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btomcik
Dodge Dakota
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1/20/2005
14:24:20
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 Subject: Cold-Air Intake - improves gas mileage?
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I'm not exactly the smartest when it comes to cars and how everything works and the theory behind all modifications, so maybe someone can teach me on this.
I just installed a cold-air intake by 360 on my '04 4.7L. I heard that the CAI will increase power and slightly increase gas mileage. I'm confused on the gas mileage part. With the stock intake, you have theoretically less air going into the engine. The computer would recognize this and then tell the fuel injectors to inject less fuel in order to establish the proper air/fuel ratio, correct? Less air and fuel means less power.
So, if you allow more air to enter the engine with a CAI, the computer will then send for more fuel. Yes this would be more power, but it seems that this would decrease the gas mileage.
Am I right? If not, please explain. Thanks.
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Zach
Dodge Dakota
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1/20/2005
16:08:56
| RE: Cold-Air Intake - improves gas mileage?
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I think the improved gas mileage comes from less restriction in the intake. Consider the engine a giant vaccum and the stock intake is say a 2 inch diameter hole, an aftermarket is say a 3 inch. The engine doesnt have to work as hard to get the same amount of air through with the aftermarket because more air can flow through it. At least that is how I would consider it to make better gas mileage.
~Zach
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dude
Dodge Dakota
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1/20/2005
16:22:17
| RE: Cold-Air Intake - improves gas mileage?
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What he said plus at lower throttle input, such as daily driving the amount of extra fuel wouldn't be very much at all.
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Ted
Dodge Dakota
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1/20/2005
16:23:16
| RE: Cold-Air Intake - improves gas mileage?
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CAI do not increase fuel economy on a fuel injected engine. Any reduced restriction from the new air intake will be countered by the throttle plus a little more since the air is more dense.
As the air gets denser (colder), the throttle will have more restriction to get the same mass of air through. Power output of the engine is proportional to the mass of air taken in. So for the same power output, the CAI will have more restriction (air intake + throttle) and therefore be less efficient.
If you want better fuel economy, you want warm air going into your engine.
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Ed_210
Dodge Dakota
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1/20/2005
23:40:38
| RE: Cold-Air Intake - improves gas mileage?
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Think of it like this.
An engine is an air pump. It sucks air in, uses it in conjunction with fuel and spark to create an explosion, and is then expelled through the exhaust system.
Colder air (depending on how much colder...I live in Texas, so keep that in mind) is always a good thing for an engine (again, assuming you're not in freezing weather). Less restriction and cooler air make the engine more efficient. That's good.
Now, an engine can be so efficient that it's gas mileage sucks (there's a threshhold) - just look to race cars. Their engine might kick out a thousand horsepower, and be running at close to a hundred percent efficieny (NHRA has classes that measure engine efficiency, not performance), but the gas mileage is pathetic.
Generally, yes, a cold air intake will help most any engine's gas mileage. The engine runs cooler, produces more power with less fuel, and doesn't heat up to the point that the radiator fan comes on (this hurts gas mileage as much as the A/C, and even more so in some engines).
Generally, what I've noticed, is that you can do all these mods for increased fuel mileage, anything after these will only hurt it (this is generalization, so hold the flaming);
Cold Air Intake Kits
MSD/ACCEL Ignition
Aftermarket Intake Manifold
Aftermarket Headers
Now, it all depends on the parts, but if they are fifty state legal and have CARB numbers, then chances are they are going to increase fuel mileage (if barely). I don't mention exhaust systems because so many people put the wrong exhaust on the wrong engine. I don't know how many people I know who put dual exhaust on their six-cylinder cars/trucks and wonder why the engine isn't up to snuff (it's because an engine needs a certain amount of back pressure...but we won't get into that here).
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JB
Dodge Dakota
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1/20/2005
23:42:34
|  RE: Cold-Air Intake - improves gas mileage?
