The Desmo Engine: A Review of Its Strengths and Weaknesses

In the world of high-performance engines, the desmodromic engine has earned a reputation for its unique sound and characteristics. But what makes this type of engine tick? And is it suitable for road cars or limited to super bikes?

One of the key features of a desmo engine is its use of rocker arms to pull up the valves. This design eliminates the need for springs, which reduces the force required to close the valve. However, as the rocker arm slides back and forth, it creates a slapping sound that can be quite unpleasant. Imagine a thousand mortars hitting a pestle - it's not exactly music to the ears.

The Ducati 900SS is one of the most well-known desmo engines, with four cylinders and less than 250 horsepower. While this makes it suitable for super bikes, it may not be enough power for everyday driving. But even in these smaller engines, the slapping sound can be a problem. And as engine size increases, so does the noise level.

The slappy valve is a character that loves getting spanked. In reality, the desmo engine's unique design creates stress on the valve seat and cylinder head, which can weaken the metal over time. The forced closing of the valve also creates friction between the cam and rocker arm, which can lead to premature wear and tear.

Maintenance on a desmo engine is more frequent than most valve trains due to its unique design. Super bike engines are already driven less than car engines, with an average of 3,000 miles per year compared to 12,000 miles for the average car. This means that desmo engines are subjected to less wear and tear, but still require regular maintenance.

Frigging costs is also a major issue with desmo engines. The added components and complexity make it more expensive to build and maintain than other types of engines. A desmodronic hatchback would be incredibly expensive due to these additional costs.

While the desmo engine may not be suitable for everyday driving, its unique sound and characteristics make it a thrill to hear on a super bike. But with its limitations and maintenance requirements, it's clear that this type of engine is best suited for enthusiasts who can appreciate its quirks and flaws.

In memory of lost innovations

As we reflect on the desmo engine's legacy, we remember its unique contributions to the world of high-performance engines. Though no longer with us due to safety regulations, their up and down design will live on in our hearts forever. Here is a special performance from Epidemic Sound, please welcome Nolan J. Sykes.

(Piano music plays softly)

Show your respect for pop-up headlights by going to donutmedia.com. It's got a beautiful airbrush design and honestly, it's hard to put a price on such a legacy. But if I were to guess, they're available for $29.98 - which is in fact way less than $30.

(Brief piano music continues)

Bless up and down - Thank you guys so much for watching this episode of B2B. Hey, we did another bike video maybe next year? Maybe that's what's on the horizon? So if you could, click that subscribe button. Click that like button if you liked this video. Leave a comment down below, let me know what you think.

If you want to see more content, go click the join button. You'll be in the donut underground - it's all a bunch of fun, extra stuff behind the scenes you get to see. Follow us on Instagram at @donutmedia and on TikTok, Tik Tok, Tik Tok, follow me on TikTok, Silence of the Lambda.

Until next week, bye for now.

