This BMW has variable Connecting Rods that can vary its length and Compression of the Engine 🤯 VCR

[@repairman22]

Thanks for leaving your like!

[@Eduardo_Espinoza]

Np :)

[@HanginInSF]

Nissan makes one that against all odds is actually doing pretty well.

[@matthewcarter5746]

I can't imagine how fast this system would fail

[@brad4edat]

max 1-2years, may be 4 :)

[@martinhann1672]

Might last longer than Ford’s wet belt!

[@izalman]

Miss one oil change and the system will be dead..

[@izalman]

I admire your optimism @@brad4edat

[@hotdog9262]

depend how well they manufacture it like most things

[@Pyroteknikid]

Just when you think BMWs could not get any more complicated...

[@kwitwerikok8o863]

Too much monkey motion.

[@wrongsensexec5185]

Yeah but if it working and they can do it realible than is awesome

[@davef.2329]

Too much money when something goes wrong.@@kwitwerikok8o863

[@glenncronise7775]

@@wrongsensexec5185 BMW engines are not reliable today.

[@xeong5]

​@glenncronise7775 my 2006 3l inline 6 begs to differ.

[@keisuketakahashi3597]

Most german invention ever . An engineering nightmare eventhough it works.

[@Klappspaten_TV]

This is the kind of stuff that's going to be a horror to repair. And even with the high-quality machining here in Germany and Austria this looks so fragile I doubt it'll go more than 300k km.

[@cedhome7945]

And just wait until the warranty goes so will this goofy thing

[@cardboardboxification]

everything works once

[@jessewoody5772]

@@Klappspaten_TV the second owners of these cars will be left with some serious repair costs.

[@procrastinator1842]

​@@manitoba-op4jx that's....clever!

[@7MGTE]

As a mechanic i can almost smell the money...

[@Alan_Hans__]

It would seem easier to me to make the changes at the head end rather than the end that it moving all the time. A 10cc "bolt" that can be screwed into and out of the cylinder is about all the difference required to vary a 6 cyl 3000cc engine from 11:1 compression to 9:1.

[@martin-vv9lf]

Agreed, and also a common modification to motorcycles is to fit an extra gasket between the crankcase and lower cylinder head to lower the compression ratio. I would think it more reliable to design a car engine like that and fit the off centre ring shown here in the variable con rod in the lower cylinder head instead.

[@FontaineLovers]

you sir just solved their million dollar "innovation"

[@ArneChristianRosenfeldt]

How do you seal against the 100 bar? We already have leakage through piston and valve. So you add a concentric piston ring? Like a sleeve engine in WWII British bombers? Or you really mean an eccenter around the main bearings? I don’t like that all these things soften the confinement of the “boom”. Just build a hybrid! It is 2024!

[@antonrichter5032]

Or an additional valve that opens and closes in the combustion chamber. Can be solenoid activated as it does not need to be adjusted every revolution - simple

[@ArneChristianRosenfeldt]

@@antonrichter5032 uh, you want the combustion to reach through it? You drive pre-chamber Diesel. Also for the claimed efficiency we need continuous adjustment. Valvetronic instead of VTEC.

[@myboy051]

I’m an Automotive tech of 21 years. When the owner doesn’t stay on top of their oil changes or the shop doesn’t use the correct oil viscosity. When do we all think is going to happen to the oil control valves? Or when the oil control valve on the crank fails. What a job that’s going to be. Yup looks German to me. Always trying to break something that works good.

[@TowerCrisis]

That's already an issue on almsot any modern car. Folks grenade engines left and right from not following the service interval or using the wrong oil. This may be complex, but for the secondary oil galley version I can't imagine it being more failiure prone than current oil pressure based VVT systems. They use TIGHT tolerances on those, and contamination or deteriorated oil regularly destorys them already.

[@RockSolitude]

Well aint you a bundle of sour grapes

[@1234567890CAB]

For those interested, Saab built a variable compression engine in the 2000's by using a hinged block that moved the cylinders and the head closer and further from the crank.

