Thielert Centurion 2.0

[mdredmond]

The car accelerates better in Run 2 because performance is determined by power, not torque. Or, if you like, performance is determined by torque times rpm, not torque alone.

Yup. By producing your torque at higher RPM, you can use gearing to 'concentrate' it. The Lycoming doesn't.

But my point is that diesels produce VERY high torque at a low RPM. The Lycoming produces less torque at a much higher RPM. The net result is a virtual wash but the Lycoming's measured horsepower is higher because its higher RPM outdoes higher torque of the diesel in the equation.

That's why a 90hp turbodiesel can take on my 170hp Honda with impressive results.

[Kevin Horton]

Originally Posted by mdredmond

Yup. By producing your torque at higher RPM, you can use gearing to 'concentrate' it. The Lycoming doesn't.

But my point is that diesels produce VERY high torque at a low RPM. The Lycoming produces less torque at a much higher RPM. The net result is a virtual wash but the Lycoming's measured horsepower is higher because its higher RPM outdoes higher torque of the diesel in the equation.

That's why a 90hp turbodiesel can take on my 170hp Honda with impressive results.

OK, I'm glad we can agree that performance depends on torque and rpm, not just torque alone as you stated earlier.

As far as the performance of a 90 hp diesel vs your 170 hp Honda, which car models are you talking about? What does each of them weigh, and how do the quarter mile times and top speeds compare? I'm betting the 170 hp Honda is a much better performer than a 90 hp diesel, unless the diesel powered car is much, much lighter. Look at the actual test data, and it should show that the car with the better power to weight ratio is the better performer, no matter which one has the higher torque. Same thing with airplanes.

[Deuskid]

Originally Posted by Kevin Horton

OK, I'm glad we can agree that performance depends on torque and rpm, not just torque alone as you stated earlier.

As far as the performance of a 90 hp diesel vs your 170 hp Honda, which car models are you talking about? What does each of them weigh, and how do the quarter mile times and top speeds compare? I'm betting the 170 hp Honda is a much better performer than a 90 hp diesel, unless the diesel powered car is much, much lighter. Look at the actual test data, and it should show that the car with the better power to weight ratio is the better performer, no matter which one has the higher torque. Same thing with airplanes.

A TDI Golf v. a gasser Civic [or Golf] would be comparable examples. The Civic would be faster 0-40. The Golf 40 on up....

On the highway I've actually simply kept crusing at the same speed up long inclines and passed gasser vehicles that were loosing speed up the hills.

If you follow the link I posted earlier you could read the pilot's impression a portion of which is: <snip>

Observations:
- The engine runs very smoothly, the typical vibration usually occurs on Cessna didn't exist
- The engine noise sounds like driving a car on a freeway, doesn't sound like an airplane, actually sounds a lot nicer than an airplane, I have never liked the typical Cessna-sound
- The control in the fadec is very sensitive. Very small movements, millimeter forward or backward makes a big difference.
- Is faster than the other our flight club's Cessna C172 which is equipped with 150 hp engine and fixed pitch prop.
- Takeoff is significantly faster and more aggressive than on the 150 hp Cessna despite the Thielert is only rated for 135 hp. On the other hand, thanks to the CS prop, the engine outputs 100% power on takeoff, not something like 60% power because of too steep blade angles. The Thielert-Cessna felt more like 200 hp RV-8 than a normal C172 on takeoff, the MT Propeller makes a _HUGE_ difference. However, after getting up from the runway, the climb rate is not much different from ordinary C172 and loses ezily to a 200 hp RV-8.
- There is no manual leaning, carburetor heat, propeller pitch etc. things to take care of. The FADEC controls everything and the single lever interface works pretty nicely.
- on landing, instead of lowering engine rpm, the engine rpm goes up, that is because the FADEC-prop combination does braking on approach
- we didn't go higher than 3000 feet because it was very cold up there and the heating system is not that efficient and we were freezing.... <snip>

The theory of diesel v. gasser can be discussed until the cows come home...

Having lived with both for some time I can say that today's turbo'd diesel with modern fuel metering system is wonder.

If you are skeptical then I suggest go and drive a TDI.

In theory ... theory and practice are the same...
in practice - theory and practice are not so much the
same....

I don't believe speculating what a diesel can or can not do is necessary - actual experiences are available.

John Stobbs

[Kevin Horton]

Originally Posted by Deuskid

If you follow the link I posted earlier you could read the pilot's impression a portion of which is: <snip>

Thanks for posting the details. I followed the earlier link and it went to a forum post, but the pilot report wasn't there.

The performance comparisons between the Lycoming and Thielert powered 172 are muddied by the fact that the Lycoming powered one has a fixed pitch prop, and the Thierlert powered one has a constant speed prop. The engine on the Lycoming one does not turn at high rpm during take off and climb, so it is developing much less than the rated 160 hp.

