How turbo cars are fuel efficient? help!

[cr8zyjap07]

So im trying to do a paper on how a turbo car can be fuel efficient. I have a good idea on why its fuel efficient but im not 100% sure. if some one can show me some good links containing some solid info or can explain why i would greatly appreciate it.

[The Captain]

What do you mean fuel efficient?

They're fuel efficient when not in boost.

[Fujito]

I wish I could tell you. Mine sure isn't.

[SvicksTc]

there was a whole article in Car and Driver i wish i remember what issue...there is a ton of info out there on this topic....not fuel effiecnet when in boost, however, can be more fuel efficent when not then a naturally aspirated car

[cr8zyjap07]

im sorry, i mean how turbo cars CAN be fuel efficient without a heavy foot. if your not in boost turbo cars are more efficient than normal cars. thats the info im trying to find.

[92sileighty]

turbo and fuel efficient should never be in the same sentence

[Fujito]

They can be fuel efficient if you stay out of boost, which means granny shifting below 3000 RPM in most cases. By doing so the driver is basically driving a slow whatever-it-is. Were you assigned this topic or did you pick it yourself? If it's the latter then you should rethink your topic.

[SvicksTc]

turbo and fuel efficient should never be in the same sentence

for ricers like us yes...

[92sileighty]

for ricers like us yes...

lol :mrgreen:

[cr8zyjap07]

like said above, when not in boost it gets better gas milage than a naturally-aspirated car. my sti gets 32mpg highway(accessport measurement) when driving like a girl then i go in full boost and it gets like 1.6~0.7mpg lol.

[cr8zyjap07]

They can be fuel efficient if you stay out of boost, which means granny shifting below 3000 RPM in most cases. By doing so the driver is basically driving a slow whatever-it-is. Were you assigned this topic or did you pick it yourself? If it's the latter then you should rethink your topic.

i didnt start yet and i wanted to do this topic, i have a list to choose and then i have to break it down to a smaller topic. i was thinking this would be good under environment but i cant find solid info on it so i might just do something else. i was trying to get out easy lol

[KingKong8247]

My mileage went up when I turbod my car but in boost forget it.

[tort9320g]

Google "Turbocharger efficiency" and "How turbos work". Lots of valuable information, you should find what you're looking for there.

Good luck...Dave

[ndubz]

If u stay out of boost it will be kind of efficient. But thats really only by comparison to cars with larger motors that put out the same power. Like my sti averages 20mpg and has a bit over 400bhp, a gto or CTS-V will average somewhere in the high teens, this is because they have 6.0L V8s and my car has a 2.5L flat 4 with a turbocharger. My car gets good milage by comparison to other cars of similar power levels, but at the end of the day turbos are for making more power. They force more air into the motor and more air always requires more fuel, so the answer to ur paper subject is that they dont help gas milage at all. They actually hurt it quite a bit compared to if a car of the same displacement were to be run N/A with a conservative tune that is just meant to be a normal car. Yes staying under boost helps u get better milage, but remember that turbo cars run less compression than N/A cars, so when ur running under boost the cars efficiency is actually down quite a bit compared to an N/A car of the same displacement and layout. Turbos are purely for performance though dude, if u want great gas milage, then get a diesel VW or a prius, or any other little econo box that is designed to use as little fuel as possible and sacrifice performance for economy.

But if ur stuck with this paper, then use the Sti and evo VS mustang and GTO economy comparison. Cars with small displacement turbo engines only have a fuel economy advantage ove cars that put out similar power using much larger motors.

[OMGz Turbo]

Want a great answer??? Ecoboost. Great power with great MPG's

[DPancoast]

lol my gas mileage gets cut in HALF when comparing boost to no boost...

like... I'll get 22-23mpg if I stay out of boost (about 300 miles to 12 gallons), but if I do the same in boost I get about 12-15mpg (about 150 miles to 12 gallons)

[mann]

there are a few theories and you can read Corky Bell's "Maximum boost" to really get a good technical idea, but a turbo is more efficient than NA and SC due to:

1. Small engine for same size HP. An 2.0 inline 4 turbo has less rotating friction and mass than than a similar HP V6 or V8. Even when they "turn off" cylinders in some of the newer ones they have to rotate.

