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ASP .91 > DLE-20 ??

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Old 04-22-2012, 07:20 PM
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Default ASP .91 > DLE-20 ??

Hello,

I have an older Goldberg Yak 54 67" running an ASP .91 2 stroke. To me, it seems underpowered. In addition to this, I'd like to convert to gas. I can pickup a DLE-20 for a reasonable price, but I'm unsure if it will yield the same/any more power than the .91. Googling specs shows the ASP .91 has a 2.9HP rating, practical RPM of up to 17K and runs a 14x8 or a 15x6 prop. The DLE-20 says it has 2.5HP at 8500RPM, and has a recommended 16x6 prop. The ASP weighs about 25oz w/muffler and the DLE-20 shows a total weight of 29.7oz..

Can anyone give me a clue whether the DLE-20 would be an acceptable alternative?

Thank you
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Old 04-22-2012, 08:58 PM
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Default RE: ASP .91 > DLE-20 ??

id get the dle20 hands down
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Old 04-23-2012, 12:47 AM
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Default RE: ASP .91 > DLE-20 ??

DLE 20 will hang with the 1.20 size 4 strokes if not do a bit better.
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Old 04-23-2012, 04:40 AM
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Default RE: ASP .91 > DLE-20 ??

I have a Magnum 91 2 stroke, which is one of the best engines I have owned. I like it. It has nowhere near the power of the 20cc gasser. The 91 turns 15X6 prop at around 8600-8900 rpm, the 20cc will turn a 17X6 at around 8300-8400 rpm, much more power to fly the plane.

Forget those horsepower comparisons. they are meaningless.You don't know what rpm the glow engine developes its max HP do you? Do you think it is anywhere near the rpm range you operate to fly the plane?

Go for the gasser.
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Old 04-23-2012, 06:45 AM
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Default RE: ASP .91 > DLE-20 ??

If you don't mind flying slower I am sure the DLE will be fine.  The specs show less housepower but more torque.  So more thrust but less speed.
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Old 04-23-2012, 10:22 AM
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Default RE: ASP .91 > DLE-20 ??

The DLE 20 has much more power than a ASP 91. There is no comparison. Forget the specs.
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Old 04-23-2012, 11:17 AM
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Default RE: ASP .91 > DLE-20 ??

DLE-20 AAA+++
go for it and fly
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Old 04-23-2012, 11:34 AM
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Default RE: ASP .91 > DLE-20 ??


Quote:
ORIGINAL: w8ye

The DLE 20 has much more power than a ASP 91. There is no comparison. Forget the specs.
My .91 ASP will turn a 14-6 at about 10,500. Ibelieve it turns a 15-6 over 9,000 RPM. The DLE turns a much larger prop much slower. Idon't have the prop chart data butth 17-6at over 8,000 sounds about par for horsepower, but the latter has more thrust.
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Old 04-23-2012, 11:37 AM
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Default RE: ASP .91 > DLE-20 ??

If you go out to the flying field you will see what I mean.

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

Sport - you know all this anyway.
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Old 04-23-2012, 12:19 PM
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Default RE: ASP .91 > DLE-20 ??

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

The engine with more power will pick that smaller higher pitched prop with more RPM increasing speed even more.   However the ASP/CS .91 is only fair to middling for a glow engine.  The DLE with its rear carb and possibly other features probably makes up for its less powerfull fuel.
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Old 04-23-2012, 02:08 PM
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Default RE: ASP .91 > DLE-20 ??

The DLE 20 seems to be a good engine but will not last as long as some glow engines, based on a number of posts here. It also will not stand up to very high rpm so you will need to use a higher pitch prop to keep the rpm down to the limits shown in a number of previous posts. But the DLE20 will fly your yak very well as an aerobatics plane and will likely fly it much better than the Asp .91 if you want to try 3d. it all depends on the all up weight. But there will be a learning curve when converting to flying a gasoline engine.

So - do you have someone you know who can help you learn the ropes of gasoline engines? Or are you willing to spend some time - hours maybe - reading the wealth of information in the threads here that discuss the DLE20?

Ed
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Old 04-23-2012, 03:58 PM
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Default RE: ASP .91 > DLE-20 ??

Gas is inexpensive however the DLE requires an additional 4.8V battery for ignition. The engine will add additional weight to the airframe and increase your wing loading. The bottom line is up to you but if you want more power without increasing weight than swap out your .91 for a 1.08 or 1.6 glow engine. I flew a GP Extra 300 with an OS 1.6 glow and it was a great combination. People are switiching over to gas because of the cost of glow fuel and the cheap made in China gas engines. The DLE brand is a good engine but Zenoah is excellent.
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Old 04-23-2012, 06:04 PM
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Default RE: ASP .91 > DLE-20 ??

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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Old 04-23-2012, 09:22 PM
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Default RE: ASP .91 > DLE-20 ??