[@jaredbawden6707]

I remember this, it never went into production however. Think they had too many issues making it reliable

[@1234567890CAB]

@@jaredbawden6707 According to Google it was killed by GM due to budget

[@jaredbawden6707]

@@1234567890CAB SAAB did have a reputation of spending more than they were making. So that's unsurprising. Still 20 years on, the tech was never utilised.

[@PiDsPagePrototypes]

That would be interesting on a test bed, but in a vehicle with all the fuel, inlet and exhaust connections having to flex as the head moves, to likely to fail.

[@rocketpigrecords3719]

That was also a stupid idea, which is why Saab had to rely on GM engineering & rebadging Subarus before inevitably dying off.

[@baeruuttehei1393]

Trying something new is never wrong. I have to see how this works out, being in a hot and loadsensitive part of the engine.

[@sezwo5774]

Probably a bad idea. Good concept if you are an engineer looking for employment in reseaqrch and development, but terrible for mass implementation.

[@pepeshopping]

Not new. Nissan has had turbos with variable compression for the least 4 years…in a cars, on the street.

[@BadWolf762]

As a machinist it reminds me of a few engineers I had to school. Just because you can you can design it in CAM doesn't mean it can be made by ordinary processes.

[@ThatOneCatNyx]

I would say that is why we innovate new processes and techniques to manufacture things.

[@GeneralFOPPA]

Great! more things that can very easily go wrong whit the engine.

[@cardboardboxification]

BMW already has 10,000 things to go wrong , might as well add another one

[@OldsmobileCutlassSupremeConver]

Can you imagine how long this will last with people that don't change oil often.

[@RenatoBolzoni]

Very glad to have held one of those rods in hands. And even more especial that a Brazilian university, UFSM, is working together in this project. Hope it gives IC another breath!

[@PiDsPagePrototypes]

It won't. It's complexity where none is needed - the same sorts of gains can be had via mixture control.

[@crackedemerald4930]

​@@PiDsPagePrototypes It's good training time for students

[@Kyntteri]

Con rod. The time bomb edition.

[@ralfdeckers1703]

Another step forward. The internal combustion engine still has a lot of potential. The video is also very well done. Hopefully it will be serialized soon.

[@automatteck3477]

Nissan already has this in production - the VC-Turbo series engines have variable length connecting rods to give them variable compression, and they're about as (un)reliable as you'd expect

[@pepeshopping]

Figures? Numbers? Examples? Any details at all for such “common” failures?

[@spiKey0svetlana]

I somehow don't believe 5-8% would justify the increase in higher cost due to increased material quality and complexity of the mechanism. Also as much as I'd love to see hydrogen cars, it's not viable. It'll leak trough any gasket so over time you loose it, must be under high pressure, low energy density, no infrastructure..... And I'm not sure if it's entirely emission free to produce. I remember there are two ways of producing hydrogen.

[@peterjohnson9438]

Hydrogen *can* be produced virtually emissions-free on-site by using solar energy, either solar-thermal or photovoltaics, or wind, or hydroelectric or geothermal, etc. However, due to requirements for production at scale, any hydrogen produced will likely be created through electrolysis with electricity from a coal power plant and transported to filling stations in heavy diesel trucks.

[@jackking5567]

It's not just gaskets and seals that suffer. Hydrogen reacts over time with metal it comes into contact with. The hydrogen molecules are so small that they react with metals at an atomic level. Excess hydrogen in metals can affect them lots. Structural integrity being a major problem.

[@Jani_Ikävalko]

If you have no idea how these problems are solved, then why you're against them? You have virtually zero knowledge on engines and these topics anyway and don'¨t work or research the subject. How about leaving these probs to an engineers to solve and introduce hydrogen engines to market? Your satanistic attitude where you're so much against this is making me ill.

[@PiDsPagePrototypes]

Hydrogen in cars won't happen, and it's not because of the problems in engineering the cars or making the Hydrogen. It's the infrastructure. Producing at volume, transporting and storing the Hydrogen, it's complete ground up new hardware, at scale. Even places where there's high usage of LPG, that hardware could be repurposed, but the cost to do so,... All of the engineering needed, and all of the materials issues, it's one of the reasons that the new generation of rocket engines are using Methane instead.

