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K&N air filter = better gas mileage

SkaredShtles

I love NEWCASTLE and will ONLY drink NEWCASTLE!!!!
Sep 21, 2003
50,185
3,768
In a van.... down by the river
pixelninja said:
If the oil barons here in the US have anything to say about it, it will. I'm sure they'll come up with all sort of excuses to explain the high prices and eventually the sheep, er, population of the US will just get used to it.
I bet that we will see prices under $2/gal again.
 

VooDoo

asshat
Dec 21, 2001
142
0
Toronto
Westy said:
You can also run more efficiently by shifting earlier, most engines are actually most efficient at low rpm's with a wide open throttle.
Please, you have got to be joking, right?
Cars run most efficiently with the least amount of throttle, doesnt matter the RPM's.
Do you know how much gas the computer (or carb) is dumping into the motor at full throttle? that's why it's so sluggish.
On anything but a v8 (a bigger one at that) you are wrong.
I have found it more efficient to run at a higher RPM/ lower gear with less throttle than a higher gear with more throttle, make sense?
You win the award for the stupid post of the day.
 

buildyourown

Turbo Monkey
Feb 9, 2004
4,837
0
South Seattle
VooDoo said:
Cars run most efficiently with the least amount of throttle, doesnt matter the RPM's..

Not on a turbo. On my truck, anything above 2000 rpm = lotsa boost, great throttle response and horrible mileage. It doesn't really matter how much your pushing on the pedal.
 

Westy

the teste
Nov 22, 2002
37,489
4,339
Sleazattle
VooDoo said:
Please, you have got to be joking, right?
Cars run most efficiently with the least amount of throttle, doesnt matter the RPM's.
Do you know how much gas the computer (or carb) is dumping into the motor at full throttle? that's why it's so sluggish.
On anything but a v8 (a bigger one at that) you are wrong.
I have found it more efficient to run at a higher RPM/ lower gear with less throttle than a higher gear with more throttle, make sense?
You win the award for the stupid post of the day.
Way to get all Pinkbike with a reply. Do you understand how a throttle works? It restricts the air from going into the engine. The engine is basically an air pump, add the proper amount of fuel to the mixture and a spark and you get power out of it. An engine has to work to get that air, a closed throttle requires more work than an open one.

The power output of the engine is basically proportional to the amount of air taken (with proper fuel mixture) in minus the frictional losses. The air intake is proportional to the the speed(rpm) and the air density. The air density is set by the throttle restricting the air flow. Parasitic losses come from friction due to basic mechanical friction, hydrostaic losses from the oil and the work done to intake air, remember this is a big ****ing are pump.

Let us look at an example: A basic motor at lets say 5000rpm with a nearly closed throttle outputting enough power to push a car along at 55 mph compared to the same motor at 1000 rpm with a wide open throttle pushing the same car at 55 mph. The engine at both speeds is outputing the same power, the difference in efficiency is that the motor at 5000 rpm with a closed throttle is expending a lot more energy to pull air through a tiny throttle opening, not to mention working harder to move the oil around in the engine, making it less efficient.

An easy way to test this is see how much throttle you have to give an engine in neutral to get to 1000 rpm, then see how much you have to give to get it to 5000 rpm. With no load all the fuel being burnt goes to just parasitic drag.

Back in college a bunch of geeks would have efficiency races. They would rig up a small fuel container to each car and race around a closed loop at the same average speed, farthest distance on a quart or so of gas won. The winners would drive in their highest gear at wide open throtte to get slightly above the required average speed and coast back down in neutral before thwacking the throttle again.
 

beestiboy

Monkey
May 21, 2005
321
0
Merded, ca
This might be a little bit of a strectch but the facts are true. 3 years ago the high milage vehicle competition(sponsored by SAE and GM FORD) anyway
The teams (collegiate with a couple of high school teams) build a highly aerodynamic vehicle powered by a 5 hp Briggs and Stratton motor. Most schools design a vehicle to run at a slow speed sub 20mph at a near constant rpm. Fluxuation in the rpm kills gas milage. For some reason my buddy and his team decided/designed their vehicle to run at over 40mph. Not all of us crunched the numbers but many of us thought they were taking a gamble.

Long story long they averaged over 600 mph and lapped the entire field in the competition.

sometimes the rabbit wins
 
Jul 17, 2003
832
0
Salt Lake City
buildyourown said:
Not on a turbo. On my truck, anything above 2000 rpm = lotsa boost, great throttle response and horrible mileage. It doesn't really matter how much your pushing on the pedal.
I thought a lot of cars had turbos installed and tuned specifically to improve gas mileage? I know for a fact the Subaru Impreza WRX wagon gets better mileage than the Impreza RT.
 

VooDoo

asshat
Dec 21, 2001
142
0
Toronto
Westy said:
Way to get all Pinkbike with a reply. Do you understand how a throttle works? It restricts the air from going into the engine. The engine is basically an air pump, add the proper amount of fuel to the mixture and a spark and you get power out of it. An engine has to work to get that air, a closed throttle requires more work than an open one.

The power output of the engine is basically proportional to the amount of air taken (with proper fuel mixture) in minus the frictional losses. The air intake is proportional to the the speed(rpm) and the air density. The air density is set by the throttle restricting the air flow. Parasitic losses come from friction due to basic mechanical friction, hydrostaic losses from the oil and the work done to intake air, remember this is a big ****ing are pump.

Let us look at an example: A basic motor at lets say 5000rpm with a nearly closed throttle outputting enough power to push a car along at 55 mph compared to the same motor at 1000 rpm with a wide open throttle pushing the same car at 55 mph. The engine at both speeds is outputing the same power, the difference in efficiency is that the motor at 5000 rpm with a closed throttle is expending a lot more energy to pull air through a tiny throttle opening, not to mention working harder to move the oil around in the engine, making it less efficient.

