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I think you're starting to get closer to where you need to be. Friction losses are roughly area dependent, increasing at a 1:1 ratio. Hydrodynamic losses are very different, increasing with the square of speed! Double the rpm, and the drag increases four times!
This is an important distinction, since there is practically no metal-to-metal contact in a modern engine, during operation. In other words, there is next-to-no "friction" at operating speeds. The parasitic drag is due to the moving parts operating in an oil film, and the fluid or hydrodynamic drag which comes from that.
That's why there is so much emphasis on the use of lower-viscosity oils these days. They reduce hydrodynamic drag (thus increasing power and fuel economy). as long as they don't get so thin that they result in metal-to-metal contact.
GM (and others) have the friction numbers from tests. I'm confident from what I did in my Street Rod to reduce coolant temp at idle by altering the area exposed to exhaust gases that area has a significant affect of energy conducting into the coolant. Too long (even for me) to quote the references here.
However GM went to a 2.7 Liter double overhead cam turbo engine for the Silverado for good reason and tests!
The DOHC V-8 solves no problems and just adds cost and weight.
Whatever the reasons, GM has the tests and understands it better that you or I for their engines. They went to a 2.7 Liter double overhead cam turbo engine for improved efficiency. Has more to do with using some of the otherwise wasted exhaust - but whatever- it's more efficient.
A double overhead cam allows independent adjustment of intake and exhaust cam timing. A single cam that can only change both the same amount as in the C7.
They can be optimized to provide best mpg at low throttle openings when cruising and for max power at high power levels. These are all factors in engine efficiency for different conditions.
That 2.4 L 4 banger comes up way short in the Silverado when it comes to work. May be good for general transportation but not work.
Two wheel drive crew cab with short box towing numbers:
I get it, but if I scale up the 2.7L I-4 to pull 15,000 lb.s, the displacement only moves up to 3.4L. This is not unheard of for an I-4. It will likely be what replaces the V-8's in the not to distant future.
I get it, but if I scale up the 2.7L I-4 to pull 15,000 lb.s, the displacement only moves up to 3.4L. This is not unheard of for an I-4. It will likely be what replaces the V-8's in the not to distant future.
If you scale it up enough to match the V8 then what was the point, just go with the V8 to start with.
Friction losses are area dependent and probably higher at higher rpm but my guess not in proportion. GM has the numbers.
The surface area conducting combustion gases into the coolant (where ~30% of the energy is wasted) are much more dependent on area.
GM and other manufacturers know the numbers and they produced the 2.7 Liter double overhead cam turbo engine for the Silverado (585,000 sold in 2018) because of efficiency. That is why engines in most parts of the world are smaller, not that they like the buzz!
Funny you bring up the Silverado 2.7L I4, you must of missed it when I posted that above.
In real world driving the I4 Silverado gets WORSE gas mileage than the V8... AND the Denali with its 6.2L V8 tied the 2.7L I4 in MPG... https://www.caranddriver.com/news/a2...-economy-test/
And according to the EPA tests the 5.3L silverado gets equal or better highway mileage and only gives up 3mpg city driving to something that is roughly half the displacement.
Only in the US are we enamored with big cid- like my 502 cid! If building a Street Rod today would use the 572 cid crate engine!
Yes because we are one of the only countries without idiotic displacement taxes/displacement related charges. Most other countries have penalties ($$$) on displacement, don't allow modding (or only allow certain modding), or have such high gas prices that hotrodding isn't anywhere near as big as it is in the US, and by "hotrodding" I don't mean just big CI classic cars, I mean the whole performance car scene in general.
Hell, in Japan you have to pay more (heavy) taxes for older cars, incentivizing you to buy a new car every so often and sell off anything old.
God bless the US for how our automotive laws are based, we have one of the most free markets there is.
OK, so why is the new Silverado 2.7L more efficient than the 5.3L V-8 it is replacing ? Answer is the turbo which increases volumetric efficiency and compression ratio, and the the fact that it is an I-4 which means large pistons. Large turbo I-4's are the future, gents. Couple a 3.0L I-4 with an integral starter generator and a big battery, and you have the IC engine of the future, including Corvette.
