I think its relative to how you drive. If you have a heavy foot then a 4 might be driven harder resulting in less efficiency since a 6 wont require as much to get up to speed. I have had great efficiency with both so hard to say
V6 More Efficient?
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The Grand Prix would get better mileage than the Camry if it was driven by me on a daily basis. Mom is too inconsistent and doesn't use her cruise. Why? A torque-y engine with a widely geared transmission that I would be able to keep below 2k RPM all day. The Camry is usually above 1.8k rpm all the time. The weigh close enough to be comparable. The Prizm on the other hand gets incredible mileage regardless.
Originally Posted By: B320i
At least in theory, a bigger engine shouldn't have to work very hard at all at highway speeds, whereas your typical 4-cylinder might be working harder.
Theoretically higher efficiency would come from the smallest engine that could cruise at a certain speed. How hard an engine works may actually mean it's more efficient.
Power generating equipment is the most efficient when near maximum output. It's not quite the same situation as a car though.
At least in theory, a bigger engine shouldn't have to work very hard at all at highway speeds, whereas your typical 4-cylinder might be working harder.
Theoretically higher efficiency would come from the smallest engine that could cruise at a certain speed. How hard an engine works may actually mean it's more efficient.
Power generating equipment is the most efficient when near maximum output. It's not quite the same situation as a car though.
Originally Posted By: y_p_w
Originally Posted By: B320i
At least in theory, a bigger engine shouldn't have to work very hard at all at highway speeds, whereas your typical 4-cylinder might be working harder.
Theoretically higher efficiency would come from the smallest engine that could cruise at a certain speed. How hard an engine works may actually mean it's more efficient.
Power generating equipment is the most efficient when near maximum output. It's not quite the same situation as a car though.
If you look at Cujet's post above, you'll see peak efficiency at around 2,000 RPM and about 80% load. I've seen this is true for a lot of engines. Not full load, just short of that. And most current engines seem to like 2k RPMs.
Conclusion: If you can manage to run an engine somewhere close to 2k RPM and near 80% load (approx), then you're running at peak efficiency. Hybrids try to do that, using the electric motor assist or generation to add or subtract vehicle commanded power.
If you read the original post's question, he just wanted the statement "V6s are more efficient than all else" debunked, thats all.
Sure we could, and have, launched into all kinds of tangential subjects here.
Originally Posted By: B320i
At least in theory, a bigger engine shouldn't have to work very hard at all at highway speeds, whereas your typical 4-cylinder might be working harder.
Theoretically higher efficiency would come from the smallest engine that could cruise at a certain speed. How hard an engine works may actually mean it's more efficient.
Power generating equipment is the most efficient when near maximum output. It's not quite the same situation as a car though.
If you look at Cujet's post above, you'll see peak efficiency at around 2,000 RPM and about 80% load. I've seen this is true for a lot of engines. Not full load, just short of that. And most current engines seem to like 2k RPMs.
Conclusion: If you can manage to run an engine somewhere close to 2k RPM and near 80% load (approx), then you're running at peak efficiency. Hybrids try to do that, using the electric motor assist or generation to add or subtract vehicle commanded power.
If you read the original post's question, he just wanted the statement "V6s are more efficient than all else" debunked, thats all.
Sure we could, and have, launched into all kinds of tangential subjects here.
Efficiency and fuel consumption are not the same thing.
BSFC is important in heavy duty, aircraft and similar applications where the engine needs to be constantly loaded. It simply means you get the most out vs in at that state.
However, in a typical automotive application, if you take the same vehicle and load one up 80% and another 20%, the less loaded one will get better fuel economy despite having less BSFC.
BSFC is important in heavy duty, aircraft and similar applications where the engine needs to be constantly loaded. It simply means you get the most out vs in at that state.
However, in a typical automotive application, if you take the same vehicle and load one up 80% and another 20%, the less loaded one will get better fuel economy despite having less BSFC.
Originally Posted By: TiredTrucker
Originally Posted By: d00df00d
The car around the engine has to be considered, too. A small inline-4 could get great fuel economy in a compact econobox. Put the same engine in a 3-ton SUV and it might do worse than a big V8. Even a bigger inline-4 wouldn't be a good idea because you'd get massive vibration above a certain displacement.
The question would then be.. what displacement would be too much? GM offers a 5.2L inline 4 diesel in some of their medium duty trucks. Have not heard of any issues with that.
Generally from about 2 litre displacement the manufacturers include balance shafts in a 4 cylinder engine. But it's a comfort thing really, some people will notice i you cut the balance shaft drive, others wont.
Originally Posted By: d00df00d
The car around the engine has to be considered, too. A small inline-4 could get great fuel economy in a compact econobox. Put the same engine in a 3-ton SUV and it might do worse than a big V8. Even a bigger inline-4 wouldn't be a good idea because you'd get massive vibration above a certain displacement.
The question would then be.. what displacement would be too much? GM offers a 5.2L inline 4 diesel in some of their medium duty trucks. Have not heard of any issues with that.
