- One of the highest revving production cars
on the road today is the beloved S2000,
peaking at 9,000 RPM.
But 9,000 RPM, those are frigging rookie numbers
compared 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 with technology from the 1950s.
So I want to know how is Ducati
making such high revving engines
with tech older than a consumer microwave?
The answer lies with the desmodromic valve system,
and it is an ingenious way to pump
those rookie rev numbers up.
So today, we're going to take a closer look
at the secret Ducati sauce that is desmo.
Figure out how it works and more importantly,
see why we don't see car manufacturers
using this tech in their engine.
I bet after this video,
a lot of you're going to start Googling
Ducati v4 engine swaps into your Honda Civic.
It could happen, I've seen weirder things.
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The desmodromic valve system or desmo if you're cool
is a valve system where the cams
both open and close the valves.
And before we get into why you'd want this,
let's talk about the more traditional valve train setup
most commonly used in engines today.
Now in a conventional engine, as the cams rotate,
they push open the valves via a system
of push rods or rockers or bucket lifters.
This is how air gets in and exhaust gets out of the engine.
The cam lobes push the valves open
for a precise amount of and distance
and then as the cam lobe rotates away,
the spring closes the valve again.
This spring is putting constant pressure
on the valve to hold it close
and that's known as seat pressure.
And the valve train has to overcome that pressure
in order to open the valve.
So as the cam spins faster, the valve opens faster,
but it will always close at the same speed.
The spring rate of a standard valve spring is constant.
If the cams spin too fast,
the cam could start pushing the valve open again
before the spring has had time to close.
This is called valve float
and there are a number of problems
that could come from valve float.
First off, if your valve is not sealing
your cylinder properly,
you could be losing compression during combustion,
and that could stop your engine from making power.
Second off, it could mean that unburnt fuel
is getting into exhaust and igniting
causing backfiring or damage to your catalytic converter.
While that last one does sound pretty, pretty cool,
if you have an interference engine,
you're not going to like what happens next.
An interference engine is an engine that is designed
to have the valves extend past the point
where the piston would be at top dead center.
That normally is not a problem because the valve
is always closed when the piston is up.
But if the valve is closing too slowly,
the piston will reach top dead center
before the valve has moved.
And your valve and piston
are going to get into a little fist fight.
And when a valve and a piston 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, but he can't fix his broken heart.
Now, a lot of people fix this problem with stiffer springs,
springs that can close the valve faster.
But the problem with that is now the engine
has to work harder to overcome
the stiffness of those springs.
The valve seat pressure is higher.
When the force being put into the engine from combustion
can't overcome the force of the spring,
the revs will stop increasing.
So springs need to be stiff enough to close,
but soft enough to open.
With modern springs, most car engines
can't rev higher than 7,500 RPM.
And there are some fancy solutions
like progressive springs or even beehive springs,
but even the highest revving supercars
are 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 springs
so there's no tension in the valve train.
Instead it uses a cam shaft
that has two lobes for every valve.
One to push the valve open like normal,
and the other pushes on an inverted rocker arm
that pulls the valve back up.
For this to work, a valve with a special collar
and grooves need to be used called a poppet valve.
So as the engine revs up,
the valves opening and closing speed
will increase at the same time.
So now there's no spring force for the engine to overcome.
There's no valve float and the valves all seal
exactly when they're supposed to.
And while Ducati didn't come up with this technology,
they did start using it as early as 1956
and have had desmodromic valves
on almost all of their flagship bikes ever since.
If you want to know more about that bike,
click that link right there.
That was the first B2B a guy very similar looking to me did
it 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 engines
for the mechanical marvel that they are,
but if that doesn't get you going, fricking sound will.
Since a desmodromic valve system
mechanically forces the valves closed,
the sound made by the engine has a roughness to it
that is like no other engine.
Unlike in an engine with valve springs,
the valves in a desmo engine are being slammed closed
with no elasticy.
The sound you're hearing is the metal of the valve
hitting the metal of the valve seat,
hundreds and hundreds of times a second.
Ducati still uses the desmodromic system
in their engines today and it was an ingenious way
around the internal forces created 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 engines
from Yamaha, Honda and Suzuki all reached higher RPMs
with the introduction of lighter materials.
See the valve spring engines have to overcome
the force of the spring,
but the valve itself is lighter than a poppet valve,
therefore it has less inertia.
And since the desmo engine
needs an extra rocker and more cam lobes,
the whole valve train has more mass to move.
So eventually, materials got light enough
that the desmodromic valve train
wasn't any more efficient than a standard one.
The playing field leveled out.
But Ducati decided to stick with their desmo engine
because it's what they know best,
desmo is Ducati.
(chair wheels rolling)
The first Ducati desmo system was in the 1956 125GP bike.
