| Author | Message | ||
     Hughlysses |
Apparently, Infiniti will be the first to put one in production in 2018: http://www.motortrend.com/news/infiniti-prepares-worlds-first-variable-compression-engine-for-2018/  As the article mentions, Sabb was working on this some years ago and had a prototype engine with a movable cylinder head to vary the compression ratio. Looks like Nissan is using a mechanism in the crankcase along with some funky connecting rods. Patent: https://patents.google.com/patent/US6505582B2/en | ||
| Fast1075 |
It has to work by limiting the down stroke only, otherwise the quench goes all to hell. | ||
| 86129squids |
Last time I was at TWoS, I got to read a MCN issue in the lodge dining area that covered the technical side of Gurney's new motor patents. Had I been maintaining my subscription to MCN, I'd already had read it- not having a great mechanic type brain, I could only fast-scan the article. Let's see if I can "webcast" for it... https://www.google.com/?gws_rd=ssl#q=dan%20gurney% 20motorcycle%20engine http://www.momentcancelling.com/ http://www.cycleworld.com/2015/09/09/dan-gurney-mo ment-canceling-four-stroke-motorcycle-engine-paten ted Personally, I'd love to try out one of his Alligators! Dude's right up there with Erik for good brains. | ||
| S21125r |
SAAB did one back in the 2000-ish though it never saw production. Was a 2 piece block that lifted the head and liners. | ||
| Aesquire |
Great idea, but supercharging does that with a bit less monkey motion. Especially turbo-supercharging. Not without cost in complexity and attention paid to inlet temperatures. I'm generally skeptical of most alternative crank systems. Some work ok with minimal cost in friction and weird loadings, some have always been kludge disasters in progress, despite coming back time and again like the Scotch Yoke. Sure, mainstream car & bike makers are conservative, but very few of the miracle replacements for the traditional crank make it commercially, and most fail because the steam era technology they were originally designed for don't do well at high rpm. | ||
| Aesquire |
http://www.pattakon.com/pattakonCrankVCR.htm I have more than doubts about the practicality of most of this guy's inventions, but he has actually built some real running engines. Not just computer graphics.. although he does enjoy them. | ||
| Natexlh1000 |
Lots of odd sneaky stuff out there in the engines these days. My 2007 Fit has an odd little 1500cc engine. The centerline of the bores are offset a bit to make the power stroke apply less sideload on the pistons. This reduces the friction. Imagine an engine with a longer power stroke than the compression stroke? https://en.wikipedia.org/wiki/Atkinson_cycle People have been at this for quite some time! | ||
| Azxb9r |
The Miller cycle engine is essentially a variable compression engine. Using a supercharger to vary compression eliminates the need for extra crank complexity. Mazda used them for a while. | ||
| Arcticktm |
But the supercharger itself is an efficiency penalty, since it has to use power from the engine to compress the air. turbos are getting less and less expensive as they become the dominant engine choice, so maybe that will encourage more Miller cycles in production. It sure seems like all the engine OEM's are working on it recently, thanks to better turbos and especially to very advanced variable timing systems becoming standard issue. Offsetting the piston bore very slightly from center has been used for decades to reduce "piston slap" as a standard practice. I hadn't paid attention to the offset cylinder bores, so thanks to Nate for mentioning that. | ||
| Aesquire |
The hot rodders that are getting silly horsepower out of the GM LS series engines have discovered that at high power the crank driven superchargers are breaking cranks with torsional resonance issues. That plus the fact that the power to drive a blower is directly taken from total power makes turbos much more attractive. The problem with turbos is finding room for the plumbing and the charge coolers. Also you need exotic materials for the turbos. & insulation from the glowing hot parts. In WW2 America had been doing turbo research since the 1920's and had the only mass production airplanes with turbochargers. That gave us a major advantage. B-17's and B-24's both used turbos, as did the P-38 & P-47. ( as part of a 2 stage blower setup. The Turbo fed an engine mounted centrifugal blower. ) Rolls Royce concentrated on mechanical 2 stage blowers with inter coolers. ( Spitfire + Mustang + some Mosquitoes ) That's right, one blower feeding the input of another to produce sea level or higher manifold pressure. The Reno Sport Class racing planes with turbos are leaning on ADI ( anti detonation injection ) squirting water/methanol mix both in the intake to cool the air, and on the engine & oil & charge coolers to cool them when extracting 700 hp out of a 300 hp engine. Not a good solution for normal use. Some use a 15 gallon tank of fluid in one race. | ||
| Fast1075 |
A Top Fuel engine that produces 10,000 horsepower needs 900-1,000 horsepower to drive the supercharger. Those engines run 90-100% nitro (depending on what rules are in effect) at the time. | ||
| Reepicheep |
I like the turbo in my Saab V6. Great economy, great power. I actually liked the turbo inline 4 in my previous Saab a little better... a little less power, but much simpler, easier to work on, and possibly more reliable. Maybe not though, that Saab V6 motor has some pretty fancy internals. But oh the sound of the supercharged Mini Cooper S (R-53)... The turbo may work better. But the noises that mini makes make me giggle happily. There is a lot to be said for that.  |
