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Engine flooding was a very common and well known event.
Indeed an aircraft with a flooded engine was very often reported as being hit and going down trailing black smoke when in fact all that had happened was the pilot had flooded the engine usually by slaming the throttle open and or taking evasive diving manouvers.

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Originally Posted by Ze-Jamz (Post 322646)

you serious?

Obviously i didn´t made the comparison in the right way :oops::mrgreen:

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Originally Posted by Crumpp (Post 322791)

The fuel metering system does not change and the air/fuel ratio does not change very much.

That is the whole purpose of leaning the mixture to maintain that ratio as the density altitude gets higher.

What ever you say Eugene.:rolleyes: You can contact Graham White and tell him he is a clueless gamer.

The fuel metering certainly does change when the fuel pump is pushing more fuel through the jets.

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The fuel metering certainly does change when the fuel pump is pushing more fuel through the jets.

I did not catch your explaination of the your "stages" Milo, it is clearer what you are saying. I thought you were saying it was more serious in the second stage of the supercharger.

If you are in the second stage of your supercharger then your altitude is increased and the air density is decreased. To maintain the same ratio of fuel and air you must reduce the amount of fuel.

It is not a two "stage" event, it is two different types of cut outs you can experience with a float type carburetor. You can experience both of them in one flight pulling negative G's in your float type carbureted engine.

You either have a lean cut out or a rich cut out. A lean cut out occurs when you subject the airplane to rapid onset negative G such as a bunt. The float rises up and shuts off the flow of fuel.

A rich cut out occurs when you subject the airplane to low amounts of prolonged gradual onset Negative G. The float does not rise up and shut off the flow of fuel. Instead fuel continues to flow, the engine sputters and skips but does not cut out. The fuel collects in the top of the bowl forcing the float down, opening the fuel flow to maximum and flooding the engine. This is more serious because the engine will not automatically restart like a lean cut out will. The engine is flooded and the fuel amount must be reduced in the cylinders.

If you take a float carburetor and subject it to negative G's, the engine cuts out immediately in a lean cut out.

Even in a small 180hp Lycoming engine.....sipping 10 gallons per hour empties the bowl immediately.

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Accident - The pilot of a southern California Long-EZ was seriously injured and his passenger suffered a broken hip when the airplane crashed into a dry riverbed. The eyewitnesses to the accident reported that the airplane was doing aerobatics. It appeared to enter the beginning of a loop, did not have enough speed, fell out of the maneuver. The engine stopped. (negative "g" will cause a carbureted engine to suffer fuel starvation) the aircraft nosed over and spiraled down to about 100 feet, where its wings were leveled and it descended until it struck the ground. The aircraft hit a 20 degree embankment almost wings level and slid forward only about two feet. There was no fire, although the right fuel tank was ruptured.

http://v2.ez.org/cp34-p5%28.htm

You take a large 12 cylinder Merlin gulping 120 gallons per hour and the small amount of fuel in the carburetor bowl will not last a blink of eye.....

The engine will quit....
The prop will windmill....

AND as soon as the float opens back up and fuel flow is restored the engine will restart.

Anything else is gamer fantasy.

Even with a TBI or pressure carburetor, if you pull asymmetrical loads, the engine will skip as the fuel metering changes....

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The TBI must be mounted in an orientation that places the metering tube in a horizontal plane. If the metering tube is not in a horizontal plane, positive or negative "G" forces acting on the diaphragm will alter fuel metering.

http://www.ellison-fluid-systems.com...l/section2.htm

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Originally Posted by Crumpp (Post 324743)

Anything else is gamer fantasy.

Please understand most of us know that the ingame behaviour is incorrect and that the flight models are not 1:1 with reality in many aspects. It's not "gamer fantasy" so much as it's "the simulation model is incomplete".

Your reading comprehension certainly leaves a lot to be desired Eugene. So nice of you to repeat what I already said.

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Your reading comprehension certainly leaves a lot to be desired Eugene. So nice of you to repeat what I already said

No it was not a repeat. It was to clearly put out what happens in a float bowl type carburetor when subjected to negative G.

You wrongly stated it was a "two stage" event with the implication being it takes time.

No, it happens almost immediately and is two separate events brought about by subjecting the fuel metering system to negative G.

In a lean cut out, it immediately quits but will restart as soon as fuel is delivered.

A rich cut out immediately begins skipping and then quits.... It does not restart immediately and delivery of more fuel only prolongs the restart.

Even a pressure carb or TBI will have issues under Negative G. It is a distinct disadvantage for piston power fighters using such a metering system.

Only a direct injection metering system is immune to accelerations.

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I understand and don't take offense please at the "gamer fantasy." I refer to people who distort the way the physical works to get some desired advantage in a game.

There was a distinct disadvantage in fuel metering technology. One that was frustrating for Allied pilots in a dogfight. Solving it got the attention of aeronautical research agencies on both sides of the Atlantic.

Pressure Carbs and TBI helped considerably but were not in use during the Battle of Britain.

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Originally Posted by Crumpp (Post 324883)

LOL!!! :rolleyes:

It is a 2 stage event. First there is the lean cut out which is followed by the rich cut out. They don't, and can't, occur simultaneously. Yes it takes time!!! Your 'almost immediately' says so.

It is not a two-stage process. What you are describing are two separate phenomena, occurring sequentially.

A lean mixture cutout is not necessarily followed by a rich mixture cutout.