And if this is the case just give me a full EV Corvette at that point. I don't want a buzzing, farting I4 under the hood of something like a Corvette, doesn't belong/doesn't fit the character.
The DOHC V-8 solves no problems and just adds cost and weight.
Funny you bring up the Silverado 2.7L I4, you must of missed it when I posted that above.
In real world driving the I4 Silverado gets WORSE gas mileage than the V8... AND the Denali with its 6.2L V8 tied the 2.7L I4 in MPG... https://www.caranddriver.com/news/a2...-economy-test/
And according to the EPA tests the 5.3L silverado gets equal or better highway mileage and only gives up 3mpg city driving to something that is roughly half the displacement.
Yes, it's bizarre how prevalent the belief is that smaller engines automatically provide better fuel economy, despite evidence to the contrary. But as long as people believe this, I suppose it would be poor marketing if the auto companies didn't try to take advantage of it.
The EPA highway test is a strange one, since it uses lower speeds and loads than typically encountered on a freeway. Unless one actually drives an average of 50 mph on the freeway, which would probably get you killed around here.
My wife's little four-banger gets excellent fuel economy at 50 mph (where it is operating in its best efficiency range), but this seriously degrades at 70-75 mph. This in not what people will read on the window sticker though, and that's all most people know.
Last edited by Warp Factor; 03-18-2019 at 05:43 AM.
^^^
First an exec at GM Trucks said these initial EPA #'s have nothing to do with what is clearly better mpg in typical driving. They will work out whatever it takes to get better EPA numbers!
You fellows make me laugh! You find anecdotal comparisons and think car companies, with many engineers, making many prototypes, using the latest gas flow and combustion simulation computer software, crunching in Cray computers don't know what they are doing! Yep they should listed to your subjective opinions!
You should read the SAE paper on the C7 combustion chamber and piston top design developed with one cylinder models! Yep, with direct injection, using the optimum intake and exhaust cam timing can get lean mixtures properly igniting for optimum mpg.
Sure all they had to do was get a 572 cid (9.4 Liter) crate motor off the shelf and have it run at 500 rpm and they can get 50 mpg! Knew those "oil companies" had that secret approach they have been keeping under raps all these years!
I'm always surprised there are folks who still believe the oil companies have purposely kept secret the ways "THEY KNOW" can double mpg!
I do agree it depends on use and if you are towing with a Silverado no doubt best to get the 3 Liter diesel when available!
^^^
You fellows make me laugh! You find anecdotal comparisons and think car companies, with many engineers, making many prototypes, using the latest gas flow and combustion simulation computer software, crunching in Cray computers don't know what they are doing!
LOL, having an understanding of what the auto companies are doing, and why, is not a suggestion that they don't know what they are doing! On the contrary, they are very good at designing engines which are specifically targeted to provide good emissions and fuel economy under the exact set of testing conditions the regulating bodies use. What the engines do under other conditions (even if performing better under the test conditions makes them worse under other conditions) doesn't matter so much, because it's not what the government looks at, and doesn't get printed on the new car window sticker.
In other words, "your mileage may vary".
Originally Posted by JerryU
Sure all they had to do was get a 572 cid (9.4 Liter) crate motor off the shelf and have it run at 500 rpm and they can get 50 mpg!
They probably can, in steady-state freeway driving where the engine weight doesn't matter, and with a cam designed to give maximum efficiency at that rpm.
Look at over-the-road tractor trailer powerplants, where fuel economy really makes a big difference in expenses and profitability:
One example is 780 cubic inches, and makes 300-500 horsepower. Do they need such a large displacement to achieve that power level? Heck no! What it allows them to do is make that power at 1500-2200 rpm, using extremely lean fuel/air ratios, and that is what turns out to be best for fuel economy. Not a smaller engine making the same power.
Last edited by Warp Factor; 03-18-2019 at 09:03 AM.
