does ram air affect economy?

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I picked up about 1 mpg on my 5.9 Dakota when I put the Shaker hood on it.
And the fresh air really made a difference while towing...and it sounded better too.
 
IMO it's not the colder air, but the greater potential energy of the same volume of air, that makes the difference. The economy doesnt come from not needing to maintain the proper AF ratio, but the less throttle needed to maintain the same power output.

dodge - As far as aircraft vs earthbound, there are a few similarities, but due to fuel chemistry and altitude requirements I don't think knowing a lot about tuning an aircraft will really apply.
 
Piston engine aircraft use the same fuel we do, yes, it is 100 octane, (some) but most up here have an STC for 90 octane car gas. Airplanes are also low compression, most under 7-1. The high octane fuel is needed because of the low RPM. Aircraft engines also have a really really tight lobe sep too, LOL.

In reality, tuning is tuning, cars run at altitude, in different humidity just like small planes do, not saying it is exact, but similar. The planes are also more complicated, thus the better understanding of how the fine tune/ram air effect, (air intakes are in the cowl getting direct wash) temperature, humidity, and manifold pressure, (vacuum in the auto world) effect performance. ( most have digital EGT guages).

It's not the same, but the same, if that makes sense.

You are right about the greater potential of the air. All effected my humidity, altitude, temperature, etc. Water injection, for example, creates a denser charge of air in two ways, one, the air is replaced by water, two, the air is cooled/compacted by the direct cooling effect of the water mist. This also allows leaner mixtures (especially if the fuel temp is hot) to get the same amount of power. Kinda an example, a long time ago the military used water injection to decrease take off distance by making more power, while mixture settings on take off were full rich, no additional fuel was added with the water mist, not only did they make a substantial bit more power, but cylinder/exhaust temperatures were lowered.....

Totally off the subject of the original OP's question, but it's interesting to me. (tuning goes far beyond AF, timing, etc.

Like Moper said, the greater potential of the air to make power is what makes the ram air work, and the greater potential, will actually raise the vacuum. (well, probably not by a measurable amount really, but it will) This will happen until the boost from the ram air is equalized with the intake vacuum, which probably wouldn't happen with the systems out there, until WOT, if that.
 
What's an STC? I'm definately NOT an aircraft guy.. That would be my dad and he's into military turbines...lol. However, my first tech school teacher was military in the USAF when piston engines were still in use and his opinion was aircraft fuel is chemically different and while it does carry the octane it is not the same as automotive fuel. I've never, nor would i ever run a car on it for that reason.
I knew about the water injection, and also the Germans and thier NO2, plus you have all the kits from the 70s for water injection too...
 
STC (suplement type cert) is an FAA approval to run car gas, depending on the engine model, it's as simple as a few gaskets, seals, and of course a mountain of paperwork.

Avgas, 100LL for instance, is held to a higher standard than car gas, for one, instead of toulene and benzene, avgas has TEL (tetra ethyl lead) added for octane, and believe it or not, is actually more toxic, which is why thye don't run it in cars ANYMORE..... A long time ago, I guess you could get premium fuel called "ethel" or something? That was simply AVgas..... Both are hydrocarbons from petroleum, alkylate, and reformate.....

Race fuel is simply essentially Avgas, if it is TEL, it's been a while, but KLOTZ, which is what we were able to get up here, was TEL based when I was interested in what was in it when I was a kid. The other, and greatest advantage of TEL gasoline, is it is far more stable because it is formulated to run at high altitudes, it is also almost impossible to get to vapor lock in your average race auto. (just like race fuels)

So yeah, he WAS right, it IS different, but, is actually better for a high compression auto engine than typical car gas, but worse for the enviroment.

Sorry to bore you with a total unrelated post about nothing, LOL.

*I ran 100LL for a whole summer in my everyday driver, probably 10K miles, with no issues other than it smells interesting when idling in a 600 lift roller engine*
 
fcm42000 said:
Without ram air the area forward of the throttle blades is a given negative pressure, period. With ram air it may not be enough to make positive pressure, but there will be a difference in pressures (negative) on both sides of the throttle blades. Now what happens when there is a pressure difference in two areas and a non sealed wall between them (throttle blades), hmmmm, well naturally they want to equal them selves out, if you argue with that you just plain don't get it.

Just to clarify, I am not asking in reference to air fuel ration, ok, get it? Just if anyone KNOWS if the lower vacuum (closer to zero/ambient) will affect how much the distributor advances at cruise because the affects of a higher pressure from ram air.
Click to expand...

No, I'm afraid you don't get it. So, let me put this plainly...

THERE IS NO POSITIVE PRESSURE. THERE IS NO CHANGE IN PRESSURE AT ALL BECAUSE OF THE RAM AIR SCOOPS

Since there is no change in pressure,

THERE IS NO CHANGE IN VACUUM DUE TO PRESSURE DIFFERENCES.


