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Old 06-08-2006, 05:00 PM   #11
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Quote:
Originally Posted by Matt Timion
I don't think he was actually talking about you compaq. I believe his 45lbs figure wasn't in reference to you.

That being said, the EPA says that every extra 100 lbs is 1-2% decrease in fuel economy.


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You also realize that there is a cutoff for this type of statistic.

I think if you really want to save weight you need a smaller car. 30-40lbs isn't going to do much in terms of fuel economy. I even think 100lbs isn't going to be noticable.
Matt, I know you are pretty knowledgable about statistics. Would it even fall outside of the statistical significance range?
True, I wasn't thinking of any car in particular. I used 3,000 pounds for easier figuring.
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Old 06-08-2006, 05:02 PM   #12
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physics says yes, however the amount of savings will not be noticable. it will only be worth mentioning for city driving.

it will effect an automatic car more than a manualbecause of the shift points but it depends largely on the initial weight.

you cant guess with weight either, ive taken thing out thinking i dropped 25lbs, i weight it and its like 12, with other things i think its like 3 lbs turns out to be 10.

you have to weigh everything to get the exact weight. what did you pull? i have done a good amount of weight reduction while maintaining a full interior but with all the things ive put in my car i still have a feeling its around the stock weight.
Quote:
Originally Posted by 95metro
The rule of thumb from engineers on this issue is that with every ten percent of weight reduction mileage is improved by about 7%.
ill buy that for city driving
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Old 06-08-2006, 05:06 PM   #13
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Quote:
Originally Posted by thisisntjared
physics says yes, however the amount of savings will not be noticable.

it will effect an automatic car more than a manualbecause of the shift points but it depends largely on the initial weight.

you cant guess with weight either, ive taken thing out thinking i dropped 25lbs, i weight it and its like 12, with other things i think its like 3 lbs turns out to be 10.

you have to weigh everything to get the exact weight.

what did you pull? i have done a good amount of weight reduction while maintaining a full interior but with all the things ive put in my car i still have a feeling its around the stock weight.
I don't put weight in the car, only take out. I took out the spare, jack and some stuff in the engine bay. Plus I weigh less than 130 fully clothed so I consider that a weight reduction.
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Old 06-08-2006, 05:08 PM   #14
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Quote:
Originally Posted by diamondlarry
Matt, I know you are pretty knowledgable about statistics. Would it even fall outside of the statistical significance range?
True, I wasn't thinking of any car in particular. I used 3,000 pounds for easier figuring.
With statistics it all depends on the number of comparisons you make. If we took 100 cars and drove a test strip and then removed 100 lbs and drove the same test strip (all else being equal... weather, driver, EVERYTHING).. 1-2% would probably be statistically significant. It's difficult to say though for sure without seeing the data.

Now just saying that one person shaved .1 seconds off of their quarter mile time due to 100lbs of weight reduction i can promise you that there is no statistical significance there. First of all the sample is of 2-3 events. They were not on the same day, and a number of other possible errors could have been introduced into the equation.

It's not uncommon to have 1 second differences between quarter mile runs with no modifications. Driving style, reaction time, weather, etc. all play a part. To say that removing 100lbs gave a person 10HP is no different than saying that there is a magic pill that will increase fuel economy.
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Old 06-08-2006, 05:09 PM   #15
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thisisntjared physics says yes, however the amount of savings will not be noticable.
I agree. I think it will make some difference but the return-on-investment would take forever. The most improvement in mpg will come from improving the least efficient component in the drive train. I believe this would be the engine. This would involve getting more of the fuel to burn IN the engine and not in the exhaust/catylitic converter. After that, you could start working on weight reduction and aerodynamics.
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Old 06-08-2006, 05:13 PM   #16
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The most improvement in mpg will come from improving the least efficient component in the drive train.
I need to start making a collection of diamondlarry quotes.
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Old 06-08-2006, 05:16 PM   #17
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I need to start making a collection of diamondlarry quotes.
Gee MAtt, your going to make me blush. What else do you got?
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Old 06-08-2006, 05:23 PM   #18
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I made a lot of runs and best I could muster is 17.03
After I removed some of the interior parts I dipped into 16's. So that means it works at the track.

I already fixed my least efficient components in the drivetrain. I had warped disc brakes which killed my rolling. I had a bad temp sensor which made my car run rich. I replaced that too. So now my car rolls longer and runs leaner than before.

To keep things clear all the stock runs were made in 2004. Even the 16.9x runs. I fixed all the stuff this year so the repairs don't affect what I said.
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Old 06-08-2006, 05:35 PM   #19
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You know how anal you guys are when it comes to your milage runs, well the guys at the strip can make you guys look like rank amateurs! It is well known in the racing world that a 100 lb. is worth a tenth.
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Old 06-08-2006, 05:38 PM   #20
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I think weight is very noticable at the track.

In talking to disco about this at length, I learned that weight's importance increases proportionally to the rate of acceleration.

So, if you floor it to redline everywhere, you might notice the difference, if you drive carefully, doubt it, though it will be there.

Someone should test the weight/CODFISH distance relationship.
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