https://jalopnik.com/the-four-cylinder-chevy-silverado-got-worse-mpg-than-th-1831955316
C&D just had an article on this as well. This engine is EPA gaming and it still cost them millions of dollars to develop while being objectively worse pretty much across the board from what they are already have. So sad.
Not surprised.
I didn't know they were starting to put 4-cylinders in Silverados. Woooooof no thank you. I'll take a GM V8 any day over that.
Most of these new 4cyl engines only get the economy achieved when out of boost.
I can't tell whether this means the 2.7T is crap, or the 5.3 is a very good engine.
Take it with a pinch - probably more - of salt but GM says "don't look at the label."
https://www.autonews.com/article/20181119/OEM06/181119749/gm-on-pickup-mpg-don-t-look-at-the-label
The explanation they gave is a wive's tale. The reason C&D's testing showed this is pretty straightforward. At a steady cruise, the truck only needs maybe 50 horsepower to maintain speed, so both engines will be loading along at partial throttle. The vehicle weight difference matters when accelerating, but is negligible for steady cruise. Their respective aerodynic properties are the same. The V8 has cylinder deactivation, so it will be running on only 4 cylinders (now a 2.65L 4-banger). So now you have two engines of similar displacement generating similar power, so it becomes a game of efficiency. The turbo 4 is likely off-boost in steady cruise like this, so it's efficiency will be worse than a naturally aspirated engine by virtue of high pressure ratios on the NA motor.
The C&D test would be like taking an NA 2.0 Focus and a Focus ST and running them at steady cruise. Of course the NA motor is going to return better mileage.
so the question is, do people drive every day more like magazine writers, or the EPA test machine???....
Quote from: AutobahnSHO on January 22, 2019, 12:29:45 PM
so the question is, do people drive every day more like magazine writers, or the EPA test machine???....
The EPA highway driving cycle assumes a mix of interstate and rural highway driving with changing speeds and at least one acceleration to highway speed from a stop. Hence why most cars, when doing long-distance, steady speed interstate driving tend to have little difficulty beating EPA highway.
2.7 is pretty big for a 4 cylinder engine, but it really seems that GM hasn't got the hang of putting turbo on a smaller displacement engine for the sake of efficiency. The comment about having to run it on racing fuel to achieve the numbers pretty much says that.
As for the V8, the cylinder deactivation no doubt adds something to the efficiency, but the heavier engine as well as dragging non-active pistons up and down in the cylinder sleeves really doesn't sound like the best approach to overall efficiency. Done right, a small displacement turbo engine with comparable output stats can always achieve better mileage; unless you're carrying/dragging the maximum weight with the gas pedal to the floor.
Quote from: FoMoJo on January 22, 2019, 12:55:01 PM
2.7 is pretty big for a 4 cylinder engine, but it really seems that GM hasn't got the hang of putting turbo on a smaller displacement engine for the sake of efficiency. The comment about having to run it on racing fuel to achieve the numbers pretty much says that.
As for the V8, the cylinder deactivation no doubt adds something to the efficiency, but the heavier engine as well as dragging non-active pistons up and down in the cylinder sleeves really doesn't sound like the best approach to overall efficiency. Done right, a small displacement turbo engine with comparable output stats can always achieve better mileage; unless you're carrying/dragging the maximum weight with the gas pedal to the floor.
When cylinders deactivate, the valves are closed so you basically have air springs on the pistons. The net drag on the engine will be very low. Certainly less of an efficiency hit than running a turbo off boost.
I've driven a lot of Silverados with cylinder deactivation (picking them up for detailing). If I have a stretch of highway to tackle, I like to toggle to the info screen that displays whether you're in 4- or 8-cylinder mode. And also the MPG screen, if course. It doesn't deactivate as often as you might think or hope, but it does seem to make a difference...pennies add up.
Quote from: MX793 on January 22, 2019, 01:04:16 PM
When cylinders deactivate, the valves are closed so you basically have air springs on the pistons. The net drag on the engine will be very low. Certainly less of an efficiency hit than running a turbo off boost.
Still gotta compress that air. Anyways, the least elegant way of achieving improved efficiency, imo.
