Single Engine Speed Increase Tecniques

[TDTURBO]

Has anyone rigged a bottle of O2 to feed in the intake by a tube to increase air(O2) after 8k density altitude to see if it made a big difference?

 

[seethru]

Let me see if I understand you correctly... You want to introduce pure oxygen into a combustion process?

Sounds like a recipe for disaster (boom).

Greg

 

[minitour]

I'm sure you'll get a unique response from the airplane...

Just make sure you sign the rental agreement first...

-mini

 

[avbug]

The oxygen content entering the intake is only part of the picture. In order to increase engine power, you're far better concentrating on raising the combustion pressures, rather than temperatures, and the way to do that is to boost induction pressure...not induction oxygen content.

Far more air is used for cooling than burning in the combustion process. Adding oxygen isn't going to cause an explosion or fire, but will require a mixture adjustment, and that's about it. However, as far as adding performance capability or efficiency...you're going to have to carry a lot more weight in oxygen tank and equipment than you would to carry a comparable turbocharger or supercharger, and you're not going to realize any appreciable difference...especially in a piston engine at the lower RPM's at which the engine must typically operate for propeller efficiency.

Having said that, you're far better off to clean up the airplane in order to gain speed, than to try to boost power. Especially true of a light piston airplane. Very large power increases are required for progressively smaller gains in forward speed. Increasing power will increase climb peformance, but won't net large values in terms of speed increase.

Aerodynamically cleaning up the airplane is another matter completely. Reducing gaps, adding fairings, and in many cases very simple changes can net reasonable increases in speed that are far in excess of what one might hope to get by adding a bigger engine or boosting engine power. In fact, as one tries to boost power, often it's a point of diminishing returns as weight increases...the power gets consumed by it's own requirement to carry itself, and the additional fuel necessary that goes with that requirement.

Instead, look at cleaning up the airplane for performance gains. It's free, so to speak...you're not enhancing the airplane, you're just taking away the detrimental aspects that are holding it back.

 

[Tired Soul]

Using pure oxygen will seriously lean out the mixture and melt your pistons.

Guys that run nitrous in their cars have two solenoids; one that regulates the flow of nitrous, the other regulates the flow of extra fuel.
More oxygen needs more fuel otherwise meltdown.....
The guy that does the altitude records in the Exxon Tiger sponsored plane runs nitromethanol as fuel. He had to make a couple of deadstick landings in the past, one at the sun'n fun in Lakeland couple of years back.
For faster cruise (+4-6 kts) go for an aft CG, less downforce on the tail, less wing loading and less drag.
For Pipers and stuff you can get the LoPresti speedkits, they cost about $1000 per knot speedincrease.
New cowling w/ low drag intakes, aileron seals, flap seals, gear door seals, wingtips and the scavenger exhaust.
There's somebody out there who tricked out his Cherokee 140 and it flies almost as fast now as a "stock" Arrow, 138kts on 8gallons/hr.
You would be surprised how much speed a good paintjob will reveal.
I regularly fly an Aztec now that at the beginning of this year would barely do 185 mph TAS with old paint, old engine and crooked ailerons.
With new paint, new engines and flying straight it does 185 KNOTS TAS, 210 mph. Wooohoooo..my baby, let's go kick a Seneca's @SS !!!

 

[Corona]

Well, let's look at the math here: Suppose you use an 80 cubic foot oxygen tank (size of a scuba tank) with a 360 cubic-inch engine. Each engine revolution displaces 360 cubic inches, right?


So, assuming you get 100% of oxygen each revolution after you open the valve on the tank, you get about 2.6 revolutions before you run out of O2. Assuming you're cruising @2300 RPM, you'll be out of O2 in approx. 1/1,000th of a minute, or about 0.067 seconds.

Then again, you could just put wings on a Liquid Oxygen truck...

Disclaimer: It is possible that most, or all, of the above calculations are bogus.
C

 

[Big Duke Six]

Poor man's Turbo?

I've seen Formula One racers at Reno, and several other homebuilts, that have an extended intake throat that goes up to within a half inch or so of the back of the propellor disc. I imagine the theory is that with each passing blade, the engine gets a boosted shot of air. I don't know any particulars, but I'm sure timing is everything with this sort of setup. It DOES work though, at least according to the people who own them, but I can't help but wonder why production airplanes don't use them too. It truly is free.

Anyone know the ups or downs of this?