Quote:
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.

The wing loading does not need to increase with the DLE 20. I have one in a GP .60 size Extra 300 which is both balistic and lighter than a like power glow.

Consider 10 minutes of full throttle fuel weight with a small reserve:

Your .91 2 stroke glow will need a 14 oz tank that must be pumped or kept close to the engine which yeilds a changing CG during flight.

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!
I like the Beechwood props on these gassers myself which is another weight savings over the heavy APC which glows seem to perform best with.
As for speed, 15 x 10, 16 x 8, 17 x 6, yeild fast, medium and hover.
For ignition battery I am using a single Li-ion cell with a voltage booster. This is over 4 hours of run time at a weight of less than 2 ozs.

The Zenoah is easily put on a diet. Its stock muffler is steel and weighs 6 ozs. Its ignition is heavy too, I have replaced mine with a RCexel.
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Old 04-23-2012, 11:37 PM
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Default RE: ASP .91 > DLE-20 ??

I'd check (besides of power) the weight of the whole engine including ignition. DLE 20+all gear is for sure heevier than the ASP91. You might consider to place there some 4 stroke. I changed a 91 by a OS120III succesfully with out any issue except for 15 grams of lead on the tail...

Make a simulation; place the weight of the desired DLE20 on the nose of the plane and check the CoG.

Regarding to the power; I'm not the pserson who knows the DLE20, but I'd bet my trousers that you'll be flying slower but with "infinite" vertical performances thatnks to more torke (bigger propeller Ø).

Hope it helps!!!
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Old 04-24-2012, 02:08 AM
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Default RE: ASP .91 > DLE-20 ??

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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Old 04-24-2012, 02:19 AM
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Default RE: ASP .91 > DLE-20 ??


Quote:
ORIGINAL: TimBle

more torque, is more horsepower.
Not true. Just an example: a race car has about 400Hp while a truck has the same power but is capable of moving many tons.

Torque is the capability of "creating force" on a single piston cycle; while power is also related to the rate of that force is being created or:

Torque = Force (on top of cylinder) * Radius of crank
Power = Torque * rpm = Force (on top of cylinder) * Radius of crank

hope it helps...

(sorry if I missed some specific word in english)
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Old 04-24-2012, 03:35 AM
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Default RE: ASP .91 > DLE-20 ??

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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Old 04-24-2012, 03:44 AM
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Default RE: ASP .91 > DLE-20 ??

Quote:
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.
Not necessaryly; but only if they produce the same RPM. normally all 2strokers are rated at high rpm (14-16K rpm) while 4 strokes at about 10 to 12. Gasser are about 8 to 9K...
There is also the fact that energy available on fuels are different; this fact was already mentioned in this thread.
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Old 04-24-2012, 03:57 AM
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Default RE: ASP .91 > DLE-20 ??

Quote:
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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Old 04-24-2012, 04:07 AM
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Default RE: ASP .91 > DLE-20 ??


Quote:
ORIGINAL: Sport_Pilot

Quote:
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.
Using metric measuring system avoid this type confusion jejejejej!!!

Thanks. Good to know that difference.
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Old 04-24-2012, 04:41 AM
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Default RE: ASP .91 > DLE-20 ??


Quote:
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.

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.
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Old 04-24-2012, 04:49 AM
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Default RE: ASP .91 > DLE-20 ??

Quote:
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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Old 04-24-2012, 06:46 AM
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Default RE: ASP .91 > DLE-20 ??


Quote:
ORIGINAL: Sport_Pilot

Quote:
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.

good analogy
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Old 04-24-2012, 09:08 AM
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Default RE: ASP .91 > DLE-20 ??


Quote:
ORIGINAL: Sport_Pilot


Quote:
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.
Your arguement suggests that Power is inversely proportional to torque and that is incorrect. They are proportional. More power, more torque.
P=2.pi.N.T / 60

Power is proportional to rpm and torque or Force x radius.

What you observe wen you compare the high speed petrol engine to the low speed diesel is the ability to convert chemical energy to work. If the two engines were similar they would have similar power and torque.
The losses incurred are also different due to designed in differences.
Engines for larger thrust usually burn more fuel and therefore have more displacement. So comparing a 1600cc high speed engine to12,000cc hauling diesel is not quite the same thing is it.

Quote:
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.

Again a few myths.
running rich only produces more power if that fuel can be burned, But th very nature of the word rich implie incomplete combustion because rich means you have more fuel than oxygen, even if you're adding your own oxygen via the fuel -the stoichiometry takes this into account when the terms lean or rich are applied. The higher rpm comes from sufficient oil to reduce friction and the flame speed of Methanol.

your arguement again goes south when you say higher octane of methanol makes it burn slower. Look at the size and shape of the methanol molecule and compare it too gasoline molecules and your answer lies within..
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