View Full Version : Thielert Diesel
Donalk
3rd Apr 2009, 09:04
Am looking at the group purchase of a 2007 PA 28 (glass cockpit) with the Thielert 2.0 litre diesel. However the one nagging doubt is about the performance of the diesel both in terms of reliability and availability of parts. For example I rmember seeing something on the net about Thielerts rarely achieving full service life, issues with the fadec control and high pressure pump problems.
However the attraction is obvious - new technology, fuel costs etc.
Does anyone have any experience with these engines?
toolowtoofast
3rd Apr 2009, 09:10
suggest you look past the fuel costs to the hourly running costs, which include overhaul/maintennance and engine TBO. the thierlet is reasonably reliable, fadec is great and will run well with a total electrical failure for about 30 minutes when the battery goes flat. the 300hr gearbox overhauls could get a little tiresome.
personally, i'd be going for the io360 CSU for longevity and bulletproofness.
Donalk
3rd Apr 2009, 12:12
quite correct - obviously fixed costs remain the same and there is very little difference in maintenance costs over the existing lycoming that we run in the old aircraft due to a well negotiated agreement with our service provider.
I was'nt aware of the 300 hours gearbox check but will do some digging on that.
wsmempson
3rd Apr 2009, 12:25
Having seen Thielert only recently emerge from receivership, I'd be nervous of buying an aircraft fitted with an engine produced by a company which may well not survive this recession. All the previous consumers of these engines had their warrantees voided overnight, which can't have amused them much.
A have also heard from a North London flying school which operates a PA28 with a converted a-class engine that the revised w&b turns the a/c into a 2 person machine.
BackPacker
3rd Apr 2009, 12:35
I was'nt aware of the 300 hours gearbox check but will do some digging on that.
As I remember it wasn't a check but a full replacement every 300 hours. However, the costs of this replacement were included in the "Pro Rata" deal that Thielert made on the engine so this would not cost a dime but was included in the purchase price.
The Thielert bankruptcy voided this agreement and owners had to pay what Thielert called a "normal market price" for a gearbox change every 300 hours. This jacked up the price per hour for the engine alone with something like 20 euros.
I think Thielert has come to the conclusion that this scared off too many owners and have now substantially reduced the price of a gearbox change. But it will still cost you a fair bit of money.
I'm not too sure about the exact numbers, so don't quote me on that.
Justiciar
3rd Apr 2009, 14:29
No numbers i have seen stack up for the diesel unless you are doing huge hours, and that is without recent problems. Seems to me that there are some very practical issues with this configuration, e.g. decreased range and payload, lack of Jet A1 at the type of fields you are likely to fly to and the maintenance points already mentioned. Diesel had its attractions because of cheaper Jet A1 and uncertainty over the future of Avgas. The first has gone because of the duty hike in Europe on diesel for private flying; the latter is questionable as the demise of avgas has been predicted for years yet it is still around. If you believe that a long term replacement for avgas will eventually appear then what is the case for diesel?
Avtur is much easier to get in the far corners of the 3rd world - basically in quite a lot of places south of the Alps :) I think that's about it. That's actually a huge plus for touring, but only if no compromise exists elsewhere.
But not many Diamond diesel owners are flying very far nowadays; presumably out of concern for whether the engine(s) will make it, and to stretch out those 300hr periods.
englishal
3rd Apr 2009, 17:13
Oh I don't know....I did 600 nm in a Twin Star (in 4 hrs I might add) - that is Bournemouth to Prague or Bournemouth to Nice and used 50 USG of Jet fuel...;)
My own view is this....If you want to buy a NEW machine for fast IFR touring, then don't bother buying anything buring Avgas now....wait until you can get a decent jet burner and rent / beg / borrow /steal in the meantime. If you are after a "cheap runaround" then get an Avgas burner....
For me it'd be the new Twin Star, but in a few years. Safety of two engines, convienience of Jet fuel, FADEC, safety and comfort of the cabin and relatively fast at about 190 Kts.
Justiciar
3rd Apr 2009, 20:06
If you want to buy a NEW machine for fast IFR touring, then don't bother buying anything buring Avgas now....wait until you can get a decent jet burner and rent / beg / borrow /steal in the meantime.
Yes, but WHY??
Why not avgas? What is the disadvantage of a TB20, Cirrus Mooney? What is the fast long distance IFR pilot waiting for? Is there any evidence that diesel will take off in the next 5 to 10 years? Sure, if you plan to fly in Africa or the third world then lack of avgas is a problem, but most tourers they will not leave the western world! You might as well go for a mogas burner and travel very light, though availability of fuel is still a problem. At least you can run your rotax on avgas if necessary.