Searching Comments GM Made re Silverado 2.7 L MPG; Found Them PLUS An Interesting Possibility Mentioned in The Article:
GM Comments: "I don't think we're done with the fuel economy piece yet," said Tim Herrick, executive chief engineer of GM's full-size trucks, during a Silverado media drive here. "We learn more and more every day.""Don't look at the label," said Herrick. "We're as good or better than them in every step." EPA testing methods as well as a larger design footprint also may have played a role in the lower-than-expected ratings, which GM may look to address soon.
GM said the new engine package goes from 0 to 60 mph in less than 7 seconds and weighs 380 pounds less than the previous model. GM also made changes to reduce turbo lag."We wanted it to exceed our customers' expectations, all while delivering requirements that the government has set," said Kevin Luchansky, engine architect and assistant chief engineer of the 2.7-liter turbo. "The fact that it doesn't have two more cylinders on it doesn't hurt our customers at all."The focus on low-end torque was crucial, Luchansky said, because it provides better acceleration where drivers spend most of their time and helps with fuel economy in those settings. Brinley said that despite the EPA's fuel economy numbers, if the four-cylinder trucks indeed perform better in real-world driving, that's "more important" to consumers than a number on the sticker.
My Thoughts: Looks like they optimized the engine for performance so buyers would be "happier" with the small cid L4. My guess is it could be optimized for mpg. There was an interesting addition mentioned and referenced in the article BUT not directly attributed to GM! Wonder if the author was given an "off the record comment" that made him add it! Be more logical then just tripping across it! (Have done that with tech magazine writers, myself!)
Perhaps GM is waiting for the addition of a small light weight hybrid to optimize the 2.7 Liter engine?? That article also showed a ZF DCT that incorporates a electric motor/generation between the clutches and the gear box! The link it referenced said what I have been predicting the C8 would use to significantly increase mpg, i.e. Stop/Start coupled with a small KERS hybrid! Then the ICE would NOT start from a stop until the car/truck reached ~cruising speed in normal diving! Only need a relatively small battery like F1 where it weighs ~30 lbs! So where all ICEs, particularly a small engine, get low mpg, accelerating to cruising speed, with this small KERS system it doesn't have to! And it charges the extra battery when braking or costing (similar to our current BMW X5 SUV!)
ZF Article: In systems for mild hybrid drives, the electric motor provides up to 15 kilowatts (20 hp) of power at torque of over 200 newton meters (147 ft-lbs.) This means that the additional torque of the electric motor provides support upon acceleration. This is also known as an electric "boost". In addition, the electric motor enables operation with automatic engine stop. Thanks to the electric support, the combustion engine runs in its optimal efficiency range during driving. This reduces fuel consumption and CO2 emissions. Full hybrid systems even offer the advantage of being able to cover short distances solely using electric power,with zero emissions locally. A separating clutch is therefore built into the full hybrid variant of the 8-speed automatic transmission, between the combustion engine and the electric motor. This disengages the combustion engine for these operating phases.
Someone often thinks of my best ideas before I "Invent them!"
There are some neat internal combustion engine things waiting on the shelf, or in the pipeline, for the time when they were needed.
One of these is the compression-ignition gasoline engine. This allows three things:
1. Extremely high compression ratios, which contribute to extracting the most motive power from fuel.
2. No throttle blade restricting air flow, so reduced air pumping losses. Energy is wasted filling a cylinder from an intake manifold which is under vacuum. The piston basically needs to "suck harder" , and that energy is taken from the crankshaft.
3. The ability to run extremely lean air/fuel ratios. A flame front ignited by a spark needs something close to a stoich mixture to spread and propagate. A compression ignition engine does not. It can operate just fine under ridiculously lean conditions.
Unfortunately, various under-informed politicians and "green people" have been so seduced by the notion of electric vehicles, that some of these Internal combustion engine advancements will probably never make it into the marketplace. Internal combustion engines are scheduled to be totally outlawed in some European cities. Does GM want to sell cars there?
If so, they are better off putting more of their emphasis on electric vehicles. GM's attorneys are really good at fighting warranty and class-action claims, but legal finagling doesn't work so well when it comes to selling vehicles in countries like France and China.
