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By Boxkite
#1653067
According to Wikipedia, the O-320-E2A can be either 140hp or 150hp at 2450rpm or 2700rpm respectively. So how does one determine what is the actual power rating when in a particular aircraft? Take a DR400-140 for example, of which some (all?) are supposedly 150hp.
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By Flying_john
#1653094
The spec of the engine is normally give as 'maximum horsepower'.
It may be calculated from torque at a certain rpm.
The engine may deliver different horsepowers at different RPMs .

So horsepower is RPM x torque.

So you can see it is RPM dependant and RPM is not just governed by the throttle position, but also the load on the engine (i.e the prop diameter and pitch).

Torque measures the force the rotation of the engine can deliver. Because RPM is a multiplier, more HP may be made by an extremly high revving engine than a slow but high torque engine.

Compare a screaming Suzuki at 7000RPM producing 100hp and an 0-200 at 2200rpm. If you could make the 0-200 work at 7000rpm you would get more horses :-)


Back to the question, if the Robin 140 only makes 2450 due to a large pitch prop then the power is 140hp. If you are permitted to run it with a finer prop allowing the engine to rev to 2700 then you will get a higher max HP
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By Boxkite
#1653570
Thanks John,
I guess you are talking about max static RPM in the above examples?
Most DR400/140s seem to have the same prop, so if one is being sold as a 150hp then it must be in the manual somewhere to say so?
(strangely a DR400-140B has a 160hp engine!)
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By Paul_Sengupta
#1653575
Boxkite wrote:I guess you are talking about max static RPM in the above examples?


Don't know anything about specifics, but I would guess that would be dynamic. Getting 2700 static on the ground would be interesting in the cruise!

I guess the difference is just where the red line is painted. Sometimes an engine limited to a lower RPM will have a longer TBO, but it's not that common.

Flying_john wrote:Compare a screaming Suzuki at 7000RPM producing 100hp and an 0-200 at 2200rpm. If you could make the 0-200 work at 7000rpm you would get more horses :-)


Some people run racing O-200s to something like 4000rpm, but their TBO is much reduced!

Boxkite wrote:(strangely a DR400-140B has a 160hp engine!)


A 160hp engine will be higher compression.

It's interesting to see Lycoming's engine line-up, particularly for the 540 engine. This has (essentially, in common use) two compression ratings and two RPM limits.

The low compression engine with a 2450rpm limit makes 235hp. (e.g. Cherokee 235)
The high compression engine with a 2450rpm limit makes 250hp. (e.g. TB20)
The low compression engine with a 2700rpm limit makes 260hp. (e.g. some Cherokee 6s)
The high compression engine with a 2700rpm limit makes 300hp. (other Cherokee 6s, Extra 300s, etc).

These are off the top of my head, so forgive any errors...

Personally I like the higher compression engines as they're more efficient and give better fuel consumption, but they need higher octane fuel (i.e. won't run on standard 95 mogas).
By cockney steve
#1653913
Each component is individually fettled to the exact dimensions of the Blueprint (Actually an engineering drawing that gives all-round views and dimensions for an item) Things like a ridge ,where 2 halves of a die'press-tool or mould come together, are removed. Items are weighed and balanced, so, in other words, perfect, hand- finished components. -A Rolex as opposed to a Timex both are watches , both tell the time :wink:

* blueprint , because the original drawing was pencil on white paper (lines and notes may well have been inked over afterwards.
The early copying-process cave a dirty-looking blue "negative" with the drawing and graphics in something that passed for white. :|
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By Rob L
#1654186
Paul_Sengupta wrote:I hope they did that with my engine, given the amount I paid for the overhaul!.


What...you want to make a profit out of aviation? :twisted:

Sell the Bulldog and buy some horses...or a yacht....then you will learn how to waste money. :wink:
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By Sooty25
#1654190
Paul_Sengupta wrote:I hope they did that with my engine, given the amount I paid for the overhaul!

I'm not going to take it to 4000rpm to find out though.


I very much doubt it!

The race engine may well have gone through a cryogenic process as well https://www.enginebuildermag.com/2017/03/big-chill-cryogenic-metal-treatment-benefits-may-not-visible-real/

Blueprinting and cryo treating would probably add 1000 hrs to the TBO of a stock engine operated within the normal parameters.
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By skydriller
#1663639
Boxkite wrote:Take a DR400-140 for example, of which some (all?) are supposedly 150hp.


Pretty sure both our Aeroclub DR400-140Bs are 160HP... I didnt know a 140 or 150 horse version existed!!
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By GrahamB
#1663650
Boxkite wrote:According to Wikipedia, the O-320-E2A can be either 140hp or 150hp at 2450rpm or 2700rpm respectively. So how does one determine what is the actual power rating when in a particular aircraft? Take a DR400-140 for example, of which some (all?) are supposedly 150hp.

Simples - is the tacho redlined at 2700 or 2450 rpm?
By Boxkite
#1663685
skydriller wrote:
Boxkite wrote:Take a DR400-140 for example, of which some (all?) are supposedly 150hp.


Pretty sure both our Aeroclub DR400-140Bs are 160HP... I didnt know a 140 or 150 horse version existed!!

The 140B has a D2A engine which has only one rating of 160hp according to wiki.
By Boxkite
#1663686
GrahamB wrote:
Boxkite wrote:According to Wikipedia, the O-320-E2A can be either 140hp or 150hp at 2450rpm or 2700rpm respectively. So how does one determine what is the actual power rating when in a particular aircraft? Take a DR400-140 for example, of which some (all?) are supposedly 150hp.

Simples - is the tacho redlined at 2700 or 2450 rpm?

I wouldn't assume that just because an engine rating is quoted at a particular RPM that that also defines the max rpm - power drops off beyond peak power with increasing RPM. But in this case you may be right.