Interesting article for the engineers
 

Interesting ideas... Variable compression achieved by a variable stroke mechanism.

At my last job, I did some testing of a variable compression ratio engine funded by the DOE. It used a Honda head, but spun the normal way and was controlled by a MOTEC. It was kind of neat how it worked. The crank spun inside an eccentric that could be rotated relative to the block running in a really big set of crank bearings (~5" diameter). CR could be varied from 8:1 to about 15:1. Power was ok. Reliability was crap. $1,000,000 for 3 engines to be built that ran for probably less than a combine 100 hours. I don't think VCR will ever make production. For the cost associated with it, it has very little pay back. HCCI is a better choice in the long term. Playing with the MOTEC was the highlight of that project...

SAAB successfully built a variable displacement/compression engine years ago. It's a museum piece now.

That site looks a lot like Coates...

The problem is the device necessary to drive the vcr mechanism generally uses more energy than you gain back from running the high compression ratio at light throttle. You can't run a high compression ratio at higher power points because the efficiency gained is lost by having to run less spark advance due to the knock limit.

One can't help but thinking that if it was any good "name your own car maker with lots of money ie Porsche" would have bought him out aleady

Very interesting, thanks for the link.

Red flag: On the "Intellectual Property" page of the site, all but the last 3 of the links are broken. They're not broken 404, but return "no result from search" at the patent databases.

20020194987 — Basic Balancing
20020106238 — Piston Joint
20030138331 — Metering Pump With Proportional Output

These 3 links work and are some dense reading indeed, especially with missing illustrations - which may be my browser. I must admit I don't have the mental horsepower (depite being modestly Jedi-level at spatial relations) to picture this crazy system without pictures.


The big claim is combining a low-friction well-balanced variable CR rotating-assembly system with a super-lean-burn system. It looks great on paper.

Here's a link to the site that orginated the article that captured my attention.. if you're an engineer type.. this is one of the coolest sites... filled with some interesting engineering news and items.. :)

http://www.manufacturingcenter.com/dfx/e_archive.asp

That's the engine with the head that raised and lowered, right?

What became of it? Seems easier and more practical to move an engine part that's relatively fixed, at least compared to big rotating assemblies.

How about a wankle engine. Fewest moving parts, good power, and clean burning. I believe that motor shows promise if porsche technology is applied.

To be precise, the head was canted to the side - it had some form of variable head gasket. I don't think they could get it to hold together for very long was the problem.

Except for exceptionally bad fuel economy and oil burning. Mazda has been using them for 30 years, and hasn't really been able to get over those hurdles. So efficient in that in can make a lot of power out of a small displacement, but doesn't make the equivalent fuel economy of the same size reciprocal engine.

Seems like Benz is onto something with their compression/ignition engine.

Rotaries are not clean burning engines. They are relatively dirty due to all the sealing issues. Catalysts can take care of that sort of stuff though. The two things they are very good for are racing and hydrogen fuel research. They don't have as much of a crank case to turn into a bomb due to blow by.

One of the reasons I quit RX-7s was the Wankel.

One of the hardest hitting negative attributes is the extremely poor combustion chamber shape. It's this long narrow gap between rotor and housing, and getting a homogenous mixture to burn evenly across it is next to impossible.

The bad fuel ecomomy comes from the rich mixtures needed to get burning mix across the chamber - and to prevent instant-death-detonation from getting lean (imagine having piston rings made of glass - that's apex seals).

The oil burning comes from the necessity of feeding oil into the chamber for lubrication on the rotor sides.

I hope Mazda solves all these issues someday... they do make fun little cars.

Wasn't the rotary originally designed as a two stroke......or at least should use higher oil content fuels??