2. Exhaust gas energy. When the byproducts or combustion are released out of the exhaust you have 1500 degrees of heat at a rapid velocity coming out into the atmosphere. That heat energy is thrown away. A turbo will reuse that heat energy to compress the intake charge and shove it into the engine, thereby increasing its overall efficiency. If you are consistently using the engine at its peak power though it will obviousley get worse gas mileage. Power is gas...

3. Turbo vs SC--there are two factors here. First off the SC will need belt drive, and since its not using the exhaust energy it is a parasitic drag on the motor, usually about 10-20%. For example, with a miata at 9 psi with a SC you will dyno 200whp, with a turbo 240whp. Most superchargers are also less efficient then turbos when compressing, and this causes the SC intake charge to be hotter and thereby less efficiency.

The trick is not comparing a 2.0 NA to a 2.0 T, the T will put out more HP, and thereby use more gas. Having the turbo in the exhaust stream is actually a little less efficient since at low loads its actually a restriction. However the 2.0T needs to be compared to an engine of the same HP, not displacement. So if you compare a 2.0T to an NA V6, the turbo motor will be more efficient.

A good analogy is the mazda 6 series. The 2.3 mazda 6 has 21/28 and 160 HP, the 2.3t has 17/23 and 274 HP, the v6 has 17/24 215 hp . You can see for about the same MPG you get a TON more HP with the turbo car (note the 2.3 is AWD and if it was fwd like the v6 it would get another 1-2 mpg at least)

end of FI 101...

[jpalamar]

If u stay out of boost it will be kind of efficient. But thats really only by comparison to cars with larger motors that put out the same power. Like my sti averages 20mpg and has a bit over 400bhp, a gto or CTS-V will average somewhere in the high teens, this is because they have 6.0L V8s and my car has a 2.5L flat 4 with a turbocharger. My car gets good milage by comparison to other cars of similar power levels, but at the end of the day turbos are for making more power. They force more air into the motor and more air always requires more fuel, so the answer to ur paper subject is that they dont help gas milage at all. They actually hurt it quite a bit compared to if a car of the same displacement were to be run N/A with a conservative tune that is just meant to be a normal car. Yes staying under boost helps u get better milage, but remember that turbo cars run less compression than N/A cars, so when ur running under boost the cars efficiency is actually down quite a bit compared to an N/A car of the same displacement and layout. Turbos are purely for performance though dude, if u want great gas milage, then get a diesel VW or a prius, or any other little econo box that is designed to use as little fuel as possible and sacrifice performance for economy.

But if ur stuck with this paper, then use the Sti and evo VS mustang and GTO economy comparison. Cars with small displacement turbo engines only have a fuel economy advantage ove cars that put out similar power using much larger motors.

My GTO gets about 24 highway and 18 city. The EPA estimates are very close on my car. Even when I beat on it hard, it only really drops to about 17. And comparing a small turbo motor to a V8 isn't really a comparision because we have more power at all RPMs, its the equavilent of a I4 turbo under boost at all times which doesn't happen. Hence our fuel economy is typically less.

Bottom line, turbos do not have anything to do with fuel effeciency. They are designed to allow a small underpowered motor to give the needed HP when under harder acceleration. More HP = more fuel needed.

Your paper has fail all over it.