Generally from about 2 litre displacement the manufacturers include balance shafts in a 4 cylinder engine. But it's a comfort thing really, some people will notice i you cut the balance shaft drive, others wont.
Originally Posted By: artificialist
Given how many kinds of V6 engines there are, I would have a difficult time determining what engine design is ideal.
That in mind, there is one kind of V6 that I don't consider ideal for anything. That would be the kind of V6 which is basically a 90 degree V8 with 2 cylinders cut off. It is even worse when a balance shaft is added to compensate for the uneven design.
In theory, yes, the 90 deg V6 is not very good. In practice the GM 4.3 V6 is a super reliable engine. UOAs on my engine show it to be very low wearing and I expect never having to open up my engine during the twenty years I plan on keeping it. Rust will eventually claim the body but the truck will go to the scrapyard with a mint condition engine.
I don't have any regrets about going with the V6 on my truck.
Given how many kinds of V6 engines there are, I would have a difficult time determining what engine design is ideal.
That in mind, there is one kind of V6 that I don't consider ideal for anything. That would be the kind of V6 which is basically a 90 degree V8 with 2 cylinders cut off. It is even worse when a balance shaft is added to compensate for the uneven design.
In theory, yes, the 90 deg V6 is not very good. In practice the GM 4.3 V6 is a super reliable engine. UOAs on my engine show it to be very low wearing and I expect never having to open up my engine during the twenty years I plan on keeping it. Rust will eventually claim the body but the truck will go to the scrapyard with a mint condition engine.
I don't have any regrets about going with the V6 on my truck.
Engine efficiency is a measure of how much power/torque can be extracted from a given volume - a 100hp 1 litre engine is twice as efficient as a 100hp 2 litre engine.
Originally Posted By: Olas
Engine efficiency is a measure of how much power/torque can be extracted from a given volume - a 100hp 1 litre engine is twice as efficient as a 100hp 2 litre engine.
That is just one measure of engine efficiency. There are many others, including mechanical output for a given amount of fuel consumed.
Engine efficiency is a measure of how much power/torque can be extracted from a given volume - a 100hp 1 litre engine is twice as efficient as a 100hp 2 litre engine.
That is just one measure of engine efficiency. There are many others, including mechanical output for a given amount of fuel consumed.
Originally Posted By: B320i
34mpg from a full-size sedan in 2017 in the USA? Can tell you a certain European manufacturer's V12 was getting close to that figure in the 1990s.
The Inline-6 in my Euro gets up to 35.5mpg, that is only a tad worse than the factory claims - but this is A/C on at highway speeds. I've never been able to test A/C off on the highway - it gets uncomfortable.
At least in theory, a bigger engine shouldn't have to work very hard at all at highway speeds, whereas your typical 4-cylinder might be working harder.
As an anecdote, a friend's Daihatsu Sirion (a whopping 3cyl engine) when 3 passengers and two small dogs was constantly between 3rd and 4th at about 100km/h. 4th was enough mostly, but you'd have to plant your foot every so often to keep things going.
I suspect that you are using two different gallons in your comparisons...the rest of the world uses one that is 20% bigger than the US gallon.
You know, making a subtle switch would be a quick way to up the mileage of all US cars...
34mpg from a full-size sedan in 2017 in the USA? Can tell you a certain European manufacturer's V12 was getting close to that figure in the 1990s.
The Inline-6 in my Euro gets up to 35.5mpg, that is only a tad worse than the factory claims - but this is A/C on at highway speeds. I've never been able to test A/C off on the highway - it gets uncomfortable.
At least in theory, a bigger engine shouldn't have to work very hard at all at highway speeds, whereas your typical 4-cylinder might be working harder.
As an anecdote, a friend's Daihatsu Sirion (a whopping 3cyl engine) when 3 passengers and two small dogs was constantly between 3rd and 4th at about 100km/h. 4th was enough mostly, but you'd have to plant your foot every so often to keep things going.
I suspect that you are using two different gallons in your comparisons...the rest of the world uses one that is 20% bigger than the US gallon.
You know, making a subtle switch would be a quick way to up the mileage of all US cars...
A forced induction 4 cylinder engine can be efficient and smooth without a balancer shaft. The 1.6L supercharged engine in my car produces 154 HP and 170 ft/lbs of torque. It's returned a long term average of 44.5 MPG (imp) or 37 MPG (US).
In Europe 3 cylinder turbo engines are becoming very common in smaller cars, in fact naturally aspirated engines are fast becoming the exception. The big benefit of forced induction is low rev torque and the tall gearing that makes possible.
In Europe 3 cylinder turbo engines are becoming very common in smaller cars, in fact naturally aspirated engines are fast becoming the exception. The big benefit of forced induction is low rev torque and the tall gearing that makes possible.
Originally Posted By: Virtus_Probi
I suspect that you are using two different gallons in your comparisons...the rest of the world uses one that is 20% bigger than the US gallon.
You know, making a subtle switch would be a quick way to up the mileage of all US cars...
I happen to be well aware certain countries measure efficiency in another unit (Imperial Gallons as opposed to US Gallons).