Why? Because if you could create pressure with a ram air scoop, you're basically making free horsepower. Even a tiny change in pressure would result in more power from what would basically be a level of forced induction. Every Tom, Dick and Harry would have big ram air scoops on their cars, trucks, race cars, motorcycles, airplanes, all of it. It'd be like turbocharging, without any added maintenance on the turbo or parts cost. Not only that, the automakers would be all over it. Why? More power from a smaller engine. Less materials, lighter car, better gas mileage overall. And it'd be practically free! No downsides!

Holy crap! Why isn't everyone doing this?!

Because it doesn't work like that. :sad11:

So please, stop trying to drag on about positive and negative pressures from the throttle blades and all that. I spent 4 years studying Aerospace Engineering and got plenty of theory on pressure change and engine efficiency there. The ram air scoops are there to look cool. They may even pull a little cold air. That's it. If you want better mileage, change your air filter, spark plugs, and air up your tires. If you really want to get serious, get a A/F gauge and tune the crap out of your carb. And if you're that worried about it, sell the freaking muscle car and get a Prius. Its not supposed to get great mileage, its supposed to be fun!
 
moper said:
IMO it's not the colder air, but the greater potential energy of the same volume of air, that makes the difference. The economy doesnt come from not needing to maintain the proper AF ratio, but the less throttle needed to maintain the same power output.

dodge - As far as aircraft vs earthbound, there are a few similarities, but due to fuel chemistry and altitude requirements I don't think knowing a lot about tuning an aircraft will really apply.
Click to expand...
Bingo we have a winner !! i noticed more power butt dyno, and slightly better mileage when sealing my 71 demon hood. give me 80* air over 180* any day. Also the post about the 03 dakota dropping mileage in the cold is due to the trans staying in low gear longer until trans temp comes up then it shifts into hi, when 0* out my truck can take up to 10 miles before shifting into 5th gear, i fixed this by blocking the radiator now on 0 degree days it shifts into 5th in about 3 miles still milage is a bit lower but its due to the sender in the trans fluid.
 
...............Hey dodgetkboy78.........go to VP Racing, in no way is AV gas racing fuel.......ur rite about the hi alt, but its only 4 low rpm, 3500 tops.......kim........
 
EL5DEMON340 said:
Bingo we have a winner !! i noticed more power butt dyno, and slightly better mileage when sealing my 71 demon hood. give me 80* air over 180* any day. Also the post about the 03 dakota dropping mileage in the cold is due to the trans staying in low gear longer until trans temp comes up then it shifts into hi, when 0* out my truck can take up to 10 miles before shifting into 5th gear, i fixed this by blocking the radiator now on 0 degree days it shifts into 5th in about 3 miles still milage is a bit lower but its due to the sender in the trans fluid.
Click to expand...

Not if its a manual trans :headbang:
 
I was just talking to a coworker this am about this.. He found with his stock 300ZX, if he cruises in 6th gear at 70, he gets roughly 2/3 of the milage he gets when he cruises in 5th...
Economy is all about the engine parts and driveline working together perfectly, and even in a modern computer controlled car, it's a floating target. IMO, for best economy, a clean, cotton air filter, well tuned carb and ignition, a good alingment, tires near their max pressure, and keep your foot smooth, is the way to get all you're going to get..lol.
 
oldkimmer said:
...............Hey dodgetkboy78.........go to VP Racing, in no way is AV gas racing fuel.......ur rite about the hi alt, but its only 4 low rpm, 3500 tops.......kim........
Click to expand...


Kim, where did you find the burn rate info, all I saw read was a sales pitch, no comparison....

Last time I checked the burn rate of 100LL was closer to 91 car gas than 87 is to 91........
 
moper said:
I was just talking to a coworker this am about this.. He found with his stock 300ZX, if he cruises in 6th gear at 70, he gets roughly 2/3 of the milage he gets when he cruises in 5th...
Economy is all about the engine parts and driveline working together perfectly, and even in a modern computer controlled car, it's a floating target. IMO, for best economy, a clean, cotton air filter, well tuned carb and ignition, a good alingment, tires near their max pressure, and keep your foot smooth, is the way to get all you're going to get..lol.
Click to expand...

Anyone who has owned a 94+ dodge ram with 3.55's and a 318 knows it gets worse MPG in O/D too.....
 
You'll sometimes see worse economy in a taller gear due to the engine speed being lower. Might sound dumb, but since the engine is spinning slower, the intake cycle takes longer. (Milliseconds) Plus the throttle may need to be open a fraction farther to meet the greater torque requirements of the taller gear. This can add up to more fuel being used.
(Hell I've even owned cars that have a lower top speed in 5th than in 4th)
 
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