[SheaButter]

Why just focus on gas engines. Look at a turbo diesel's they can actually be very fast and powerful and have over 100mpg. Discovery Channel did a special on this racecar that got 134 mpg and it was a 1.8 turbo diesel. Just a thought for you and ur paper

[Scapegoat]

they are certainly more gas efficient... as in an elemental form. A turbo charged vehicle is making better use of both the incoming and outgoing gases. a turbo charged vehicle isn't just wasting exhaust gas, but using it. making it a more efficient motor. I think we're confusing fuel efficiency and MPG here as well. turbo charged motors are mote fuel efficient by far... especially when you get into tuning and leaning them out to get more power.

we're effectively using a more efficient air fuel ratio than both non-turboed and non-tuned vehicles.

If you make the distinction clear that you're not writing about MPG's but about actually efficiencies with the system, then you will be fine

[jpalamar]

they are certainly more gas efficient... as in an elemental form. A turbo charged vehicle is making better use of both the incoming and outgoing gases. a turbo charged vehicle isn't just wasting exhaust gas, but using it. making it a more efficient motor. I think we're confusing fuel efficiency and MPG here as well. turbo charged motors are mote fuel efficient by far... especially when you get into tuning and leaning them out to get more power.

we're effectively using a more efficient air fuel ratio than both non-turboed and non-tuned vehicles.

If you make the distinction clear that you're not writing about MPG's but about actually efficiencies with the system, then you will be fine

That isn't comparing apples to apples. Tuned VS unTuned. Bad arguement. His paper topic wasn't about what is more effecient either, it was about MPG.

[ndubz]

My GTO gets about 24 highway and 18 city. The EPA estimates are very close on my car. Even when I beat on it hard, it only really drops to about 17. And comparing a small turbo motor to a V8 isn't really a comparision because we have more power at all RPMs, its the equavilent of a I4 turbo under boost at all times which doesn't happen. Hence our fuel economy is typically less.

Bottom line, turbos do not have anything to do with fuel effeciency. They are designed to allow a small underpowered motor to give the needed HP when under harder acceleration. More HP = more fuel needed.

Your paper has fail all over it.

I knew the GTO was a mehhh example when i wrote that, cuz those pushrod V8s actually do quite well for their size mpg wise.......but it was late and I was too tired to think of other **** lol. but either way, we both told him the same thing......E- High five :supz:

[ScubaSteve]

I think everyone is trying to mix up too many concepts at once. If you're trying to maximize your fuel efficiency you want to extract the most amount of work possible from the combustion of the least amount of fuel required. This depends on multiple factors but most importantly it will come down to the air/fuel ratio and ignition timing. If you turbocharge an engine all you're doing is allowing for higher peak pressures inside of the cylinder to maximize the amount of work being done on a movable piston (remember that work= force*displacement as a scalar). So turbocharging the motor allows for a higher force (force= pressure*area) and if you intend to achieve a maximum force for a given amount of air being sent into the cylinder you'll need to have a proper air/fuel mixture for the ideal combustion (referred to as the stoich. ratio which is around 14.7 parts air to 1 part fuel. This ratio allows for the complete combustion of all air/fuel). Hopefully from all this you can realize that fuel efficiency isn't the same as using the least amount of fuel required to do work. To use the least amount of fuel you're not going to get the maximum amount of work from you're engine which is what we're trying to achieve with turbochargers. I know this is a drastic simplification of the engine cycle but hopefully it suffices. If I were you I would focus on the tune to reach max mpg and not the turbocharger.

Ecoboost is an entirely different story and relates to the efficiency of smaller engines with boost as compared to larger NA engines. If you're interested in engine efficiencies due to compression ratios look into Carnot engine cycles.

edit: I'm not 100% sure what you're trying focus on with your paper so ignore my post if it's not what you were looking for.

[ndubz]

That isn't comparing apples to apples. Tuned VS unTuned. Bad arguement. His paper topic wasn't about what is more effecient either, it was about MPG.

X2.......... he should get a new topic for it.

[bl@ckvr4]

My VR4 gets 9-10mpg.