This is an apples and oranges comparison that proves nothing, other than the fact that Thielert understands that they need to turn the engine at an rpm where it develops best power, rather than being happy with high torque at low rpm.

Originally Posted by Deuskid

I don't believe speculating what a diesel can or can not do is necessary - actual experiences are available.

I've driven turbo diesels in Europe - they are a wonderful engine. I'm not arguing otherwise. I am simply attempting to correct some misconceptions about torque vs power. Motor vehicle performance is determined by horsepower, not torque. Period. Anyone who wishes to arque otherwise should look up the normally accepted equations that define motor vehicle performance. You won't find torque in those equations - instead you will find power.

More info on aircraft performance.

[Deuskid]

Kevin -

I linked the wrong thread, sorry. Karolina had started 2 threads at the same time [one on her impressions and the other on the 'new' 2.0 Thielert [similar to this thread here]] and I grabbed the wrong one earlier. Here are both:

Pilot impressions:

http://canardaviationforum.dmt.net/s...ead.php?t=3447

Thielert 2.0 thread:

http://canardaviationforum.dmt.net/s...ead.php?t=3471

I agree with you on both counts: her comparison is somewhat apples to oranges [although both are C172s she flies] and torque in 'absolute' terms isn't the only variable to determine function.

I also recognize that [as in all issues] there are significant trade-offs when using a diesel.

I still believe that a small turbo'd diesel with current fuel metering systems would be ideal for a X-C aircraft [e.g. a -9] but less appealing for those seeking pure performance.

A diesel also allows for the uncertainty of fuel availability into the future.

All your points are well made and appreciated by me. I just don't want anyone to 'dismiss' diesels based upon your observations without 'rounding out' their understanding with the rest of the story.

Happy New Year!

John Stobbs

[mdredmond]

Another plus to diesel is that you can burn untaxed 'agricultural' diesel (legally), decreasing your fuel costs by several dollars an hour (44.4 cents per gallon in Texas, more or less in other states).

[rv6ejguy]

People confuse the torque and hp thing all the time. Torque is force, hp is work. Torque is irrelevant in moving objects or accelerating them. All vehicle specs being equal, the engine which produces the highest average hp within its working rpm range will accelerate the vehicle quicker. In the case of aircraft, it will climb faster and go faster.

Tests on the Thielert diesels indeed show inferior performance below 6-8000 feet compared to Lycoming powered airframes when using similar propellers on the DA42.

[catmandu]

Originally Posted by mdredmond

Another plus to diesel is that you can burn untaxed 'agricultural' diesel (legally), decreasing your fuel costs by several dollars an hour (44.4 cents per gallon in Texas, more or less in other states).

That was what I thought when we got ours, but the 'diesel' specification for Thielerts is not readily available in the US. Jet-A is the only thing we can put in the tanks.

[Pilottonny]

OK, The "9" is designed for 120 to 160 hp....... So, the Thielert with 135 hp would fit real nice !....... Now, the fact that it "only" has 135 hp is irrelevant! Above something like 8.000 ft. it wil put out more power than the 160 hp Lycoming, and therefore go faster ! (Turbo !!!) And........ a lot cheaper also! Take-of and see-level flight is no problem either because of the CS-prop!

Come on, anybody who is still thinking that an Avgas slurper is running cheaper than any Diesel is kidding himself! Have you compared the fuel prices ? Do you think Thielert sold more than 1.500 engines, so far, because all their customers are stupid?

And, more important, what about the world your kids are going to live in?

Regards, PilotTonny

[osxuser]

Originally Posted by Pilottonny

OK, The "9" is designed for 120 to 160 hp....... So, the Thielert with 135 hp would fit real nice !....... Now, the fact that it "only" has 135 hp is irrelevant! Above something like 8.000 ft. it wil put out more power than the 160 hp Lycoming, and therefore go faster ! (Turbo !!!) And........ a lot cheaper also! Take-of and see-level flight is no problem either because of the CS-prop!

Come on, anybody who is still thinking that an Avgas slurper is running cheaper than any Diesel is kidding himself! Have you compared the fuel prices ? Do you think Thielert sold more than 1.500 engines, so far, because all their customers are stupid?

And, more important, what about the world your kids are going to live in?

Regards, PilotTonny

Um, economics here in California doesn't make sense for the Diesel airplane engines. Jet-A is sometimes cheaper than avgas, sometimes not. But the effciency isn't that much better than the Lycoming, and certainly the initial purchase cost doesn't get made up easily if running a Lycoming LOP in cruise. Complexity of install is another issue... In Europe, it may be fine, here doesn't make sense.