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View Poll Results: Do you think that more Horsepower leads to better gas milage?
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No 7 63.64%
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Old 07-17-2007, 06:45 AM   #1
DavidReuben
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Gas milage, and overdrive

Does anyone know if there is any after market add ons that will actually improve gas milage?

I just put a K&N air filter in my '02 Passport, I'm not sure if it was a fluke or if it was just how we drove it on this last tank but it got about 40 more miles than usual.

And does anyone know why instead of building Hybrids, they just don't just build better over drives? It seems to me that if the just built better overdrives, then they wouldn't need hybrids, or engines that shut half the cylinders down.
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Old 07-17-2007, 06:20 PM   #2
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Quote:
Originally Posted by DavidReuben
Does anyone know if there is any after market add ons that will actually improve gas milage?

I just put a K&N air filter in my '02 Passport, I'm not sure if it was a fluke or if it was just how we drove it on this last tank but it got about 40 more miles than usual.

And does anyone know why instead of building Hybrids, they just don't just build better over drives? It seems to me that if the just built better overdrives, then they wouldn't need hybrids, or engines that shut half the cylinders down.
Unless your old filter was really dirty, I don't see how a K&N will help you that much. I've got one and doubt that I gain any MPG or performance, but it fits a lot better than the paper ones on my car.

I know next to nothing about tranny's but I'll still opine on this one. My car does 70mph at about 2,000 rpms in OD, and I still only get high 20's in MPG on the highway. Many cars don't make enough power that low in the RPM range to propel a car through the wind at highway speeds. Even still I'm only gaining maybe 5 MPG in OD and I'm cutting a good 1,000 RPMS off. Highbrids and cars with cylinder shutoffs are much more efficient. Although If I'm not mistaken many highbrids charge their batteries by way of the brakes, and you're not doing much braking on the highway.
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Old 07-17-2007, 08:08 PM   #3
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I still belive they can do more with Gasoline Engines than they are. I'm just sick and tired of the Global Warming Bull@#$%, and the government trying to dictate which kind of cars we can and can't drive.

I would like to hear some more oppinions about transmissions.

I also hear that the more power you have the better gasmilage you get, which is also wrong. With the limited knowlege of engines that I have, I know that it takes a certain amount of air, and fuel to run properly. And the more air(which leads to more power) the more fuel it needs to ballance the ratio. And therefore more fuel per mile.

If I'm wrong pleas correct me!
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Old 07-17-2007, 10:46 PM   #4
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Quote:
Originally Posted by DavidReuben

I also hear that the more power you have the better gasmilage you get, which is also wrong. With the limited knowlege of engines that I have, I know that it takes a certain amount of air, and fuel to run properly. And the more air(which leads to more power) the more fuel it needs to ballance the ratio. And therefore more fuel per mile.

If I'm wrong pleas correct me!

More power is the result of a more efficient combustion process. So, to a certain extent, more power will result in better gas mileage assuming you're not racing the car from every red light/stop sign...An engine is essentially a big air pump...the more air you can get in and out of it, the more effienciently it will run.
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Old 07-18-2007, 08:41 PM   #5
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Originally Posted by Sick88Tbird
More power is the result of a more efficient combustion process.
I guess you mean if we're talking about the same engine. I can have a 7 liter V12 that makes 205 hp, but I don't consider it more effecient than a 2 liter that makes that 200 hp.

To the OP: Although I agree that it seems cars with more HP get worse MPG, you're bit about the more air/fuel was missing one thing. When that more powerfull engine takes in more air/fuel than it's less powerfull counterpart, it obviosly makes more power, propelling the car further than the "more efficient" car.

As far as ODs go, the transmission can only do so much. Even if my car could magically cruise the highway at 1,000RPMS, I still wouldn't get the MPG of most hybrids.

And please elaborate on how the gov. chooses which cars we drive. Unless you're talking about safety requirements I'm lost.
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Old 07-19-2007, 05:36 AM   #6
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I'm not saying that right now the Gov is telling us what we can and can't drive, but I don't think that those days are far off.

Quote:
Although I agree that it seems cars with more HP get worse MPG, you're bit about the more air/fuel was missing one thing. When that more powerfull engine takes in more air/fuel than it's less powerfull counterpart, it obviosly makes more power, propelling the car further than the "more efficient" car.

giant016 - I'm confused as to what you mean by that statement.

More fuel burned per mile = less miles per gallon.
Less fuel burned per mile = more miles per gallon.

If the engine is a big air pump, the more air it pumps then the fuel it takes to keep the engine running, right?

So less cylinders means less fuel is being burned per revolution. But still, if you turn up the air, it requires more fuel to keep the engine running. So more power = less efficient fuel burning.

