Porsche Variable compression rod

[user-612937456]

Just some cool stuff. It may have been posted before but in case not I thought it was cool enough to share. I am familiar as are most of you with variable valve timing or VVT/V-Tec..... controlling camshaft timing with oil pressure. This is for variable compression height of the piston controlled via oil pressure actuating little pistons and rods inside the larger connecting rod rotating a cam in the little end of the rod. Letting an outside control vary the actual engine compression ratio.

[Carnut1]

That looks like a horrible idea. Heavy, complicated. I could imagine what would happen if the wrong viscosity oil was used. What happens to your quench? Must be a quenchless pentroof chamber? Just what would happen after the engine wears a little? I think Volvo had a design that moved the head in reference to the deck. Seems problematic to me.

[Schurkey]

German engineering. Overly complex, expensive, likely to create as many problems as it solves.

[GARY C]

German engineering. Overly complex, expensive, likely to create as many problems as it solves.

Thats what happens when a Government controls a business, it's amazing how stupid one can be with other peoples money. Does anyone know what benefit this provides?

[Truckedup]

Yes it's complex....But exotic engineering like this often get filtered down into usable designs.....If it wasn't for innovative ideas we all might still be talking side valve engines and splash lubrication

[peejay]

Definitely an interesting idea. I wouldn't think the change in quench would be a good thing but, who knows? If there's even the slightest actual benefit in power and economy then it is worth looking into. The trend is to lower revving engines so the weight tradeoff is probably not that critical anymore. Variable compression would be a benefit for a highly turbocharged engine, not a high revving naturally aspirated engine. High compression at idle and low load for good efficiency, drop compression when under high load and the turbos are forcing 30+psi into the engine.

Of course oil viscosity is important. On the other hand, it's already important for anything with variable cam timing, which is practically everything made nowadays, so nothing has changed. And combine this with BMW-style infinitely variable valve lift/duration, you can have an engine that behaves however is best for the torque request, with no compromises.

I wonder how in the world you control it, though! It's interesting enough with camshafts and that has only one phaser on the very end. For the con rods, separate drillings in the crankshaft for compression control galleries? Might not be too difficult to do for a two or three cylinder engine...

[oldjohnno]

Are you sure this wasn't originally an April Fools Day prank?

[induction apprentice]

It looks amazing to me. The rotary continues to struggle with fundimental design issues as well. But it still is an amazing concept and if for no other reason tends to help our imaginations to flourish. It is very concievable some good spin off thinking or designs may arise from this active connecting rod crazyness. I think it is so ludicruis, That it might actually be a good idea? The oil viscosity issue is likely no issue at all. There are many ways to manage hydraulically controled devices. The extra weight is probably not a concern if the majority of the rod would be of titanium or a composite. But if it's advantages are primarily fuel consumption? Then I would say it's moot. From my understanding, If we woke up tomorrow morning and all vehicles suddenly had been converted to run on CO2 instead of gasoline. The oil pumping would continue as it is and they would just burn off the lights to dispose of them instead of sell them. gasoline is probably the least important product derived from crude. We will always be refining oil as long as man kind is alive. we have to do something with the gasoline. We may as well put it to use.

[CharlieB53]

Too complex for production. Why not cast or mill additional space in the combustion chamber with a 'window' sort of door, that slides open/closed. Closed the compression volume remains smaller, open adds volume to reduce compression.

I don't remember which Honda motorcycle engine used a similar slide to open/close exhaust ports so to keep exhaust gas flow speed higher at lower rpm.

[induction apprentice]

Too complex for production. Why not cast or mill additional space in the combustion chamber with a 'window' sort of door, that slides open/closed. Closed the compression volume remains smaller, open adds volume to reduce compression.

I don't remember which Honda motorcycle engine used a similar slide to open/close exhaust ports so to keep exhaust gas flow speed higher at lower rpm.

That works for me. A third valve that can be opened or not that just joins to another smaller chamber pocket to alter volume. Probably would spin off into some other bizarre advantage? Maybe it would be utilized to trap exhaust gas and be used to cool the chamber. Replace the egr valve kinda thing. or a million other possibilities? Could also be positioned to alter the quench or chamber shape for other outcomes as well as altering compression pressure.

Maybe the complex rod idea will morph into an active hydraulic shock absorption device to increase load potential or lifespan in top fuel engines or something?

You read it here first. Lol......

[user-612937456]

Too complex for production. Why not cast or mill additional space in the combustion chamber with a 'window' sort of door, that slides open/closed. Closed the compression volume remains smaller, open adds volume to reduce compression.

I don't remember which Honda motorcycle engine used a similar slide to open/close exhaust ports so to keep exhaust gas flow speed higher at lower rpm.

That works for me. A third valve that can be opened or not that just joins to another smaller chamber pocket to alter volume. Probably would spin off into some other bizarre advantage? Maybe it would be utilized to trap exhaust gas and be used to cool the chamber. Replace the egr valve kinda thing. or a million other possibilities? Could also be positioned to alter the quench or chamber shape for other outcomes as well as altering compression pressure.

Maybe the complex rod idea will morph into an active hydraulic shock absorption device to increase load potential or lifespan in top fuel engines or something?

You read it here first. Lol......

This brings to mind the early 90's Mitsubishi 2.6 which has a small third air valve I think it was EGR or some emissions related purpose besides misterbitchy products it also came in some Dodge caravans and other Chrysler products like Dodge D50's raiders and

[plovett]

The most brilliant engineering solutions are the most simple ones. Just adding more and more moving parts is not necessarily the best solution, in my opinion.

paulie

[pdq67]

I do remember a third little-bitty intake valve that was used to feed a rich mixture of fuel/air into the chamber that was filled with a really lean mixture. I forget if it worked or not?

I want to say, an early attempt at, "stratified charging", of the cylinders? They wanted to run the engine up at like 19 to 22 to 1 instead of at Stochiometric(Sp?) F/A so needed a rich, "match" to light it off because at that ratio it wouldn't light off. At least I think that was the concept?

pdq67

[peejay]

It doesn't look THAT complex to me, really. It looks like just a couple of pistons, a plunger that does "something", some drillings, and an eccentric. There are far more complicated components mass-produced for cheap cars on a daily basis, this should be no problem at all for a $150k+ car. And the tech would only get cheaper over time.

I am assuming that Porsche attacked this angle because they, as a company, are committed to boxer and vee engines, not inline fours like SAAB was with their hinged block idea, which was something they had been working on since at least the early 90s. (I suspect SAAB was waiting for computing power to catch up to what would be required to real-time juggle compression ratio, boost, timing, and fuel, on a proactive instead of reactive basis)

Plus, Porsche is an engineering firm that sells cars. Even if they don't use it, they are showing off what they could do for someone else. I wonder if the design is stout enough for Diesel use. High compression for starting and idling, then when you lean on it you drop the compression so you can reduce NOx without DEF/catalyst trains or making lots of soot.

[MadBill]

... From my understanding, If we woke up tomorrow morning and all vehicles suddenly had been converted to run on CO2 instead of gasoline. The oil pumping would continue as it is and they would just burn off the lights to dispose of them instead of sell them. gasoline is probably the least important product derived from crude. We will always be refining oil as long as man kind is alive. we have to do something with the gasoline. We may as well put it to use.

Good point. In the late nineteenth century gasoline was a waste product and was dumped in the ditch by the refineries.