Quote from: FoMoJo on January 22, 2019, 01:19:05 PM
Still gotta compress that air. Anyways, the least elegant way of achieving improved efficiency, imo.
The net difference of compressing the air and having it spring the cylinder back is (hopefully) negligible.
I think deactivation makes a lot of sense.
Quote from: CaminoRacer on January 22, 2019, 01:22:02 PM
The net difference of compressing the air and having it spring the cylinder back is (hopefully) negligible.
I think deactivation makes a lot of sense.
No doubt, with the advance of computer technology, the engine will behave a lot better than the previous version from a few decades back and actually save a bit of fuel when not under load. The trick, I guess, is deciding when it's okay to deactivate cylinders without impacting the performance so that it's not too noticeable to the driver. A friend mine, years ago, had one of the Cadillac 4-6-8 models and it was an absolute pig.
As for comparing the cylinder deactivation technology with a comparable performance version of a small displacement turbo engine, I think the small displacement turbo engine has a lot more flexibility in tuning; that is in respect to determining when power is needed vs. efficiency; if it's done right.
Quote from: FoMoJo on January 22, 2019, 01:19:05 PM
Still gotta compress that air. Anyways, the least elegant way of achieving improved efficiency, imo.
But then that compressed energy is released on the downstroke, cancelling out the work put in to compressing it.
Quote from: 2o6 on January 22, 2019, 12:11:13 PM
Most of these new 4cyl engines only get the economy achieved when out of boost.
I can't tell whether this means the 2.7T is crap, or the 5.3 is a very good engine.
All turbo motors under deliver and the GM 2.7T is no different - see the countless comparos that show the Silverado 6.2L getting as good or better MPG than the F-150 Ecoboost. 98% of MPG is weight and aero. A 2.7T DOHC is gonna weigh say 100-150 lbs less than a pooprod V8, but in a 5,000-6,000 lb vehicle, the % difference is negligible, plus then ad the issues of bias toward a richer A/F mixture and low compression ratio (= lower efficiency) off boost. As with turbo motors, automakers full well know that turbos under deliver, but they can game the EPA test method and prepare for European-esque displacement taxes. All the while WtP are left with a worse product that is worse for the environment.
Quote from: MX793 on January 22, 2019, 01:42:48 PM
But then that compressed energy is released on the downstroke, cancelling out the work put in to compressing it.
Cancelling
some of the work of compression ;).
GM did a good job programming their cylinder deactivation on Silvies. It's totally unnoticeable, and probably errs on the conservative side.
Quote from: Xer0 on January 22, 2019, 11:40:59 AM
This engine is EPA gaming and it still cost them millions of dollars to develop while being objectively worse pretty much across the board from what they are already have. So sad.
In other words it's the predictable outcome of onerous regulation.
Since the topic of cylinder deactivation and compression of air has been brought up; would it not make sense to make them non interference engines and keep the valves open when deactivated?
Quote from: MX793 on January 22, 2019, 01:42:48 PM
But then that compressed energy is released on the downstroke, cancelling out the work put in to compressing it.
Yes, that is true. The non-functioning pistons still require energy to be moved.
Quote from: Galaxy on January 22, 2019, 01:49:16 PM
Since the topic of cylinder deactivation and compression of air has been brought up; would it not make sense to make them non interference engines and keep the valves open when deactivated?
That would create issues with vacuum and the combustion process of activated cylinders as the deactivated cylinders would be pushing air back up into the intake manifold.
Quote from: Galaxy on January 22, 2019, 01:49:16 PM
Since the topic of cylinder deactivation and compression of air has been brought up; would it not make sense to make them non interference engines and keep the valves open when deactivated?
I think that might introduce a few other problems regarding air blown into the intake plenum as well as exhaust from the functioning cylinders.
Quote from: GoCougs on January 22, 2019, 01:57:15 PM
That would create issues with vacuum and the combustion process of activated cylinders as the deactivated cylinders would be pushing air back up into the intake manifold.
