New Deltahawk 2-Stroke Diesel V4 Airplane Engine Explained

[@LetsGoAviate]

X-24 Engine (Rolce Royce Vulture) Explained : kzbin.info/www/bejne/a4exn3WNbMyAorc WWII Aero V12 Engines Design Explained : kzbin.info/www/bejne/iqubp4ekoZKjd7c Adept V6 Makes Boxer 6 Obsolete?: kzbin.info/www/bejne/iH_cZ5eCaLqketU

[@russelllowry1061]

Just read an article about the engine from Nov. 2023. They have already raised the price to 110,000 for the engine. Millionaires used to buy jets, now they by diesels, and the billionaires by jets. The rest of us, fly southwest.

[@robjohnson8522]

That is firewall forward, not just the engine. I converted a 172 from a Conti O-300 to a lyc O-360. The cost for the firewall forward conversion was much higher than just the cost of then Lyc 0-360. BTW, I have owned 4 airplanes. I currently have a Cessna 182 with an Auto-Fuel STC. I am not even CLOSE to a millionaire. The payment is $350 per month and insurance is $750 per year.

[@sobhi05]

I refuse to use Southwest, period! lol

[@ssranon]

That's a deceptive statement. IIRC, the Kitplanes article said $110K includes engine, FWF kit, and propeller. Not the base engine.

[@Bakes-z4c]

The legacy engines, where development costs were sunk decades ago, are in no way cheap, check out the price

[@muskepticsometimes9133]

? serious Q: this engine is 110k brand new, about 200 HP. How much would continental or lycoming 200 hp engine sell for new?

[@gtr1952]

When I was a teenager and in collage, I was building and modifying engines for snowmobile racing. One I was proud of was an in-line 3 cylinder with 800cc displacement making 210 hp @ 3800 rpm, naturally aspirated. The engine was strong and reliable, the weak point was the clutch. They kept exploding. We couldn't find a material at the time to handle that power in that application!

[@dominicbakken]

I thought the problem was reliability of the crank seal and head gaskets CSC 2003 mankato state MNU

[@gtr1952]

That engine was a 1970ish Polaris 800cc triple, used for grass drag racing in the summer. That was popular then. The crank was 360'ed, and the transfer ports enlarged. It ran on alcohol and water injection. After ~200 experiments, we could control back pressure waves to act as a 'valving' with expansion pipes. We kept the CR to about 12:1 so it stayed together. It was fussy to start and keep running. We used a 3500rpm clutch, it would only semi-idel at 3000rpm. It wanted to run wide open. The whole thing weighed ~400lbs, all aluminum, except for parts of the track. The second time the clutch blew, it sent a big part of it ~150 feet in the air, and it came down in the crowd! Lucky no one was hurt!! That was the end of that!! It did win a dozen races though. There is a lot more to the story, my memory is a little fuzzy these days, I'll be 72 in a week or so. 8) --gary

[@twotrackjack2260]

Absolutely love your story, my dad was a big Polaris fan back then. He had a '74 Starfire factory drag sled with a triple in it when I was a kid. Even in factory trin, it just wanted to RUN! Loved the noise it made. The engine you built sounds like an absolute monster, would have loved to hear it run!

[@jiminycricket9877]

I’m calling bs on that power figure. Are you sure you didn’t mean 8300rpm?

[@gtr1952]

@@jiminycricket9877 You don't have to call BS, you could say "is that really what you meant"? You are correct, only we limited the RPM to under 7k. For grass drag racing we wanted max torque at lower RPM. So the stroke of the pistons were longer than the bore. That results in higher piston speed per RPM. At much over 7500 it would start to melt pistons, and/or weld the rings to the slots. We re-bored it 3 times because of that, the final displacement was closer to 900cc. We wanted the clutch to engage at 5500-6000 at first. But it got so much traction it would tear the chain-drive final off its mounts. That was all 1968-70 technology. We were inventing things as we went, and learned a lot!!. Thanks, Peace --gary

[@realvanman1]

The mechanically driven scavenging blower is not a supercharger, even though it is identical in construction. It's the application that makes the distinction. In this case it merely sweeps the cylinders clear of exhaust gasses (scavenging), in preparation for the compression stroke. It does not pressurize the cylinders before compression begins (supercharging). That is the role of the turbosupercharger (turbo).

[@Jessersadler]

in this motor, it is absolutely functioning as a supercharger (much less that's the actual name of the mechanical air pump). Unless it had some form of Valve timing adjustment, it will absolutely provide positive pressure in the cylinder.

[@Dave5843-d9m]

A “normal” two stroke also force feeds the upper cylinder. It’s done by air being compressed into the crankcase. A scavenge blower simply replicates that feature.

[@orthopraxis235]

@@Jessersadler This motor has no valves, it is a two stroke compression ignition engine. No valves, no valve train, no camshafts, no spark plugs. Two strokes are simpler design, less moving parts, less parts to fail, it takes less energy to run fewer parts. Read up on two strokes, if you don't understand them you as missing part of this discussion.

[@Jessersadler]

@@orthopraxis235 Valve = port. It's still timing. Timing on a 2 stroke is achieve with placement of the ports. Which just helps solidify the absurdity that this supercharger wouldn't be providing boost. (although there is the "power valve". . . which is exhaust timing. . . by a slide valve (doubtful these motors have it). . .) I comprehend engines, very well.

[@alanbrown397]

@@Jessersadler It's a turbocompound engine

[@matthill1727]

Well covered. Keep up the great videos. Love to have a DeltaHawk someday. I run nearly all my Turbo Diesels at +20% with an ECU reprogram. Hopefully DH's will do this too.

[@robertweekley5926]

Nothing to Program, since it isn't computer managed, but all mechanical, as he stated!

[@Bakes-z4c]

I like that the installation isn’t festooned with hoses. Big saving in routine maintenance

[@JimBronson]

This video is not really about the DeltaHawk per se but rather a rundown of the general principles involved in it's operation and how those contrast with other engines.

[@davidgierke7582]

Exactly. Besides, who designated 2700 rpm as the limit for aircraft propellers-as with much of your other "facts" the term over-generalization comes to mind. Do you understand that turbocharging and supercharging are one and the same, with many variations possible? Your comparison of two-stroke and four-stroke engine power-periods is flawed. A BS presentation (and engine).

