Cold air intake kit for better gas mileage?

I've been looking at ways to increase gas mileage on my 2003 Silverado

1500 with 4.8L V8. It already gets 20-21MPG in the summer, and 17-18 in the winter, so I really don't have much to complain about for a full-size truck. It would be cool if I could get 1-2 more. 5-10% more out of a gallon of fuel is 15-30 cents right now. 20 gallons a week would mean $3-$6 a week, or $156-$362 a year. That's if prices don't go up.

Cold air intake kits are advertised to increase horsepower and improve gas mileage.

A cold air intake kit for my truck runs between $250 and $280, depending on which one I get. If I could get an extra 1 to 1-1/2 MPG, it would pay for itself at current gas prices in a year or so.

What are people's thoughts on these? Do they live up to the promises? I know when they do the cold air kits on those hotrod how-to shows, then do dyno runs, they get a few extra horsepower, but they don't mention gas mileage.

Reply to
mkirsch1
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A filter or no filter on your engine cannot increase gas mileage. Your engine runs(most of the time) in closed loop mixture control. A change in air flow causes a corresponding change in fuel flow maintaining the proper air-fuel mixture throughout the normal driving range as follows: the engine control system measures how much air is inducted and dispenses the proper amount of fuel as indicated by the oxygen sensor in the exhaust manifold. Air filter performance makes no difference.

A plugged filter will reduce power, but that's all. A low restriction filter will increase power at full throttle and high RPM, and will also pass more dirt.

Randy

Reply to
R. O'Brian

I'm actually talking about one of those low-restriction intake kits, commonly, but incorrectly, called "cold air intakes."

Is there not a cost, in terms of horsepower, to drawing air into an engine? The premise here is that between reducing this parasitic load on the engine, and maintaining normal driving habits, the total amount of power necessary to move the vehicle down the road is reduced, air flow is reduced, and fuel flow is reduced.

Thanks for the very insightful reply!

Reply to
mkirsch1

yep, what he said :), and, ever notice that "cold air intakes" pull air from the hot engine compartment, but the stock ones will pull it from outside. They sure are shiny and pretty so that should get you more mileage and power right? :)

Reply to
ShoeSalesman

my theory is that what ever you do, within reason to improve the efficiency and increase the horse power/power out put of your engine should increase fuel mileage when your not under load. yes it will use more fuel when you are rodding on it but under normal driving conditions it should take less throttle to perform the tasks at hand. I new someone with a chevy iroc,who went hi flow filter. hi flow exhaust and i hyperchip and advanced base timing...it sucked fuel like a banshee..actually about 20% more that stock, when he was racing with it..however on the highway he got fuel mileage that seriously rivalled a Geo metro...out in the prairies the car run about 120kph at under

1500 rpm in overdrive...and that was the same thing i was told about another iroc owner..that doesn't mean go out and buy an iroc but it does go with what i said earlier. try this , do some research. see what gets better fuel mileage..6.0 the 5.3, the4.8 and the 4.3...i'm not suggesting the 6.0 will get the best rating, i don't know, but i think the 5.3 will be better than the 4.8 and 4.3 bigger engine, more displacement..less effort to move
Reply to
redeye-racing

Yep, I was talking about the same thing. Don't forget that your throttle plate is about 90% closed while cruising down the highway. If thats not choking the intake system then slap my ass and call me Sally. In a nutshell, I would guess that other than wide open throttle AND high RPM the intake/filter you put on the truck would do anything at all....if then.... Oh, and read your statement above "air flow is reduced". I thought you wanted more air. See what I mean? As someone posted before, on a computer controlled engine the fuel/air ratio is carefully metered by the ECM. If you are really worried about "flow" you should look at the exhaust side. Headers and a good muffler should help but there is A LOT of science to that too. Bigger is not always better.

Reply to
ShoeSalesman

I want the air to flow easier, so the engine wastes less horsepower sucking it in. That's horsepower I don't need to make the truck go. The engine's sucking extra air and fuel to make the horsepower to suck the air and fuel. If it doesn't have to do that, then overall, it sucks less air and less fuel.

I'm no dummy here. I understand the whole more air = more fuel concept. I also remember my fluid dymanics classes from college, and I know that bends, kinks, and odd shapes cause SIGNIFIGANT losses. The more the air has to change shape and direction, the more energy it takes to suck it through the tube. Looking at the intake on my truck, there are a lot of bends and kinks, as well as that odd-shaped "pancake" thing at the throttle body. A round tube with fewer, smoother, bends is much more efficient.

I am just looking for real-world experience on the subject. What I would like to know is, has anybody fallen for the "shiney" aspect of the thing, and seen any real-world results?

Reply to
mkirsch1

Note the RPM you referenced was ~ 1500. My 2003 Z06 Vette gets 28-30 mpg on the highway too. In 6th gear 60 mph=1400RPM and 100 mph = 2000 rpm. IF I keep my foot out of it I get outstanding mileage. However it does need premium fuel and the cost of tires with their short life (~15-20K) pretty much cancels any savings. So, I drive the Silverado mostly and the Vette on good weather Sundays. The truck sees ~1800 RPM @ 60 mph in

5th gear fuel consumption is a nominal 3.5-4.0 gph at that speed.
Reply to
Mike Copeland

Those $200+ intake kits don't seem to do much. I put a real cold air intake on my truck and it cost me about $40. It does make a difference. How did I do it? I bought a hood scoop at an auto fair for $20. It was off a 74 Trans-Am.

I also bought a gutter downspout to 3 inch pipe connector and a 3 inch to 2.5 inch reducer that is for a dryer vent.

Simply cut a hole in your hood big enough to accomodate the dryer vent piece, pop rivet it on, Then pop rivet (or however you want to do it) the hood scoop over the hole. Use the air cleaner box off a 93 Caprice LTZ. Cut a hole in the top of the air cleaner box and close off the old intake hole. Put the gutter piece in square end down and fasten it.

When the hood shuts the dryer vent inserts into the gutter piece far enough to seal it.

I get an extra couple miles per gallon now, and have slightly more power. And it looks cool (at least to me. I've seen a few people snicker) I was behind a tractor trailer on the interstate the other day. I was close enough to be drafting him. When he pulled over and the full force of the air hit my scoop my truck accelerated 10 miles per hour before I could let off the gas. I could feel the effect happen.

The only drawback is my air filter gets dirty faster and when it rains really, really hard a small amount of water does get into the air cleaner box. Not enough to get the filter wet, but it does leave spots on the dust.

Reply to
Ookie Wonderslug

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