I don't really have any facts to back this up. But from some of the reading that I have done this is what always made sense.
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Old 07-19-2007, 04:34 PM   #7
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Originally Posted by DavidReuben
I'm not saying that right now the Gov is telling us what we can and can't drive, but I don't think that those days are far off.
What makes you say this?


Quote:
giant016 - I'm confused as to what you mean by that statement.

More fuel burned per mile = less miles per gallon.
Less fuel burned per mile = more miles per gallon.

So less cylinders means less fuel is being burned per revolution.
Yes, but the car is making less power. A V8 that is running at 3000RPMs will propel a car further than an V6 running at 3000RPMs in the same time frame. This is assuming the only difference between the engines is the displacement. So, yes less fuel is being burned per revolution the smaller engine, but the car is going a shorter distance per revolution as well.

Thats one of the ways I look at it, but I'm probably incorrect.
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Old 07-19-2007, 08:14 PM   #8
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I don't have any factual info of the Government wanting to regulate what vehicles can and can't be on the road. Rush Limbaugh was talking about the Democrats wanting to curb high output vehicles such as Porche's, and Lambo's, or Ferrari's, and only allow them on the race track. Only because a high performance/high HP vehicles produce more carbon. I'm not saying that whatever Rush was talking about is going to happen soon, or that I'm sure what he was even talking about. But it just ticks me off to hear all this "carbon foot print" BULL. I don't even own a high performance car, but I want to some day. And I don't like people telling me what I can and can't own, this is a free country. Anyway's! Back to the real disscussion.


Quote:
A V8 that is running at 3000RPMs will propel a car further than an V6 running at 3000RPMs in the same time frame.

I know what your trying to say, but I don't think that what your saying is correct.


So if you have two vehicles driving down the road at the same speed. One is a V8(Horse power, type of trans, and tire size don't matter at this time), and one is a V6, and they are both acheiving set speed let's say that it's 70mph at 3000rpms. The V8 would be burning 33% more fuel to acheive this speed at 3000rpms. Because it has two more cylinders than the V6. So if the V6 gets 20mpg, then the V8 is getting around 15mpg. Because no matter what if an engine is spinning at 3000rpms, it doesn't matter how many cylinders it has it's still 3000rpms. The only thing that could change that would be how fast the wheels are turning, which would be determined by the trasmission. So if the V8 had better gear ratios and instead of 3000rpms, it achieved 70mph at 2000 rpms, it would be more efficient than the V6. And that would lead you to believe that if you up the HP so that it could achieve 2000rpms at 70mph then it would be more efficient and would get more miles per gallon. But to up the HP the engine would still have to consume more fuel to reach high HP's. And it would really be better to look at Torque ratings than HP be cause HP is really a power(torque) to weight ratio.


This is of course according my simple mind and how it computes things.

Last edited by DavidReuben : 07-19-2007 at 09:50 PM.
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Old 07-20-2007, 02:51 AM   #9
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Quote:
Originally Posted by DavidReuben


So if you have two vehicles driving down the road at the same speed. One is a V8(Horse power, type of trans, and tire size don't matter at this time), and one is a V6, and they are both acheiving set speed let's say that it's 70mph at 3000rpms. The V8 would be burning 33% more fuel to acheive this speed at 3000rpms. Because it has two more cylinders than the V6. So if the V6 gets 20mpg, then the V8 is getting around 15mpg. Because no matter what if an engine is spinning at 3000rpms, it doesn't matter how many cylinders it has it's still 3000rpms. The only thing that could change that would be how fast the wheels are turning, which would be determined by the trasmission. So if the V8 had better gear ratios and instead of 3000rpms, it achieved 70mph at 2000 rpms, it would be more efficient than the V6. And that would lead you to believe that if you up the HP so that it could achieve 2000rpms at 70mph then it would be more efficient and would get more miles per gallon. But to up the HP the engine would still have to consume more fuel to reach high HP's.
I understand that the final gear ratio has a lot to do with the RPM at a certain speed, but HP comes in to play as well. There is no way a stock (torque-wise) Civic could go 70mph at 2,000 RPM, no matter what the gear ratio is. If you put the same gears that my V8 has in a V6, the V6 would still have to drive at a higher RPM to stay at 70mph. To stay at that speed it requires X amount of HP, and a V8 makes that HP at a lower RPM. So, say that my extra 2 cylinders make me use 33% more fuel than your V6 at a fixed RPM. But, your V6 would have to be running at a higher RPM rate to run at the same mph as me, lets say 33% higher. This means that each of your cylinders is having 33% more combustions per second, burning 33% more fuel in each cylinder compared to each of my cylinders.