[@PRH123]

​@@davidgierke7582 depends on the size of the prop of course, to avoid tips going supersonic... "2700" I suspect and if I remember correctly is mentioned because that is full power on an a/c like a C172... Yes, a turbocharger is properly called a turbo-supercharger... at some point in history people got lazy and shortened the word....

[@johnarnold893]

@@davidgierke7582 A 2-stroke diesel engine requires a supercharger to force air into the combustion chamber, the turbochargers are to increase the amount of air into the cylinders. Every Detroit diesel engine has a super charger or it won't run. They are considered NA unless they have exhaust powered turbo chargers on them. Over a certain RPM the propeller tips would go supersonic. 2700 is pretty much the norm for prop speed. This is a direct drive to the prop engine.

[@AwestrikeFearofGods]

...and not even a good one. 1:47 3:57 4:09 Stroke: One movement of the piston up (or down). Revolution: One rotation (i.e. 360 degrees) of the crankshaft (i.e. two strokes) Cycle: A complete loop of stages, repeating after a specific number of strokes (i.e. 2 or 4) I could go on.

[@orthopraxis235]

@@davidgierke7582 low prop rpm is associated with lower noise, better climbs. If you have a high rpm you need to have a short prop blade to avoid the non laminar flow of air that results as the prop blades approach the sound barrier. The blades will stall around that speed near the tip. The sweet spot for props is somewhere between 1600 and 2200 rpm. As with the other guy that dismissed torque as insignificant for aircraft engines. the more torque you have at a lower rpm is better for a mulitude of reasons for prop driven aircraft.

[@claytonpozzer]

Good video! Congratulations from brasil!

[@MrJord1994]

They had one of these on display at Oshkosh last year. Was really interesting looking at it and they answered a ton of my questions

[@williamstel9330]

Besides the 8V92 Detroit Diesels that we ran in our Pilot boats that along with the GMC blower also ran a turbo these engines developed 600hp. The big cargo ships the one I was shown was a 9 cylinder inline 2 stroke I believe that had an electric motor powered blower motor for starting and had 3 giant turbos for running on. All the ancillary systems such as oil pump , oil and water heaters , and water pump.

[@jlo13800]

I fill and run BRP XD-100 in my 475hp silver 8v92 2 stroke, works great!

[@ThePaulv12]

We are Detroit Diesel and EMD 2 strokes engines and we've had valves since about 1938 and we're still in widespread use. We also have Roots blowers and turbochargers on the same engine - and wet sumps. Heavens above! The 'supercharger' in this Deltahawk engine appears not to be a supercharger from your description. It appears to be a positive displacement scavenge pump very similar in operation to the blower on a Uniflow Diesel engine, though I can't find much info I must say. People mistakenly think the blower on a Detroit Diesel 2 stroke is a supercharger but it isn't. Detroit Diesel and EMD even categorize their blower only 2 strokes as N for Natural. I wonder if the Supercharger on this Deltahawk really is a supercharger since you did mention starting and idling for it? On turbocharged Detroit Diesel 2 strokes, the Roots blower is retained for starting and idling also causing me wonder about the role of their 'supercharger.' Until we know more I have to give them the benefit of the doubt that it is a supercharger but life burns one and mechanics like me get rather cynical about manufacturers' unsubstantiated claims. In an EMD turbochrged engine they use a centrifugal hybrid arrangement for the forced induction. For starting and idling the compressor acts as a crank driven blower and indeed does provide true supercharging in low RPM high load situations (unlike Detroit Diesels and EMD N engines) and as the RPM rises the the turbocharger turbine takes over driving the compressor via an overrun clutch. I would've thought for the amount of effort they've put into this Deltahawk engine they could've come up with perhaps a bit more of a compact and sophisticated forced induction/scavenge pump than off the shelf tech supercharger and what looks like an eBay turbo LOL. It seems like a 3/4 baked cake with the customer a full paying beta field tester. Time will tell.

[@JimBronson]

The DD 2 strokes cannot run without the blower as they blow in fresh air through the cylinder ports, and the pressure involved is barely above atmospheric. It is not supercharging because it doesn't provide boost pressure over ambient. It merely provides aspiration. This DeltaHawk engine seems (and sounds!) similar.

[@Arivera41682]

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[@jfess1911]

The Deltahawk uses a Lysholm screw-type supercharger housed in the "V" between the cylinder banks. It is visible in the cutaway of this Deltahawk video: kzbin.info/www/bejne/rHvOcmuMfpuEmrs

[@jfess1911]

Just in case KZbin won't allow my link, the Lysholm screw-type supercharger is housed between the cylinder bank (5:23 in this video). Lysholms have been around a long time and were used in the Mazda Millenia and are common in large commercial air compressors.

[@ThePaulv12]

@@jfess1911 I was just reading these comments about the Lysholm screw compressor and thought of Mazda's Miller Cycle V6.

[@michaelklepacz]

Where are you from and how do you know so much! fascinating walk through of this long awaited engine!

[@AndyMatrix]

Velocity V-Twin specs. Range at 65% Lycoming IO 320 1400 NM 185 ktas 75% Lycoming IO 360 1150 NM 200 ktas 75% Titan IO 370 1150 NM 205 ktas 75% Deltahawk Diesel 1900 NM 250+ ktas 75% UL520T 1150 NM 230+ ktas 75%

[@Sideways71]

THIS!

[@halrichard1969]

Thank you.

[@gendaminoru3195]

what is the Vne / Vmo for the V-twin?

[@demagescod9657]

@@Sideways71 No not this... it does not even pass the sniff test... I took the factory tour and even a demo flight in the V twin... It is an amazing aircraft,However even Velocity personnel told me the Deltahawk Diesel is too heavy and complicated to install. Furthermore, explain how the Deltahawk engines will be faster that the lighter and just as powerful UL520T's ?

[@Sideways71]

@@demagescod9657 It won't be lighter and won't be faster (180 hp vs 220 hp) compared UL520T. It will burn less fuel and that fuel costs less and is much more available world wide the 100LL. Remains to be seen, but it will likely be simpler to work on and require less maintenance. I don't blame anyone for being skeptical given the long history. There is still a lot to be proven still but to me this looks like it is becoming a reality and that is a good thing for GA.

[@FlyingNDriving]

This thing has been in a perpetual state of "next year" for the last 14+ years

[@nipponsuxs]

Not anymore, FAA certified in April 2023

[@PistonAvatarGuy]

@@nipponsuxs Still not in production.

