Horsepower vs. Torque

[Trey Kule]

i was reading an article comparing diesel piston engines and avgas piston engines


At this evolutionary point they mentioned that for the same displacement, avgas engines produced more horsepower but less torque.


As all the planes I have flown recently set power in terms or torque, this got me wondering what the practical implications of this are.


Anybody care to explain the practical implications of this ( not really concerned about theory 101). But how it will affect small aircraft performance.

[anofly]

you read the same article as me in an old flying magazine? Garrison wrote a piece on that , I will see if i can find it.

[anofly]

for one i will point out that the 135 HP thielert centurion engine is a 1.7 litre engine, about one third the displacement of the lycoming 0-320. (2 litre is about 120 cubic inches).
both of these engines have similar torque about 300 ft pounds to the prop.
most of the diesel conversions use some type of variable pitch prop. That makes a way for  getting all the hp out of the diesel ,, when the 0-320 usually has a fixed pitch prop that is a compromise and the engine rarely gets to use its full 150 horsepower. It does not get to a high enough rpm to make its rating on takeoff.
strangely enough the engines weigh about the same. The big difference comes in fuel burn (the diesel burns quite a bit less per hour) so one can use that to increase cabin load for a specific trip length.
they are expensive to overhaul and tbo is a bit shorter than we are used to.
they are expensive to buy.
they burn jet fuel
thats more important in places like europe and africa where they really have little infrastructure for 2 fuel streams..


we dont have the infrastructure here to look after 2 streams of engines, try calling the next floatplane joint over and asking for the equivalent of a cyl for a cessna 180  to borrow?

[Colonel]

Horsepower is work, and torque is force - they are completely different animals.

Horsepower is in fact defined as torque times RPM: force through a distance
(albeit rotational) per unit time.

You can make horsepower with either lots of torque (diesel engine) at low
RPM, or lots of RPM with less torque (gasoline engine).

The huge advantage of a diesel engine on a light aircraft, is that ideally you
don't need a gear reduction unit, as you will with a gasoline engine, to
drive the prop.

6,000 RPM is a good speed for a gas engine, but not a prop.

2,500 RPM is a good speed for a diesel engine, and a prop.

Reducing the RPM from a gas engine to a prop is not easy, and can
be very heavy and expensive and unreliable, if not done right.

The ultralights use rubber bands.  I know a guy, his gear reduction
unit had a resonance and ground itself to pieces on final at Cornwall,
and into a field he went.

Pilots and owners generally hate the gear reduction units found in
the C421, T-bone and hot-rod Harvard.  I love them.  Planetary gear
reduction on a radial kicks ass, imho.

Many people have used diesels in aircraft - going back to WWII - but
I am not a fan.

[url=https://en.wikipedia.org/wiki/Junkers_Jumo_205]https://en.wikipedia.org/wiki/Junkers_Jumo_205[/url]

[anofly]

https://www.flyingmag.com/how-do-thielert-diesels-do-it


here read this as well, i found it online, but have the magazine and was reading it last week. i need to throw more stuff away....

[Colonel]

Is he in jail?

[anofly]

who ?Garrison? for blasphemy? or fumbling the technical ?

[Colonel]

Heh - no.  While many might opine that Garrison should be
locked up (for his own good?) I was referring to the criminal
charges as the Thielert company wound down.

https://www.defenseindustrydaily.com/th ... nch-04801/

[quote]Thielert is facing advanced stage criminal investigations for serious accounting fraud, providing false evidence, and more.

court rulings to date have voided the firm’s financial statements from 2003-2005.

Allegations include the use of ghost invoices (i.e. false orders) to obtain bank credit and pump up the stock’s value for share offerings[/quote]

[anofly]

ouch,, maybe did continental buy them out? first volkswagen.....

[Trey Kule]

I believe Continental is now owned by a Chinese company.


On a tangent, not having mags, prop and mixture controls is going to make those learning in these aircraft require extra training to transition to a 172.  It willbe interesting.


In any event, as I understand it , low RPM torque is a good thing.