Plus the pumping losses. Closing the valves isn't totally loss-less, but it's a very low loss solution
Quote from: GoCougs on January 22, 2019, 01:44:18 PM
All turbo motors under deliver and the GM 2.7T is no different - see the countless comparos that show the Silverado 6.2L getting as good or better MPG than the F-150 Ecoboost. 98% of MPG is weight and aero. A 2.7T DOHC is gonna weigh say 100-150 lbs less than a pooprod V8, but in a 5,000-6,000 lb vehicle, the % difference is negligible, plus then ad the issues of bias toward a richer A/F mixture and low compression ratio (= lower efficiency) off boost. As with turbo motors, automakers full well know that turbos under deliver, but they can game the EPA test method and prepare for European-esque displacement taxes. All the while WtP are left with a worse product that is worse for the environment.
Fiesta
Quote from: MX793 on January 22, 2019, 02:21:21 PM
Plus the pumping losses. Closing the valves isn't totally loss-less, but it's a very low loss solution
Compressing the air within the cylinder is better than pumping it in/out of the manifold?
Not discounting the other downsides, just curious about that particular aspect.
Quote from: BimmerM3 on January 22, 2019, 03:46:21 PM
Compressing the air within the cylinder is better than pumping it in/out of the manifold?
Not discounting the other downsides, just curious about that particular aspect.
Yes. The trapped air acts like a spring. The energy used to compress it is mostly returned on the downstroke. Pumping air in and out uses significant energy both ways.
Quote from: Soup DeVille on January 22, 2019, 03:55:24 PM
Yes. The trapped air acts like a spring. The energy used to compress it is mostly returned on the downstroke. Pumping air in and out uses significant energy both ways.
Yeah, but what if you diverted some exhaust pressure from the active cylinders into the compression strokes of the deactivated cylinders, and let them re-exhaust just enough of that exhaust to balance the net energy loss of the deactivated cylinders.
Quote from: Eye of the Tiger on January 22, 2019, 04:06:06 PM
Yeah, but what if you diverted some exhaust pressure from the active cylinders into the compression strokes of the deactivated cylinders, and let them re-exhaust just enough of that exhaust to balance the net energy loss of the deactivated cylinders.
I'm gonna have to lie down for a while and think about that.
Quote from: Eye of the Tiger on January 22, 2019, 04:06:06 PM
Yeah, but what if you diverted some exhaust pressure from the active cylinders into the compression strokes of the deactivated cylinders, and let them re-exhaust just enough of that exhaust to balance the net energy loss of the deactivated cylinders.
You might need a free valve system to make that work.
Okay, but I have the copyright on that idea. I can't afford a patent.
Quote from: Eye of the Tiger on January 22, 2019, 04:34:53 PM
Okay, but I have the copyright on that idea. I can't afford a patent.
Essentially you'd be making the dead cylinder almost like the second expansion cylinder of a compound steam engine, but you'd need to completelt seperate cams, one for the normal operation, one for this: not to mention whatever plumbing trickery would be needed.
Quote from: GoCougs on January 22, 2019, 01:44:18 PM. As with turbo motors, automakers full well know that turbos under deliver, but they can game the EPA test method and prepare for European-esque displacement taxes. All the while WtP are left with a worse product that is worse for the environment.
Car and Driver did a piece on this that determined without a debt you are wrong and turbo engines most often exceed EPA numbers
Quote from: Soup DeVille on January 22, 2019, 04:37:03 PM
Essentially you'd be making the dead cylinder almost like the second expansion cylinder of a compound steam engine, but you'd need to completelt seperate cams, one for the normal operation, one for this: not to mention whatever plumbing trickery would be needed.
Ahh, we could use coolant and exhaust heat to create steam to fill the deactivated cylinders and help clean them. Easy.
Quote from: FoMoJo on January 22, 2019, 04:29:59 PM
You might need a free valve system to make that work.
I invented free valves 20 years ago. I just didn't call it that.
Quote from: Eye of the Tiger on January 22, 2019, 04:06:06 PM
Yeah, but what if you diverted some exhaust pressure from the active cylinders into the compression strokes of the deactivated cylinders, and let them re-exhaust just enough of that exhaust to balance the net energy loss of the deactivated cylinders.
