Are turbo engines more efficient when driven hard?
07-25-2015, 06:14 PM
#46
Rennlist Member
But you don't have to be driving full throttle to dramatically reduce your mileage and remove most of the difference. Just driving relatively spirited in sport mode around town will significantly reduce the mileage I get in any of my cars. The only way you get the prime MPG is if you drive it like a grandma, and very few people buy a sports car to do that.
Unless you are one of the few who only drive these cars one or twice a week on a sunny weekend, but these are Porsches after all, they are meant to be sports car that are also excellent daily drivers.
While it doesn't make much sense for low volume exotics like Ferrari and Lamborghini to care about emission and fuel efficiency, it does for Porsche due to the nature of their car and their targeted market.
07-25-2015, 06:35 PM
#47
Rennlist Member
The article gets a lot of the science wrong. This one, still light on the science, at least is accurate in the little it does say. http://www.popularmechanics.com/cars...12765/4306310/
FWIW, I have not heard of a modern turbo engine that is less efficient in the real world than an NA engine with the same output, driven the same way. Maybe if you are pedal to the metal *all* the time - although even then a well-designed turbo engine should be in the same ballpark, and much more efficient when you're cruising on the highway. And it turns out most spend less time accelerating sharply than you do maintaining speed.
(FWIW, this applies to supercharges too - any kind of well designed forced induction is, IRL, more efficient than a larger displacement NA).
FWIW, I have not heard of a modern turbo engine that is less efficient in the real world than an NA engine with the same output, driven the same way. Maybe if you are pedal to the metal *all* the time - although even then a well-designed turbo engine should be in the same ballpark, and much more efficient when you're cruising on the highway. And it turns out most spend less time accelerating sharply than you do maintaining speed.
(FWIW, this applies to supercharges too - any kind of well designed forced induction is, IRL, more efficient than a larger displacement NA).
Turbochargers allow the engine to make the same power output at a small engine displacement. So at idle or low boost scenario, the engine will be a lot less thirsty comparing to a NA engine that makes the same power output. Why? Because due to the larger displacement of the NA engine, it needs more air and fuel just to keep it spinning (since you cannot lean out the engine too much without running the risk of burning your valves or engine knocks), while a turbocharged engine, with small engine displacement, sucks in less air at low boost scenario which in turns uses less fuel.
At high boost, high power output scenario, you are still burning through the same amount of air and fuel (DFI combined with turbos do allow for slightly leaner AFR however) to produce the same peak power. So the fuel saving is less noticeable despite the decreased in the engine displacement.
07-25-2015, 10:09 PM
#48
Take the time to read. A very good article ...
"WE DON'T LIKE THE TURBO," SAID THE MAN WITH THE ITALIAN ACCENT
I'd like to hear any debate from anything in the article!
http://www.roadandtrack.com/car-cult...turbocharging/
"WE DON'T LIKE THE TURBO," SAID THE MAN WITH THE ITALIAN ACCENT
I'd like to hear any debate from anything in the article!
http://www.roadandtrack.com/car-cult...turbocharging/
Jim
07-25-2015, 10:55 PM
#49
Interestingly, not everyone is going the turbo route. I just got an email about the new Lexus GS F which has a 5L normally aspirated engine that they have been able to tweak to 467 hp using older technologies like forged connecting rods and titanium valves all the while getting 3% better efficiency. This is the kind of progress I like the sound of. I wonder if it is a 'European thing'. I had an old Lexus GS400 for a long time and it was a really good reliable car.
Jim
Jim
07-25-2015, 11:56 PM
#50
Interestingly, not everyone is going the turbo route. I just got an email about the new Lexus GS F which has a 5L normally aspirated engine that they have been able to tweak to 467 hp using older technologies like forged connecting rods and titanium valves all the while getting 3% better efficiency. This is the kind of progress I like the sound of. I wonder if it is a 'European thing'. I had an old Lexus GS400 for a long time and it was a really good reliable car.
Jim
Jim
07-26-2015, 12:33 AM
#51
FWIW, on the RC-F that engine yields 25% less torque and 10% less power than a 911TT (33% and 21% less than a 911TTS), with about the same rated gas mileage. Fun fact: Turbocharging (and supercharging) was invented to increase performance with less increase in weight and size, not to save fuel - that's just a nice side effect.