An easy way to test this is see how much throttle you have to give an engine in neutral to get to 1000 rpm, then see how much you have to give to get it to 5000 rpm. With no load all the fuel being burnt goes to just parasitic drag.

Back in college a bunch of geeks would have efficiency races. They would rig up a small fuel container to each car and race around a closed loop at the same average speed, farthest distance on a quart or so of gas won. The winners would drive in their highest gear at wide open throtte to get slightly above the required average speed and coast back down in neutral before thwacking the throttle again.
Ooohhh pinkbike... haven't been there for 5 years...

I still disagree with all your claims.
Maybe, if the engine is designed to run at 1000RPMS, then OK, i dont know about your car, but when i have mine at WOT, it bounces off the rev limiter or goes way past the speed limit.
You have to remember that cars have a certain aerodynamic limit, hammering the gas at 100mph in a suv willl get terrible mileage compared to cruising along at 55mph (very little throttle).

If your gearing is low enough to be at 1000RPMS at 55mph, unless it's a torque monster or a turbo diesel all it's gonna be doing is lugging and pinging at WOT.

Yes, the engine is a large air pump, but what you are forgetting is that the wider the throttle is open, the more gas it uses, and the more gas it uses, the worse mileage it will get.
I see where you are trying to go, but your statement is completely false, what it would be correct for would be an air pump (lol), not an internal combustion engine.

And on the topic of turbo's, some are designed to give more power with less throttle, but most turbo motors have larger fuel injectors which make them consume more gas, and the reason for this is because since you are getting more air into the cylinders, you need more gas to mix with it.

Oh, and a turbo shouldn't be screaming unless there is a load on an engine. When driving a 7.3 powerstroke, i can drive the whole time with no boost, but once you want to accelerate hard, that is when the turbo begins to spool up. You can notice when going up a hill, if you watch the boost gauge the boost will go up if you are trying to keep a constant velocity, even though the RPM's wont.
 

ohio

The Fresno Kid
Nov 26, 2001
6,638
4
SF, CA
VooDoo said:
Ooohhh pinkbike... haven't been there for 5 years...

I still disagree with all your claims.
Sorry VooDoo, you're wrong on this one. Think of it this way:
a unit of gas always produces the same amount of energy and utilizes the same amount of O2 (assuming efficient combustion). So in a frictionless world with perfect combustion, an engine burning one unit of gas per cycle at 2000RPMs would produce the same output as an engine burning 1/2 unit of gas per cycle at 4000RPMs.

However, you lose energy at higher RPMs for the following reasons:
- less time for combustion to complete = greater likelihood of unburnt fuel
- each cycle has an associated frictional loss: there are twice as many losses per unit of fuel in the second scenario

Obviously there are other factors, such as for which engine speed the valve timing and ignition timing has been optimized, and in some performance cars the computers are over-ridden at WOT to run a rich mixture (which is part of the reason why at really low RPMs, WOT can cause some ke-chuggin'), but these can go either way depending on the engineer... the first two factors are always true.

By the way, I found the spare hanger for your Turner DHR. If you PM me your address again, I'll send it to you.
 

VooDoo

asshat
Dec 21, 2001
142
0
Toronto
ohio said:
Sorry VooDoo, you're wrong on this one. Think of it this way:
a unit of gas always produces the same amount of energy and utilizes the same amount of O2 (assuming efficient combustion). So in a frictionless world with perfect combustion, an engine burning one unit of gas per cycle at 2000RPMs would produce the same output as an engine burning 1/2 unit of gas per cycle at 4000RPMs.

However, you lose energy at higher RPMs for the following reasons:
- less time for combustion to complete = greater likelihood of unburnt fuel
- each cycle has an associated frictional loss: there are twice as many losses per unit of fuel in the second scenario

Obviously there are other factors, such as for which engine speed the valve timing and ignition timing has been optimized, and in some performance cars the computers are over-ridden at WOT to run a rich mixture (which is part of the reason why at really low RPMs, WOT can cause some ke-chuggin'), but these can go either way depending on the engineer... the first two factors are always true.

By the way, I found the spare hanger for your Turner DHR. If you PM me your address again, I'll send it to you.
I agree with you there, but we are not in the perfect world, so i stand by my argument consulting real world factors. I'm saying i get worse mileage the farther i hold the throttle open.

The thing your talking about running rich at WOT, that is called open loop/closed loop, in open loop it reads the A/F mixture from the o2 sensor and adds gas accordingly, but at high acceleration that is over-ridden and the computer reads off of a set fuel map which "makes" he most power and adds fuel accordingly.

Hrm, are you trying to say the engine is more efficient at WOT, nt more economical? That would make much more sense.
 

ohio

The Fresno Kid
Nov 26, 2001
6,638
4
SF, CA
VooDoo said:
Hrm, are you trying to say the engine is more efficient at WOT, nt more economical? That would make much more sense.
What's your definition of each?

And yes, open loop is what I'm talking about. At the highest end (most open throttle) of that range is when you will most efficient. Unless we are talking about something other than fuel economy, then it is also more economic.

The reason you burn more gas at WOT is because you are accelerating. We're talking about using the highest gear possible for the lowest RPMs while maintaining a steady speed. This may not be foot to the floor, because many/most newer cars in the US have power to accelerate even from 1000RPMs unless you're going 80+. WOT was just being used to illustrate the difference between very open throttle at low RPMs, vs. very closed thottle at high RPMs for the SAME power output.