Would the engine of Stellantis Group the TU3D Diesel be suitable for the DE?

[rki67]

The pespoken engine has a low HP but a good torque and do weight complete about 220lbs.

It's a lot of weight, indeed, but what must be done to implement such an Diesel engine into the Double Eagle?

Will the Airframe handle this weight?

This engine flies successsfully in the airframe of the Gazaile of Mr. Serge Penec, but Id like to see this rather simple and safe engine in the Double Eagle?!

Rgds Erkki

[rki67]

here a picture of the engine in mind.

[rv7charlie]

That's an extra 60 lbs, so almost 40% weight increase for the motor. And remember, torque is just force; HP is the work done. What's the actual HP? Online info is kinda fuzzy for that engine; sources say anywhere from 49 HP to over 75 HP (still marginal, with the extra weight).

[rki67]

The designer gives 53hp but a fuel consumtion of 6-7liters of diesel per hour. So for sure the engine is heavier, but you win with less fuel required to stay aloft for the same timne.

[Dan_]

Goggle machine AI responds:


The engine referred to as the TU3D is historically known as the PSA TUD3, a 1.4-liter (1,360 cc) naturally aspirated, indirect-injection diesel engine. It was developed by PSA Peugeot Citroën—a core founding pillar of today's Stellantis Group—and produced from 1988 until 1994.Historical Overview of the TUD3 (TU3D)Design & Architecture: The TUD3 was derived from the highly popular TU3 petrol engine family. It shared the same aluminum cylinder block but utilized stronger, reinforced wet liners to handle the higher compression and mechanical stresses of diesel combustion.Performance: It produced a modest 50 to 53 horsepower and roughly 82–84 Nm of torque, utilizing a mechanical injection pump supplied by Bosch or Lucas.Legacy and Issues: The engine was notoriously prone to early head gasket failures. Because of these cooling and structural vulnerabilities, PSA quickly phased it out in 1994 and replaced it with the larger, more reliable cast-iron block TUD5 (1.5L) engine. It was widely used in classic superminis like the Citroën AX, Peugeot 106, and the Rover Metro/100 series.

The original head gasket issues of the TUD3 were never permanently resolved within that engine design; instead, PSA engineered an entirely new iron-block replacement (the TUD5), and while the TUD3 saw pioneering use in French homebuilt aircraft like the Gaz'Aile 2, modern aviation conversions have largely moved away from it.Head Gasket Problem StatusThe Root Mechanical Cause: The TUD3 attempted to run a high-compression diesel cycle (22:1) on a lightweight cast-aluminum crankcase with wet cylinder liners carried over from the gasoline TU3. Under prolonged combustion heat and high cylinder pressures, differential expansion between the aluminum block, cylinder liners, and aluminum head led to uneven clamping force, warping, and premature gasket failure.The Production Fix: While upgraded multi-layer steel (MLS) replacement gaskets, reinforced studs, and careful head skimming mitigate the risk in surviving engines, PSA essentially solved the problem by replacing the TUD3 entirely with the TUD5 in 1994. The TUD5 shifted to a heavy-duty cast-iron monoblock design, completely eliminating the liner-seat movement and head gasket vulnerability.Aviation & Flying UseThe Pioneer: The TUD3 achieved notable fame in the European experimental and ULM (ultralight) world through designer Serge Pennec's Gaz'Aile 2. The Gaz'Aile was specifically designed around the automotive TUD3/Citroën AX engine because its all-aluminum construction made it uniquely lightweight for an automotive diesel (~53 hp, around 200–220 lbs fully dressed).Current Status in the Air: While early Gaz'Aile 2 airframes flew successfully on modified TUD3 engines, builders encountered thermal management challenges and the chronic head gasket vulnerability under the sustained 75%+ continuous power settings typical of cruise flight.The Modern Successors:TUD5 (1.5L): Many builders initially swapped to the iron-block TUD5 for bulletproof reliability, accepting a weight penalty of roughly 30–40 lbs.PSA DV6 (1.6 HDi): Today, almost all modern Gaz'Aile diesel builds use the aluminum-block common-rail PSA DV6 (1.6 HDi). It delivers vastly superior power (78–110 hp), far better power-to-weight ratios, and modern turbocharging at high cruise altitudes.

