this will interest some of you:
http://www.motortrend.com/news/infiniti-prepares-worlds-first-variable-compression-engine-for-2018/
http://www.motortrend.com/news/infiniti-prepares-worlds-first-variable-compression-engine-for-2018/
variable compression engine coming to production
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sorry meant to post in automotive general topics not here.
Not exactly new, the camless valve train has been around for a couple years now.
Opposing thoughts:
1. This will be a dead-end technology - it will malfunction regularly, and repairs will be complex to the point that it's cheaper to replace the engine. Aftermarket override software will be adopted by most of the owners whose engines survive. Nissan will drop it quickly.
OR
2. It's the way of the future, and will be just as reliable as the best-done variable valve-timing systems.
We'll know in a few years.
1. This will be a dead-end technology - it will malfunction regularly, and repairs will be complex to the point that it's cheaper to replace the engine. Aftermarket override software will be adopted by most of the owners whose engines survive. Nissan will drop it quickly.
OR
2. It's the way of the future, and will be just as reliable as the best-done variable valve-timing systems.
We'll know in a few years.
I don't like the idea of all that rotting hardware and linkage in the crankcase making the engine a great big oil blender. I like Ford's idea of a truck engine, 2.7 liter V6 with twin turbos. At 325hp and 375lb-ft of torque. That would be considered good for a big V8 a few years ago.
Interesting read. Aside from a super complex engine, this sounds as though it can be great!
Originally Posted By: OneEyeJack
I don't like the idea of all that rotting hardware and linkage in the crankcase making the engine a great big oil blender. I like Ford's idea of a truck engine, 2.7 liter V6 with twin turbos. At 325hp and 375lb-ft of torque. That would be considered good for a big V8 a few years ago.
Except the Ford ecoboost products are not known for great fuel economy. This engine claim to fame is much better fuel economy.
In saying that, I would not want one after the warranty is up.
I don't like the idea of all that rotting hardware and linkage in the crankcase making the engine a great big oil blender. I like Ford's idea of a truck engine, 2.7 liter V6 with twin turbos. At 325hp and 375lb-ft of torque. That would be considered good for a big V8 a few years ago.
Except the Ford ecoboost products are not known for great fuel economy. This engine claim to fame is much better fuel economy.
In saying that, I would not want one after the warranty is up.
SAAB tried it a while back. Not one of their better ideas.
Quote:
Infiniti Preparing World’s First Variable-Compression Engine for 2018
I guess it depends what they mean by "First".
It's been nearly 100 years since Sir Harry Ricardo invented the variable compression engine.
Infiniti Preparing World’s First Variable-Compression Engine for 2018
I guess it depends what they mean by "First".
It's been nearly 100 years since Sir Harry Ricardo invented the variable compression engine.
Originally Posted By: Danno
Originally Posted By: OneEyeJack
I don't like the idea of all that rotting hardware and linkage in the crankcase making the engine a great big oil blender. I like Ford's idea of a truck engine, 2.7 liter V6 with twin turbos. At 325hp and 375lb-ft of torque. That would be considered good for a big V8 a few years ago.
Except the Ford ecoboost products are not known for great fuel economy. This engine claim to fame is much better fuel economy.
In saying that, I would not want one after the warranty is up.
The gas mileage of the 2.7 Ford should be compared to other engines developing over 300hp not use any other 2.7 engine. Power costs fuel. What you get out of this setup is a lighter engine package.
Originally Posted By: OneEyeJack
I don't like the idea of all that rotting hardware and linkage in the crankcase making the engine a great big oil blender. I like Ford's idea of a truck engine, 2.7 liter V6 with twin turbos. At 325hp and 375lb-ft of torque. That would be considered good for a big V8 a few years ago.
Except the Ford ecoboost products are not known for great fuel economy. This engine claim to fame is much better fuel economy.
In saying that, I would not want one after the warranty is up.
