Technical variable compression connecting rod; just an interesting pic

Don't know anything about this. Saw it on FB and thought y'all might also find it interesting. Perhaps you'd like to discuss it. Perhaps not.

 

Porsche and Toyota have been working on this idea for a while.
Here's some info.
https://contest.techbriefs.com/2017/entries/automotive-transportation/7858

 

https://www.enginelabs.com/news/porsche-working-on-variable-compression-connecting-rod/

 

SAAB also worked on a variable compression engine, but with the upper part of the block "hinged" so the cylinders & head would move up and down. Turned out the benefits were nowhere near as big as the theory suggested, so the project was scrapped. Could have been an interesting engine otherwise.

 

There was another effort, with actual running motor, that used a two-piece fixed-length rod. But this one didn't have the crankshaft directly connected to the piston. Instead, the rod from the crankshaft connected to a lever at one end and there was another short rod connected from the lever roughly in the middle to the piston. The lever pivot was at the other end. The variable ratio was accomplished by moving the lever pivot point back and forth. Worked rather well, as fuel economy was markedly increased. The idea was to raise the compression ratio under light-load conditions for better efficiency, but the expense of building it was too high for the benefits.

 

You make a, my head hurt

 

That’s wild looking.

 

Variable valve timing benefits make sense, but, variable compression- WTH. I'll read thru the links and theory.

 

You can change your compression by thinking about it...

 

LMAO

 

Variable ignition timing
Variable fuel delivery
Variable cam timing
Variable stroke/compression

Now all we need is an infinitely variable transmission.

 

There were some variable compression lab engines built back in the 30's of 40's to test fuel octane rating.

 

They Are available in models from Japan

 

I think it’s already here. CVT on small cars. Well, stands for constantly variable transmission, but not sure if the same as what you may be thinking.

 

DAF had it in their cars in the 70's, maybe earlier. We have it in several cars and all scooters today.

 

My wife bought two daily drivers with CVT. I thought they totally sucked as a driving experience. Idea is good but the functionality is ridiculous.

 

Call me old fashioned but seems like an awful lot of extra parts to be thrashin' around inside the cylinder. I've had enough trouble in my life keeping regular old connecting rods in one piece.

 

There are CVT transmissions for some of the smaller heavy equipment; but hydrostatic transmissions, also infinitely variable, have been in use in agriculture equipment and some material handling and road building equiment for many decades. Hydrostatic transmissions offer incredible performance advantages, but you have to deal with reduced efficiency, a lot of heat generation, and if using external oil lines there is always the issue of leaks.

Variable compression? I'm still not seeing any real advantage. Other than making an engine easier to start, what performance advantage is there from being able to temporarily reduce compression?

 

“what performance advantage is there from being able to temporarily reduce compression?”

they want to reduce spark knock or detonation. That’s a big engine killer. A lot of modern engine control systems have anti-knock sensors as high priority.

 

Do a quick search for Cartercar ...

 

I suspected that some of you were going to say it's been done.
LOL
Interesting.
To be clear, I was thinking of how a belt driven torque converter works... no steps in between gear ratio changes. And controlled according to load, RPM and throttle position for optimum gear ratio.
But we've stepped too far into the future. The space-time continuum is eroding.
Mr Wizard...

 

Interesting, but.
It would defiantly be a lower rpm engine !!
With that much weight at the top of the rod, would surly limit the rpm capability.

Lower the ratio for normal driving, raise the ratio for high speed (?) driving.

Mike

 

What Mike said, too heavy and complicated for highrpm....Variable cam timing changes compression ratio or more accurately cylinder pressure...
Modern sportbikes make 3 hp per cubic inch off the show room floor with all the complication.Some even have variable injector location...

 

Like the Comet clutch I built for the kids 4 wheeler from a old Polaris chassis? The drive pulley would be small and the driven pulley large at idle/rest. As engine accelerated the dive pully would open up and the driven would as well, but be smaller.

 

Similar principal to a BRIDGEPORT type mill variable spindle speed.

 

Here's a cutaway showing the Nissan implementation with a metallic belt and pulleys.