Might be why FI engines were the next step in WW2 aircraft engines - at altitude where air is thinner, FI engines still produce the power?
07-26-2015, 12:55 AM
#52
That's just not true, and I live in the heart of Silicon Valley. Couple commuting, where I'm often using all the power of the cars in short bursts, with the weekend pleasure driving, where I'm often revving the **** out of the car, and it really wouldn't matter what I was driving. It's not what I drive, it's how I drive. Even if I was driving a Tesla, I'd be getting crappy range and likely overheating it constantly. The average enthusiast sports car buyer doesn't drive the way the average Nissan Leaf buyer, even in the same environs.
07-26-2015, 01:05 AM
#53
Rennlist Member
That's just not true, and I live in the heart of Silicon Valley. Couple commuting, where I'm often using all the power of the cars in short bursts, with the weekend pleasure driving, where I'm often revving the **** out of the car, and it really wouldn't matter what I was driving. It's not what I drive, it's how I drive. Even if I was driving a Tesla, I'd be getting crappy range and likely overheating it constantly. The average enthusiast sports car buyer doesn't drive the way the average Nissan Leaf buyer, even in the same environs.
07-26-2015, 01:16 AM
#54
BTW, you don't have to even break the law to destroy your gas mileage. I can run through my favorite mountain road, at the speed limit, and get the ****tiest mileage imaginable, by keeping it dead in the power band so I can keep up a really good pace. Alternatively, I could drop it into auto mode, let the car make the lazy shifts, stay under the speed limit and get much better mileage. But have a lot less fun. I choose the former and, as such, it really doesn't matter what I'm driving when it comes to mpg. It's just gonna suck, no matter what.
If you want to debate fuel economy, emissions, morals, etc., we might want to take the discussion off Rennlist and over to Greencars.com, where a quorum of the posters really care.
07-26-2015, 01:18 AM
#55
Burning Brakes
I don't understand how the government can mandate what kind of engine you get in a car, especially a low volume car like a sports car.
Also, is it the case that having a smaller engine with turbos is more efficient when you're actually using the turbos? When you put your foot to the floor and the exhaust gas comes into the cylinder, doesn't it also call for more fuel? Do they test mpg with cars under hard acceleration? Everytime I read about forcing companies like Porsche or Ferrari to put tiny engines with turbos that ruins the sound and throttle input it gets me upset.
Also, is it the case that having a smaller engine with turbos is more efficient when you're actually using the turbos? When you put your foot to the floor and the exhaust gas comes into the cylinder, doesn't it also call for more fuel? Do they test mpg with cars under hard acceleration? Everytime I read about forcing companies like Porsche or Ferrari to put tiny engines with turbos that ruins the sound and throttle input it gets me upset.
07-26-2015, 01:27 AM
#56
Okay, let me try.
OP, Porsche is not a small manufacturer, from a regulatory perspective. Governments around the world have mandated certain fuel efficiency and emission standards that all manufacturers must meet across their fleet, including Porsche. The only way for some manufacturers to get there is through employing smaller, turbo charged motors, largely because of the manner in which the testing is done in Europe (i.e., turbo motors perform much better in the not so real world tests than NA motors.)
Re: the second part, when you drive both cars really hard, you're gonna wind up in basically the same place, crappy mileage. But when you drive it like a Prius owner, you'll get better mileage in the turbo car.
As an example, the twin turbo M4 coupe that everyone loves to use as an example of a successful deployment of this technology is rated 17/26 under the US standard. So just a shade under the 20/27 rating of my 991 C2S...
OP, Porsche is not a small manufacturer, from a regulatory perspective. Governments around the world have mandated certain fuel efficiency and emission standards that all manufacturers must meet across their fleet, including Porsche. The only way for some manufacturers to get there is through employing smaller, turbo charged motors, largely because of the manner in which the testing is done in Europe (i.e., turbo motors perform much better in the not so real world tests than NA motors.)