WEBVTTKind: captionsLanguage: en- One of the highestrevving production carson the road today is the beloved S2000,peaking at 9,000 RPM.But 9,000 RPM, those arefrigging rookie numberscompared to what a Ducati can do.I'm talking 12, 15, even 17,000 RPM's.And my Italian engineering buds,they can pull that off withtechnology from the 1950s.So I want to know how is Ducatimaking such high revving engineswith tech older than a consumer microwave?The answer lies with thedesmodromic valve system,and it is an ingenious way to pumpthose rookie rev numbers up.So today, we're goingto take a closer lookat the secret Ducati sauce that is desmo.Figure out how it worksand more importantly,see why we don't see car manufacturersusing this tech in their engine.I bet after this video,a lot of you're going to start GooglingDucati v4 engine swapsinto your Honda Civic.It could happen, I've seen weirder things.(upbeat music)Thanks to Morning Brew forsponsoring today's video.I used to wake up every morningand spend seemingly hours on the same appsand news sites just toget ready for the day.But thanks to Morning Brew,I only need five minutes.Scrolling through social media, mindless.(crash)(grunting)Watching dense morning television, boring.(smashing)Who even reads a newspaper anymore?Get out of here, paper cuts.(bat hits the ground)(torch firing up)This right here is all you need.Morning Brew is a completelyfree daily newslettersent directly to your emailthat'll get you up to dateon the day's importantnews in just five minutes.Kick off the day with stimulatingtopics that matter to youlike tech, business and finance.I checked out this article about Google'ssister, company Waymo,bringing their robotic taxiservice to San Francisco.And let's just say itisn't going that smoothly.They should have hired me.Find out for yourself.It only takes 15 seconds to subscribeand like I said, it's completely free.So start saving time anddo more with your moneyby clicking the link belowto subscribe to Morning Brew.Now let's get back to the show.The desmodromic valve systemor desmo if you're coolis a valve system where the camsboth open and close the valves.And before we get intowhy you'd want this,let's talk about the moretraditional valve train setupmost commonly used in engines today.Now in a conventionalengine, as the cams rotate,they push open the valves via a systemof push rods or rockers or bucket lifters.This is how air gets in andexhaust gets out of the engine.The cam lobes push the valves openfor a precise amount of and distanceand then as the cam lobe rotates away,the spring closes the valve again.This spring is putting constant pressureon the valve to hold it closeand that's known as seat pressure.And the valve train hasto overcome that pressurein order to open the valve.So as the cam spins faster,the valve opens faster,but it will alwaysclose at the same speed.The spring rate of a standardvalve spring is constant.If the cams spin too fast,the cam could start pushingthe valve open againbefore the spring has had time to close.This is called valve floatand there are a number of problemsthat could come from valve float.First off, if your valve is not sealingyour cylinder properly,you could be losingcompression during combustion,and that could stop yourengine from making power.Second off, it couldmean that unburnt fuelis getting into exhaust and ignitingcausing backfiring or damageto your catalytic converter.While that last one doessound pretty, pretty cool,if you have an interference engine,you're not going tolike what happens next.An interference engine isan engine that is designedto have the valves extend past the pointwhere the piston wouldbe at top dead center.That normally is not aproblem because the valveis always closed when the piston is up.But if the valve is closing too slowly,the piston will reach top dead centerbefore the valve has moved.And your valve and pistonare going to get into a little fist fight.And when a valve and apiston get in a fist fight,you know who wins?Your mechanic.He loves when those two fight.He loves unhealthy relationships.He can fix moving metal, buthe can't fix his broken heart.Now, a lot of people fix thisproblem with stiffer springs,springs that can close the valve faster.But the problem withthat is now the enginehas to work harder to overcomethe stiffness of those springs.The valve seat pressure is higher.When the force being put intothe engine from combustioncan't overcome the force of the spring,the revs will stop increasing.So springs need to bestiff enough to close,but soft enough to open.With modern springs, most car enginescan't rev higher than 7,500 RPM.And there are some fancy solutionslike progressive springsor even beehive springs,but even the highest revving supercarsare only really making about 11,000 RPM.So now we understand the problem.So let's look at the solution.That Italian solution.Solution-ay.