AN2 Driver
4th Apr 2009, 04:12
There seems to be other problems coming up for Diesel users.
http://thenog.org/docs/Exxonrefusesfuelda42.pdf
It appears that some powers that be seem to think Jet A1 is not for Diesel engines and refuse to supply Jet Fuel to Diesel equipped airplanes. Not sure how much influence Exxon has in Europe but in today's day and age actions by fuel suppliers like the ones above may well bring the Diesel vision to an abrupt and screeching halt. What if certification authorities jump on this bandwagon and demand true diesel fuel only? In this case, diesel equipped airplanes would become static displays faster than we can appreciate.
Rumours out West claim that Exxon seems to do this as a CYA action, others say it is an effort to get rid of unwanted competition and/or to keep (expensive) fuels en vogue, can't say, but I certainly do not like the idea of fuel suppliers refusing to supply any type of aircraft engine.
Best regards
AN2 Driver
toolowtoofast
4th Apr 2009, 04:41
you have to ask why Daimond is now offering the twin star with IO360 power
Croqueteer
4th Apr 2009, 07:26
:ok: I think all certified a/c should get rid of their diesels. Anyone got a cheap diesel for sale for my LAA aircaft?
BackPacker
4th Apr 2009, 10:42
It appears that some powers that be seem to think Jet A1 is not for Diesel engines and refuse to supply Jet Fuel to Diesel equipped airplanes.
I thought this was old news and Exxon would supply you Jet-A for your aircraft - assuming the POH specified Jet-A as an approved fuel of course - after signing some limitations of liability paperwork or so.
Be careful to separate "Diesel - the technology of self-ignition in piston engines" and "Diesel - the fuel that's mixed to certain specifications and goes into your tank" in the discussion. The Thielert engine is an engine that uses Alfred Diesels principle of self-ignition to ignite the fuel that goes into it. It's been adapted from an engine that would take automotive diesel fuel exclusively, into an engine that's very happy with Jet-A fuel.
englishal
4th Apr 2009, 10:43
Why aren't there more small tubines available? in the USA you can get C172 turboprop conversions...Why aren't manufacturers starting to move towards small turbines for small aircraft?
Much more reliable, prices will drop, old technology......I can't see any reason why not - other than the overage PPL couldn't fly one of course!
bjornhall
4th Apr 2009, 13:24
Why aren't there more small tubines available? in the USA you can get C172 turboprop conversions...Why aren't manufacturers starting to move towards small turbines for small aircraft?
Aren't turbines frightfully inefficient, in terms of fuel economy? My understanding is that turbines are good in all the ways you said, at the cost of significantly higher fuel flow. That fuel flow increase is partly offset in a high performance aircraft by the increased top speed you get for free with a turbine (due to the different ways power falls off with airspeed in turbines vs pistons), but the cost per hour can only go up.
Small turbines are around 1.5x less efficient than pistons. There is as yet no indication anybody has cracked this problem.
They also cost around 5x more to buy to start with.
It's a good technical solution for a narrow market.
Pilot DAR
5th Apr 2009, 11:33
In addition to the foregoing correct reasons,
To be permitted STC'd, or TC'd installation, an engine and it's combined propeller, must also be type certified (very expensive and time consuming). I am not aware of any TC'd turboprop smaller than the Allison at 300+ hp - far too much for small GA aircraft, in every way.
Pilot DAR
PlasticPilot
5th Apr 2009, 14:08
The recent financial problems at Thielert are not sounding very encouraging. Now that Diamond received certification for the new AustroEngine (for DA42 only for the time being), I would not be surprised if this engine would become available to a broader market.
Regarding operations, the Thielert engines are fine. I flew with in a DA40 and in a retrofitted C172. You have to relax and trust the FADEC. It does not manages the prop as we learn to, and it can be a bit surprising. That being said, single-lever operation is cool and makes procedures easier, and engine start are a non-event.
I am sure that 5 years from now the diesel situation will be different... the whole show has been set back by that long as a result of the Thielert debacle.The brave ones will not wait that long :)
horizon flyer
8th Apr 2009, 21:39
The Thielert 4 stroke 4 cylinder engine or any 4 stroke engine deisel is not a good design to drive a prop. To many harmonics and large power pulses.
That is why it needs a gear box and harmonic damper. Does not follow the KIS concept, Keep It Simple.
The SMA needs a very tough prop that can take it.
Externaly blown 2 strokes are far better, I think you need to wait for the Delta Hawk V4 160/180/200 hp or the Wilksch 4 cl 160hp no FADEC in either.
Far better design concepts.
The 8 cyl twin row 2 stroke radial Zoche would be the best and smoothest but it seems to be a scam to get EU grants and will never see the light of day, been in development for at least 20 years.
I would steer clear of Diamonds own, to heavy and all the problems of the Thielert.
I agree about Lycoming IO360 or O360, lots of valve and cam problems due
to poor oil flow to the valve gear and oil draining off the cam and rusting, if not flown regulary. 40 hours a month, so Lycoming say.
I agree about Lycoming IO360 or O360, lots of valve and cam problems due
to poor oil flow to the valve gear and oil draining off the cam and rusting, if not flown regulary. 40 hours a month, so Lycoming say.
