jasonj80 Posted November 16, 2017 Share Posted November 16, 2017 Pretty cool engine tech - not sure I'd be the first one to own it though.http://www.autonews.com/article/20171116/OEM/171119828/nissan-engine-infiniti-qx50-turbo 1 Quote Link to comment Share on other sites More sharing options...
akirby Posted November 16, 2017 Share Posted November 16, 2017 I can't read the article but I thought a European mfr already had a variable compression engine - or was that one not yet in production? Quote Link to comment Share on other sites More sharing options...
akirby Posted November 16, 2017 Share Posted November 16, 2017 I can't read the article but I thought a European mfr already had a variable compression engine - or was that one not yet in production? It was Saab who had the concept years ago, but it got shelved when they were bought by GM. Quote Link to comment Share on other sites More sharing options...
mustang_sallad Posted November 16, 2017 Share Posted November 16, 2017 it really says something about how incredibly valuable fossil fuels are when you see how complex engines can become just to eek out 26mpg. It's amazing to me that all of the engineering effort was deemed worthwhile. 1 Quote Link to comment Share on other sites More sharing options...
92merc Posted November 16, 2017 Share Posted November 16, 2017 I think I read an article awhile back. But it was labeled at the time as a Nissan engine. Kudo's for engineering ability. But I guess I just don't see the point. Doesn't turbo essentially give you variable compression? Higher boost equals higher compression. Low boost is low compression. I guess I'd rather see Ford go the HCCI route with compression detonation than this. Quote Link to comment Share on other sites More sharing options...
akirby Posted November 17, 2017 Share Posted November 17, 2017 Not really. Forced induction puts more air into the cylinder at the beginning (and therefore more oxygen). Compression ratio is how much you compress that air inside the cylinder. Quote Link to comment Share on other sites More sharing options...
fordmantpw Posted November 17, 2017 Share Posted November 17, 2017 I think I read an article awhile back. But it was labeled at the time as a Nissan engine. Kudo's for engineering ability. But I guess I just don't see the point. Doesn't turbo essentially give you variable compression? Higher boost equals higher compression. Low boost is low compression. I guess I'd rather see Ford go the HCCI route with compression detonation than this. Forced induction is closer to variable displacement than variable compression. If you force twice as much air in (14 PSI on the turbo at sea level), then you essentially double the displacement of the engine. 1 Quote Link to comment Share on other sites More sharing options...
rperez817 Posted November 17, 2017 Share Posted November 17, 2017 Doesn't turbo essentially give you variable compression? Higher boost equals higher compression. Low boost is low compression. Most turbocharged and supercharged spark ignition and diesel engines in production cars and trucks have a constant compression ratio. This is the difference between volume in the combustion chamber when the piston is at BDC and when the piston is at TDC. The turbocharger doesn't change this ratio. For example, on the JLR Ingenium 2.0L turbo diesel the difference between BDC and TDC is always 15.5:1. The original Miller Cycle patent in the 1950s was effectively a variable compression ratio design. Modern engines that use Miller Cycle like Nissan HR12DDR have a constant compression ratio but a larger expansion ratio by holding the intake valve open longer compared to Otto Cycle. http://www.nissan-global.com/EN/TECHNOLOGY/OVERVIEW/hr12ddr.html 1 Quote Link to comment Share on other sites More sharing options...
old_fairmont_wagon Posted November 24, 2017 Share Posted November 24, 2017 For a "recent" smaller application of the Miller cycle, take a look at one of the V6 engines that was offered in the Mazda Millenia S. The problem with "Spit-Back" is that it does make meeting environmental emissions a bit more difficult vs. the normal Otto cycle. The Nissan approach here attempts to get all of the benefit and as little of the problems as possible. It does, however, add to engine complexity. Quote Link to comment Share on other sites More sharing options...
LSchicago Posted November 24, 2017 Share Posted November 24, 2017 International was doing this since the 30's, but mostly on tractors. It was on a diesel truck too. Compression was lowered, it would start on gas, then after warming up a bit switch to diesel while increasing compression. Best way to start cold diesels back then. Quote Link to comment Share on other sites More sharing options...
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