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When getting a turbo or super charger, what does it do to you gas mpg? i know you usually need higher injectors so wont this make your mpg lower?
 

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To answer your question, yes. A turbo compresses air like crazy. Compressed air takes up less room in your cylinders so a lot more air is going in. In order to keep the air/fuel mix proper, much more fuel is needed.


But it's worth it. hehe
 

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In order for the air to be compressed though , the turbine needs certain rpm to spool up, if you don't push your car to that rpm and beyond all the time you'll get pretty good gas mileage.
 

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I know hardly anything about boost... but I've heard the term "negative boost". Does that mean that you're not getting any boost, or you could actually be losing compression? Either way, if you're not boosting at all, wouldn't it not hurt gas mileage?
 

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Louse76 on Dec/11/02 said:
I know hardly anything about boost... but I've heard the term "negative boost". Does that mean that you're not getting any boost, or you could actually be losing compression? Either way, if you're not boosting at all, wouldn't it not hurt gas mileage?
Positive boost : air pressure above atmospheric

Atmospheric pressure : air pressure of 14.7 psi or 105KPa or 1bar

Negative boost : obviously air pressure below atmospheric

Negative boost applies to all internal combustion engines , forced induction or not.

When the intake valves start to open and the pistons descend in the engine cylinders it causes vacuum within the combustion chamber , so air from the atmosphere enters through the intake resonator , passes through the air filter , through the intake pipe and intake manifold , intake runners , past the valves and right into the combustion chamber and cylinder to eliminate the vacuum . At certain rpm the cylinders are filled completely with air (100% V.E.) . At that rpm maximum torque is reached because there no losses in airflow.

Theoritically the vacuum caused in the air intake when the piston descends should climb up to 14.7psi again because of the incoming charge.But does it? No. Why? Answer : restriction.

Any restrictions in the air intake system that cause pressure drop is considered as negative boost.

In turbocharged cars negative boost is exists before the turbocharger.

Hope that makes sense.
 

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I see, thanks a whole lot for helping me learn something today!!

Someone said a while back that they don't use that much gas or something on their turbocharged car because for daily driving they run around in "negative boost" most of the time. I'm thinking they may have been referring to the position of the dial on their boost gauge though... a possibility?
 

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yes they were referring to the boost gauge , but vacuum is a more precise description than "negative boost" .
 

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Michael Delaney on Jun/06/02 said:
do you really care about mpg when you save up and eventually buy a SC or turbo kit?

that's like going to a supermodel show or bikini contest and saying, why do they wear those awefully uncomfortable shoes?
all the preaching around here about going off topic on post, and here's a fine example.
 

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ctx97 on Dec/11/02 said:
Quote: Michael Delaney on Jun/06/02do you really care about mpg when you save up and eventually buy a SC or turbo kit?
that's like going to a supermodel show or bikini contest and saying, why do they wear those awefully uncomfortable shoes?
all the preaching around here about going off topic on post, and here's a fine example.

[/quote] um...actualy i thought that answered the question quite nicely.if you need to get a higher flow fuel pump to effectively have a decent turbo setup then apples and oranges should tell you that you will use more fuel

also i think one reason why honda didnt do a lot of work with turbos is because their whole thing was fuel efincency.
 

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Well if your running a FMU at like 12:1 for sure your wasting more gas thats a given LOL, but out of boost it should waste no more than normal....
 

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Louse76 on Dec/11/02 said:
Well really the question was, how will FI effect MPG... not should I worry about MPG when I go FI...
I hope you can resist the temptation to mash the throttle:)
 

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Integra15lb on Dec/11/02 said:
Im not trying to be a d**k here or nothing,but worring about your mpg after you super or turbo charge your integra is like worring about mpg if you buy a porche.
Personally, if I weren't worried at all about MPG, I'd just get a V8 and not worry about modifying a Honda. What's the point of turbocharging if you're not worried about fuel efficiency? The whole reason they invented turbocharging was to get large-displacement-like performance out of a small-displacement engine, so you don't have to suffer with large-displacement fuel economy when you're not accelerating.

Why can't anyone just give the man a decent answer? If he were so rich that he didn't give a rat's ass about fuel efficiency, he'd just buy a Porsche or something.
 

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Well, turbos are the most efficient way to add horsepower period. I dont feel that boosting should have any effect what so ever in MPG UNLESS, you are getting on the pedal. You see, when driving down the highway, you car is going to still be running the same A/F ratio as normal (unless modified), with or without boost to keep the same speed. With boost, you will have the throttle body open less than stock, letting less air in to maintain your speed. Until you get on the gas, then who gives a crap about MPG, you have a turbo.

Thats my take, other thoughts?
 
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