[turboman808]

A turbo can help you save on gas by being light weight and able to fit into a smaller car. Keep in mind when we here TURBO we think of a small high power motor. Imagine if you will a small half liter motor that needs a turbo just to produce a 100 hp. Now you have a very fuel efficient car.

coming at people telling them how much more fuel efficient your EVO is then a Mustang is however a joke. Both are high horsepower cars and neigther one is fuel efficient.

Keep in mind that although cars have gotten better and faster they have gotten worse with fuel economy. The technowhiz bang toyota prius doesn't even comes close to the fuel economy of a 82 corrolla and it had carbs.

[jpalamar]

A turbo can help you save on gas by being light weight and able to fit into a smaller car. Keep in mind when we here TURBO we think of a small high power motor. Imagine if you will a small half liter motor that needs a turbo just to produce a 100 hp. Now you have a very fuel efficient car.

Please tell me how a turbo makes an engine more effecient. It doesn't. All it allows it to do is burn more gas with the added air. Burning more gas = power, not more effeciency. Gas powered motors are very ineffecient. Thats a fact. Note the preforance on the Tesla. 0-60 in like 3 seconds. But a gas turbo in it and the amount of power needed to do the same thing is exponentially more due to effeciency

A turbo can help you save on gas by being light weight and able to fit into a smaller car.

Again, putting the ability of putting a small turbo into a small car and putting a bigger motor into a bigger car isn't comparing apples to apples.

Imagine if you will a small half liter motor that needs a turbo just to produce a 100 hp. Now you have a very fuel efficient car.

If you have a 2500 pound car. One has a 2.0 turbo with about 210hp, the other has a .5l turbo putting out 100 hp. The .5L won't be more effecient as it has to work twice as hard as the bigger motor. In the end, an under powered motor will not get good MPG, plus can't be as effecience as a normal sized motor because the too small one is working harder and in turn is going to create more heat. Last time I checked, motors aren't converting heat to enegery so therefore a lost of effeciency.





A fair comparision. Take the same car, one with a 2.0 n/a and then the same car with a 2.0 turbo. Tune both so that each are running at their optimum.

At WOT, the n/a will get better fuel economy as it isn't even possible to burn the same amount of fuel as the turbo motor.

At idle, the n/a and turbo motors will get about the same, maybe the n/a a slight better since there is less exhaust lag?

At a DD pace, the n/a may take a little longer to get up to speed and burn gas at a medium rate while the turbo will accel faster and burn gas at a high rate for a shorter time. In the end, I would assume that the fuel used in the turbo would still be more then the n/a

[turboman808]

Are we talking racing or driving to work. If I know which I will give the right response.

Actually give one scenario without mixing things up and being misleading. Give the amount of power you want the car to have, the weight of the car and wether it's for racing or driving to work.

[antman0408]

Turbo engines get better fuel economy when you compare it with the same size engine at the same power level. Comparing two same sized engines that have different power levels is pointless, same with two different sized engines making the same power.

[jdubs]

Turbo cars may or may not be more fuel efficient, but they are more thermodynamically efficient.

You are turning some of that heat energy normally lost in the exhaust into translational energy of the turbine.

[ScubaSteve]

Turbo cars may or may not be more fuel efficient, but they are more thermodynamically efficient.

You are turning some of that heat energy normally lost in the exhaust into translational energy of the turbine.

The turbine spins due to the exhaust gases exiting the motor at a high velocity. The higher temperature of the molecules relates to the speed they exit at but I would hardly say that the thermal energy is being efficiently recycled. I understand what you're saying but focusing a paper on the efficiency of a turbocharged motor in relation to the useful work done by exhaust gases would be a weak argument.

[den9]

my vw tdi gets 40 mpg and its turbo, im pretty sure it would get less mileage if it wasnt because id have my foot floored the entire ride to keep it at 50 mph.

on the other hand if you have a T88 im sure that wont help your mileage at all.

[ScubaSteve]

my vw tdi gets 40 mpg and its turbo, im pretty sure it would get less mileage if it wasnt because id have my foot floored the entire ride to keep it at 50 mph.

on the other hand if you have a T88 im sure that wont help your mileage at all.

