke engine and the fuel going into the carb was kept a constant.
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Some food for thought.
I'm not to sure what size engine your testing but lets say for calculating reasons its a 1.0L.
Example 1)
a 1.0L four stroke engine at 10,000 rpm with a VE of .85 and a intake temperature of 50*F will flow 11.62 lbs/min of air.
Example 2)
a 1.0L four stroke engine at 10,000 rpm with a VE of .85 and a intake temperature of 257*F will flow 8.26 lbs/min of air.
So you see that the extra 3.36 lbs/min of air can help the engines efficiency and pull past the 10,000 rpm mark.
Your carburetor and main jet adds fuel base on the amount of air in cfm, not weight that moves across the venturi. So with the examples above the same amount of fuel will be flowed on both examples. So what will change is the air to fuel ratio.
So with the examples above.
Example 1) will have a air fuel ratio of 14.7
Example 2) will have a air fuel ratio of 10.5
This very rich condition of 10.5 will slow the flame speed down during combustion. A slow flame speed is a huge determent in the higher rpm range. Because the pistons starts to catch or out accelerate the flame front. This is why you need more ignition advance at a higher rpm.