This has been bugging me
 

Ok, so this is kind of a contemplative thread to help answer a question I have. Here it goes, I will try to explain it as best I can. I often hear people with turbos saying "oh yeah, my highway mileage went up a few miles per gallon." I am not dismissing this information as false, I am just posing a question. How does this work? I have thought about it a lot, and I just don't get it. I understand the fact that turbo's use exhaust gasses to make power, I'm not a complete noob, but it still doesn't pass the common sense test on how this increases fuel efficiency. A turbo pumps more air into the engine, which must be compensated with fuel. No matter what size turbo you have, it still takes the same amount of energy to keep the car at a given speed on the highway and I just don't get how you can get around the facts that it requires a certain amount of fuel to react with the air for combustion. If you are using a turbo, it doesn't make sense to me how that could reduce the units of fuel per unit air required for combustion. Therefore, at a given constant speed, I don't understand how mileage could improve.

As a disclaimer, I would like to say, please don't post nonsense in this thread that has been seeping into other threads. I would prefer to have no responses like "my buddy has better mileage now" or "i have better mileage with my turbo". I am looking for objective responses that not only present data of better mileage, but explain the WHY and HOW of this issue. That is my true question. Thanks for reading, I know it was kind of long.

On a side note, this question also pertains to people that claim they get better mileage with their intakes/headers/exhausts. I just don't get, even if the air does flow easier, it still takes the same amount of fuel per unit air to get a complet combustion.

RE: This has been bugging me
 

Yea I agree about the whole turbo thing. Besides, if your goin around doggin your car even without a turbo, you wouldnt be getting better gas miledge anyway. And if you did havea turbo and decided, hey im not gonna go zip around in my car today and actually filled the car up and drove it like a controlled human being and found out you did get better gas miledge, show me the charts. And it has been said that a CAI will give you about 1 more MPG. Havnt proved it, just what I have been told from Injen

RE: This has been bugging me
 

It takes less throttle to maintain any certain speed, Less throttle percentage = less fuel being used.

RE: This has been bugging me
 

Marty are you a car Guru?

RE: This has been bugging me
 

What do you mean?

RE: This has been bugging me
 

if you don't get into boost the milage skyrockets:) As soon as you start boosting that's the end of it...I get anywhere between 12mpg to 29mpg depending on my mood.

RE: This has been bugging me
 

Turbos use wasted enery to make more energy... it's like recycling
:)

RE: This has been bugging me
 

Well here is what I understand of it:
With am I/H/E, it is easier for your car to breathe, there is less pull on the engine to take in the right amount of air, and there is less pressure on the back of the engine which allows the engine to rotate easier. This in turn allows the overall energy consumption of the car at a given speed to be reduced, thus requiring less fuel, and in turn raises MPG. basically it is kinda like exercising, the better you breathe and exhail, the more you perform...

With a turbo, the same principle can be said, the gain in backpressure is overcompensated by the gain on intake pressure. this allows an efficient rotation of the engine, thus requireing the same amount of fuel to keep the engine running. I dont know if it increases MPG, but I do know that it can remain the same. I have heard however, (and I could be wrong) that higher compression pistons will increase MPG, because it uses the same amount of fuel and air to create more power... so I guess this same efficiency principle can be applied to a turbo since both increase cylinder pressure... Also, this efficiency allows the car to consume more fuel when the pedal is pushed because of the increased amount of air being crammed into the intake, so like Roto said, MPG can really drop too!

Anyway, that is my understaning of it (could be wrong), hope that helps :eek:.

RE: This has been bugging me
 

:eek:

RE: This has been bugging me
 

Its quite simple if you really think about it. Turbochargers are powered by wasted exhaust gasses coming through the exhaust manifold....When in boost, they move tons of CFM's and force more air into the motor, adding more fuel making more power. However, when they are NOT in boost, they boost fuel economy because...........An engine is a big air pump.....and the turbo causes the engine to use wasted energy to aid in the suction of new air, so the engine is fed the air. Turbochargers also atomize the air, when you have a finely atomized mixture of oxygen and fuel, it burns much more effieciently. The combination of that and the exhaust gasses spinning the compressor wheel, give great mileage, but only when not in boost. I had a turbo automatic SOHC motor, I was getting around 45 mpg on the highway, being very easy with the throttle.