[@fnorgen]

It's going to be the same old story. Bringing new general aviation motors to market is an absurdly expensive process due to the extreme demand for reliability testing, yet it's a pretty niche market with low production volumes, so price per unit needs to be really high just to stand a chance at covering the cost of development. But then no one ever actually uses the shiny new engine because nobody wants to pay a large premium for tech that inevitable still has some kinks to work out and nobody knows how to service yet. Sure the fuel costs would be lower, but those usually only makes up a modest fraction of the costs of running a small aeroplane anyway. So everyone just keeps feeding low-lead avgas to their boring old ubiquitous Lycoming. Innovation is hardly worth it when you just want to fly.

[@PRH123]

​@@fnorgentrue, although the military drone market changes that equation somewhat now... due to that the market for small aviation engines the market is probably larger than it's ever been before in the last 70 years...

[@halrichard1969]

@@PistonAvatarGuy I am guessing the price tag securing new buyer contracts or just drumming up customers for this engine may be one of their largest problems getting into production.

[@Dave5843-d9m]

The (sadly defunct) Zoche two stroke aero diesel was a radial format with two up and two down cylinders. All four con-rods were carried on one crank pin. There was zero primary and zero secondary vibration. It was available in 2.5 litre single row and 5.0 litre twin row formats. Rotating mass is reduced the crank simply has to counterbalance the con rod weights.

[@BenjaminRowe-hc7uo]

Unfortunately small aviation companies don't get treated the same as the the aviation giants and we all miss out on new,exciting opportunities and technologies these small companies could achieve, it's a sad state of affairs.

[@pogonator1]

The Austro AE330 4-Stroke Diesel Engine has also 180 Hp, uses less Jet A, is just 25kg heavier ( = 34 l Jet A) and coast around half the price. And yes, it is a complex engine, but it's also a very reliable engine. And with this price tag, you can afford plenty of working hours of a professional mechanic. If I really needed an easy to repair aircraft engine, I definitely would prefer an air cooled 4-stroke over a liquid-cooled 2-stroke engine. I do not know anyone who had engine trouble caused by a simple valve drive, but I know some people that an engine defect caused by a faulty water pump.

[@markraumer2336]

Great video. One thing you didn’t cover in detail was the decision to have it an inverted V layout. Other than access to injectors and plugs and perhaps the CG what benefits are there to this. I presume the oil savage system has top and bottom sumps to scavage from (sometimes flying upside down) and even sumps at the forward and back ends of engine. This would require a ballbearing type oil pickup “one way “ valve to avoid cavitation of the pump?

[@kennenandersen]

As a long time mechanic, my experience with inverted engines gives you the ability to swing a bigger prop. Diesel engines have good torque, so your prop could be larger.

[@skeetamacgyver1821]

That makes sense cheers.

[@qbi4614]

good point + a cooling system Not light at all

[@northernandyboy]

Great video thanks! The end fuel numbers on the diesel were a bit disappointing. Most of your old Continentals are burning 8 gallons an hour in 180 hp engines. Another issue with Diesels is they are usually TBR and not TBO so that is a new engine not a rebuild when your hours are up.

[@1Longranger]

How do compression ignition engines go when restarting at high altitude? No turbocharging boost means compression temperature would be low thus very hard to start.

[@tomconner5067]

The prop diameter governs the maximum rpm, due to tip velocity, the wider or larger the diameter or hub center to blade tip radius, the faster it is traveling at a given RPM, when the tip breaks the sound barrier a wood prop becomes a shower of toothpicks, a ducted shroud or canard augmented prop blades are used, less radial air dispersement occurs and drag from boundary layer tip vortices is reduced

[@floycewhite6991]

Thus more blades instead of higher RPM.

[@c.a.mcneil7599]

So what your saying the prop choice would limit the rpm? Got it.

[@101jtag]

ULPower 520 has same HP weighs 108 kgs iso 162kgs. It weighs 50% more ! I want to see how that compares including fuel and range, but mostly COG wise. It would require all new airframe designs.

[@pilotavery]

Yeah but this has more power at high altitude and it uses less than half the fuel for the same power

[@gadgetg9479]

When it sits dose it fill the heads up with oil and shorten the rods when you hit the key???

[@paulmaxwell8851]

An excellent video but you made one little error at 12:50. The piston moves slower at the bottom of its stroke, picks up speed part way up and then slows as it approaches top dead center. Your point regarding accelerating and decelerating mass still holds true, though.

[@LetsGoAviate]

Thanks, appreciated. It's actually correct, because as the piston moves down from TDC, the conrod goes sideways, shortening it (relatively speaking). This pulls the piston down additionally, accelerating it. Past mid-stroke, the conrod starts going upright again, conrod getting longer (relatively speaking), and with the piston going down, the lengthening conrod slows down the piston. Same thing on the way up.

[@robertrobinson3861]

@paulmaxwell8851 You are right about the piston 'loitering' at bottom of the bore. Because the big end is swung out to the side at the 90 degree crank position, the piston is then sitting a lot lower then half way down the cylinder (this is the cause of secondary imbalance/vibrations). With the crank turning at any particular speed, the piston spends more time in the lower length of travel than in the upper positions, and therefore travels at a lower average speed at the bottom.

[@Iflyagrasshopper]

Just a small detail but the 2 stroke doesn’t produce torque at 50% since the exhaust port is uncovered at about 60% of the stroke so so really it’s more like 35-40% which is still better than the 4 stroke.

[@LetsGoAviate]

Thanks, you are correct. Every second stroke creates torque, but as you said, not the whole stroke after combustion happens creates torque because of the exhaust stage overlap.

[@coreyfro]

But what if you are using a supercharger...as a valve...to close the intake during the power phase of the stroke... and only opening the intake...once the exhaust has closed? BOOM!

[@coreyfro]

I know this is what they are doing because you can't normally turbo charge a 2 stroke... You need something restricting the energy bleed between the inducer and the exducer. I guarantee you they are using the supercharger not just as a power adder but also as a valve to cut off intake.

[@LetsGoAviate]

Take a look at the video from Deltahawk's KZbin channel at 5:23. You think this is possible with the illustrated layout? It could restrict airflow but doesn't look like the supercharger is used as a valve. Let me know.

[@coreyfro]

@@LetsGoAviate it doesn't have a valve, it is the valve! A supercharger is a interval pump, so at times it is pushing air, at other times it is compressing in air. If you are clever, you can make it so that it does this at a different interval for each cylinder.

