bigpeet

I've seen a little discussion on this board and lots of conflicting information on the net. Do superchargers/turbos add MPGs?

I've read some say yes because it makes the engine more efficient overall, meaning you have to press the accelerator less to get and stay moving.

Some say that's exactly why they get worse gas mileage because it burns more fuel as it takes in more air, lowering MPGs.

Who has either and can comment on actual real-world results? No speculation or second-hand info, please.

74Novaguy

Yes and No... If you put one on under normal driving yes it does my brothers truck (chevy 4.8l) with a procharger gets 29 hwy and 24 in town with the procharger and before that it was like 22 hwy stock. now when he gets on it hes see as low as 15 to 18 in town. He also put down 480 hp on the dyno and the guy had to back out because his dyno only went to 160mph.

bjankuski

The answer is no, the supercharger or turbo charger is designed to add additional air into the engine above atmospheric pressure. When a car is traveling down the road attempting to get good gas mileage the car is running with an intake manifold vacuum and is putting out low HP numbers. For example let’s say to cruise at 60 MPH it takes 20 HP, the engine that puts out the 20 HP most efficiently will get the best gas mileage. A supercharger or turbocharger will add additional drag to the engine that burn up power yet the engine still only puts out the 20 HP required to move the car at 60 MPH. The power to spin the blower is being wasted and contributes to slightly worse gas mileage. The turbo charger builds slightly more exhaust backpressure and increases the pumping losses and contributes to slightly worse gas mileage. The key to remember is cruising gas mileage is always achieved with a low specific output and anything that add drag to the engine will burn more power or gas. The engine does not care how it achieves the 20 HP output it just needs to do it the most efficiently.

74Novaguy

Then why does my brother truck almost get 30mpg with the supercharger with 480 hp? when stock was 22mpg?

bjankuski

I would question the accuracy of his numbers before and after?

74Novaguy

I dont question. Im pretty good at math. x miles divided by y gallons = z miles per gallon Ive driven it before and after and was there while it was on the dyno being tuned. During cruising its better mpg but when your driving it hard its alot worse than stock. and we had a custom tune done which is better than what procharger provides. and prochargers when your not in throttle they dont produce boost they have a gate valve in the intake so the engine isnt being feed under boost but yet its not really haveing to work to get air either since the procharger is still trying to build boost but what ever the engine isnt using is blown out to atmosphere.

bjankuski

I am not attacking you so please do not be offended. As you stated there is a gate valve that blows the air from the supercharger back to atmosphere. That means you are doing work (Pumping air) and it is doing nothing to move the truck. In other words you can only use more gas to accomplish this. If the truck is getting better mileage it is something else like the tune or additional modifications from stock.

74Novaguy

Im not taking it as you attacking me. I agree with you that the procharger take HP (gas) to produce air but on the other end the engine doesnt have to fight (vacuum) to get air. and its a bone stock 4.8L with procharger and had it dyno tuned. before I ever installed it I told my brother that his mpg were going in the toilet if he wanted 500 hp and he didnt care now he has 480rwh which is about 540 hp crank I assume since he has an automatic. and now im the one eating crow since he gained 6 mpg out of the deal. it did cost him 6k though. but it is fun to drive a stock looking 1500 chevy and beat the sports cars on the street.

MC305SS

I will add something that could solve this debate raging.
If the vehicle in question ( Truck ) was severely under powered to begin with that required much more pedal effort to maintain speed and then swapped out for a better power plant that required much much less pedal effort, then yes it would get better gas mileage.
On average with a vehicle that does not exhibit such a problem, mileage would drop at least 1 mpg driving it normally.

freaky

i had a 05 srt4 i bought brand new ,they pushed out of the show room for . i tracked every tank of gas i put in the milage ,bone stock i got 28 mpg driving on the highway an never going into boost once i put the 50 trim turbo on it i got 32 mpg on the highway never seeing boost . now i raped the car alot an i seen as low as 14 mpg but under average conditions i still seen an improvement of 2-3 mph after going to a bigger turbo . also i had a brand new 04 neon sxt n/a car an never seen over 25 mpg on the highway . so i'm gonna have to conclude a turbo makes for a more efficient motor there for better gas milage an the right turbo is even better . but i'll let you know more about this 92 turd i got now after the lt1 cam an vortec heads an turbo are in place ....