Diesel engines will completely change the discussion.

[ndubz]

Please tell me how a turbo makes an engine more effecient. It doesn't. All it allows it to do is burn more gas with the added air. Burning more gas = power, not more effeciency. Gas powered motors are very ineffecient. Thats a fact. Note the preforance on the Tesla. 0-60 in like 3 seconds. But a gas turbo in it and the amount of power needed to do the same thing is exponentially more due to effeciency



Again, putting the ability of putting a small turbo into a small car and putting a bigger motor into a bigger car isn't comparing apples to apples.



If you have a 2500 pound car. One has a 2.0 turbo with about 210hp, the other has a .5l turbo putting out 100 hp. The .5L won't be more effecient as it has to work twice as hard as the bigger motor. In the end, an under powered motor will not get good MPG, plus can't be as effecience as a normal sized motor because the too small one is working harder and in turn is going to create more heat. Last time I checked, motors aren't converting heat to enegery so therefore a lost of effeciency.





A fair comparision. Take the same car, one with a 2.0 n/a and then the same car with a 2.0 turbo. Tune both so that each are running at their optimum.

At WOT, the n/a will get better fuel economy as it isn't even possible to burn the same amount of fuel as the turbo motor.

At idle, the n/a and turbo motors will get about the same, maybe the n/a a slight better since there is less exhaust lag?

At a DD pace, the n/a may take a little longer to get up to speed and burn gas at a medium rate while the turbo will accel faster and burn gas at a high rate for a shorter time. In the end, I would assume that the fuel used in the turbo would still be more then the n/a

I agree with u on the turbo thing and ur point about gas motors. But the tesla is faster than other gas powered cars with similar weight and power because electric motors are connected directly to the wheels and dont have to go through a drivetrain and transmission. So it essentially has ~265rwhp, or similar to that of gas cars with well over 300bhp. But yes, electric motors are more efficient than gas motors, I wasnt trying to argue or anything, i was just trying to point that little tid bit out and be a know it all douche :cool:

[The Captain]

But the tesla is faster than other gas powered cars with similar weight and power because electric motors are connected directly to the wheels and dont have to go through a drivetrain and transmission.

No drivetrain or transmission? Where did you hear that? :eek:

[ndubz]

No drivetrain or transmission? Where did you hear that? :eek:

U dont put an electric motor through a transmission, that takes away every advantage it has over a gas engine, they make peak torque at zero rpm so it doesnt need a tranny, the electric motor is hooked straight to the drive wheels, there may be a little bit of a drivetrain due to the layout of the car, but deff no transmission. It has two speeds, but they arent mechanical gears.

[jpalamar]

U dont put an electric motor through a transmission, that takes away every advantage it has over a gas engine, they make peak torque at zero rpm so it doesnt need a tranny, the electric motor is hooked straight to the drive wheels, there may be a little bit of a drivetrain due to the layout of the car, but deff no transmission. It has two speeds, but they arent mechanical gears.

You think it would make a difference doing it from the crank? Removing the drivetrain aspect?

[ndubz]

You think it would make a difference doing it from the crank? Removing the drivetrain aspect?

Idk what u mean here. But if u mean hooking up an internal combustion engine directly to the wheels, then no way. ICE's need a tranny to make low end torque to get the car moving at low speeds cuz they have a positive torque curve. Electric motors sould be hooked directly to the wheels because (in theory) they have a linear torque curve, ie they make peak torque from zero rpm and therefore dont need to go through a transmission to make the car move. (they may have a torque curve, but if it is curved, then it starts at peak torque and slopes downward as rpms increase.)

[CleanNeon98]

Why are we talking about electric cars and gas mileage?

[jpalamar]

Why are we talking about electric cars and gas mileage?

Because the origional topic for the paper probally won't work so it appears the thread has given some good suggessions and people are debating stuff. Isn't that what it's all about?