[@Swaggerlot]

Two stroke diesels have been around for years, but mainly in large locomotives. A refinement, not a giant leap forward.

[@WilhelmKarsten]

2-stroke Diesel engines have been used in aviation since the 1930s

@@WilhelmKarsten and even opposed piston ones

[@WilhelmKarsten]

@ The Jumo 205 was the most fuel efficient engine in the world in 1931.

[@yolo_burrito]

@Fairbanks-Morse has entered the chat.

[@orthopraxis235]

Were they this efficient? Did they have the other easily replaceable features that this one has? bottom line, we don't have any now, and if this does as intended it has many advantages, you would have to do a comparison or value spreadsheet to really see exactly how this might work for your application.

[@markhatch1267]

Is it possible to mitigate peak pressure, in an engine with a mechanical diesel pump, by altering the fuel pump cam lobe profile to delay some of the fuel delivery during the combustion event to spread out the combustion pressure curve, but still deliver all the fuel necessary for best power output?

[@grandyhynes1636]

Sounds like it will run on Amonia as well ??

[@xpeterson]

It would be really cool to see a head to head on this engine vs the Rotax 916 is. I know there's fundamental differences, but it seems like these 2 engines are going to be some of the prime choices for many people so comparisons are going to be inevitable. At a glace the Rotax produces 20 hp less while weighing 170 lbs less - might be enough of a difference to overlook some of the electrical wiring mess that comes with the Rotax.

[@robjohnson8522]

As I recall the Rotax has a reduction drive so it runs at like 5,000 rpm. So much lower TBO. I think it is like 500 hours

[@xpeterson]

@@robjohnson8522 2000 hr for the 912, 912is, 914, and 915 and they all have reduction drives

[@xpeterson]

@@robjohnson8522 the 912, 912is, and 914 all have that reduction drive and have a TBO of 2000 hrs. Don’t have official specs on the 916 but I would imagine it would follow suit

[@garyradtke3252]

2 stroke diesels have been around since the beginning of the compression engine. Detroit Diesel was famous for their 71 and 92 series and most if not all large ship engines are 2 stroke but as far as I know they all use exhaust valves and most are forced air intake. There are naturally aspirated but very low power. They all use recirculating oil systems. My point is this technology is mostly adopted from other systems but I agree that this should be a better choice for aircraft. The one thing I question is the inverted cylinders and the probability of oil pooling in the backside of the pistons and seeping through the rings when not running. I think this is why they have to hand rotate radial engines prior to start up and hand rotating a diesel with oil in the combustion chamber could be a dangerous situation.

[@Milosz_Ostrow]

Most Diesel engines require glow plugs and glow plugs need to be preheated for the engine to start. It is unlikely anything would happen with a cold engine being slowly rotated by hand.

[@bertpenney3526]

My suspicion is that there would be some sort of compression release on any engine that needs to be hand cranked prior to attempting a start. Not only does this make the hand cranking easier and safer, it would also alleviate the possibility of hydro locking the engine if any appreciable amount of oil had accumulated in the cylinder(s) since last run.

[@ndenise3460]

I know a couple airports that have a few nimbys trying to shut them down. If I ever win lotto max,expect I'll start doing circuits in a 185 at 7am

[@gps831coast]

People, chill out on pissing match. Interesting video. I was not aware of this engine. A engineer had a long night thinking.

[@WilhelmKarsten]

JUMO already proved the technology for aircraft applications

[@InquisitiveSearcher]

@@WilhelmKarsten : The JUMO was an Opposed Piston (OP) configuration with 2 crankshafts. The Deltahawk engine has only one crankshaft. There is a modern version of the OP engine called the "Gemini" engine, with only 3 cylinders but I don't know it's availability. The last I knew it was still an "experimental" engine with no plans to get certified.

[@WilhelmKarsten]

@@InquisitiveSearcher Jumo built 2-stroke Uniflow Diesel engines (Oechelhäuser Cycle) In 1,2,3 and 4 crankshaft configurations.

[@kurtdobson]

What is the brake specific fuel consumption?

[@Stellaknot]

Thanks for the video. Commenting for effect. Keep up the great work, clearly not thrown together on the fly

[@LetsGoAviate]

Thanks, appreciated

[@petesteirer]

That was great and very informative! Thanks

[@Kevin-vv6oe]

Interesting indeed. I still like opposed piston engines too . Don't see either replacing jets though.

[@surlyogre1476]

I think it's not intended to replace Gas Turbines, rather it is a small piston engine designed to burn Jet-A, which is available worldwide as opposed to High Octane AvGas which can be hard to find in some markets.

[@andrewday3206]

The opposed piston 2 stroke does not have cylinder heads so it radiates out less than the DeltaHawk design. If the opposed piston had ceramic cylinder liners there would be very little heat sent out through the block and even better efficiency.

[@eastindiaV]

The intake and exhaust are on the turbo, I think the super is in between, compressing the intake. The exhaust pipe can be used to create a motor jet Or just be used as an exhaust pipe. Transmission and propulsion system would go around the gear on front. So it's just a car motor, re arranged.

[@RealDougFields]

2 strokes do have exhaust valves sometimes. Detroit Diesels were some of the most popular. Full mechanical, compression ignition, and direct injected. H.O. versions were also turbo charged.

[@sailingcitrinesunset4065]

Supercharged & tutbo charged 2 stroke diesels have been used in buses, trucks, trains ships for decades, so it's no surprise to use smaller versions in aircraft running on Jet A1, like the Diamond DA2 has a diesel running on Jet A1

[@Condor1970]

Can it run on standard diesel fuel as well?

[@LetsGoAviate]

Yes

[@Jessersadler]

​@@LetsGoAviateif that's the case, the power output would be higher, as well as EGTs.

[@LetsGoAviate]

@@Jessersadler I can't think of much reason to use standard auto diesel though, other than perhaps emergencies where Jet A not available. Jet A is less than half the price of diesel in the USA and generally good availability.

[@Jessersadler]

@LetsGoAviate Jet A average today is 6.14 a gallon. diesel is around 4. Red diesel is even cheaper. . .Not to mention diesel will make more power, and have better lubrication. Seems like plenty of reason.

