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How do I reduce horsepower?

watdahel

watdahel

Golden Member
I have a 1/2 ton 5.7L V8 truck that sucks up gas like its free. I was wondering if there's anything I can do to improve on gas mileage, perhaps a computer plugin or have the engine run on 6 cylinders instead of 8.
 
The biggest factor you can change sits between the seat and the steering wheel. And as a bonus it's a free mod.

Drive slower on the highway. Accelerate less aggressively. Coast more often. Use cruise. Basically hypermile as much as a 5000 pound brick can.
 
Originally posted by: erwin1978
I have a 1/2 ton 5.7L V8 truck that sucks up gas like its free. I was wondering if there's anything I can do to improve on gas mileage, perhaps a computer plugin or have the engine run on 6 cylinders instead of 8.
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There are some companies that have things to reprogram your truck's computer for more power or better mileage. Check around for your vehicle in particular, some of those companies are more reputable than others. None of them will just turn off cylinders though, that's relatively complicated to do and I wouldn't really hold your breath for any huge improvements. Honestly though, you'll see a bigger change just by driving with a lighter foot.
 
The single biggest thing you can do (for highway mileage at least) is to install taller gears for the final drive. A set of 2.73 gears for the differentials could really make a difference on the highway. Of course, you'd have to re-calibrate the speedometer.

Honestly, aside from replacing the truck with a different model that has a smaller engine there aren't a lot of realistic options.

ZV
 
We have a 2009 Ford F250 at work.
Owner (boss) drives = 8-9 mpg.
I drive = 13-14 mpg.
It's all in your foot.................

Of course he's paid by the job and I'm paid by the hour!
 
The reality is you own a large truck with a big engine, everywhere you go you're hauling around five thousand pounds of steel. It's never going to get very good gas mileage.
 
Just be very gentle on the gas pedal. Treat it like there is an egg under your foot. Mileage will go up for sure. And when you can, use the cruise control if you have one. Try to keep highway speeds at no higher than 70MPH (if the road is like a 65MPH zone, or about 60MPH in a 55MPH zone) You will see an increase in mileage. Run with windows up and ventilator open when you can. Again mpg will go up a bit. And try to anticipate a light changing, as opposed to flying up to it and hitting the brakes, then reaccellerating.
 
Put a wideband on it and see if the tuning is rich on it. If needed then you could tune it to run a bit leaner which will net a slight increase in mpg and would actually give more power.
 
Some of these replies are interesting.... I dont think people understand what alters fuel use. The intake restriction is an example 😛

To travel at 60mph for instance, your vehicle might need 40hp. Whether you have a V8, V6, F4, V12, V16, it will still require 40hp. To generate 40hp, you need to bring in enough air to combust to produce 40hp, and the stoich ratio of fuel. If you want to save on fuel costs, reducing horsepower isnt going to help. You need to decrease weight, or improve aerodynamics.
 
I find that getting gas mileage is more dependent on how I use my brakes rather than how I use the gas pedal.

Every time you use your brakes, you are converting the energy from the gas you paid for into heat. IMO slamming on your brakes is worse than doing a burnout.

The trick is to always try to maintain your momentum. Don't speed. Use your cruise even in the city, and use it to accelerate if you can (there should be little +/- buttons on it). If you're at a long red light, kick it to neutral. When you're about to start off again, let your foot off the brake for a few seconds before applying the gas.

If you do all that you're looking at a 30-40% improvement, perhaps more. I was getting 800kms+ on a 40L tank of gas in my 06 Civic doing this when the gas prices were high. It didn't even matter if I drove in the city; I still got great mileage.
 
Hmmm.....I wonder why they put airbox intake restrictors on race cars to reduce their power? It's very common to see air intake restrictors used to "equalize" race cars.

I always thought that if you restricted the airflow, the engine computer would automatically lessen the fuel used to match, and thus reduce power.

Within reason, of course. You can only go so far. There is only so much range of adjustment that can be made by the computer.

And vice-versa, thus the efforts to improve airflow into the engine by removing silencers and complicated ducting, or even increasing the size of the throttle body, to get more air into the engine, which would cause the computer to add more fuel, and thus make more power.



 
Originally posted by: LTC8K6
Hmmm.....I wonder why they put airbox intake restrictors on race cars to reduce their power? It's very common to see air intake restrictors used to "equalize" race cars.

I always thought that if you restricted the airflow, the engine computer would automatically lessen the fuel used to match, and thus reduce power.

Within reason, of course. You can only go so far. There is only so much range of adjustment that can be made by the computer.

And vice-versa, thus the efforts to improve airflow into the engine by removing silencers and complicated ducting, or even increasing the size of the throttle body, to get more air into the engine, which would cause the computer to add more fuel, and thus make more power.
Click to expand...

His goal as far as I read it is to decrease fuel consumption. Providing an intake restriction will not accomplish this, I would venture to say the opposite actually, because the engine will have to work harder to pull in the required amount of air.

He will still need xx amount of horsepower to travel at xx mph.... engine size, engine performance really has nothing to do with this.
 
Reduce rolling resistance by making sure your tires are inflated to the proper air pressure. A few extra pounds will reduce rolling resistance further at the expense of a harder ride and possibly increased tire wear.
 
Originally posted by: LTC8K6
He will still need xx amount of horsepower to travel at xx mph
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Yes, it would not effect cruise much, only acceleration, but that's where you use the most fuel.
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Actually, it would make fuel consumption worse on acceleration too.

The biggest losses an engine experiences are pumping losses caused by having to suck in air past a restriction (usually the throttle butterfly). This is why it is overall more fuel efficient to accelerate with 80-90% throttle while short-shifting than it is to accelerate at 50% or even 30% throttle.

Throwing in an additional restriction in the intake tract will only reduce the engine's efficiency and hurt mileage. Power will drop, of course, but so will mileage.

ZV
 
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