 

[A Squared]

Disclaimer: It is possible that most, or all, of the above calculations are bogus.
C

Partially bogus, a cubic foot is 1728 cubic inches, not 144, so you'd get 384 revolutions to a scuba tank

I've seen Formula One racers at Reno, and several other homebuilts, that have an extended intake throat that goes up to within a half inch or so of the back of the propellor disc. I imagine the theory is that with each passing blade, the engine gets a boosted shot of air. I don't know any particulars, but I'm sure timing is everything with this sort of setup. It DOES work though, at least according to the people who own them, but I can't help but wonder why production airplanes don't use them too. It truly is free.

Anyone know the ups or downs of this?

Yes I think that the LoPreisti designed cowlings are set up to take advantace of this, seems like there was some airframe manufacturer who was doing this also, mooney perhaps? ANyway, it takes careful matching of prop, intake opening, intake length and such to make the most out of it, but it does provide "free" extra power.

 

[FracCapt]

Partially bogus, a cubic foot is 1728 cubic inches, not 144, so you'd get 384 revolutions to a scuba tank

It's a moot point, anyways. An 80cf scuba cylinder will take 2-3 minutes minimum to dump ALL the gas in the cylinder when the valve is fully opened.

Injecting pure O2 into the intake will only screw up the mixture, not help you gain any significant power. Increasing the pressure of the gas into the engine, however, would help....hence the reason that turbochargers and superchargers work.

 

[GravityHater]

It would be more efficient to strap on a JATO bottle, no?
Maybe throttle the outflow so it would last an hour or so instead of 3 minutes!

 

[DGdaPilot]

You mean a RATO bottle?

Sorry, I couldn't resist.

 

[Rogue5]

Why not just take a tip from the guys who race at Reno and just reduce drag as much as is humanly possible...

 

[troy]

correct me if I'm wrong, but I believe that the percentage of 02 remains the same with an increase in altitude. What decreases is the atmosperic pressure. Less dense air means less 02 per piston stroke/less air per blade revolution/etc. That is why turbo/superchargers are so common with high perfomance engines and standard O2 delivery systems don't work at extremely high altitudes.

 

[TDTURBO]

correct me if I'm wrong, but I believe that the percentage of 02 remains the same with an increase in altitude. What decreases is the atmosperic pressure. Less dense air means less 02 per piston stroke/less air per blade revolution/etc. That is why turbo/superchargers are so common with high perfomance engines and standard O2 delivery systems don't work at extremely high altitudes.

Troy,

That was the whole gist of my question. Since a normally aspirated engine at altitude is "starving" for air, why wouldn't adding O2 improve performance? I realize turbos and superchargers are the answer but I was thinking of a simpler solution and you just answered it.

Thanks!

 

[A Squared]

Troy,

That was the whole gist of my question. Since a normally aspirated engine at altitude is "starving" for air, why wouldn't adding O2 improve performance? I realize turbos and superchargers are the answer but I was thinking of a simpler solution and you just answered it.

Thanks!

TDturbo *theoretically* you're right. What matters is not the pressure of the intake air, but the number of oxygen molecules in the intake air charge. As I'm sure you're aware, there isn't really that much oxygen in air (21%) theoretically, if you could supplement the oxygen content of the air flowing into the engine (say to 42%) and you had the ability to supply the correct amount of gasoline for the amount of oxygen molecules, you could operate at an altitude where the air density is half that of sea level (approximately 22,000') and still make sea level power.

As a practical matter, no. Even if you had some method of regulating fuel flow to match the amount of oxygen present in the cylinders, you just wouldn't be able to carry enough oxygen to make a diffference. Your 540 running unthrottled at 2400 rpm will have about 375 cubic feet of air running through it each minute. To supply even a small percentage of that flow would require a huge cylinder of oxygen. (as Corona pointed out a scuba tank holds 80 cubic feet)

If you were using a scuba sized tank to double the oxygen content of the intake air, it would last about a minute.

 

[PropsForward]

Warning! Pure oxygen and petroleum products (oil, fuel, grease, etc) don't mix. If the O2 hits the smallest bit of oil the wrong way, then you could become a greasy spot!
This is why that automotive folks use nitrous-oxide. You get the same results your are seeking with a safer gas around an oil covered engine.


If you do decide to add NO2, you need to add more fuel as well, and lots of it! Going "full rich" will not be sufficient - or you would have to severely restrict the amount of NO2 you provide to balance out with the amount of fuel available at full rich.

This whole topic screams of getting some high altitude training. It same concepts that affect your physiology is affecting the engine. This is why turbo charged airplanes don't necessarily go faster, but rather they can go higher.

Regards,