[@ElAnciano92071]

A lot of the principals mention in your interesting report were incorporated in the engines of the WWII era sub on which I was stationed in the early '60s. It was a 9 cylinder/18 piston achate cycle supercharged diesel. The upper and lower crankshefts were couipled together by what they called a vertical crankshaft. The supercharger caused the cross flow with fresh air displacing the exhaust. Ignition took place between the two pistons when the were at their closest (and the fuel was injected). When commisioned, it have 4 of these, but when I got there external streamlining had been added to the hull (Seee Guppy III) and one of the engines had been removed to make room for a fresh water still and other equipment I can't remember now. Nobody was worried about pollution then, and it was a filthy beast! ;)

[@andyharman3022]

That was a Fairbanks-Morse opposed-piston engine. Uniflow scavenging via a positive displacement compressor.

[@mikeskidmore6754]

Detroit Diesel two stroke Diesels have 4 exhaust valves at the Top of the head per cylinder

[@oscarkaminski9165]

Why 4 exhaust valves but not 1 large exhaust valve?

[@johannjohann6523]

excellent video! Thanks!

[@Flies2FLL]

A quick correction: A four stroke engine does NOT produce power during 25% of its cycle. The power stroke starts when the fuel is ignited and ends when the exhaust is allowed to leave the cylinder. The exhaust valve opens around 120 degrees beyond top dead center on most engines, since there is little to gain by keeping it closed and opening it early helps scavenge the cylinder. Thus, the effective length of the power stroke is around 120 degrees on an Otto cycle engine. This works out to about 16.7%, not 25%..... 👍

[@leonmusk1040]

or with an offset on the pistons and an atkinson cycle you can push that a little further but lowers the power to weight delivery and gains efficiency which will get you to nearly 22%

[@Flies2FLL]

@@leonmusk1040 I'd like to see where you get that 22% figure. Atkinsons are used on a lot of hybrids for efficiency reasons and they could care less about power. They gain efficiency due to the increased expansion ratio. This happens because the intake valve is held open longer, pushing some of the charge/air back into the intake manifold, effectively reducing volumetric efficiency. Since the exhaust valve opens later, the cycle runs closer to full expansion. Typically, diesel engines run around 30% more efficient than gasoline Otto cycle, so I have a hard time buying that 22% number.

[@SoulTouchMusic93]

@@Flies2FLL i believe toyota cracked 40% efficiency. they were bragging about something like 41% with dual injection which puts them in diesel teritory. another thing about otto is that you can have a 2 cam profile engine having both otto and miller so you have fewer pumping losses at part throttle operation.

[@Flies2FLL]

@@SoulTouchMusic93 I wasn't talking about efficiency, I was talking about duration of the combustion stroke. I'm not sure about Toyota's engine, but if they achieved that level you can bet it was during laboratory conditions.

[@WilhelmKarsten]

​@@Flies2FLLThe production Toyota Prius 1NZ-FE engine depending on the exact model ranges between 36.5% and a very impressive 40%. VW TDI engines that came out 30 years ago were already 43%. The 2-stroke Jumo 204 was 40% in 1930!!!

[@andrewwallenstein9575]

Another issue is it is almost certainly restricted to composite propellers because of crazy diesel power impulses and prop inertia. That doesnt seem that bad untill you fly through heavy rain, or hail, hit a bird, wet grass, picks up a rock, and turns to fluff

[@davewitter6565]

Does the engine loose horsepower with higher altitude are does the turbo compensate?

[@LetsGoAviate]

It should produce full power up to around 15,000 feet

[@derrelcarter9401]

Great Video. DH is also getting ready to release a 235 HP version of this engine. Which is what I am curently interested in. Higher HP V-6 versions are also on the way. Sounds like rotating assembly components of teh V6 will be interchangeble with its V4 brother?

[@LetsGoAviate]

They are really moving this forward. Looks like the higher HP V4 versions will be the same weight too. Great power to weight balance there.

[@stevehill4615]

Very interesting video, a couple of thoughts I had whilst watching was: it's spoken of as a diesel (compression ignition) engine ruunning on jet fuel , but could it be setup to use diesel to use in say gensets? also with the direct drive engine RPM is limited so an increase in torque (for power) is desirable so is the engine "undersquare" (longer stroke than bore size) to take advantage of "leverage" (and the slower speed longer stroke gives more "port" movement timie) and the other thing noticed was regarding the supercharger which on the animation looked to be a lobed Rootes type and also a lot of commentary about engine balance would an ecccentric vane Wade type (iirc) be usuable as not only a supergharger but as a form of balancer as well have any advantages?

[@LetsGoAviate]

Interestingly this engine is actually square as per the bore and stroke length displayed on their website. I'm not sure if the supercharger could be used to even-out the secondary imbalance as it would need to spin 2x crankshaft speed. I think that would would be unnecessary though, as the secondary vibrations in the V4 is small enough to basically "ignore". It would likely be smoother than the rocking couple secondary imbalance in a boxer 4.

[@floycewhite6991]

I'd certainly go undersquare if I were designing it for just that reason.

[@username-mk8gf]

Yes! 2 stroke engines are the future, namely, crossflow diesel with journal bearings because it's force induced 2 stroke engines. No valves, no scavenging loss, and no rebuilds, the only thing that would make it better is if it used expansion chambers to achieve resonance scavenging and used a lighter electric centrifugal blower for starting only, diesels have a narrow rpm band and are constantly WOT anyway, and idling is now a hate crime thanks to stop start.

[@markbrzezinski8889]

What happens if the oil seal to the turbo fails and the engine rpm runs aways? Can someone explain that please.

[@WilhelmKarsten]

Some Diesel engines have a safety device that closes the air intake to safely shut down in the case of a false fuel runaway event.

[@RulgertGhostalker]

Torque is a function of Displacement and BMEP .... BMEP is somewhat generally limited by the fuel in question....and a turbo makes more power by effectively increasing the displacement.

[@andrekemp5059]

Price and Availability stock?

[@robertweekley5926]

That Jet Fuel vs Diesel Freezing Point, suggests, only run Jet A1 on your Diesel Trucks in the Winter, would help! 😮

[@jimrobcoyle]

How will the NOX emissions be eliminated?

[@andrewday3206]

Zoche had a very promising air cooled, radial, 2 stroke diesel. From an engineering standpoint it was a winner but business issues kept it from market.

[@arihanagibbons4485]

Didn't the Germans use opposing piston diesel aircraft engines during the war? Hyper efficient and powerful. Looks like they reinvented the wheel and probably took so long to develope to get around licensing perhaps.