If you are actively planning an auto-conversion engine for an experimental homebuilt airframe, avoiding the TUD3 is a highly practical decision. Designing a firewall-forward package is a major undertaking, and starting with a platform prone to thermal warping under continuous load will add unnecessary stress.Because auto engines operate at wildly different duty cycles than aircraft—cars use peak power only for brief acceleration, while aircraft run at a grueling 75%+ continuous power for hours—your engine selection and layout choices are critical.The Realities of a Diesel Auto-ConversionIf your goal is to burn Jet-A1 or Diesel for global fuel availability and exceptional efficiency, three key modern alternatives outclass the old TUD3 while keeping the weight manageable:PSA / Stellantis DV6 (1.6 HDi): This is the gold standard for European light aircraft conversions. It is an all-aluminum block, common-rail turbo-diesel. In the Gaz'Aile 2 community, the DV6C or DV6D variants have completely replaced older options. Dressed for flight with a Propeller Speed Reduction Unit (PSRU) and cooling, it weighs around 108 kg (238 lbs) and comfortably yields 80 to 110 hp with a turbocharger that handles high altitudes beautifully.Volkswagen 1.9 or 2.0 TDI: Incredibly robust and backed by several commercial conversion companies over the years. The iron-block variants are heavier than the PSA DV6, but their industrial-grade bottom ends handle continuous high boost effortlessly.Smart Car 0.8L OMD (Three-Cylinder Diesel): If you are building a very light, low-drag single-seater or an ultra-efficient motorglider that only needs 45–50 hp, this lightweight Mercedes-engineered Mercedes-Benz OM660 engine is a popular micro-diesel choice.Core Engineering Hurdles You Must SolveWhen converting any automotive engine for experimental flight, the engine block is only a small fraction of the battle. Your build log will largely focus on solving three critical integration challenges:1. Propeller Speed Reduction Unit (PSRU) & Torsional VibrationAutomotive diesels achieve efficiency and power at higher RPM ranges (3,600 to 4,000+ RPM). Propeller tips lose efficiency and become dangerously loud as they approach the speed of sound, limiting optimal prop speeds to 2,300–2,700 RPM.You will need a spur-gear gearbox or a multi-V-belt drive system (typically a 1.4:1 to 1.8:1 reduction ratio) to match the engine's sweet spot to the propeller.The Killer Factor: Diesel engines produce brutal torsional vibration spikes from high-compression power strokes. Without a high-quality rubber torsional dampener (like a Centaflex coupling) between the crankshaft and the PSRU, the pulsing forces will destroy gears, shafts, or your propeller.2. Thermal Management & Catastrophic RedundancyUnlike air-cooled aircraft engines that shed heat via cooling fins, an auto conversion relies entirely on a water jacket, radiator, and liquid coolant.No Room for Air Bubbles: You must design a self-bleeding cooling system with a robust header tank. If an air pocket gets trapped in an aluminum cylinder head under a 75% flight load, it will cause instant local boiling and warp the head—recreating the exact failure mode you are looking to avoid.Weight Penalties: Your weight calculations must include the weight of the radiators, hoses, brackets, and several liters of coolant.3. Stripping the ECU "Ghost" CodesModern diesel engines rely heavily on an Engine Control Unit (ECU) tied to an array of automotive inputs (ABS sensors, airbags, automatic transmissions, and emissions equipment).For aviation, you must either flash the factory ECU to run in a standalone "limp-free" marine/industrial mode, or map a specialized aftermarket diesel ECU.Systems must be completely stripped of any logic that automatically cuts engine power if an emissions sensor fails.

[rki67]

For sure the Smart 880OM would be a perfect engine, but the main issue is to be able to lay the hands on two items, the modified ECU with its required harness and second the PSRU, which is difficult to get .

On the other hand, the TU3D doesn't need an ECU, its purely mechanical, and the PSRU items are available troughout the network of the Gazaile.

For sure it's not a hotrod, the pure Diesel engine, but in the Gazaile it helps to achieve some more than modest performances.

So for the Double Eagle, this would mean a rather inexpensive engine to lay the hands on, and even cheaper to operate.

Even with a small fuel tank, you'll be able to fly around the whole day.

[Dan_]

AI: 🤖


For an experimental aircraft conversion using a Propeller Speed Reduction Unit (PSRU) where weight is the critical constraint, the Kubota D902 (0.9L 3-cylinder) equipped with an aftermarket turbo setup is the primary candidate, with the vintage Daihatsu CL-10/CL-11 (1.0L 3-cylinder Turbo) serving as the lightest factory automotive alternative.
Kubota Engine Division +2
The automotive diesels mentioned earlier (VW 1.6/1.9 TD or Kubota 4-cylinder V2003) weigh between 280 to 400+ lbs bare. Once you factor in cooling fluid, an intercooler, an exhaust manifold, and a PSRU, the aircraft becomes excessively nose-heavy.
Van's Air Force +1
Evaluating the lightest setups providing at least 50 hp while maintaining a mechanical injection pump yields the following options:
1. Kubota D902 with Aftermarket Turbo (The Modern Light-Aviation Standard)

    Dry Engine Weight: ~159–165 lbs (72–75 kg) bare.
    Kubota Engine America +1
    Displacement & Layout: 898 cc, Inline-3, indirect mechanical injection.
    Kubota Engine Division
    Injection System: Mechanical inline cassette pump with an all-speed mechanical governor.
    Kubota Engine Division
    Power Output: Naturally aspirated, it produces ~25 hp. However, small tractor and turf vehicle tuners routinely fit small turbos (like an IHI RHB31 or Garrett GT12) at 10–14 psi boost, which pushes the D902 to 50–58 hp at 3,400–3,600 RPM.
    Kubota Engine Division +1
    Why it fits aviation: Because it weighs under 170 lbs bare, the total firewall-forward package (engine, mini turbo, coolant, PSRU) sits around 200–215 lbs, which is well within the envelope for light-sport (LSA) and experimental experimental designs.

