Friday 2010-12-10 Dev. video update and Discussion

Originally Posted by Richie

That's a very good question. I think because of the fuel injection of the German fighters the Allied aeroplanes will have more fun with the flames.

...what do you mean exactly?

[T}{OR]

Originally Posted by Sternjaeger

...what do you mean exactly?

When burning fuel in the cylinder, if we're talking about an ideal process - you need exactly the same amount of fuel and air in your mixture. Since space in cylinder is limited, there is only so much air and fuel you can put in there (if we're not talking about turbo or supercharging). And certain amount of fuel requires exactly certain amount of air (I forgot the exact ratio but I can dig it up if you want, I have it one of my books).

The biggest downside of carburetors is that they can produce such ideal mixture only on certain RPMs, or RPM ranges. While direct fuel injection is much more flexible and can provide the engine with better mixture on all RPM ranges.

I am talking theory here, but I believe this is what Richie meant with:

That's a very good question. I think because of the fuel injection of the German fighters the Allied aeroplanes will have more fun with the flames.

[W32Blaster]

well not as simple as that.

The ideal mixture is about 14:1, also called lambda=1.

But if you have certain parameters of use like
RPM
accelaration,
Airtemperature high, low
Airpressure high, low
Cold motor (less evaporating fuel in cylinder and thus richer mixture needed)

etc. etc. etc.

you get lots of changes in actual needed air to fuel ratio. Many FuelInjection Systems are a not specified to recognize all those factors, where some really complicated carburators do.

So it´s not that simple one could say:
Fuel Injection is working better than a carburator in terms of providing the RIGHT mixture for all operating conditions.

Originally Posted by W32Blaster

well not as simple as that.

The ideal mixture is about 14:1, also called lambda=1.

But if you have certain parameters of use like
RPM
accelaration,
Airtemperature high, low
Airpressure high, low
Cold motor (less evaporating fuel in cylinder and thus richer mixture needed)

etc. etc. etc.

you get lots of changes in actual needed air to fuel ratio. Many FuelInjection Systems are a not specified to recognize all those factors, where some really complicated carburators do.

So it´s not that simple one could say:
Fuel Injection is working better than a carburator in terms of providing the RIGHT mixture for all operating conditions.

Amen

[Azimech]

Originally Posted by W32Blaster

well not as simple as that.

The ideal mixture is about 14:1, also called lambda=1.

But if you have certain parameters of use like
RPM
accelaration,
Airtemperature high, low
Airpressure high, low
Cold motor (less evaporating fuel in cylinder and thus richer mixture needed)

etc. etc. etc.

you get lots of changes in actual needed air to fuel ratio. Many FuelInjection Systems are a not specified to recognize all those factors, where some really complicated carburators do.

So it´s not that simple one could say:
Fuel Injection is working better than a carburator in terms of providing the RIGHT mixture for all operating conditions.

I'm curious which injection systems you are talking about.

The main problem with a carburetor: it's very hard to distribute the mixture to all cylinders equally. Plus fuel injected engine are less prone to icing, they have a faster throttle response and are easier to start when cold.

Originally Posted by T}{OR

When burning fuel in the cylinder, if we're talking about an ideal process - you need exactly the same amount of fuel and air in your mixture. Since space in cylinder is limited, there is only so much air and fuel you can put in there (if we're not talking about turbo or supercharging). And certain amount of fuel requires exactly certain amount of air (I forgot the exact ratio but I can dig it up if you want, I have it one of my books).

The biggest downside of carburetors is that they can produce such ideal mixture only on certain RPMs, or RPM ranges. While direct fuel injection is much more flexible and can provide the engine with better mixture on all RPM ranges.

I am talking theory here, but I believe this is what Richie meant with:

erm... no, in a nutshell: mixture has different ratios, which need to be varied according to your altitude (leaner/richer mixture), besides a 50/50 mixture ratio would probably send your valves into orbit (Disclaimer: just wanted to make a joke here, please don't take it literally and start posting copy/paste engineering blabber..)
What Richie said just doesn't make sense: engines won't produce different flames if they're direct injected or carburator injected. Or maybe I got it wrong in the first place.

[Letum]

Originally Posted by Sternjaeger

erm... no, in a nutshell: mixture has different ratios, which need to be varied according to your altitude (leaner/richer mixture), besides a 50/50 mixture ratio would probably send your valves into orbit (Disclaimer: just wanted to make a joke here, please don't take it literally and start posting copy/paste engineering blabber..)
What Richie said just doesn't make sense: engines won't produce different flames if they're direct injected or carburator injected. Or maybe I got it wrong in the first place.

I have a sneaky suspicion that Thor might know what he is talking about when it comes to engines...

Originally Posted by Letum

I have a sneaky suspicion that Thor might know what he is talking about when it comes to engines...

..I bet I know a couple of things too

[Spinnetti]

Originally Posted by Sternjaeger

erm... no, in a nutshell: mixture has different ratios, which need to be varied according to your altitude (leaner/richer mixture), besides a 50/50 mixture ratio would probably send your valves into orbit (Disclaimer: just wanted to make a joke here, please don't take it literally and start posting copy/paste engineering blabber..)
What Richie said just doesn't make sense: engines won't produce different flames if they're direct injected or carburator injected. Or maybe I got it wrong in the first place.

ideal mixture is still basically the same at any altitude. The difference is that the air density decreases as you go up, requiring mixture adjustments to maintain the same air/fuel ratio. Some planes had auto compensation, but most did not, so mechanical tune and operator capability also come into play here.

[Richie]

Originally Posted by Sternjaeger

erm... no, in a nutshell: mixture has different ratios, which need to be varied according to your altitude (leaner/richer mixture), besides a 50/50 mixture ratio would probably send your valves into orbit (Disclaimer: just wanted to make a joke here, please don't take it literally and start posting copy/paste engineering blabber..)
What Richie said just doesn't make sense: engines won't produce different flames if they're direct injected or carburator injected. Or maybe I got it wrong in the first place.

I don't really explain things very well. I think that fuel injection is a much more precise system than a carbureted engine and much less likely to flame up when being started. In all of the videos I've watched of 109s being started not once have I seen one have a stack fire. That's why I said I thought the Allied pilots will have more fun with the flames and over priming than the Germans will. Does that make sense? Put BF 109 in youtube and watch 109s start.