[@Jessersadler]

they're licensed. And yes Junkers had a opposed diesel, but they weren't reliable. Made the radials look reliable

[@radhikatommaso873]

Yes, it was the engine of the stuka, that can be seen in the museum of transport in Luzerne, Switzerland.

[@AustinCharles2112]

Yes. Achates has refined the design and actually teamed with Cummins to build opposed piston engines for next generation military vehicles.

[@Jessersadler]

@@AustinCharles2112 achates has been around for almost 20 years. it will go nowhere

[@AustinCharles2112]

@ Google Cummins Achates and see for yourself. They already built it 😊

[@WONMARK]

So how does an engine without cams or electronics time when to inject fuel? I'm assuming that am engine without valves wouldn't need cams unless there specific cams for the injectors. Thanks for the video.

[@WilhelmKarsten]

The injection pump is timed to the crankshaft

[@WONMARK]

Thanks...

[@phantomforester9337]

I thought I would throw in that one advantage of a direct-drive engine is that the propeller can serve as a flywheel--geared engines have to have a separate flywheel adding cost, complexity, and weight. There are practical limits to compression ratio--above a certain point, NOX starts to form in an endothermic reaction which robs power, creates noxious emissions, and reduces TBO by introducing acidic products with the H20 from fuel combustion. Diesel engines also require longer connecting rods, to increase piston dwell time at the to of the stroke, which adds weight with the rods, the larger counterweights needed to balance them. and the higher deck height required. (This is also a major reason why conversion of spark ignition engines to Diesel is problematic.)

[@chippyjohn1]

That's why so many direct drive engines still have flywheels. Instead of having dead mass, you can have a generator in place of a flywheel. Do you see a flywheel on Rotax? Diesels don;t require longer rod for dwell time, diesel actually ignites and expands quicker than petrol. Slightly longer rods are negligible on weight. Diesels dont have any higher rod ratios than petrol, the main advantage of a longer rod ratio though for a low revving engine is reduced thrust loading as diesels have far higher combustion pressure.

[@WilhelmKarsten]

BORE DIAMETER limits dwell time and rpm range. Bore diameters larger than 100mm reduces rpm and dwell time

[@WilhelmKarsten]

​@@chippyjohn1Any engine with less than 12 cylinders needs a flywheel. Not true, Diesel engines are Stratified Mode, Compression ignition. Dwell time is reduced because it is limited to After TDC... Otto Cycle engines can Rev higher because spark ignition can be Advanced, prior to TDC.

[@chippyjohn1]

@@WilhelmKarsten Not every engine needs a flywheel. A flywheel is for momentum, once an engine is running at high speed the flywheel has little purpose, why do you think race cars use lightened or no flywheels. If you didnt have a flywheel on your car everytime you release the clutch it would stall. Diesels also inject fuel well before TDC, every engine is different. Diesels experience far higher cylinder pressures meaning they need heavier components to cope, heavy components dont like high rpm. There are many factors why diesels aren't made to rev high, but nothing to do with not being able to advance injection timing.

[@phantomforester9337]

Perhaps--but what you say does not negate what I said--the way I learned it, Diesel combustion differs from SPICE combustion in having much less of a relative pressure spike, but the pressures are much higher overall and necessarily maintained for longer--that is one reason rpms are lower--the ignition is spread out--and also starts later in the stroke. There is less proportion of the stroke for ignition. The higher compression pressures required for Diesel ignition are maintained longer with a longer dwell,. I would think that a generator serving as a flywheel would have to be direst drive itself, unlike that in a car engine--but if it replaces a flywheel to allow geared drive, you still have the weight, cost, and maintenance of the drive gearing. Longer con rods may add negligible weight themselves--the big weight addition comes from the knock-on effect of a higher block height they require,. Thanks for your addition to the conversation.

[@mjyan3599]

We have a hybrid of the 2-stroke and 4-stroke, called Differential-stroke (D-cycle), which complete 4 strokes different in both displacements and periods per revolution. It has the pros of both, but no con of either. It weight between its hybrid parents, but more on the 2-stroke side. (see KZbin with D-cycle)

[@jeffreyfwagner]

Two stroke Diesels are NOT supercharged. The thing you are calling a supercharger is a "scavenging blower." It is necessary to provide air for combustion. I worked for some time for a company that makes 2 stroke Diesel engines.

[@LetsGoAviate]

This info comes from Deltahawk's website as well as several aviation news sites. They are calling it a twin-screw type supercharger.

[@floydreed9272]

Actually I remember the old Gimmy diesel that I worked on years ago and that engine was a 2 stroke with a super charger. And 1/4 mile racers used those super chargers on Himi engines.

[@bryce2249]

This engine uses a centrifugal turbosupercharger and a positive displacement air pump

[@Jessersadler]

Says twinscrew on website. There are plenty of people that have supercharged and turbocharged on the same engine. I will point out, in the video, stated that the supercharger isn't used after turbo kicks in is false. The supercharger is positive displacement, and sits downstream (closer to the intake), it's still going to be compressing the air, just will be compressing the compressed air from the turbo. Same idea as a compound turbo setup, except what would be the small turbo, is a supercharger in this case. **edit. A supercharger and scavenging blower are the same thing in this application.

[@Jessersadler]

Detroit 71 series was a 2 stroke OHV with a supercharger, and later models had both supercharger and turbo charger. In production from 1938-1995. They sound wicked.

[@ecoop20]

Great video on a new engine! I love seeing new, innovative ideas for GA. It feels like a lot of it, especially engines, hasn't changed much for decades. Speaking of which, I recently came across the Veloce aircraft (2, 4, and 6 seaters) and saw they recommend the AeroVolare 43T engine. Would love to get your opinion on it. On the airplanes too, but especially the engine. Thanks for your hard work!

[@Milosz_Ostrow]

Have you visited the AeroVolare Web site? The home page is rife with spelling and capitalization errors. Such lack of attention to detail may translate to lack of attention to detail in the design and workmanship of their engines. No thanks.

[@ridhobaihaqi144]

Diesel... which CN is needed? Is CN 51 enough? How about biodiesel?

[@radomirblazik]

So basically a Detroit Diesel screamin' Jimmy in a new package?

[@martinsaunders7925]

Ha ha ha, less the valves which made it more efficient. Now has extra porting to catch the rings. Screaming Jimmy must be 80 years +old if WW2 landing craft are factored in. Still the southern oceans do appear to be behind in technology.

