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ORIGINAL: w8ye

The DLE 20 has much more power than a ASP 91. There is no comparison. Forget the specs.

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If you want to go fast - use less diameter and more pitch.

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ORIGINAL: toniintc

Gas is indeed inexpensive.  I can't see moving to a different engine without moving to something that will allow me to spend 80% less per gallon on fuel.  Yes, the wing loading will increase, but the plane lands well now and I don't expect the additional weight will change that significantly.

From everything above it seems the consensus is that the DLE-20 will perform better that the .91.  I appreciate the insight.

As to the comment about Zenoah - the closest analogy to the DLE-20 is $50 more expensive and 10oz heavier.

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ORIGINAL: TimBle

more torque, is more horsepower.

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ORIGINAL: TimBle

So from P = T x N

it can be seen that Power and Torque are proportional for a given engine geometry at a certain N or rpm.

SO if an engine produces more torque it is also producing more power.

It may not be able to covert the power in speed.

What you are looking at relating to each other is BMEP (brake mean effective pressure) of the engines.

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The gas plane engine, Zenoah 20 or DLE 20 (I have both) will need only an 8 oz tank which can be placed on the CG because of the walbro carb's pump. That's a 6 oz advantage right there!

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ORIGINAL: Sport_Pilot

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The gas plane engine, Zenoah 20 or DLE 20 (I have both) will need only an 8 oz tank which can be placed on the CG because of the walbro carb's pump. That's a 6 oz advantage right there!

Fuel tank sizes are in Fluid Ounces.  That is a volume not weight.  The weight differences depend on the fuel.  High nitro glow fuel weighs more than gas, low nitro about the same depending on the oil used.  The differance is likely about 4 ounces weight, maybe a little more.

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ORIGINAL: TimBle

more torque, is more horsepower.
for the ASP .91 to make similar Bhpyou will need to spin it up to silly speeds.

againsome erroneouscomments on Methanol being a more powerful fuel. check the heating values please. even adding in stoichiometry you're only on par for heating value on a mass flow per second basis.
Methanol burns faster and allows higher rpm because of that. The engine is still limited by mechanical constraints; balancing, rotating mass and carburettion.

The DLE is more powerful by a long way over a OS 91 FX. So I am pretty confident its more powerful than the ASP.91

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SO if an engine produces more torque it is also producing more power.

It may not be able to covert the power in speed.

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ORIGINAL: Sport_Pilot

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SO if an engine produces more torque it is also producing more power.

It may not be able to covert the power in speed.

Only if it is running at the same speed.  Here we are comparing two engines of similar power, one with speed and less torque, and another with torque and less speed.  For 3D the latter is what is most needed.

Compare a high performance car with 400 HP and a simi truck of the same power.  The car can go fast but not pull as much load, and the truck can pull more load, but not at as high a speed.  Both are doing the same work and thus have the same power. 

You can compare this to your own body, you can run and get just as tired as say pushing your car.  You will likely do the same amount of work but you will not push the car as fast as you can run.

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ORIGINAL: Sport_Pilot

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ORIGINAL: TimBle

more torque, is more horsepower.
for the ASP .91 to make similar Bhpyou will need to spin it up to silly speeds.

againsome erroneouscomments on Methanol being a more powerful fuel. check the heating values please. even adding in stoichiometry you're only on par for heating value on a mass flow per second basis.
Methanol burns faster and allows higher rpm because of that. The engine is still limited by mechanical constraints; balancing, rotating mass and carburettion.

The DLE is more powerful by a long way over a OS 91 FX. So I am pretty confident its more powerful than the ASP.91

Torque is a force.  Power is a measure of work.  To do work you have to move an object.  So pushing on a wrench without turning a bolt is a force but not power.  If however the bolt is turning you are doing work with  the wrench by applying force.  For engines with equal power and one is turning faster then another then the faster engine has less torque.  Generally for aircraft engines, more torque means larger props which are better for more thrust.   Yes you can increase the pitch and go to a smaller prop, but if the engine has a limited RPM you are limited on the size and pitch of the prop.

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Methanol does have less BTU per either weight or volume, but because it include oxygen you burn more fuel for a stoichiometric burn, and up to a point it has more power with a richer burn than stoichiometric.  So it is more powerful, but not as efficient.  Nitro takes this to an extreme.  It has so much oxygen it is a monopropellent, that is it can burn with no additional oxygen.  However this is far richer than the stoichiometric mixture.  But because of this you will run faster the richer it burns, if proper ignition can be maintained.  That is why dragsters run 44 amp magnetoes, enough power to weld with.  I am not aware that methanol burns faster than gasoline, this is attributed to nitromethane not methanol.  I cannot find flame front speeds for this but the higher octane rating (112) suggests that methanol burns slightly slower not faster than gasoline.