[@Jani_Ikävalko]

@@PiDsPagePrototypes China, Korea, Japan and Europe already decided to go to hydrogen, so please take your head out of your ass really, perhaps you have no idea about these things

[@stasiekpiekarski]

How about reciprocating mass increase? Apart from durability...

[@NoNationHero]

Same can be achieved by varying the intake time. Simply by keeping the valve closed for a bit longer, the compression ratio can be varied from inherently high (100% open) to practically any, depending on piston position and boost pressure.

[@SSmallwood]

on what stroke lol? CR is a fixed number. volume of the cylinder to volume of the combustion chamber.

[@NoNationHero]

@@SSmallwood How do you get a turbine compression ratio, then? It has no pistons at all. Compression ratio is a function of pressure, not volume. Those two are related, that's why you confused them. If you close the intake volume half the way of an intake stroke, you'll get half the compression ratio. Because you'll gonna have only half of the air mass to compress. Mazda did it. They already did a variable compression ratio engine, that, btw, if combined with a supercharger, can work both as 2 and 4 stroke.

[@pepeshopping]

Yes, but most valves only have 2 “stages” or timings. You need infinite variable valve timing for that, and only Hyundai had that for a few years now (maybe one more maker, just recently).

[@aden3113]

5-8% in fuel savings probably won't justify the extra cost and complexity of producing an engine like this, sounds cool but I thinks it's a step in the wrong direction. They should put their money on hybrid vehicles like Toyota, not only do they achieve impressive real life fuel economy figures but they also produce less emissions and they're very reliable as they're used by fleet vehicles and taxis all over the world. Internal combustion engines simply aren't good for scenarios like stop and go traffic, they're only efficient in a very narrow RPM and load range, even with variable compression ratio it wouldn't make a huge difference. It's better to combine them with a electric motor and battery instead. Also I can't help but think of how many recalls and warranty claims this would have if it went into production, with that many extra moving parts that use oil combined with extended oil change intervals this engine would probably doomed from the start.

[@24Osx]

this is neat! I love understanding new mechanisms and I hope this design aids in the automotive industry someway or another.

[@407j]

An overly complicated BMW...what could go wrong with that?

[@Dr904]

So unnecessarily complicated. There are so many other ways to get variable compression, that would both be cheaper, and have better durability.

[@Agent-mb1xx]

move the crankshaft, problem solved for cheaper

[@FUZxxl]

... such as?

[@izalman]

They exist already, variable vane turbochargers is one that'd kill this crass idea instantly..

[@PeterChapman-rg6gr]

@@FUZxxl Try looking up the "Infiniti" engine that has variable stroke length or better still look up the modern form of the Atkinson Cycle that uses variable intake valve timing to effectively alter the compression ratio.

[@alexkei4009]

@@FUZxxl toyota makes them for ages already. Ive recently done work on one with 300+kkm. Clever design and simple mechanics, unlike this bmw BS

[@usanaluoma]

What could possibly go wrong by adding a bunch of extra moving parts on the highest stress point in the motor?

[@highpointsights]

There would also then be an element in the BMW design that is already in the one of the Toyotas presently. The cylinder is off set to the side of the crank center of rotation!! That increases torque as i understand it!! Hi quality oil were could certainly be a must!! Probably a full synthetic!!

[@levimaxton6307]

"my mini pistons have blow by!" could you imagine if one piston didnt actuate causing it to have a different compression lol

[@PiDsPagePrototypes]

Vibration of different power pulses along the crankshaft, it'd be like running with a spark plug removed, can shake the engine apart.

[@istillplayroblox6952]

​@@PiDsPagePrototypes The ultimate enemy to mechanic stuff, V I B R A T I O N

[@JxH]

It'd be so much easier to make the combustion chamber variable size, with a mechanism in the head (which is fixed, not rotating).