[@michaelalbert8474]

I worked for many years in fire suppression. Detroit Diesels were frequently used for sprinklers systems fire pumps. That big engine started and hit full throttle in seconds was incredible.

[@radomirblazik]

Then there's the Junkers Jumo 205 opposed piston diesel engine... Just sayin'

[@radomirblazik]

@@brianb-p6586 Better to uniflow than to not-flow... I actually think that going with the side port exhaust is a bad idea.

[@rebekahfrench5747]

End of the day any alloy engine from a road vehicle with a turbo and reduction box would be lighter and more reliable in the long run..🤣🤣

[@tomconner5067]

The 2 stroke doesn’t necessarily rev higher, it just fires twice as many times as a four stroke at a given RPM, and therefore a 2 stroke at 3k RPM exhaust note sounds like a 4 stroke at 6k rpm

[@jlo13800]

Yes true, the 4 joke stroke has to rev higher to make the same power, they suck even in cars/trucks to. I hate the new ugly 4 joke outboards too!

[@Arivera41682]

Everyone has great points in this debate. But the point I make is that this video is well done and extremely informative. Besides the fact that he might have misnamed certain parts. HE DID AN EXTREMELY GOOD JOB ON THIS VID. APART FROM EXPLAINING THINGS THAT OUR COMMON BRETHREN NOT COMPREHEND.

[@LetsGoAviate]

Thanks so much. Please let me know what I misnamed so I don't repeat the mistake.

[@3970danny]

When it’s done, I will volunteer to be the first paying customer for a ride around the freedom factory!

[@Partimepeasant]

How about fuel jelling at low temperature ?

[@LetsGoAviate]

Discussed at 16:09. The engine has a fuel preheat system.

[@Partimepeasant]

@@LetsGoAviate Tank too?

[@LetsGoAviate]

@@Partimepeasant I assume that's part of the pre-heat system, but don't quote me.

[@Partimepeasant]

@@LetsGoAviate An engine stagnation is not a good way to fly.

[@LetsGoAviate]

@Partimepeasant Use Jet A fuel instead of pump diesel, problem sorted.

[@obdiah1]

6 v 71 Detroit diesel shortened 2 cylinders and turned upside down

[@andyharman3022]

No. Detroits have exhaust valves in the cylinder heads.

[@gendaminoru3195]

Has to be supercharged to scavenge with positive displacement for the 2 stroke port system. BUT, that's better than oiling cams and drag levers and pushrods and lifters. Zoche tried an air cooled radial design like this that did not work well over time. There is a V-6 for the 300-350hp market under cert testing.

[@mahyadnaadlaw3112]

It would be nice if there is a fadec version like the austro

[@peterlastrucci324]

Great presentation and the theories of the Deltahawk are promising but the proverbial eating of the cake has still to be proven in the field. Much prefer this to the electric offerings though.

[@timehmalzeuzkeh7618]

Why are the prices blurred, did some company get upset at you for sharing the average prices?

[@jimi_be]

I don't get it... compared to a Lycoming O-360, it produces the same HP but fuel consumption is higher: 10.8gal/hr vs about 8gph for the O-360, it's heavier than the O-260 by about 100lbs, and it is 2x the cost of an O-360. Who exactly is this Deltahawk engine for?

[@LetsGoAviate]

It only produces the same horsepower at sea level. The Deltahawk is turbocharged and will give 180hp at all altitudes, where the non-turbochrged O-360 will lose power with altitude, roughly 23% loss at 5,000ft DA.

[@floycewhite6991]

@@LetsGoAviate But.... the partial pressure of oxygen lowers with altitude. A second stage of supercharging is needed once the maximum air intake cannot provide enough oxygen to burn all the fuel.

[@LetsGoAviate]

​@@floycewhite6991 Correct, I should have said, it will provide full power up to around 15,000 feet.

[@gregjennings9442]

There are turbo normalized 360s, right? Need to do apples to apples.

[@ChristopheSmith]

Would this engine fit on a 1956 Cessna 172 ❓ Would one need a redrive on it ❓.

[@LetsGoAviate]

The engine is direct drive, no redrive needed. I don't know the official answer on that from Deltahawk. Physically I'm sure it will fit, but don't know if the standard cowl will still work and can be modified, or if will need a new cowl. But I think it might be too heavy. A Lycoming O-360 weights around 270-280lbs (which we know will be fine on the 1956 C172). The Deltahawk weighs 334 lbs dry though.

[@excellenceinanimation960]

Wish I could own one! I hope it’s is a success!

[@Maungateitei]

The only advantage is that it's running on cheap kero instead of expensive petrol and two stroke oil. This is standard practice in outboard motors for near a century in many parts of the world. You start the motor on petrol mix, and switch to kero when the outboards warmed up. Best thing is to use a piezovalve compressor assisted head fuel injection, like mercury, evinrude, tohatsu 2stroke outboards, resonant exhaust supercharging, and preheat your kero before feeding into the spray injector.

[@johnarnold893]

Avgas is becoming scarce and every airport has jet fuel.

[@handy335]

Very good! Thank you!

[@aaronfreeman5264]

It's Diffusion Ratio hat gives Efficiency, Compression could be variable.

[@ianboard544]

I want to see an aircraft version of the Achates engine.

[@floycewhite6991]

Junkers Jumo 205 flew across the Atlantic to Brazil in the mid-'30s. What? Did you think Saudi Aramco invented it?

[@ianboard544]

@@floycewhite6991 no I didnt think that. I mean a modern version

[@floycewhite6991]

@@ianboard544 Ah. Sort of like the military small-boat engines of that type. Except you'd want to mount it horizontally.

[@PeterNGloor]

what about propeller pitch control? I cannot believe the propeller is fixed pitch, which would be extremely inefficient.

[@nonyadamnbusiness9887]

If it's a valveless two stroke how can it be supercharged? I think the supercharger and turbocharger just function as a scavenge blower in this case.

[@winoseti]

emissions?