Wouldn't pass smog. :lol: :lol:
Quote from: Soup DeVille on January 22, 2019, 04:37:03 PM
Essentially you'd be making the dead cylinder almost like the second expansion cylinder of a compound steam engine, but you'd need to completelt seperate cams, one for the normal operation, one for this: not to mention whatever plumbing trickery would be needed.
Multiair can in theory do this
Quote from: r0tor on January 22, 2019, 04:54:24 PM
Multiair can in theory do this
Multiair can do many things in theory. What is actually does most of the time is not work.
Just bolt in an improbability drive, boom - Fiat tech becomes reliable.
Quote from: Laconian on January 22, 2019, 05:13:44 PM
Just bolt in an improbability drive, boom - Fiat tech becomes reliable.
Except in the unlikely event that it turns back into a Fiat.
Multiair has already won the engine wars... We just haven't figured that out yet
When it dawns on you why r0tor is defending Fiat :lol: :facepalm:
I hope to avoid turbo cars after the Optima for as long as possible. 22 MPG from a 2.0T in a midsize sedan :facepalm:
Quote from: Soup DeVille on January 22, 2019, 03:55:24 PM
Yes. The trapped air acts like a spring. The energy used to compress it is mostly returned on the downstroke. Pumping air in and out uses significant energy both ways.
Ah, makes sense. Thanks.
Quote from: 12,000 RPM on January 23, 2019, 11:54:42 AM
When it dawns on you why r0tor is defending Fiat :lol: :facepalm:
I hope to avoid turbo cars after the Optima for as long as possible. 22 MPG from a 2.0T in a midsize sedan :facepalm:
City, highway, combined?
Quote from: FoMoJo on January 23, 2019, 12:13:09 PM
City, highway, combined?
Combined under my lead foot
Real world figures (Fuelly) indicate ~23-24 MPG, EPA promised 26 combined which is the most I've seen on all highway road trips
Same year Camry/Accord V6s do about 26 MPG in the real world and make more power. It's w/e, $23 or so a month at current gas prices
Quote from: 12,000 RPM on January 23, 2019, 11:54:42 AM
When it dawns on you why r0tor is defending Fiat :lol: :facepalm:
I hope to avoid turbo cars after the Optima for as long as possible. 22 MPG from a 2.0T in a midsize sedan :facepalm:
I'm getting 29-30+ in my 2.0T midsized AWD sedan -shrug-
Quote from: 12,000 RPM on January 23, 2019, 02:03:20 PM
Combined under my lead foot
Real world figures (Fuelly) indicate ~23-24 MPG, EPA promised 26 combined which is the most I've seen on all highway road trips
Same year Camry/Accord V6s do about 26 MPG in the real world and make more power. It's w/e, $23 or so a month at current gas prices
Lighten up your foot a bit. If that doesn't work, then KIA hasn't done it right.
Quote from: 12,000 RPM on January 23, 2019, 02:03:20 PM
Combined under my lead foot
Real world figures (Fuelly) indicate ~23-24 MPG, EPA promised 26 combined which is the most I've seen on all highway road trips
Same year Camry/Accord V6s do about 26 MPG in the real world and make more power. It's w/e, $23 or so a month at current gas prices
Hyundai /Kia, like Ford and Ecoboost, faced a lot of heat for poor mpg. Lots of people have been similarly shortchanged...
Quote from: GoCougs on January 24, 2019, 10:20:25 PM
Hyundai /Kia, like Ford and Ecoboost, faced a lot of heat for poor mpg. Lots of people have been similarly shortchanged...
Fake news
https://www.caranddriver.com/features/a20776954/are-turbocharged-engines-a-fuel-economy-boost-or-a-fuel-economy-bust/
Quote from: r0tor on January 25, 2019, 10:32:17 AM
Fake news
https://www.caranddriver.com/features/a20776954/are-turbocharged-engines-a-fuel-economy-boost-or-a-fuel-economy-bust/
With the exception of my MIL's surprisingly thirsty 900cc Renault, all of the turbo cars I've driven have posted surprisingly thrifty fuel economy numbers relative to their amount of punch. I flogged a Jetta TSI over the course of a week in California and still managed to get 32mpg. Amazing~.