Last edited by Warp Factor; 03-18-2019 at 10:44 AM.
^^^ They have not through the implications of all EVs! Or if so, as typical politicians won't say until the crisis exists!
All but France has no way to build the electric grid to power those EV's without fossil fuel. Electric Utilities have to build capacity to make up when it rains and wind doesn't blow. Who will pay for that added capacity? Also the maintenance cost and life of solar cell systems is not in their equation. Recently consulted for a wind tower fabricator and the life is 20 years. Than fatigue caused by those large blades passing the tower causes failure! No one cared, as the Federal subsidy said 20 year life! (In fact the reason I was consulting is some will not make 20 years because of minor weld defects that grow with each pass of a blade!)
Now in France, 75% of their power is produced by Nuclear. (Try getting that passed in the US IF we had the money.) They can build more if they had the funds! BUT will the public revolt when they find the $10/gallon gas tax that pays for their 'free' social programs is not there. Lets see perhaps a $50/loaf tax on bread! They have been through that before when Marie with "let them eat cake" lost her head!
Searching Comments GM Made re Silverado 2.7 L MPG; Found Them PLUS An Interesting Possibility Mentioned in The Article:
GM Comments: "I don't think we're done with the fuel economy piece yet," said Tim Herrick, executive chief engineer of GM's full-size trucks, during a Silverado media drive here. "We learn more and more every day.""Don't look at the label," said Herrick. "We're as good or better than them in every step." EPA testing methods as well as a larger design footprint also may have played a role in the lower-than-expected ratings, which GM may look to address soon.
GM said the new engine package goes from 0 to 60 mph in less than 7 seconds and weighs 380 pounds less than the previous model. GM also made changes to reduce turbo lag."We wanted it to exceed our customers' expectations, all while delivering requirements that the government has set," said Kevin Luchansky, engine architect and assistant chief engineer of the 2.7-liter turbo. "The fact that it doesn't have two more cylinders on it doesn't hurt our customers at all."The focus on low-end torque was crucial, Luchansky said, because it provides better acceleration where drivers spend most of their time and helps with fuel economy in those settings. Brinley said that despite the EPA's fuel economy numbers, if the four-cylinder trucks indeed perform better in real-world driving, that's "more important" to consumers than a number on the sticker.
My Thoughts: Looks like they optimized the engine for performance so buyers would be "happier" with the small cid L4. My guess is it could be optimized for mpg. There was an interesting addition mentioned and referenced in the article BUT not directly attributed to GM! Wonder if the author was given an "off the record comment" that made him add it! Be more logical then just tripping across it! (Have done that with tech magazine writers, myself!)
Perhaps GM is waiting for the addition of a small light weight hybrid to optimize the 2.7 Liter engine?? That article also showed a ZF DCT that incorporates a electric motor/generation between the clutches and the gear box! The link it referenced said what I have been predicting the C8 would use to significantly increase mpg, i.e. Stop/Start coupled with a small KERS hybrid! Then the ICE would NOT start from a stop until the car/truck reached ~cruising speed in normal diving! Only need a relatively small battery like F1 where it weighs ~30 lbs! So where all ICEs, particularly a small engine, get low mpg, accelerating to cruising speed, with this small KERS system it doesn't have to! And it charges the extra battery when braking or costing (similar to our current BMW X5 SUV!)
ZF Article: In systems for mild hybrid drives, the electric motor provides up to 15 kilowatts (20 hp) of power at torque of over 200 newton meters (147 ft-lbs.) This means that the additional torque of the electric motor provides support upon acceleration. This is also known as an electric "boost". In addition, the electric motor enables operation with automatic engine stop. Thanks to the electric support, the combustion engine runs in its optimal efficiency range during driving. This reduces fuel consumption and CO2 emissions. Full hybrid systems even offer the advantage of being able to cover short distances solely using electric power,with zero emissions locally. A separating clutch is therefore built into the full hybrid variant of the 8-speed automatic transmission, between the combustion engine and the electric motor. This disengages the combustion engine for these operating phases.