[jpalamar]

Idk what u mean here. But if u mean hooking up an internal combustion engine directly to the wheels, then no way. ICE's need a tranny to make low end torque to get the car moving at low speeds cuz they have a positive torque curve. Electric motors sould be hooked directly to the wheels because (in theory) they have a linear torque curve, ie they make peak torque from zero rpm and therefore dont need to go through a transmission to make the car move. (they may have a torque curve, but if it is curved, then it starts at peak torque and slopes downward as rpms increase.)

So what you are saying is with or without a transmission, the gas motor still isn't nearly as effecient as an electric motor:bigeek: It isn't a matter of which will go faster, which will make more power, but of effecienty. If an electric motors puts out peak power the whole time and creates less heat(wasted energy), then how is a gas motor that needs a transmission(loses power) and with combustion comes much heat(tones of wasted energy).

[CleanNeon98]

I didn't even read through.

I think turbo cars are better on gas when out of boost because the turbo optimizes airflow or something, I forget what I read. My paper this semester is on alternative fuels too so I'll be facing similar questions.

[tomustang]

Even if you're out of boost you are still running 91 octane which cost more than N/A running 87

[EggbertWaxman]

If u stay out of boost it will be kind of efficient. But thats really only by comparison to cars with larger motors that put out the same power. Like my sti averages 20mpg and has a bit over 400bhp, a gto or CTS-V will average somewhere in the high teens, this is because they have 6.0L V8s and my car has a 2.5L flat 4 with a turbocharger.


Last time I checked a CTS-V has a blower and puts out 550 horse, so I wouldn't put that in your category of 400 horse 6.0L V8's.

[CleanNeon98]

Even if you're out of boost you are still running 91 octane which cost more than N/A running 87
Were talking MPG here not running costs. Yea they are higher though.

[Honduh]

two words: Turbo Diesel.

[tomustang]

Were talking MPG here not running costs. Yea they are higher though.

Fuel efficiency deals with price

[jpalamar]

Last time I checked a CTS-V has a blower and puts out 550 horse, so I wouldn't put that in your category of 400 horse 6.0L V8's.

Only the new CTS-V has forced induction and it isn't the 6.0 either. Get smart when you got your facts straight:mrgreen:

[EggbertWaxman]

Only the new CTS-V has forced induction and it isn't the 6.0 either. Get smart when you got your facts straight:mrgreen:

Yes, it's a 6.2, I'm sorry.

[thunder_lizard]

Turbocharging makes an engine more fuel efficient in two ways: One, it captures the kinetic energy of the exhaust gases, and puts them to work to spin a turbine. This turbine drives a compressor wheel which stuffs the intake manifold full of of cool air, which brings the intake pressure as close to atmospheric as possible - airplane engineers even have a term for it : turbo-normalization. In an N/A engine the manifold pressure is always less than atmospheric; a 2.0 L engine with 4 cylinders should pull .5 litres on each intake stroke; in reality it is closer to only .2-.3 litres..The turbo manages to fill each cylinder with the maximum charge, or close to it. It may seem the engine uses much more fuel under boost, but it is only utilizing the appropriate amount for the size of the air charge in the cylinder; the 2.5 F4 cyl as our Subies have will still get better MPG than a small v6/v8.

[cr8zyjap07]

so i did my speech already. i jsut explained how a turbo works, compared turbo cars and big na engines at the same power levels and eco boost etc etc. bull****ted the whole thing and got a b+ so idc lol. this is actually a good thread tho

[jdubs]

so i did my speech already. i jsut explained how a turbo works, compared turbo cars and big na engines at the same power levels and eco boost etc etc. bull****ted the whole thing and got a b+ so idc lol. this is actually a good thread tho

Correct, generally its not what you say, but how you say it.

Nobody is going to want to listen to a long boring talk on energy and efficiency and such, but if you can tie them together on a higher level you will get paid for it.