[@andrewsmart2949]

you showed loop scavenged petrol 2 stroke in your animation,many diesel 2 strokes do have exhaust valves such as the detroit diesel 2 strokes

[@orthopraxis235]

Here is some additional data on the Deltahawk engines. The cylindar sleeves are replaceable. So factor in the 100K price tag, but also factor in likley much lower costs and simpicity of replacing parts, also external oil pump, there are other features I don't recall (from merely studying the webiste of Deltahawk) that are time savers over the typical lycontisaurus type of engine. The engine seems very sound and as explained it looks like it can do what they say. Additionally, if you factor in the simplicity of part replacement, even cylinder replacement, with the sturdiness of a compression ignition (essentially a diesel) block, in something like an experimental category, if one has a repairman certificate s/he can replace these fairly easily replaceable parts themself. So there are a lot of variables to see how this new engine, if it runs as intended, could be an excellent value added acquisition to your air travel. People think in terms of price, sometimes costs, but here the value of this 100K engine may prove to make this a lower cost of operating. Then there is the potential fuel savings, availability of using Jet A fuel instead of 100LL. A lot depends also on the company and how well they handle this next phase. It isn't out yet in production in many aircraft so we have no real world data on what's true or not in the field. The company claims it is revolutionary, just wish they would hold off on that until it proves to be so. Maybe focus your energy on getting the production run successful . Their certification of the Deltahawk engine was a huge thing, not only in itself but represents that the company will do what it takes to get this moving along (and is willing to go get more money and can do so if need be ) so it looks like this company could get this produced as intended. Wait and see.

[@altair7001]

It already has taken way too much time. I think they will be overrun by other new piston-based designs, or by the new small turboprops presently coming out.

[@russelllowry1061]

What is the TBO. I will be a believer when one of these goes 2000 hours. It does look promising. The added weight of this engine is offset by the plane needing to carry 40 percent less fuel. Added weight on front mounted engines will have to be offset with more weight in the back, either ballast or heavier trim. Someone needs to design a plane around this specific engine.

[@LetsGoAviate]

Also, when comparing weight to other engines, keep in mind this engine is turbocharged, meaning it actually produces 180hp at all altitudes. Non-turbocharged engines outputs 180hp only at sea level density altitude, and power decreases as altitude increases.

[@halrichard1969]

@@LetsGoAviate That particular problem has been solved by more than one aircraft piston engine developer.

[@floycewhite6991]

Junkers Jumo 205 two-stroke opposed-piston diesel engine was used in passenger airliners in the 1930s. No doubt using kerosene instead of diesel could have been possible.

[@xanderunderwoods3363]

Can this be put in an automobile?

[@TheBlibo]

While this is a step in the right direction it cannot hold a candel to an opposed piston diesel which is almost perfect for an aero engine

[@jefftiller5035]

sounds like a small 4 cylinder version of a detroit diesel engine they have to use a supercharger to make this work and the turbo adds efficency detroits are usually very durable engines not exactly a new ideia just maybe a new ideia for aircraft .

[@ezequielsanuy8895]

Excelente idea es casi igual a un diesel detroit 2t diesel pero no necesita arbol de levas y valvula de escape en la cabeza. Que simplicidad.

[@alanbrown397]

Aeromotive Diesel 2 strokes were a "thing" back in airship days, but they were "rather large"

[@ndenise3460]

I don't know where you are but diesel in Canada we are good to minimum -40

[@tirebiter1680]

In the early 1960s SAAB said in their engines "every stroke is a power stroke"

[@petermokry8020]

Reminds me of the Rotax direct injection two stroke engines. They were lighter, simpler, and very efficient. The oil had to be injected separately from its own tank. Problem is that people would forget to add the oil from time to time, causing the engine to seize. This gave the engine a bad reputation and sadly the engine was cancelled.

[@jasonmajere2165]

Wouldn’t that be an A4 instead of a V4. Thought diesel have more torque from the longer stroke and longer throw of the crank. More off center you push the crank the more torque you can make for the same amount of effort.

[@LetsGoAviate]

Would an upside down i4 (inline 4) then be a !4? 😆 Lame joke aside, because of longer stroke yes, as well as higher compression ratio. It's to be noted the Deltahawk is actually a square engine (bore and stroke is the same).

[@jasonmajere2165]

@@LetsGoAviate kzbin.info/www/bejne/o4fWlYqvjr2XpbMsi=KLA_G3FEg4yHBmsS

[@jfess1911]

Diesel engines tend to benefit from long strokes more than gasoline engines, that is why long-stroke diesels are common. The combustion of diesel fuel is slower than that for gasoline, so a diesel tends to run at lower revolutions, and this again favors longer stroke engines ( at high rpms, longer stroke means higher pistons speeds and greater forces on connecting rods, etc). Another reason that diesels tend to have long strokes is related to the higher compression ratio. With a short-stroke diesel engine, the piston gets so close to the cylinder head that the fuel tends to impact the piston before combusting (newer injectors have reduced this problems). Even so, many diesel engines have a bowl-like depression in the piston for this reason. A smaller diameter piston also has a smaller area to seal with the piston rings, reducing blowby (a bigger issue at the higher pressures).

[@timduncan8450]

@Lets Go Aviate 5:24 you are wrong. Thx for the video of this interesting engine but crank drillings for lube oil delivery to bearings are obvious in the cross section at 5:30. There are oil jets but they are for piston cooling not lube. 😢 details matter.

[@LetsGoAviate]

Displays in black text at 5:05 that my illustration isn't accurate.

[@timduncan8450]

@@LetsGoAviate sorry I was as off by 20 seconds, edit made. However your response doesn’t imply you understand what I’m talking about? Your commentary indicates splash lube, which is wrong.

[@davidbaldwin1591]

16:02 At my FBO, in Chesterfiled VA , AVgas 100LL is $7.18 per gallon, JetA1 is $6.64 per gallon. I don't see litres, certainly not $0.53 per litre JetA or $6.75 per litre 100LL AvGas.

[@LetsGoAviate]

Probably a conversion mistake on my end, apologies. The $6.75 for Avgas is per gallon. Where I am, Jet A1 is nearly half the price of Avgas, for what it's worth.

[@armorer1984]

It's just a shame they are so darn expensive. Those of us in the expiramental market didn't need it to be certified. We wanted a reliable piston Jet-A engine, no need for the cost associated with certification. Because DH sunk so much cost in certification, many of us can't afford em in our expiramental aircraft.

[@apuwdm2]

Wonderful analysis.

[@LetsGoAviate]

Thank you

[@markbarber7839]

You made me think of the Detroit Diesel

[@Allan_aka_RocKITEman]

@LetsGoAviate >>> *_"...consider that this engine has already overcome perhaps the single biggest roadblock that any new Aviation engine faces..."_* Even before I heard the end of that statement I guessed it would be *THE F.A.A.* 🤭