The gas mileage of the 2.7 Ford should be compared to other engines developing over 300hp not use any other 2.7 engine. Power costs fuel. What you get out of this setup is a lighter engine package.
Originally Posted By: HerrStig
SAAB tried it a while back. Not one of their better ideas.
They never put it into production, and for good reasons. It was a neat idea - moving the cylinder block relative to the crankcase - but that means one half of your engine is moving relative to the mounting points. This is a nightmare in terms of ducting, wiring, and other services attached to the engine, plus they apparently suffered some sealing issues in the 'bellows' between the two halves.
Variable compression is a great idea and this Nissan approach is similar to other concepts I have seen before (an intermediate variable fulcrum in the conrod assembly) - I doubt they would commercialise it without significant durability testing. My initial thought was that it makes the engine significantly larger and potentially heavier, but the efficiency benefits will surely overcome this (and more). They are slating it as the end of the light-duty diesel engine.
SAAB tried it a while back. Not one of their better ideas.
They never put it into production, and for good reasons. It was a neat idea - moving the cylinder block relative to the crankcase - but that means one half of your engine is moving relative to the mounting points. This is a nightmare in terms of ducting, wiring, and other services attached to the engine, plus they apparently suffered some sealing issues in the 'bellows' between the two halves.
Variable compression is a great idea and this Nissan approach is similar to other concepts I have seen before (an intermediate variable fulcrum in the conrod assembly) - I doubt they would commercialise it without significant durability testing. My initial thought was that it makes the engine significantly larger and potentially heavier, but the efficiency benefits will surely overcome this (and more). They are slating it as the end of the light-duty diesel engine.
Originally Posted By: CT8
Lots of moving parts lots ofproblems potential problems.
FTFY
Lots of moving parts lots of
FTFY
Originally Posted By: OneEyeJack
The gas mileage of the 2.7 Ford should be compared to other engines developing over 300hp not use any other 2.7 engine. Power costs fuel. What you get out of this setup is a lighter engine package.
Lighter than what? I looked up the 2.7/3.5/5.0 current engines, and it was like 10 pounds difference between the engines. Lighter than the 4.6, granted, but the 2.7 wasn't lighter (by much) than the other Ford engines. I was a bit surprised.
Am guessing a small displacement engine has less surface area to lose heat to. Bearing surfaces have to be sized for the power, but smaller bores with shorter strokes should lead to less energy lost to rings too I'm guessing.
The gas mileage of the 2.7 Ford should be compared to other engines developing over 300hp not use any other 2.7 engine. Power costs fuel. What you get out of this setup is a lighter engine package.
Lighter than what? I looked up the 2.7/3.5/5.0 current engines, and it was like 10 pounds difference between the engines. Lighter than the 4.6, granted, but the 2.7 wasn't lighter (by much) than the other Ford engines. I was a bit surprised.
Am guessing a small displacement engine has less surface area to lose heat to. Bearing surfaces have to be sized for the power, but smaller bores with shorter strokes should lead to less energy lost to rings too I'm guessing.
Originally Posted By: supton
Originally Posted By: OneEyeJack
The gas mileage of the 2.7 Ford should be compared to other engines developing over 300hp not use any other 2.7 engine. Power costs fuel. What you get out of this setup is a lighter engine package.
Lighter than what? I looked up the 2.7/3.5/5.0 current engines, and it was like 10 pounds difference between the engines. Lighter than the 4.6, granted, but the 2.7 wasn't lighter (by much) than the other Ford engines. I was a bit surprised.
Am guessing a small displacement engine has less surface area to lose heat to. Bearing surfaces have to be sized for the power, but smaller bores with shorter strokes should lead to less energy lost to rings too I'm guessing.
You have to compare the weight to a 5 to 6 liter V8 engine that produces similar power, not a 4 liter V6.
Originally Posted By: OneEyeJack
The gas mileage of the 2.7 Ford should be compared to other engines developing over 300hp not use any other 2.7 engine. Power costs fuel. What you get out of this setup is a lighter engine package.