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Actually, cold air can make more power AND better gas mileage as long as there is enough of a change to make a difference. You see, cold air is more dense then hot air and as a result has more oxygen in the same amount of space. This allows for more power from the same amount of fuel. As a result you will use LESS pedal to do the same work as the same amount of fuel is making more power. I work for a major auto engineering company and we've done alot of research in this area. The cold air systems we've tested (and we've tested them all) and have found that the gains are modest at best depending on the application. However, since this is free power (no extra fuel needed) it's not such a bad thing. The drop in inlet restriction is really good but that's not what makes more power. We've found that droping in exhaust back pressure is what REALLY makes the big difference. In that case the engine no longer has to use as much of it's power to push the exhaust out dropping the work load on the engine and freeing up some power.
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N56629
Dodge Dakota
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1/21/2005
13:12:41
| RE: Cold-Air Intake - improves gas mileage?
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Sounds like some people are confusing "cold air" and "volume."
Dakotas already have a so-called "cold air" intake. The change in air intake temperature is insignificant. If reducing the temperature of the air going into the intake by ten or even twenty degrees made a noticable difference, I should be making at lest another 100hp with my engine breathing in this sub-zero air.
For the most part, the after market air intake systems allow more air to flow and any increased density is insignificant.
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Ted
Dodge Dakota
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1/21/2005
13:19:50
| RE: Cold-Air Intake - improves gas mileage?
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Less pedal to do the same work-
This is correct for colder intake air. This means that the air is denser and less volume is needed. However, less pedal means that the throttle is closed more. This means MORE INTAKE RESTRICTION!! and therefore lower efficiency and reduced gas mileage.
Cold air gives you the potential for more power since you can get a greater mass of air into the cylinder. Cold air gives you reduced overall effiency for a given load because you are running at a more restrictive throttle position.
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last_username
Dodge Dakota
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1/21/2005
13:26:02
| RE: Cold-Air Intake - improves gas mileage?
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I do not claim to know physics, chemistry, and engineering but I know this....
NO ENGINE WILL EVER BE 100% EFFICIENT!!!!!!!!!!
Engines create heat, water, etc... that they dont use...friction losses due to oil, bearing surfaces, etc.....
.02
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Bob Lincoln
Dodge Dakota
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1/21/2005
15:21:40
| RE: Cold-Air Intake - improves gas mileage?
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Right, engines are about 30% efficient. Efficiency is defined as energy out divided by energy in.
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nub
Dodge Dakota
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1/23/2005
23:22:34
| RE: Cold-Air Intake - improves gas mileage?
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damn only 30% efficient that really boggles my mind that gasoline has so much power and were not even using half of it
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furball69
Dodge Dakota
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1/24/2005
01:55:34
| RE: Cold-Air Intake - improves gas mileage?
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"I don't know how many people I know who put dual exhaust on their six-cylinder cars/trucks and wonder why the engine isn't up to snuff (it's because an engine needs a certain amount of back pressure...but we won't get into that here)."
That may be true for carbureted engines but FI engines do not need back pressure.
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01Motorsport
Dodge Dakota
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1/24/2005
10:33:21
| RE: Cold-Air Intake - improves gas mileage?
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If you will allow some of my input on this subject from my experience. I have a '01 4.7 with HO cams, "true" 68mm TB, and Flowmaster 70 with 2 1/2" duals. I 'have a "homebrew" air intake which consists of a K&N drop-in in the stock air box, 3" aluminum alloy tubes between the air box and TB, Fernco "no-hub" 6" air inlet with a 2"x4" side slot facing the right fender, and the rubber flap removed at the radiator. Now, from my experience, the factory "snorkel" on the 4.7 is EXTREMELY restrictive, at least on a modified 4.7 that needs more air. I know this for a fact because, with no other changes, I put the stock snorkel on in place of the Ferco for 1000 miles, and my mpg DROPPED to 17mpg from a typical 18.2/18.5 overall average. I put the Fernco back on, and the mpg went BACK to the 18.5 range. I drive the Dak 32K annually, so this was a quick test for me. I let a spider make a home in stock snorkel sitting in a corner of the garage...
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terraDAKtyl
GenIII
1/24/2005
17:49:14
| RE: Cold-Air Intake - improves gas mileage?
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And a really naive question....If's the aftermarket intake is so much better, why doesn't Detroit make them standard? Wouldn't an extra 1 1/2 mpg be good advertising? That said, how about the same with TBs, headers, etc...