Do you have a reference for the 40hrs/month?
I agree re the cam rusting, due to low usage, but 500hrs/year???? I think you mean 4hrs/month which if done as a 1hr flight each week would be perfectly OK to keep the engine in good nick.
astir 8
9th Apr 2009, 07:24
Hi Mr Horizon flyer
is there a signrificant difference between a 4 cylinder diesel driving a prop compared with a 4 cyl avgas engine?
Gearing requirements are surely related to the requirements for engine speed vs prop speed. The old Lycomings etc ran slowly enough for direct drive to the prop but have the attendant inefficiencies of a slow revving engine. I would have thought that any virtually any newer, lighter engine would have to run faster, while noise limtations etc need slower props. Hence if much post-Lycoming progress is to be made, speed reduction between engine and prop will be essential (gearbox, toothed belts, gerbils on treadmill, whatever)
Diesels have a higher compression ratio and this produces sharper torque pulses in the prop shaft. A prop has a complex behaviour, with all kinds of torsional-oscillatory stuff going on, and uneven power delivery complicates things.
Hence if much post-Lycoming progress is to be made, speed reduction between engine and prop will be essential (gearbox, toothed belts, gerbils on treadmill, whatever)
Not sure I agree. It is certainly true that the way to get more power out of a given displacement engine is to increase the rpm (because power = torque x rpm, and the torque is basically a function of piston area) which is why cars have gone that way. But there is no fundamental reason why a faster revving engine is more efficient; in fact the most efficient engine is probably a very slow revving single cylinder job with a huge flywheel :)
There is no reason I know of why the old Lycos cannot be every bit as fuel efficient as the most modern car engines - given the appropriate electronics.
And even then, FADEC only helps over a range of operation; for cruise flight at say 65% power, leaning an engine to the LOP point, and assuming the spark comes at the right time for the rpm etc, there is no improvement to be had through electronics.
The main design weakness of the Lycos is that they were designed to be lightweight, which results in little metal in places, which needs careful thermal management to avoid cracking etc. Everybody having a go at the aircraft engine business has had great problems even approaching the low weight of these engines.
astir 8
9th Apr 2009, 10:55
Ta
From PPrune "The message you have entered is too short" I hope it's long enough now!:ok:
Uncle_Jay
9th Apr 2009, 16:28
I call your attention to the Maule M7-420 series aircraft, just as an example... Must be a blast to fly. You can see them at controller.com.
Also compare the Piper Malibu - Meridian - Matrix.. same airframe, huge price difference with engine and pressurization choice.
Which brings up an interesting toipic re the Diamond TwinStar, it is not pressurized and costs as much as the Matrix.
it is not pressurized and costs as much as the Matrix
But it does have two engines, and the Matrix does not have a turbine engine.
The specific fuel consumption of a Rotax is actually very sligtly worst than your typical Lycon. The slower speed of the Lycon should give better volumetric efficiency and if that can be burnt reasonably well then the slower speed engine should be more efficient.
But - there are a lot of compromises in the Lycoming (and Continental) designs. After 60 years Lycoming have final started to use roller cam followers - one to deal with the poor geometry, two to deal with the corroision issue (partially). But at the top of the engine the valve gear still has poor geometry and you have to rely upon after market modifications to sort that out.
Realistically the designs have been heavily compromised to save weight. Adopting a smaller higher power engine would allow better design detailing without weight saving being everything.
Turbines, great dream but nothing more. I still want to fly a Maule M420 - but if you fill the tanks - it is a single seater! and gives no more than 4.5 hours endurance. Mind you with an hours fuel onboard on floats it would be terrifc fun. But practical? Never, oh and the engine costs over $350,000!
But - there are a lot of compromises in the Lycoming (and Continental) designs. After 60 years Lycoming have final started to use roller cam followers - one to deal with the poor geometry, two to deal with the corrosion issue (partially). But at the top of the engine the valve gear still has poor geometry and you have to rely upon after market modifications to sort that out.I thought that the roller idea had been dropped any references???
gasax
10th Apr 2009, 07:45
Try the front page of the lycoming Textron website.
gasex
Thanks for that - looks like they're going ahead with the roller design. I'd heard on the grape-vine that it was being shelved - just shows shouldn't listen to gossip. I would guess that this still won't resolve the camshaft rust problem unless they're proposing different materials.
Pilot DAR
10th Apr 2009, 10:52
Thread drift I know, but....
"Roller Rockers" were available by STC about 20 years ago. Then, and now, the idea is great. We tried a few sets, and were initially very pleased. The problem came in that the initial test and production samples were welded assemblies, which worked well. Subsequently, they changed to a different fabrication technique, and there were a number of cases of them breaking. All the shine quickly wore off the product (as it was obviously wanting in quality) but the concept was great. I would be very pleased to see a quality version available again.