Lighter than what? I looked up the 2.7/3.5/5.0 current engines, and it was like 10 pounds difference between the engines. Lighter than the 4.6, granted, but the 2.7 wasn't lighter (by much) than the other Ford engines. I was a bit surprised.
Am guessing a small displacement engine has less surface area to lose heat to. Bearing surfaces have to be sized for the power, but smaller bores with shorter strokes should lead to less energy lost to rings too I'm guessing.
You have to compare the weight to a 5 to 6 liter V8 engine that produces similar power, not a 4 liter V6.
Originally Posted By: 02SE
Quote:
Infiniti Preparing World’s First Variable-Compression Engine for 2018
I guess it depends what they mean by "First".
It's been nearly 100 years since Sir Harry Ricardo invented the variable compression engine.
Yes- that R + M / 2 gibberish you see below the octane number on that big yellow square on the gas pump means, "Research octane" -derived from chemical analysis, plus "Motor octane" -the point at which one of Ricardo's engine designs knocks to a predetermined level as compression is increased, added up and divided by two to come to a determination of a gasoline's resistance to knock (pre-ignition, not "ping").
Quote:
Infiniti Preparing World’s First Variable-Compression Engine for 2018
I guess it depends what they mean by "First".
It's been nearly 100 years since Sir Harry Ricardo invented the variable compression engine.
Yes- that R + M / 2 gibberish you see below the octane number on that big yellow square on the gas pump means, "Research octane" -derived from chemical analysis, plus "Motor octane" -the point at which one of Ricardo's engine designs knocks to a predetermined level as compression is increased, added up and divided by two to come to a determination of a gasoline's resistance to knock (pre-ignition, not "ping").
Of course, they could do all they're trying to accomplish by getting rid of camshafts and going to hydraulically-actuated, infinitely-variable valve timing, lift and duration. Use engine oil on top of valve stem covers, controlled in the way fuel injection is, to "blow" valves open whatever distance or time the engine's conditions call for. If you wanted desmodromic, you could have the pressure work under the follower to pull them shut.
Which still won't give you the flexibility of electric motor motive power.
Which still won't give you the flexibility of electric motor motive power.
Originally Posted By: Defiant
Yes- that R + M / 2 gibberish you see below the octane number on that big yellow square on the gas pump means, "Research octane" -derived from chemical analysis, plus "Motor octane" -the point at which one of Ricardo's engine designs knocks to a predetermined level as compression is increased, added up and divided by two to come to a determination of a gasoline's resistance to knock (pre-ignition, not "ping").
Not quite. Research Octane Number (RON) is determined by the same engine as Motor Octane Number (MON), just under different conditions. From memory RON is run with variable ignition timing whereas MON runs with fixed ignition timing, making it a more severe test (hence why MON is always lower than RON). There are also some other differences (I'm stretching my memory here, but maybe something to do with inlet air temperature and some other parameters).
The maths after that is, as you say, the average of the RON and MON, sometimes called the Anti-Knock Index (AKI). Over here (and most places outside of there) we use only RON values on pump fuel.
Yes- that R + M / 2 gibberish you see below the octane number on that big yellow square on the gas pump means, "Research octane" -derived from chemical analysis, plus "Motor octane" -the point at which one of Ricardo's engine designs knocks to a predetermined level as compression is increased, added up and divided by two to come to a determination of a gasoline's resistance to knock (pre-ignition, not "ping").
Not quite. Research Octane Number (RON) is determined by the same engine as Motor Octane Number (MON), just under different conditions. From memory RON is run with variable ignition timing whereas MON runs with fixed ignition timing, making it a more severe test (hence why MON is always lower than RON). There are also some other differences (I'm stretching my memory here, but maybe something to do with inlet air temperature and some other parameters).
The maths after that is, as you say, the average of the RON and MON, sometimes called the Anti-Knock Index (AKI). Over here (and most places outside of there) we use only RON values on pump fuel.
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