bigpeet

This is very similar to most discussions I have found online. Several people say it shouldn't theoretically increase mileage, but there are still people who claim to get better mileage with one. I guess, in short, gas mileage is an estimate and could not possibly take into effect all the different factors, such as weather conditions, actual routes driven, stop signs and lights, etc., that would come into play. I guess this isn't something that can be solved once and for all. I suppose if you see an increase in MPG, that's awesome, but if you don't, you shouldn't have expected one theoretically anyway.

sailtexas186548

iTrader: (2)

I agree with this, this is why huge heavy turbo diesel trucks get better mpg's than underpowered 1/2 tons

so you saw 4+ mpg after swapping to a larger turbo but staying completely out of boost. You just reduced exhaust back pressure with the larger exhaust housing, the turbo didn't do anything to improve your milage, you basically just put a better flowing exhaust on...

So when you put most of the miles on your car (cruising) your out of boost with a less restrictive exhaust (aka larger exhaust housing) your will see better mpg's than a smaller housing.

The answer to your question OP is it depends. If your turbo/supercharging to get move power/performance your going to see reduced MPG's most of the time unless you drive like grandma. Then again if your going FI and worried about being able to afford gas you should really reconsider going FI.

flrtin1

The answer is yes...real world. All three of these motors the 6-71 in the truck, 420 in the Z/28 and 8-71 on the stand got better milage after installation of the blowers.
I factory ordered the Z/28 so have had it since new and it only got 18mpg at best new, it has had a roots blower on it since 86....last year we did the Power Tour for the 4th time went 1500mi round trip and averaged 22mpg on the highway same as when I first put the blower on (it has close to 70k blown miles on it now). The truck was getting 17-18 before and went to 20 after. Like any car the more you agressively get into it the faster the MPG drops.

flrtin1

One thing to remember also is the changes in effective compression ratio in and out of boost......I have 7.5:1 static but 12.8:1 effective on the Z/28.

freaky

i believe a forced injected motor is more efiecient ,sorry n/a guys but apppears to be true untilll booost kicks in at that point gas milage isn.t an isssue .lol

Camaro305SB

No, you don't just get better MPG with a turbo/supercharger. The thing is though, when you go forced induction you can use a smaller base engine for the same overall output. For example, compare 4.8L truck engine to a 6.0L truck engine. The 4.8s economy is better stock, and the 6.0 has more power, of course - but if you were to turbocharge the 4.8L it you would have as much, if not more, power than the 6 liter AND return better fuel economy. Its not like turbocharging an engine just decreases fuel consumption. If thats the case, than the base engine (before the forced induction) was not running as well as it could have been.

Thats what they did with the Chevy Cruze. The 1.4T option gets better economy than the 1.8 n/a. Why? Smaller base engine uses less fuel when under light load.

flrtin1

If you dont want to take my 25yrs worth of experiance than maybe this will work?

http://www.dyersblowers.com/223/268.html

"5. Will there be a severe loss in fuel economy with a Dyer's Blower Kit?

Under Normal driving conditions, you should PICK UP around 3 mpg over a normally aspirated engine. This is possible by the efficient mixing and vaporization of the fuel due to the supercharger. Also, the additional low end torque allows for a taller rear end ratio"

flrtin1

My experiance has always been with roots type blowers.....dont have any first hand experiance with Centrifugal or Axial superchargers or turbos so I cant speak to milage effects on those.

90 camaro cj

The new Chevy Cruze ECO, the one thats supposed to get the best gas millage has a 1.4l turbod i4. why would GM put a turbo on there car that's supposed to get the best gas millage if it was gonna affect it negatively....http://www.chevrolet.com/cruze/?seo=...hevy_cruze_eco read it from chevy.

Benjam88

Read about Ford EcoBoost. Yeah if set up right a turbo can add some fuel economy. Think about it this way: If you have a big syringe and pull the plunger back on it really hard its gonna resist you, because its creating a vacuum, and is drawing air through a small hole. Now apply this to an engine. The cylinder dropping in the bore is doing the same thing. Now if we add a low pressure turbo into the equation it will pump air into the engine as the piston drops, eliminating the resistance that is caused, called Pumping Loss. Cause remember an engine is nothing but an air pump.