Quote:
And it would really be better to look at Torque ratings than HP be cause HP is really a power(torque) to weight ratio.
I may not know much, but I know that HP has nothing to do with weight. Hp is (RPM X Torque)/5252
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Old 07-20-2007, 07:37 AM   #10
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I was assuming all other variables as constant. I guess I should have stated that. The only two differences were the number of cylinders. And assuming that each cyl = .5L of displacement.


But I know that HP is a power to weight ratio, look it up on www.howstuffworks.com. Do you know who invented, or first used the term Horsepower?

I hope I don't come off as a "know it all." Cause I don't think that I'm always right, I'm just trying to learn more about this stuff.

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Old 07-20-2007, 06:42 PM   #11
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I was talking to a buddy of mine, and this is what I came to the realization of.


Say we have to trucks, same exact trucks. The only difference is that one has V6 that produces 200 HP, and the other has a V8 that produces 300 HP. And lets say that the V6 gets 25 MPG, and the V8 gets 17 MPG. They are both pulling a trailor, the load(or weight) is well in the towing range of the V8, but just above the V6. I don't care weather there is V6 that is rated to pull 5,000 lbs or not, this is just hypethetical. So the load on each trailor weighs 5,000 lbs. Because the V8 produces more power per revolution of the engine, it is able to pull the trailor with out the extra weight totaly affecting how much fuel is consumed. So as they are driving down the road say at about 60 MPH, the V8 is more efficient because it is more able to handle the extra load(weight). But no matter how much horespower you cram in to a V8 it's never going to get 35 - 40 MPG.
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Old 07-21-2007, 07:52 PM   #12
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Quote:
Originally Posted by DavidReuben
I was assuming all other variables as constant. I guess I should have stated that. The only two differences were the number of cylinders. And assuming that each cyl = .5L of displacement.


But I know that HP is a power to weight ratio, look it up on www.howstuffworks.com. Do you know who invented, or first used the term Horsepower?

I hope I don't come off as a "know it all." Cause I don't think that I'm always right, I'm just trying to learn more about this stuff.
Haha, I don't really know what I'm talking about either, and I'm sure those who do on this forum are having a good laugh. I'm just enjoying the argument and being forced to think.

Maybe you're looking up the origins of the word "horsepower", but as I stated earlier it is calculated by taking the cars torque at a certain RPM, mulitplying that torque by the RPM it is at when it makes that torque, and the whole thing is divided by the constant 5252. It has nothing to do with weight, this I am sure of. Somebody want to verify this? I'm sure theres a few car nerds on here that know this.

Anyways, that's why a lot of 4cyl cars can have a decent amount of HP with so little torque. They're peak torque comes in at a much higher RPM, so the numerator in the fraction for the equation of HP is larger.

I don't really know what I was varrying when you say that everything should be constant. I'm thinking that if you had identical engines aside from the number of cylinders, the V8 would run at a lower RPM at any given speed. To run at a certain speed, it takes X amount of HP, and the V8 will reach that HP at a lower RPM because of the extra displacement from the extra cylinders.
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Old 07-23-2007, 06:01 PM   #13
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I don't care anymore!!!

The only thing I'm going to ask is.


Where does the constant 5252 come from?
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Old 07-23-2007, 06:59 PM   #14
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Cave men

Seriously I bet next your going to tell me that way back in the begining of time. Millions of years ago(as everyone belives the earth is millions of years old). There were acouple of cave men discussing horsepower, and they threw a hand full of sticks on the ground, and one said to the other, "look 5.....2......5......2!" Then the other one then said. "That's the universal constant for horsepower." And that's what we've been using for the rest of time.

I bet you didn't even look it up did you, why don't you type www.howstuffworks.com in to you URL box and check it out.
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Old 07-24-2007, 03:49 AM   #15
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Originally Posted by DavidReuben
Seriously I bet next your going to tell me that way back in the begining of time. Millions of years ago(as everyone belives the earth is millions of years old). There were acouple of cave men discussing horsepower, and they threw a hand full of sticks on the ground, and one said to the other, "look 5.....2......5......2!" Then the other one then said. "That's the universal constant for horsepower." And that's what we've been using for the rest of time.

I bet you didn't even look it up did you, why don't you type www.howstuffworks.com in to you URL box and check it out.
You didn't read it!!! You didn't even read your own f*cking proof!!! Read through the entire horsepower article on howstuffworks. Actually specifically read the last sentence in the second paragraph on the second page, "measuring horsepower". Here, I'll quote it word-for-word:

Quote:
What dynamometers actually measure is torque (in pound-feet), and to convert torque to horsepower you simply multiply torque by rpm/5,252.

Not enough proof? Google up some dynosheets. They give the torque and horsepower for a given RPM. When you put the torque into the HP equation I gave you, well... it must be a coincidince that every single one works out exactly.
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