[@fs5866]

i think a variable combustion chamber messes too much with the explosion propagation .

[@JxH]

@@fs5866 Fair point. Cheers !! 🙂

[@arthurgay5746]

That's never going to go bad and self destruct !!!!

[@ronchappel4812]

I like the way you explained compression ratio on turbo engines.Even non car people would understand it🙂

[@realkilju]

Oh so its old af news… 2016… thats more than 7 years ago. Still pretty interesting, but old

[@petermonk117]

What could possibly go wrong?

[@chriswalker4272]

😂

[@rickbackous1041]

I love technology but this seems more like a science project than something that is ever going to actually happen. While I'm on here I'm going to chime in on the BS of turbo charging for economy. There is no doubt that the turbo increases power. The economy part of the "Eco Boost" is pure BS. Just a ton of extra parts that need to be handled delicately and go bad anyway. Give me a V8 any day or an I6.

[@K-SHABAB]

it can help in new economy cars with 3 cylinders and emissions

[@repairman22]

The turbo saves fuel by having fewer cylinders than a V8, that's true but, if we compare 2 engines of 3 cylinders, the NA will have more compression and will be better.

[@rickbackous1041]

@@retiredbore378 More air forced into the combustion chamber = more gas that needs to be injected into the combustion chamber to keep the ratio at 14.7:1 and the engine from running to lean. That equals no return on investment for fuel economy. Power, yes. Economy, no.

[@thehammermanduke]

Nicely done

[@Flumphinator]

People talking about failure are only halfway there. Complexity is fine for a good enough reason, and this is a pretty good reason if it works. The real problem is that when it fails (which is soon because it’s complex), you have to remove and likely replace the entire rotating assembly.

[@Hi---There]

Good idea. At the moment variable compression is on the market, several years. That system should comparable in reliability with existing.

[@StephenWhite55]

Many years ago, SAAB engineers developed a variable compression-ratio cylinder head (for optimizing their small-displacement turbo-motor's low-rpm performance), which worked by pivoting the head and cylinder-liners a few degrees, relative to the engine block, which - of course - supported the crankshaft and connecting-rods. By 'lifting' the combustion chamber and cylinders slightly, the compression ratio was lowered, allowing massive boost at high rpm. When the combustion chamber and cylinders were dropped to their low setting, a high compression ratio was established, allowing crisp 'off-boost' performance. SAAB was able to power a full-sized luxury sedan, using a 1.4 liter engine(!), and produced well over 200 bhp, with good torque across the entire rpm range.

[@olafschermann1592]

Mazda has a similar system, but using a kind of lever which lengthens the connecting rod. Looked very complex to me.

[@pawesmola7635]

Nissan not Mazda. Used in Infiniti production model qx50 for few years already

[@animalfarm7467]

Even though backlash in the rack and pinion would limit its useful life as the squeeze lubrication would eventually lead to contact failure, giving the eccentric gudgeon the ability to have a 180 degree angular movement would reduce the reversing torque at TDC and BDC created by the acceleration second harmonic. How would this mechanism handle the shock loads from random fuel detonation?

[@Kamil56111]

Easy retrofit 🤣 7:07 had me ROFL 🤣Modifying engine "not very complex" ONLY required new connecting rods, actuators in the crankcase and ECU tuning 🤣... get it now at your nearest lube place for $14.99 + tax and enjoy your "not very complex" system for a MAYBE ~5% improved fuel economy, I can't... who come up with this stuff...

[@vincemvagusta68]

Looks awesome, that shouldn't ever fail.

[@ykozfk1406]

After seeing this, I came up with some ideas that might be better. It is a thought that contains such suggestions. It felt a little fun. thank you.

[@PeterChapman-rg6gr]

It would be far easier just to vary the inlet valve timing as most other engine makers do when running on the Atkinson Cycle. BMW are adding a huge amount of complexity and weight to the piston / connecting rod that then needs a heavier crankshaft to balance it. Also there is the "Infiniti" design of variable stroke / compression engine.

[@johnstuart3851]

BMW is not adding anything. This is a University research project.