And at the time Ducati,
they were using traditional coil springs
in their valve train.
But the metallurgy of the 1950s plus the rev limit
that the bike could achieve was enough to weaken
and fracture those springs.
So to the desmo system they went.
And as a result, the single cylinder 125GP
could rep to 13,000 RPM.
But don't think just because Ducati nailed it in the 50's
that the desmo system didn't evolve, oh no.
An early version of the desmo system
known as the Trailbero used three cams,
an intake cam, an exhaust cam and a central cam
to close the two.
It was kind of like having a dual overhead cam
and a single overhead cam at the same time.
As time went on, Ducati refined the design.
By 1987, the Ducati 851 was using four valves per cylinder
on an L twin, meaning that it would have needed six cams.
And instead of using six cams,
Ducati had started to use L-shape rocker arms
that made contact with cam loads
on either side of the same cam.
They also moved to chain-driven timing
as the cams were now separated
to either side of the V configuration.
From the gears to chains to belts.
Those are both three items
that my parents used to discipline me with.
In modern times,
Ducati is even experimenting with springs again.
The Desmosedici Stradale uses keeper springs
attached to the rockers to help them return to position.
These springs help reduce wear in the valve train
and lengthen the amount of time
between valve service intervals.
Buy hey, Ducati didn't rest on their laurels
and just twiddle their thumbs.
Oh no, they kept improving the desmo system.
And just this past year in Moto GP,
they set a top speed record of 225.5 miles per
on 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 a motorcycle engine is one thing.
What about taking this type of valve tech
and putting it into a car engine?
Do we need to enter into the 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 engines
in the auto world are already a thing.
In 1954, Mercedes won their first F1 race
with a desmodromic engine.
The W-196 had a 2.5 liter straight 8
making 340 horsepower at 10,000 RPM.
And to say this thing sounded brutal is an understatement.
It makes John Wick look like John Mulaney.
So he did all of this because 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 biggest reason why you don't see
four cylinder desmos in your everyday hatchback.
One of the hardest working departments at any automaker
is a department of noise, vibration and harshness, NVH.
It's their job to refine and meter all the sounds
that a car makes from both inside and out.
They study the harmonics of a car
and can either refine a car sound in a sports car,
or it could totally go away in an economy car.
If you ever want to see how much the NVH department
can change a car's sound,
just know that the engine in a Lotus Exige
is also in a 2012 RAV4.
And one of the places that engines create the most noise
is in the valve train.
With a modern engine valve noise is lessened
with soft, progressive springs and hydraulic tappets.
These reduce the force in the valve 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 thousand mortars hitting a pestle
might be fun in a super bike,
that doesn't really fly in the automotive world,
at least on the streets.
Ducati's largest desmo engine only have four cylinders
and they make less than 250 horsepower.
So for a car to be that loud,
it's a pretty tough sell for most auto manufacturers.
A more powerful engine with more cylinders
would obviously make even more noise
since 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 watching this it's okay, it's just fun.
Dude, slappy valve could be the thing that we,
Slappy valve is great.
- [Cameraman] I want 10%.
- I'll give you 10% of the credit and 0% of the revenue.
And those slappy valves actually cause another problem
that stops this tech from coming to road cars,
and that is wear.
The forced closing of the valve
creates stress on the valve seat
and that can weaken the metal
of the valve or the cylinder head.
Since a desmo engine also has no spring
to give seat pressure to the valve,
the valve seal can be thrown out of whack pretty easily
once that metal is weakened.
Also, because of the way the rocker arms
have to be configured to pull up the valve,
the desmo system relies on a little bit of sliding friction
between the cam and the rocker arm.
Any amount of friction in an engine is bad news.
And especially if it has something that is moving,
as often as the valve train.
Because of this maintenance on a desmo
is more frequent than most valve trains.
Superbike engines are already designed
to be driven a lot less than car engines.
The average car, it's driven for about 12,000 miles a year.
While the average superbike is 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 engines
and so many other pieces of tech
that we've talked about on this show,
frigging costs, man.
Since the desmo system uses an extra rocker
and a special valve and cam shaft,
there's added material costs.
And the added components make it more complex
to build and maintain so it means
that a desmodronic hatchback would be really expensive.
It's all about money at the end of the day.
Freaking dollar, dollar bills, y'all.
And I know what you thinking, yeah,
let me take this 4V R engine, 250 horsepower,
15,000 RPM, throw it in my Civic,
have a little Jap-Italiano, frickin sick ride.
You can even call it the Jerry Jap-Italiano.
- [Announcer] Ladies and gentlemen, 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 us due to safety regulations,
their up and down contributions
will live on in our hearts forever.
Here with a special performance from epidemic sound,
please welcome Nolan J. Sykes.
(audience applauding)
(light piano music)
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 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 for watching 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?
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