Someone often thinks of my best ideas before I "Invent them!"
See the part about the 380 pound reduction. That is correct. the truck weighs 380 pounds less than the older model truck, but the 4 banger engine is only 80 pounds less weight. The new "engine package" does not weigh 380 pounds less than the old "engine package".
The highway gas mileage is the same as the old 5.3L V8 but because the "new" 4 banger has start/stop, it does have better city gas mileage. Put the same feature on the 5.3L V8 and it's city gas mileage will also improve.
I predict that the 4 banger in the new Silverado will end up just like the 4 banger in the 1962 Chevy II. Everyone wanted the straight 6 or V8 in 1962, not a 4 banger, so the 4 banger tooling, etc was moved to South America for use in cars built there for the South American market.
About 10-12 years ago, GM designed a "new" 72 degree 4.5L diesel V8 with the HOT V turbo setup and completely tooled up for production to be used in their mid size pickups. No telling how many hundreds of million of dollars was spent. Yet it never made it into a production truck.
^^
Anything is possible BUT today there will NOT be the choice! GM needs to meet a corporate MPG goal OR they (not the buyer) pay a step penalty! If the political folks wanting no fossil fuel in 10 years get their way, there will be a push for meeting those goals faster. That V8 may first be a $4000 option then not available! The Car World is Changing Fast.
Maybe the burger world as well! Let's see, will be in CA this week visiting family. Half are vegetarians and frankly you can learn to like soy burgers!
See the part about the 380 pound reduction. That is correct. the truck weighs 380 pounds less than the older model truck, but the 4 banger engine is only 80 pounds less weight. The new "engine package" does not weigh 380 pounds less than the old "engine package".
The highway gas mileage is the same as the old 5.3L V8 but because the "new" 4 banger has start/stop, it does have better city gas mileage. Put the same feature on the 5.3L V8 and it's city gas mileage will also improve.
I predict that the 4 banger in the new Silverado will end up just like the 4 banger in the 1962 Chevy II. Everyone wanted the straight 6 or V8 in 1962, not a 4 banger, so the 4 banger tooling, etc was moved to South America for use in cars built there for the South American market.
About 10-12 years ago, GM designed a "new" 72 degree 4.5L diesel V8 with the HOT V turbo setup and completely tooled up for production to be used in their mid size pickups. No telling how many hundreds of million of dollars was spent. Yet it never made it into a production truck.
Thanks for all your contributions. You and JD AMG are willing to spend more time and research and intelligence on countering internet BS than I am.
Last edited by Warp Factor; 03-18-2019 at 01:55 PM.
^^^ They have not through the implications of all EVs! Or if so, as typical politicians won't say until the crisis exists!
All but France has no way to build the electric grid to power those EV's without fossil fuel. Electric Utilities have to build capacity to make up when it rains and wind doesn't blow. Who will pay for that added capacity? Also the maintenance cost and life of solar cell systems is not in their equation. Recently consulted for a wind tower fabricator and the life is 20 years. Than fatigue caused by those large blades passing the tower causes failure! No one cared, as the Federal subsidy said 20 year life! (In fact the reason I was consulting is some will not make 20 years because of minor weld defects that grow with each pass of a blade!)
The electric grid of the 70s could never support the internet of the 90s. Cell phone towers of the 90s could never support the smart phone revolution of today.
Parts don't last forever, so we may as well forget about using parts.
I guess we'll just have to tuck tail and give up like a bunch of American'ts.
The electric grid of the 70s could never support the internet of the 90s.
Personal computers and the interned draw hardy any power from the grid, compared to what plug-in cars are positioned to do.
Fully electric cars can have some advantages, but they are not the utopia that some imagine them to be. Electrically-powered cars require huge amounts of electricity, and most of that electricity, worldwide, is generated by burning fossil fuels.
Last edited by Warp Factor; 03-18-2019 at 02:16 PM.
03-17-2019, 08:15 PM
They have not through the implications of all EVs! Or if so, as typical politicians won't say until the crisis exists!