[@ian9toes]

Problem for me is you want to keep the piston and rod assembly as light as possible and this goes against that, so even if you gain at lower revs you’re going to lose something at the higher revs.

[@scooble]

All those extra components going up and down, round and round. That's a fair bit of mass and complexity. If the crankshaft bearings were in concentric containers, then rotating them would also raise or lower the crankshaft.

[@White.Elemant]

Nice. Now you have super heavy and complex conrods.

[@westoniii]

How does it run off-throttle at high rpm? I bet it shakes itself apart.

[@matthewmattmatthew8335]

I think the aftermath of Nissan's VC engines should be enough warning to other manufacturers to not bother

[@jonahfastre]

Reliability 📉

[@lawrancemngomezulu5653]

It's a good idea but wait until the electric oil pump blows a fuse or the oil pump control module starts to malfunction

[@thetruth7633]

"Hanzz??" "JA!?" "I havez something new, variable connecting rodz, we can changezz zem together with ze bearings"

[@Agent-mb1xx]

More problems incoming, just move the damn crankshaft instead

[@michaelre7556]

I was just about to say this as well

[@ArneChristianRosenfeldt]

This may work if you connect your transaxle via U joints in a Porsche 944. But what about the torque tube in a corvette or the bolted on clutch in a BMW? Cadillac, BMC mini and Lamborghini had so bicycle engines where you could rotate around the gearbox gear.

[@nikolaisquddos670]

It should be able to run e-fuel then….

[@nikolaisquddos670]

0:13 I think you would have to 3D print the rods

[@A92CB7]

Nice idea but with more moving parts comes more failure points

[@sarbakara7469]

The difference in efficiency caused by going from a compression ratio of between 9.7-1 and 13-1 is 18%, what here causes an 8% increase in efficiency is the fact that the compression ratio can be modified. compression at will, there are cars dedicated to generating a lot of power that have a low compression ratio that with this system will have the same consumption as that of an engine dedicated to saving fuell economy

[@ArneChristianRosenfeldt]

Would have been so cool if car manufacturers added this when they brought turbo to the streets. I am looking at Saab, Porsche, and Ferrari. Over the decades so much fuel cold have been saved. Why did the NA engines not receive valve tronic in the oil crisis?

[@Mad-Coo]

Simply bonkers. This is a good idea but in reality not much can withstand the up and down motion of the con rod and piston, little parts will be ruined in no time.

[@Remingtonrestoration]

Nissan has also tried the variable compression engines…… huge piece of shit

[@kcube2548]

The cost of fuel seems reasonable versus maintenance or failure of this bright idea

[@delta3703]

Saab did this a long time ago by increasing the height of the whole head of the engine. That way the compression chamber increased size too...

[@howboutusingyourhead7992]

Remember the movie "Westworld" where nothing can go wrong go wrong go wrong?

[@DWR438]

oil passage bore is sealed with a rubber oring and the spring in connecting rod will made of material that will wear out before said oring

[@SkaBob]

Variable camshafts are already overly sensitive often causing code and rough running engine when not working at 100% especially if the owner has gotten near or past the oil change interval. That is how motors are treated in real life. This would likely suffer the same issues and as the motor ages build up and leaking seals could cause each piston to have a different compression ratios and drivability issues. Repair costs would be very high nearly all motors require full removal to service the oil pan and and components in it. I have the feeling the typical IC engine has advanced as far about as practical and more add-ons like this will drive up repair costs and hurt long term durability.

[@frankxu2321]

CVVD: bruh just extend or decrease the intake valve open duration! /s Good to see different implementation of this system

[@thomasheinrich5199]

Nice exercise but too complex. A turbo with an additional electric boost for low revolutions has the same overall effect.