The Renault's lame fuel economy has to do with the fact that you need to hit boost to get it to do anything.
Quote from: r0tor on January 25, 2019, 10:32:17 AM
Fake news
https://www.caranddriver.com/features/a20776954/are-turbocharged-engines-a-fuel-economy-boost-or-a-fuel-economy-bust/
Substituting mag tests for real world is Fake News ;).
If it was Fake News, there wouldn't be the complaints, class action suits, and regulatory smack downs.
Yea... screw actual testing and using analytical data to form an opinion
#MAGA
I usually make the MPG in my Sonic.
I made very close to EPA fuel economy numbers with my 2013 Beetle TDI where I usually got 38-39 mpg. Mixed driving my 2007 Sonata V6 I got 20, 2009 Enclave I got 15-16, 2013 QX56 I get 14 (this is actually close to EPA), 2017 Crosstrek manual I get 23. The rest I can't remember. Only turbo was the Beetle but then again it was a very dirty diesel.
Quote from: veeman on January 28, 2019, 07:54:30 AM
I made very close to EPA fuel economy numbers with my 2013 Beetle TDI where I usually got 38-39 mpg. Mixed driving my 2007 Sonata V6 I got 20, 2009 Enclave I got 15-16, 2013 QX56 I get 14 (this is actually close to EPA), 2017 Crosstrek manual I get 23. The rest I can't remember. Only turbo was the Beetle but then again it was a very dirty diesel.
I can get 22 MPG in my heavy ass Dakota with an ancient AMC tractor engine.
Fiesta Ecoboost might beat VW TDI. 47 MPG highway. 39-ish mixed.
I basically get city rated MPGs in every car I drive in mixed conditions.
In Southern California stop and go/fast and slow conditions, the 2014 Focus gets 31 on 87 octane and 27 on E85.
Quote from: shp4man on January 31, 2019, 09:30:36 AM
In Southern California stop and go/fast and slow conditions, the 2014 Focus gets 31 on 87 octane and 27 on E85.
That's pretty good for the nightmare of California traffic. How about ye olde pickup?
Quote from: Eye of the Tiger on January 31, 2019, 10:20:14 AM
That's pretty good for the nightmare of California traffic. How about ye olde pickup?
About 12. On a good day. ;)
Why would/does anyone ever use E85? Less power, worse mileage, and more expensive(?).......lose-lose-lose.
Quote from: giant_mtb on January 31, 2019, 12:50:08 PM
Why would/does anyone ever use E85? Less power, worse mileage, and more expensive(?).......lose-lose-lose.
Farmers.
Quote from: giant_mtb on January 31, 2019, 12:50:08 PM
Why would/does anyone ever use E85? Less power, worse mileage, and more expensive(?).......lose-lose-lose.
Less expensive.per gallon, at least here in California. No real advantage, though. It's about the same cost per mile.
Quote from: giant_mtb on January 31, 2019, 12:50:08 PM
Why would/does anyone ever use E85? Less power, worse mileage, and more expensive(?).......lose-lose-lose.
More renewable is pretty much the only advantage, I think.
farmer subsidies
Quote from: CaminoRacer on January 31, 2019, 01:09:29 PM
farmer subsidies
That explains why it's produced. That doesn't explain why it's purchased.
Depending on oil prices, there can be an advantage to E85 in fuel costs. Right now, gas is pretty cheap.
But California is currently switching to summer blend fuel, which is typically 12-14 cents higher per gallon.
So I may be going back to E85.
Quote from: shp4man on January 31, 2019, 12:43:39 PM
About 12. On a good day. ;)
Ha, my '88 GMC gets 13 (on a good day)!.
Quote from: giant_mtb on January 31, 2019, 12:50:08 PM
Why would/does anyone ever use E85? Less power, worse mileage, and more expensive(?).......lose-lose-lose.
It's cheaper in Nebraska I believe.
Back in 200(6?) when gas prices spiked stupid high, E85 actually was far far cheaper than regular unleaded.
Quote from: giant_mtb on January 31, 2019, 12:50:08 PM
Why would/does anyone ever use E85? Less power, worse mileage, and more expensive(?).......lose-lose-lose.