Re: the second part, when you drive both cars really hard, you're gonna wind up in basically the same place, crappy mileage. But when you drive it like a Prius owner, you'll get better mileage in the turbo car.
As an example, the twin turbo M4 coupe that everyone loves to use as an example of a successful deployment of this technology is rated 17/26 under the US standard. So just a shade under the 20/27 rating of my 991 C2S...
07-26-2015, 01:29 AM
#57
Rennlist Member
And you'd be wrong. Maybe you're just new to sports cars.
BTW, you don't have to even break the law to destroy your gas mileage. I can run through my favorite mountain road, at the speed limit, and get the ****tiest mileage imaginable, by keeping it dead in the power band so I can keep up a really good pace. Alternatively, I could drop it into auto mode, let the car make the lazy shifts, stay under the speed limit and get much better mileage. But have a lot less fun. I choose the former and, as such, it really doesn't matter what I'm driving when it comes to mpg. It's just gonna suck, no matter what.
If you want to debate fuel economy, emissions, morals, etc., we might want to take the discussion off Rennlist and over to Greencars.com, where a quorum of the posters really care.
BTW, you don't have to even break the law to destroy your gas mileage. I can run through my favorite mountain road, at the speed limit, and get the ****tiest mileage imaginable, by keeping it dead in the power band so I can keep up a really good pace. Alternatively, I could drop it into auto mode, let the car make the lazy shifts, stay under the speed limit and get much better mileage. But have a lot less fun. I choose the former and, as such, it really doesn't matter what I'm driving when it comes to mpg. It's just gonna suck, no matter what.
If you want to debate fuel economy, emissions, morals, etc., we might want to take the discussion off Rennlist and over to Greencars.com, where a quorum of the posters really care.
Maybe you drive just really good at getting incredibly bad gas mileage on public road, maybe not??? What do I know anyway? I am just a newbie on this forum, even though I track my current car and bike (both of which are BMW) on the local road courses more than dozen of times a year.
07-26-2015, 01:40 AM
#58
I fail to see any of your ad hominem arguments bring any validity to what you are saying.
Maybe you drive just really good at getting incredibly bad gas mileage on public road, maybe not??? What do I know anyway? I am just a newbie on this forum, even though I track my current car and bike (both of which are BMW) on the local road courses more than dozen of times a year.
Maybe you drive just really good at getting incredibly bad gas mileage on public road, maybe not??? What do I know anyway? I am just a newbie on this forum, even though I track my current car and bike (both of which are BMW) on the local road courses more than dozen of times a year.
07-26-2015, 01:43 AM
#59
Rennlist Member
07-26-2015, 02:05 AM
#60
Okay, let me try.
OP, Porsche is not a small manufacturer, from a regulatory perspective. Governments around the world have mandated certain fuel efficiency and emission standards that all manufacturers must meet across their fleet, including Porsche. The only way for some manufacturers to get there is through employing smaller, turbo charged motors, largely because of the manner in which the testing is done in Europe (i.e., turbo motors perform much better in the not so real world tests than NA motors.)
Re: the second part, when you drive both cars really hard, you're gonna wind up in basically the same place, crappy mileage. But when you drive it like a Prius owner, you'll get better mileage in the turbo car.
As an example, the twin turbo M4 coupe that everyone loves to use as an example of a successful deployment of this technology is rated 17/26 under the US standard. So just a shade under the 20/27 rating of my 991 C2S...
OP, Porsche is not a small manufacturer, from a regulatory perspective. Governments around the world have mandated certain fuel efficiency and emission standards that all manufacturers must meet across their fleet, including Porsche. The only way for some manufacturers to get there is through employing smaller, turbo charged motors, largely because of the manner in which the testing is done in Europe (i.e., turbo motors perform much better in the not so real world tests than NA motors.)
Re: the second part, when you drive both cars really hard, you're gonna wind up in basically the same place, crappy mileage. But when you drive it like a Prius owner, you'll get better mileage in the turbo car.
As an example, the twin turbo M4 coupe that everyone loves to use as an example of a successful deployment of this technology is rated 17/26 under the US standard. So just a shade under the 20/27 rating of my 991 C2S...
Jim