[@thomasheinrich5199]

@@retiredbore378 It does. I meant a turbo charger which is kept at speed by an additional electric motor when the main engine is at low revolutions or idle. This can compress more air into the cylinders in any situation. You mentioned hybrid as a too complex alternative. We are currently driving a Golf eTSI 1.0 liter 3 cylinder, which is not a full hybrid but very simple: It uses one electric motor as generator, starter and short time boost. It runs permanently with the engine, does the Start-Stop and gives extra torque at low revolutions. In combination with a turbo, it's characteristics is like a turbo diesel with mostly running at low revs with good power. This results in a well done downsized gasoline engine with a half-hybrid design with low emissions.

[@HaroldParks-bd7ng]

Sixty years ago I made a quarter midget engine with a bow legged con rod that inertia would make the piston move ten percent farther in the bore effectively increasing displacement.

[@CrazedChip]

Cool idea, but how many miles till you have to replace the con rod? 20k? Every oil change?

[@speed8701]

Seems to me that a device in the head similar to one of the valves would be easier and more reliable to change the compression ratio. Like a valve that's solid.

[@HumanVsHumans]

Sounds like a nightmare

[@anon1460]

Parts pars and more parts is what we need👏there are still not enough parts 😅 The most efficient engine is one that doesn't have broken parts all the time. and you can drive for 100 years.

Regular oil changes would be vital with this system (same as multi-air), looks kinda robust

[@luisribeiro5639]

(i'm French), it"s a good idea and could improve flexfuel (etanol) engines to increase efficiency. Etanol accept more compression ratio (more efficient, less fuel) without knock. But the better solution is write by JxH : an engine with a high compression ration who works on atkinson cycle (the valve is left open more time to reduce compression ratio) seems more reliable.

[@istillplayroblox6952]

The Air fuel ratio is more of a problem

[@istillplayroblox6952]

The air fuel ratio of etanol is more of a problem

[@nidbahn]

What if the other side of the combustion chamber also moved?

[@repairman22]

It would be great to have a screw that enters or retreats as necessary.

[@PiDsPagePrototypes]

Interesting dead end. Sure it might enable peak effieincy of combustion, but it adds complexity and mass and reduces reliability, and it changes the TDC timing as the eccentric moves, which will change the thrust angles on the piston as it is pushed downwards, no doubt leading to any gains being lost through extra friction on the bores. If we don't see it in Formula1, it's not worth it for street cars, because if those engineers say 'it's not worth it', then it's really not worth it.

[@IvanLopez-kp4bh]

I can imagine our local bmw performance shop taking that engine out to put and actual powerful engine that has less parts that break

[@mpetersen6]

Not just the added complexity. Also the added reciprocating mass.

[@janofb]

So the oil is diverted from the bearing to the pin. And what happens to the bearing?

[@v4skunk739]

I believe the animation is wrong. No way it stops oil to the bearings.

[@cyyeung4879]

Will the force in combustion shift to two little hydraulic rod rather than big connection rod?

[@Soederlund]

I think that SAABs solution was a better one with less moving parts thrown around in 3000 - 7000 rpm.

[@sferg9582]

Great. More reciprocating mass to contend with, more complexity and an astronomical repair bill when it all fails, and add to that more stringent maintenance that no one will adhere to. Yes, I'm a skeptic.

[@samuelforsyth6374]

would this introduce a slight imbalance? nissan's VC engine puts a lobe on the other end of the rod, moving the piston end means it's not central in the crank to sleeve line??

[@moefuggerr2970]

More stuff to break.

[@levin645]

The best part is no part

[@teagreen2220]

Not every idea should be followed to development. Maybe fix the already standard stuff first? Love the moments those cars work though!

[@GPRaitsakas]

A BRILLIANT IDEA since there is already a turbo : why not adjust the turbo output to regulate the amount of air entering the cylinder instead of this complex mechanical mechanism. This should have the same effect on compression ratio.

[@repairman22]

When the engine is idling, the turbo does not work. You can't increase the compression in that situation. Additionally, if the throttle body is partially closed, the engine operates with vacuum in the intake manifold.

[@CP-jt6bw]

Cant wait for index 12 con rods

[@jefferyholcombe5189]

On our farm we had a 4020 and a 3020, both diesel & powershift and were the best tractors as they never broke down. Yes they will lift a lot of weight but the pressure in the hydraulic pump wouldn';t bypass when you started it so we bought a valve that would bypass the pump when you were starting it, hooked bypass to the starter wire so it would dump the pressure when starting! Don't get rid of that tractor, they are very valuable and not an electronic POS like the new ones!