1998 Forrest Green Club Cab, 4x4, 3.9 V6 with 175,000 miles.
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hybrid
Dodge Dakota
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1/24/2005
17:53:38
| RE: Cold-Air Intake - improves gas mileage?
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furball69,
"it's because an engine needs a certain amount of back pressure.."
Just wanted to clarify this a little.
An engine doeesn't need back pressure to function correctly. Actually the least amount of back pressure will yeild the most hp.
The problem with piping that is to large in diameter (or in that case split off into two pipes much larger then required for that motor) is that you lose velicity.
The need some backpressure thing is just a myth in actuality. People figured they needed some backpressure when they went too big in exhaust piping and lost all exhaust velocity, but blamed it on the lack of backpressure.
Think of it like this. If having little or no back pressure is detrimental to power why do most engines make more power when running open headers or test pipes? They make test pipes for a reason, to eliminate as much back pressure as possible to increase power.
Thats why my exhaust on my car will consist of about 3' of 2.5" piping from the turbo the rear of the front tire. I will be having it tuned that way so I will make optimal power.
There is a reason why race cars are so loud, the lack of exhaust sytem is credited to that. Contrary to some people's belief louder doesn't = more power, less restriction = more power.
The key is to go as large as possible without losing velocity, one you lose velicity you start introducing back pressure back into the equation.
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hybrid
Dodge Dakota
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1/24/2005
18:02:24
| RE: Cold-Air Intake - improves gas mileage?
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And a really naive question....If's the aftermarket intake is so much better, why doesn't Detroit make them standard? Wouldn't an extra 1 1/2 mpg be good advertising? That said, how about the same with TBs, headers, e
..
One word ..Cost.
Running n20 into the intake at all times and having a bottle mounted in the bed will increase hp by about 50hp but is it practical?
Most aftermarket intakes are louder upon acceleration and increases engine noise. Not all people want to sacrifice increased engine noise for 1mpg increase. Believe it or not, but some peope actually buy a vehicle and leave it stock.
Same goes for exhaust systems, increased cost and noise are most likely contributing factors.
Now on the other hand have you heard the exhaust on the srt-4's? They are pretty damn loud (and pop even) for a factory exhaust equiped car, they do that because the srt-4 is considered a sporty car and people buy it for the performance, not the quiet smooth ride like the normal neon.
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Bob Lincoln
Dodge Dakota
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1/24/2005
18:54:13
| RE: Cold-Air Intake - improves gas mileage?
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Less back pressure can actually mean less power at low speeds, that's the tradeoff. It's a balance that the stock systems maintain.
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hybrid
Dodge Dakota
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1/24/2005
19:47:07
| RE: Cold-Air Intake - improves gas mileage?
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Correct, you may lose a little low-end torque but it's more then made up in the top-end with a properly designed exhaust system.
There is more to an exhaust system then running what everybody else seems to like. A properly designed exhaust system will take into account the modifications and types of parts you are using. An example of part types would be header design, do you have a 4 - 2- 1 (4 individual runer down to 2 runners then combines to one collector then to the exhaust piping) or 8- 1 (8 individual runners merge to one common collector that feeds the exhaust piping) each header design will vary the powr band of the motor. Another item to consider is the cam. For the most part you cant get to precise with the "tuning" of you exhaust, but you can pick a good diameter and design that will compliment your set-up more then others.
Ultimatly the best flow will create the most usable power. Best flow DOESN'T equal the largest diameter either.
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Lurkin
Dodge Dakota
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1/25/2005
08:56:01
| RE: Cold-Air Intake - improves gas mileage?
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Whoops, y'awl forgot to mention scanvenging.
Can't have an exhaust discussion without getting into all the backpressure, exhaust velocity, scanvenging aspects.
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hybrid
Dodge Dakota
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1/25/2005
11:40:26
| RE: Cold-Air Intake - improves gas mileage?
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That comes into play with the headers and their design.
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Lurkin
Dodge Dakota
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1/26/2005
08:34:51
| RE: Cold-Air Intake - improves gas mileage?
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...also the pipe size...
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