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View Poll Results: Do you think that more Horsepower leads to better gas milage?
Yes 0 0%
No 7 63.64%
Globel Warming doesn't really exist! 5 45.45%
Multiple Choice Poll. Voters: 11. You may not vote on this poll

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Old 08-01-2007, 09:50 PM   #31
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Sorry guys that was supposed to be air. Ill fix it.
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Old 08-02-2007, 08:57 PM   #32
DavidReuben
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Quote:
Originally Posted by Enthusiast
CombustionEfficiency usually has to do with how much of the combustion components are used up not how much are and fuel get in. If you JUST add more air it would make the car run lean, on an N/A more that is good to a certain extent, too much can hurt.
Most computers compensate for more air and add mroe fuel which is why you get more HP.

But if the computer is for some reason throwin in to much fuel youll run rich and lose hp and get shitty gas mileage, but in a fi and nitrous motor, ive always been told a little rich is good for saftey, especially on a non purpose built motor.

I think that the only time you add more air, and have the mixture run lean will be on a carbuerated(spelling?) engine, but that would only be because it the fuel wasn't adjusted. When you add more air to a throttle body the computer will compincate for the added air, and add more fuel, it also compincates with the mass airflow sensor by heating up the air and making it less dense.

Why would you get less HP when you have a much richer mixture? Wouldn't it be because not all of the fuel is burned. I haven't dynoed anything. But would it really reduce the power of the engine, it might feel that way because not all of the fuel will be able to burn, also the more Oxygen the more fuel is burned also.

Was the contradiction really all that important to point out, did you really not understand what he was saying.
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Old 08-02-2007, 11:00 PM   #33
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#1) Carburetors meter fuel according to airflow through the venturi, so they would be able to compensate just fine.

#2) Mass airflow sensors do not heat the incoming air charge to make it less dense. A mass airflow meter has a small heated wire which electricity runs through(think of it as a resistor). That small "heated wire" is cooled by the incoming air, thus changing the resistance across the wire...increased temperature increases resistance and vice versa. The more air that flows across the MAF sensor the cooler the heated wire gets, which tells the computer how much air is being pulled through the sensor.

#3) The perfect air/fuel ratio is 14.7:1, which is known as stoiciometric...any number higher is considered lean, any number lower is considered rich. Run a combination too rich or too lean and you lose power.....vehicles with forced induction will naturally have to run richer...no vehicle runs an A/F ratio of 14.7:1 while under power...maybe under deceleration....most cars run 1 to 2 points richer than 14.7:1 on average.

Hope that helps,
Don
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Old 08-03-2007, 09:31 PM   #34
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Thanks, I didn't know that's how mass air flows worked.
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Old 10-22-2008, 04:13 AM   #35
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I came across this thread from a random search of the internet. Let me correct a whole bunch of information.

1. As Sick88TBird pointed out, engine speed has to do with gearing and vehicle speed, and that's all. So if a given car goes 2000 RPM at 70 MPH, it will do so as long as it makes enough power at that RPM to overcome friction and drag. Having a lower RPM DOES NOT always realize less fuel being used. If RPM is low enough that you're not making enough road power to maintain your speed, you have to increase throttle input to compensate. So, you could still be at 2000 RPM with a massive head wind, going up hill and be at full throttle, using large amounts of fuel, but not making a heck of a lot of power. This is what's called being "under load."

2. Optimum Air/Fuel ratios change based on whatever condition you're hoping to be in. The optimum air/fuel ratio for best power, least emission and least fuel are all different. Stoichiometric A/F ratio is 14.7:1, and this is the ratio in which the engine burns fuel the cleanest, given fewest emissions. Best power is usually between 12:1 and 13:1 range. Best fuel economy is usually up around 16:1 or higher.

3. Mr. Watt's horse didn't do 33,000 ft/lb per minute, he did 22,000 ft/lbs, but he added 50 % "for good measure."

4. I forget whom said it, but they were correct in saying it requires a specific amount of horsepower to maintain a specific speed. The key is something called Brake Specific Fue Consumption. It's the ratio in which an engine makes the most power with the least fuel being used. It's always highest at wide open throttle, and always before peak torque. I can guarantee that if your car revs at 2500 RPM at 65 mph, then that's probably where your engine is making the most power for that throttle input, and using the least fuel. Auto manufacturers know their stuff, so they design these things that way.

5. A car may or may not get better fuel economy if it makes more power. If an engine makes more horsepower because it uses less friction or has to overcome less pumping losses, then it will be more efficient. For instance, every engine uses up power to overcome friction and pumping losses(energy used to suck in air and blow it out the tail pipe). Let's say an engine has a "rated output" of 200 hp. That engine is probably creating 250 hp, 50 of which are lost to friction (seen as heat) and sucking air in through the intake tract and blowing it out the tailpipe. If that manufacturer redesigns their piston skirts and uses a different cylinder wall material to cut friction, and the engine is now rated at 205 horsepower, then that engine will get better fuel economy. Because if it takes 20 horsepower to maintain 60 mph, then .5 % of the energy that was originally going to overcoming friction, can now go to moving the car down the road.

6. I don't know where the 5252 constant comes from, that's why I did a Google search and found this thread. I'll let you all know when I find it.
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Old 10-22-2008, 04:45 AM   #36
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5252 comes from 33,000 ft-lbs divided by 2π (6.28...)
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