The figures I quoted were used US Gallons for the MPG figure; obviously with a conversion from the standard Litres per 100 kilometres measurement used in Australia and many other countries utilising the metric system.
So yes, all the numbers in my post were comparable.
I suspect that you are using two different gallons in your comparisons...the rest of the world uses one that is 20% bigger than the US gallon.
You know, making a subtle switch would be a quick way to up the mileage of all US cars...
I happen to be well aware certain countries measure efficiency in another unit (Imperial Gallons as opposed to US Gallons).
The figures I quoted were used US Gallons for the MPG figure; obviously with a conversion from the standard Litres per 100 kilometres measurement used in Australia and many other countries utilising the metric system.
So yes, all the numbers in my post were comparable.
Originally Posted By: George7941
Originally Posted By: Olas
Engine efficiency is a measure of how much power/torque can be extracted from a given volume - a 100hp 1 litre engine is twice as efficient as a 100hp 2 litre engine.
That is just one measure of engine efficiency. There are many others, including mechanical output for a given amount of fuel consumed.
You're making the same pont as me, but the other way round. For a given AFR a given amount of fuel dictates a given volume. You can rearrange the equation but its still the same.
Originally Posted By: Olas
Engine efficiency is a measure of how much power/torque can be extracted from a given volume - a 100hp 1 litre engine is twice as efficient as a 100hp 2 litre engine.
That is just one measure of engine efficiency. There are many others, including mechanical output for a given amount of fuel consumed.
You're making the same pont as me, but the other way round. For a given AFR a given amount of fuel dictates a given volume. You can rearrange the equation but its still the same.
Originally Posted By: Olas
You're making the same point as me, but the other way round. For a given AFR a given amount of fuel dictates a given volume. You can rearrange the equation but its still the same.
I don't think so. The 1 litre engine might make the same power as the 2 litre engine but might waste energy, sending it down the exhaust by opening the exhaust valves early. So you would get the power output at the cost of wasted fuel.
You're making the same point as me, but the other way round. For a given AFR a given amount of fuel dictates a given volume. You can rearrange the equation but its still the same.
I don't think so. The 1 litre engine might make the same power as the 2 litre engine but might waste energy, sending it down the exhaust by opening the exhaust valves early. So you would get the power output at the cost of wasted fuel.
V6s are only the most efficient when run on 0w20 oil
V6 is the most efficient, and I6 is the torquiest. Toyota's last a million miles no exception and are never defective. 0w20 is engine-destroying water. German cars are unreliable and expensive and Lucas Oil Stabilizer protects your engine the best. These are basic facts that everyone 'just' knows.
Originally Posted By: George7941
Originally Posted By: Olas
You're making the same point as me, but the other way round. For a given AFR a given amount of fuel dictates a given volume. You can rearrange the equation but its still the same.
I don't think so. The 1 litre engine might make the same power as the 2 litre engine but might waste energy, sending it down the exhaust by opening the exhaust valves early. So you would get the power output at the cost of wasted fuel.
But the definition of efficiency is energy converted to work divided by energy supplied to the engine in fuel.
Regardless of where the design wastes the energy, the definition is the same...
Originally Posted By: Olas
You're making the same point as me, but the other way round. For a given AFR a given amount of fuel dictates a given volume. You can rearrange the equation but its still the same.
I don't think so. The 1 litre engine might make the same power as the 2 litre engine but might waste energy, sending it down the exhaust by opening the exhaust valves early. So you would get the power output at the cost of wasted fuel.
But the definition of efficiency is energy converted to work divided by energy supplied to the engine in fuel.
Regardless of where the design wastes the energy, the definition is the same...
Agreed, but I am saying the 1 litre engine might be using more fuel, because of energy loss down the exhaust, and thus less efficient.
"Engine efficiency is a measure of how much power/torque can be extracted from a given volume - a 100hp 1 litre engine is twice as efficient as a 100hp 2 litre engine." The volume Olas is referring to is engine displacement, not the volume of air/fuel mixture consumed.
"Engine efficiency is a measure of how much power/torque can be extracted from a given volume - a 100hp 1 litre engine is twice as efficient as a 100hp 2 litre engine." The volume Olas is referring to is engine displacement, not the volume of air/fuel mixture consumed.
Originally Posted By: Olas
Engine efficiency is a measure of how much power/torque can be extracted from a given volume - a 100hp 1 litre engine is twice as efficient as a 100hp 2 litre engine.
No. Torque per unit displacement volume is essentially BMEP (brake mean effective pressure). Power per unit displacement is specific power. Both are significant values to describe an engine, but they are neither energy efficiency (defined above by Shannow) nor volumetric efficiency.
Engine efficiency is a measure of how much power/torque can be extracted from a given volume - a 100hp 1 litre engine is twice as efficient as a 100hp 2 litre engine.
No. Torque per unit displacement volume is essentially BMEP (brake mean effective pressure). Power per unit displacement is specific power. Both are significant values to describe an engine, but they are neither energy efficiency (defined above by Shannow) nor volumetric efficiency.
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