[@rosegold-beats]

So the oil pressure is fighting the cylinder pressure just to attempt to get higher compression? Better use port injection for low rpm and high rpm and direct for the middle if you really want better torque at low speeds

[@generictuff]

Can’t you do that with variable valve timing? If you wanna increase compression, you just make the intake valve and exhaust valve overlap, and/or the exhaust valve be open for longer so the piston is higher up slightly than bottom dead center. Sure you cram less air into it, but you increase the compression, and this system also crams less air when it makes the compression go up, I believe. Nonetheless it’s really interesting, but I don’t trust this will ever come to market, after all, messing with parts that bears such huge forces that are not rotational, move in a complex non rotational way and adding moving parts to them can’t be good for the reliability, especially at higher rpm.

[@mikeanthonybrooks]

why not just use something similar to the atkitson cycle, like prematurely open the exhaust valve to allow a bit of the compression out of the cylinder in high boost situations? especially with beemers valvetronic system. it seems a variable rod length adds unneccesary complexity

[@alexlo7708]

As a plain BMW engine , it always needs more headache maintenance than a Japanese car already. By adding more complex parts , I suggest you buy an aeroplane engine.

[@wizardindustriesusa]

😂

[@istillplayroblox6952]

Buy the entire plane instead

[@sajidmohammad3190]

Using electronic valves will be much better I guess as you can close them quickly or lately so that less or more air and fuel gets into it and control the compression.

[@myloveislebanon2031]

Why don't they raise and lower the cam on the surface of the piston itself using oil pressure? (piston in the piston) Less complexity, simpler and less weight

[@franksprecisionguesswork501]

I recall this was tried in the past. (Piston in a piston). Circa 1970-80. Regular crank oil pressure routed to the piston was pushed up with a small orifice and check valve and it also had a pressure relief valve that would allow oil to escape when there was sufficient oil pressure. So in a lightly loaded engine the piston would move to the upper position and operate at higher compression. Conversely when the engine was heavily loaded, the relief valve would open and allow the piston to move down to the lower compression position.

[@ovekarlsson777]

If the aim is to compensate for low compression on a turbocharged engine the obvious solution would be to use a crank driven compressor instead of going through all that trouble.

[@KellySchrock]

BMW diddling with fundamental mechanics at the heart of an engine: This is going to go well.

[@SergeiSugaroverdoseShuykov]

Isn't electrically assisted turbocharger solves exact the same problem, but with introduction of a single electrical motor while engine stays the same? Since this concept requires electrical oil pump as well as addition of huge amount of moving parts into most stressed areas of the engine, i would call it a dead end

[@ttc5000]

It is hard enough keeping the valves and pistons separated from each other in higher performance engines now. Now I have a new component that can break and marry the pistons and valves together... Don't see this making it to anything but the highest performance engines where the owners aren't too concerned about reliability

[@trevormanley8531]

Nissan already has a variable compression engine in production it’s in altimas and rogues. It’s kind of cool but I don’t know if it’s worth the extra complication. It only gets Marginally better mileage and power than the base motor.

[@cromo7743]

It should use compression ratio of up to 20:1, 30:1 at low load.

[@BadWolf762]

You want perfection? The small block Chevy V8. Simple, easy to work on and inexpensive. What you lose in efficiency is more than made up for in cost of manufacture and repair. We have been going backwards for the last few decades.

[@DepakoteMeister]

Very inefficient.

[@istillplayroblox6952]

Plus it JUST KEEPS GOING while new engines break down as soon as you buy the car

[@bomberaustychunksbruv4119]

Just build it to the higher compression, and close the exhaust valve later for lower comp.

[@JMJM75257]

Just adding more ways for an engine to go kaboom! Sure when it's working it has benefits but what do the mechanics who inevitably will have to work on this stuff think?