(upbeat music)Ducati's desmo engine doesn't use springsso there's no tension in the valve train.Instead it uses a cam shaftthat has two lobes for every valve.One to push the valve open like normal,and the other pushes onan inverted rocker armthat pulls the valve back up.For this to work, a valvewith a special collarand grooves need to beused called a poppet valve.So as the engine revs up,the valves opening and closing speedwill increase at the same time.So now there's no spring forcefor the engine to overcome.There's no valve floatand the valves all sealexactly when they're supposed to.And while Ducati didn't comeup with this technology,they did start using it as early as 1956and have had desmodromic valveson almost all of theirflagship bikes ever since.If you want to know more about that bike,click that link right there.That was the first B2B a guyvery similar looking to me didit wasn't me though, it was weird.He wasn't as good as I am.Let me know how he is now.It's easy to love desmo enginesfor the mechanical marvel that they are,but if that doesn't get yougoing, fricking sound will.Since a desmodromic valve systemmechanically forces the valves closed,the sound made by theengine has a roughness to itthat is like no other engine.Unlike in an engine with valve springs,the valves in a desmo engineare being slammed closedwith no elasticy.The sound you're hearingis the metal of the valvehitting the metal of the valve seat,hundreds and hundreds of times a second.Ducati still uses the desmodromic systemin their engines today andit was an ingenious wayaround the internal forcescreated by valve springs.But just because you're on top,doesn't mean you're going to stay there.And in the 90's, valve spring enginesfrom Yamaha, Honda and Suzukiall reached higher RPMswith the introductionof lighter materials.See the valve springengines have to overcomethe force of the spring,but the valve itself islighter than a poppet valve,therefore it has less inertia.And since the desmo engineneeds an extra rocker and more cam lobes,the whole valve trainhas more mass to move.So eventually, materials got light enoughthat the desmodromic valve trainwasn't any more efficientthan a standard one.The playing field leveled out.But Ducati decided to stickwith their desmo enginebecause it's what they know best,desmo is Ducati.(chair wheels rolling)The first Ducati desmo systemwas in the 1956 125GP bike.And at the time Ducati,they were using traditional coil springsin their valve train.But the metallurgy of the1950s plus the rev limitthat the bike could achievewas enough to weakenand fracture those springs.So to the desmo system they went.And as a result, the single cylinder 125GPcould rep to 13,000 RPM.But don't think just becauseDucati nailed it in the 50'sthat the desmo systemdidn't evolve, oh no.An early version of the desmo systemknown as the Trailbero used three cams,an intake cam, an exhaustcam and a central camto close the two.It was kind of likehaving a dual overhead camand a single overheadcam at the same time.As time went on, Ducatirefined the design.By 1987, the Ducati 851 wasusing four valves per cylinderon an L twin, meaning that itwould have needed six cams.And instead of using six cams,Ducati had started touse L-shape rocker armsthat made contact with cam loadson either side of the same cam.They also moved to chain-driven timingas the cams were now separatedto either side of the V configuration.From the gears to chains to belts.Those are both three itemsthat my parents usedto discipline me with.In modern times,Ducati is even experimentingwith springs again.The Desmosedici Stradaleuses keeper springsattached to the rockers tohelp them return to position.These springs help reducewear in the valve trainand lengthen the amount of timebetween valve service intervals.Buy hey, Ducati didn'trest on their laurelsand just twiddle their thumbs.Oh no, they kept improvingthe desmo system.And just this past year in Moto GP,they set a top speedrecord of 225.5 miles peron a Desmosedici GP21.Think I can go 225 on this thing?Let's see.(engine revving)Close, I was close.My mom said don't do it.That's the only reason why I stopped.But using desmo in amotorcycle engine is one thing.What about taking this type of valve techand putting it into a car engine?Do we need to enter intothe Donut multi-verse?Theorize a vehicle and engine combo?Talk about what might've been?Answer the big what-ifs?No, no, we don't.That's because the desmodromic enginesin the auto world are already a thing.In 1954, Mercedes won their first F1 racewith a desmodromic engine.The W-196 had a 2.5 liter straight 8making 340 horsepower at 10,000 RPM.And to say this thing soundedbrutal is an understatement.It makes John Wick look like John Mulaney.So he did all of thisbecause his dog got killed?What a joker.