Turbo b0000000st!
Quote from: giant_mtb on January 31, 2019, 12:50:08 PM
Why would/does anyone ever use E85? Less power, worse mileage, and more expensive(?).......lose-lose-lose.
Race cars can use it. Moar bewst.
Quote from: AutobahnSHO on January 31, 2019, 02:24:00 PM
It's cheaper in Nebraska I believe.
Back in 200(6?) when gas prices spiked stupid high, E85 actually was far far cheaper than regular unleaded.
Fair enough, that's why I put the "?" 'cause I wasn't sure how it compared price-wise. Nobody here has E85 so I never see prices. :lol:
With proper tuning, you can actually make a lot more power with e85
Quote from: r0tor on January 31, 2019, 02:54:03 PM
With proper tuning, you can actually make a lot more power with e85
If you have large enough injectors.
Quote from: r0tor on January 31, 2019, 02:54:03 PM
With proper tuning, you can actually make a lot more power with e85
But what car has an E85 tuning? The Koenigseggs do, but other then that?
My Focus is a kind of rare SFE model. It's flex fuel capable and tuned for fuel economy, as apposed to the other sedans that are PZEV vehicles, tuned for low emissions.
The FSE has rear disc brakes, 16 inch wheels and extra air dams underneath to give it better coefficient of drag on the freeway.
Ok, so it's not that big of a deal, but, you know... :lol:
Quote from: Galaxy on January 31, 2019, 03:12:32 PM
But what car has an E85 tuning? The Koenigseggs do, but other then that?
2014 Silverado
Quote from: shp4man on January 31, 2019, 03:20:11 PM
My Focus is a kind of rare SFE model. It's flex fuel capable and tuned for fuel economy, as apposed to the other sedans that are PZEV vehicles, tuned for low emissions.
The FSE has rear disc brakes, 16 inch wheels and extra air dams underneath to give it better coefficient of drag on the freeway.
Ok, so it's not that big of a deal, but, you know... :lol:
I know. My Fiesta is also a kidn of rare SFE model. But it's not flex fuel, it doesn't have rear disc, it doesn't have special air dams or under body panels, and it came with steelies.
Quote from: Eye of the Tiger on January 31, 2019, 03:51:08 PM
I know. My Fiesta is also a kidn of rare SFE model. But it's not flex fuel, it doesn't have rear disc, it doesn't have special air dams or under body panels, and it came with steelies.
I think it stands for Super Fuel Economy. :lol:
Quote from: shp4man on January 31, 2019, 04:56:51 PM
I think it stands for Super Fuel Economy. :lol:
I thought it meant Sometimes Fuel Efficient.
Quote from: shp4man on January 31, 2019, 12:56:12 PM
Less expensive.per gallon, at least here in California. No real advantage, though. It's about the same cost per mile.
But you burn way more of it. Like it might be 10% cheaper, but you burn 20% more of it.
Only people I know who are into it are internet dyno hoes who like to brag about having E85 tunes.
Quote from: 12,000 RPM on January 31, 2019, 05:45:38 PM
But you burn way more of it. Like it might be 10% cheaper, but you burn 20% more of it.
Only people I know who are into it are internet dyno hoes who like to brag about having E85 tunes.
My friend's car make 40AWHP more on E85, and that's very noticeable vs 265AWHP on 93
E85 eats up certain kind of rubber though, so the motor had to be built for it.
Quote from: AutobahnSHO on January 31, 2019, 07:14:42 PM
E85 eats up certain kind of rubber though, so the motor had to be built for it.
Mostly the fuel system.
The 10% ethanol that most gas is now also plays hell with a lot of older cars.
Anything carbureted with a mechanical fuel pump at altitude has a very rough time with warm temperature.
Quote from: Soup DeVille on January 31, 2019, 09:09:32 PM
Mostly the fuel system.
The 10% ethanol that most gas is now also plays hell with a lot of older cars.
Anything carbureted with a mechanical fuel pump at altitude has a very rough time with warm temperature.
What's high altitude?
My car does fine. I have an Edelbrock, though. A Holley or other carb design with gaskets below the fuel level might struggle more.