Similarly a rich mixture cutout can happen without being preceded by a lean mixture cutout.

Crump took some time to argument his reply so please take some too before answering.

Unless you are here to impose the ridicule point of views of spitperf.com and alike I don't know how you can't agree with simple logic and commune observation.

There is some vid on youtube with ppl playing with liquids and G wile doing some acrobatic flying. Have a look !

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Exactly

Here this genius tries some Negative G's in a carburetor C172. This is why I don't rent airplanes.

He experiences a lean cut out. Listen to the engine. As soon as Negative G are applied, the engine quits and restarts at the end.

http://www.youtube.com/watch?v=RCIPx...eature=related

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There is some vid on youtube with ppl playing with liquids and G wile doing some acrobatic flying. Have a look !

Yes, you can see as soon as the float comes up, it cuts the flow of fuel to the engine.

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Originally Posted by Viper2000 (Post 301186)

The supercharger is driven by the engine.

If you reduce the power consumed by the supercharger then you increase the brake horsepower and reduce the SFC.

Supercharger power consumption is just W*Cp*deltaT, ie W*deltaH.

Supercharger isentropic efficiency is

deltaH[actual]/deltaH[isentropic]

In the case of the Merlin, this figure was about 70%.

For isentropic, adiabatic compression,

T2 = T1(P2/P1)^(gamma/(gamma-1))

Hence it's trivial to calculate the isentropic deltaT, and deltaH.

DeltaT and deltaH both get smaller if we reduce T1.

Injecting fuel upstream of the supercharger reduces the temperature by about 25 K due to the latent heat of evaporation of the fuel.

This reduces the temperature rise across the supercharger, which is equivalent to increasing its adiabatic efficiency.

Clearly this confers an advantage to engines which inject fuel upstream of the supercharger. Given the considerable difficulty associated with increasing the aerodynamic efficiency of compressors, this advantage is not insignificant.

Mixture distribution is going to be very good provided that the charge temperature is sufficiently high for complete evaporation to be ensured. This will basically always be the case at high powers because deltaT is 100 K or more; indeed intercooling & aftercooling start to become necessary once you've got a lot of supercharge.

These advantages vanish at low non-dimensional power settings. Cars spend most of their time at very low non-dimensional power settings, and therefore DI wins hands down most of the time, especially if you go for CI, in which case it's almost no-contest.

In the end, the nature of all engineering trade studies is that the devil is in the detail. The optimum is a strong function of engine size and duty cycle, and we just don't build the sort of highly supercharged, high power spark ignition engines for which single point injection is attractive these days.

To use an analogy, old amplifiers used valves and therefore tended to have large transformers & rectifiers to produce the high DC voltages which allowed them to function. Most modern amplifiers are solid state, and they don't need those high voltages.

This doesn't mean that high DC voltages aren't still a good idea for valve amplifiers; I've got a pair of hundred watt half stacks sat next to me which run in excess of 400 V DC and sound great. But probably 99% of modern amplifiers for domestic use are solid state and so if you just ask "are high voltages a good idea for amplifiers" then the short answer is "probably not".

Viper,

The basic premise you posted is entirely wrong for all practical purposes. Your math does not take into account the heat of the engine and heat transfer to the manifold.

The conclusion reached is incorrect when it comes to engines...

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Injecting fuel upstream of the supercharger reduces the temperature by about 25 K due to the latent heat of evaporation of the fuel.

Injecting fuel into the intake raises the charge temperature. Liquid fuel transfers and has more heat capacity than air. That means the fuel allows the charge to absorb more of the intake manifold's heat and the over all effect is the charge temperature is higher which is therefore less dense.

You can confirm this with a copy of:

V.L. Maleev, Internal-Combustion Engines: Theory and Design, 2nd ed. (New York: McGraw-Hill Book Company, Inc., 1945).

http://books.google.com/books/about/...d=fgvHHgAACAAJ

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So why does an IO-360 (fuel injected) have a higher peak power than a O-360 (carbureted)? The answer is that fuel injection reduces losses in the intake system. The first reason is that the venturi in the carburetor is another constriction in the flow, which manifests itself as a pressure drop in the intake manifold. This pressure drop is eliminated with a fuel injection system, thus allowing a higher pressure to reach the cylinders, and thus a larger amount of fuel/air charge to enter the cylinder.

The second reason is that the fuel/air charge is colder, and thus denser when it reaches the cylinder, again allowing a larger amount of fuel/air charge to enter the cylinder. Just like when you add carb heat, the density of the fuel/air charge is reduced when it is heated. So you're asking "Why would it be heated?" In some carbureted engines, the intake manifold is heated to assist distribution. Even without intake manifold heating, the intake manifold will be hotter than the ambient air simply because it is attached to the engine. Heat transfer studies have shown that the liquid fuel on the walls on the intake manifold increases the rate of heat transfer. (Ref 1) Thus, in a carbureted engine, the small drops of fuel in the fuel/air charge cause the charge to heat up more passing through the intake manifold than dry air would passing through the same intake manifold. Therefore, the density of the fuel/air charge is decreased, reducing the amount of charge entering the cylinder. Experiments have shown that volumetric efficiency may be increased by 10% by direct injection of the fuel into the cylinders. This also prevents loss of fuel because of valve overlap. Fuel injection into the intake port (just outside the intake valve) shows a smaller, but appreciable improvement. (Ref 1)

http://www.eaa1000.av.org/technicl/e...htm#References