(audience laughing)If you want to see more John Mulaney bits,leave a comment down below.And this sound, as awesome as it is,is probably the biggestreason why you don't seefour cylinder desmos inyour everyday hatchback.One of the hardest workingdepartments at any automakeris a department of noise,vibration and harshness, NVH.It's their job to refineand meter all the soundsthat a car makes from both inside and out.They study the harmonics of a carand can either refine acar sound in a sports car,or it could totally goaway in an economy car.If you ever want to seehow much the NVH departmentcan change a car's sound,just know that the engine in a Lotus Exigeis also in a 2012 RAV4.And one of the places thatengines create the most noiseis in the valve train.With a modern enginevalve noise is lessenedwith soft, progressivesprings and hydraulic tappets.These reduce the force in thevalve as it comes to a close.But in a desmo system,as we mentioned earlier,the metal is slapping away at each other.While the sound of a thousandmortars hitting a pestlemight be fun in a super bike,that doesn't really flyin the automotive world,at least on the streets.Ducati's largest desmo engineonly have four cylindersand they make less than 250 horsepower.So for a car to be that loud,it's a pretty tough sellfor most auto manufacturers.A more powerful engine with more cylinderswould obviously make even more noisesince it had more slappy valves.Dude, slappy valve's a character due.Instead of steam boy,we have slappy valve.And slappy valve loves getting spanked.I'm slappy valve.Oh have I been naughty?Don't punish me for it. (screaming)If you're a parent watchingthis it's okay, it's just fun.Dude, slappy valve couldbe the thing that we,Slappy valve is great.- I want 10%.- I'll give you 10% of thecredit and 0% of the revenue.And those slappy valvesactually cause another problemthat stops this techfrom coming to road cars,and that is wear.The forced closing of the valvecreates stress on the valve seatand that can weaken the metalof the valve or the cylinder head.Since a desmo engine also has no springto give seat pressure to the valve,the valve seal can be thrownout of whack pretty easilyonce that metal is weakened.Also, because of the way the rocker armshave to be configuredto pull up the valve,the desmo system relies on alittle bit of sliding frictionbetween the cam and the rocker arm.Any amount of frictionin an engine is bad news.And especially if it hassomething that is moving,as often as the valve train.Because of this maintenance on a desmois more frequent than most valve trains.Superbike engines are already designedto be driven a lot less than car engines.The average car, it's drivenfor about 12,000 miles a year.While the average superbikeis around 3000 miles a year.That's like (computer beeping)like a couple thousand miles difference.You do the math.And the final problem with desmo enginesand so many other pieces of techthat we've talked about on this show,frigging costs, man.Since the desmo systemuses an extra rockerand a special valve and cam shaft,there's added material costs.And the added componentsmake it more complexto build and maintain so it meansthat a desmodronic hatchbackwould be really expensive.It's all about moneyat the end of the day.Freaking dollar, dollar bills, y'all.And I know what you thinking, yeah,let me take this 4V Rengine, 250 horsepower,15,000 RPM, throw it in my Civic,have a little Jap-Italiano,frickin sick ride.You can even call itthe Jerry Jap-Italiano.- Ladies andgentlemen, James Pumphrey.(audience applauding)- Today we honor a lost innovation.Let us remember its legacy.Let us remember it's rising light.Though no longer with usdue to safety regulations,their up and down contributionswill live on in our hearts forever.Here with a special performancefrom epidemic sound,please welcome Nolan J. Sykes.(audience applauding)(light piano music)Show your respect for pop-up headlightsby going to donutmedia.com.It's got a beautiful airbrush design,and honestly, it's hard toput a price on such a legacy.But, if I were to guess I'd say,they're available for 29.98.Which is in fact way less than $30.So go pay your respects at donutmedia.com.(light piano music)Bless up and down.- Thank you guys so much forwatching this episode of B2B.Hey, we did another bike video.Maybe may we'll do a whole bike show.Maybe next year?Maybe that's what's on the horizon?So if you could, clickthat subscribe button.Click that like buttonif you liked this video.Leave a comment down below,let me know what you think.If you want to see more content,go click the join button.You'll be in the the donut underground.It's all a bunch of fun, extra stuffbehind the scenes you get to see.Follow us on Instagram at @donutmedia.And on Tik TOk, Tik Tok, Tik Tok,Follow me on Tik TOk,Silence of the Lambda.Follow me on Instagram @Jeremiahburton.Until next week, bye for now.