2. Daihatsu 1.0L Turbo Diesel (Engine Code: CL-10 / CL-11)

    Dry Engine Weight: ~185 lbs (84 kg).
    Displacement & Layout: 993 cc, Inline-3, OHC.
    Injection System: Fully mechanical Bosch VE-type distributor pump
    .
    Power Output: 50 hp (37 kW) at 4,800 RPM stock (with 91 Nm of torque). With slight fueling and boost adjustments, it produces 55–60 hp.
    Why it fits aviation: This engine powered the mid-1980s to early-1990s Daihatsu Charade and was built around a cast block with an aluminum cylinder head. Because it is an automotive engine, it revs up to 4,500–5,000 RPM, allowing a PSRU (roughly a 2.0:1 to 2.2:1 belt or gear ratio) to deliver broad, smooth propeller thrust. The primary hurdle is availability; they must typically be imported from Europe or Japan.
    Car Folio +2

Critical Weight & Engineering Comparison
Engine Platform Cylinders Bare Weight Est. Output with Turbo Flyweight / PSRU Viability
Kubota D902 + Turbo 3-cyl (0.9L) ~165 lbs (75 kg) 50–55 HP Highest. Compact, readily available parts, widely documented conversions.
Daihatsu CL-10 Turbo 3-cyl (1.0L) ~185 lbs (84 kg) 50–60 HP High. Built for higher RPM automotive duties, but difficult to source.
VW 1.6L TD (AAZ/JR) 4-cyl (1.6L) ~285 lbs (129 kg) 70–80 HP Low. Too heavy for low-wing / light experimental balance.
Crucial Engineering Warning for Diesel Aircraft Conversions

    Torsional Vibration: Diesels operate at exceptionally high compression ratios (21:1 to 23:1). The firing pulses of a high-compression 3-cylinder engine create severe torsional harmonics that will destroy aluminum PSRU gearboxes or snap propeller shafts if not isolated. A robust torsional vibration damper / centrifugal elastomeric coupling (such as a Centaflex coupling) between the flywheel and the reduction drive input is non-negotiable.

[rki67]

 Has the Kubota flown?

[Dan_]

AI:

No, there is no documented record of a turbocharged Kubota D902 setup successfully flying an experimental aircraft.
While the concept of taking a small, lightweight industrial diesel like the Kubota D902, adding an aftermarket mini-turbo (such as an IHI RHB31) to step it up into the 50–55 hp range, and pairing it with a PSRU is heavily discussed across experimental aviation forums and groups, it remains entirely in the bench-testing and "long-term project" phase. [1, 2]
## The Current Reality of the Project

*
* Theoretical Viability: On paper, the numbers are highly attractive for weight-critical ultralights or light-sport aircraft. A bare engine weight of roughly 159 lbs keeps the overall firewall-forward package (including the turbo, PSRU, and liquid cooling) right near the 200–215 lbs threshold—making it one of the few diesel configurations that won't make a light airframe dangerously nose-heavy.
* The Engineering Hurdles: The primary reason no one has logged successful flight hours on this exact setup comes down to the grueling physics of turning an industrial block into an aero-engine. Builders who have attempted small-displacement diesel conversions routinely hit dead ends trying to design a reliable Propeller Speed Reduction Unit (PSRU) that can withstand the intense, destructive torsional vibrations (power pulses) inherent to a high-compression, 3-cylinder diesel. [1]
* Factory Alternatives Overlap: Interestingly, Kubota eventually introduced a factory-turbocharged version, the D902-T (and later the electronically controlled D902-K). However, for industrial emissions compliance, the factory clips the output to just under 25 hp, leaving builders stuck with the complex task of aftermarket mechanical fuel tuning and high-boost tailoring if they want to see a true 50+ hp aviation powerplant. [1, 3, 4]
*

As it stands, anyone pursuing the aftermarket turbo D902 route is still pioneering true "test-stand" experimental territory. [1, 2]
------------------------------
Primary Sources Referenced:

*
* For general specifications and factory dimensions of the 0.9L displacement engine, see the [Kubota Engine Division D902 Page](https://engine.kubota.com/products/detail?id=11&ln=en).
* For details on factory-turbocharged power limits under 25 hp, check the [Kubota D902-T Overview on YouTube]( ).
* For documentation regarding builders aiming for 55–60 hp at 3,200–3,600 RPM using an aftermarket turbo for flight applications (like gyrocopters), read the community build threads on the [Rotary Forum](https://www.rotaryforum.com/threads/kubota-diesel-a-long-term-project.47772/).
* For discussions surrounding tractor engine conversions, light aviation standards, and the gaps between test benches and actual flight, refer to the experimental group breakdowns on [Facebook Experimental Aviation Discussions](https://www.facebook.com/groups/7189845431073689/posts/28204513159180277/).
*