109 e3b against spitfire II

[Crumpp]

There is no such thing as a direct injection aircraft engine in General Aviation. All fuel injection is single point injection much like the Allied designs of WWII.

If an engine has bayonet probes in all cylinders, it is not unusual to see variations in CHT readings on fuel injected engines of 100o F between cylinders, and as much as 150ø F on engines with float-type carburetors.

With the latter, an important cause of the variation is
the kind of distribution of fuel and air to the individual cylinders.

Don’t be surprised to see variations in temperature between individual cylinders where there is a probe for every cylinder. It is fairly typical to see an average 100o F variation with fuel injection, and as much as 200o F variation with a float-type carburetor. The latter (carburetor) variation tends to be greater because fuel/air distribution is not as good
as with fuel injection.

In a direct injection engine, there is almost no variation in CHT or EGT between the cylinders.

It is that temperature variation that robs a single point fuel metering system of power.

http://www.costaricaaviation.com/fli...tions_rev1.pdf

[TomcatViP]

Originally Posted by Crumpp

There is no such thing as a direct injection aircraft engine in General Aviation. All fuel injection is single point injection much like the Allied designs of WWII.

In a direct injection engine, there is almost no variation in CHT or EGT between the cylinders.

It is that temperature variation that robs a single point fuel metering system of power.

http://www.costaricaaviation.com/fli...tions_rev1.pdf

Crumpp,

At first, thx for all the excellent references you are giving on many of your post.

I understand you point on DI vs SPI (single point injection). DI has clearly many advantage and was the panacea at the time.

Viper care much abt theory and given that you run at cte regime and that the ducting are of equal length after the s/c (what is not feasible) the SPI has clearly an edge in terms of practical answer.

DI however as you has pointed out offer much more advantage on reality grounds and this clearly can be seen in ehaust temp even in today cars (Ask GrandPa about engine backslash and loud bang with carburetor engined cars before the 80's GTI went out)

Coming back on the BoB, I believed that RR had however an advantage with the s/c being inline with the engine witch simplified the routing of the air with a relative symmetry (the DB has some prob and a slight differences btw raws of left and right cylinder due to the s/c being on the port side ). This tend to makes the RR simpler ... and what is simpler is much easier to improve : a strong point for any strategical war item

[Crumpp]

I'd rather have less drag than more horsepower,

As a pilot, slick aircraft are problematic when it comes to maneuvering. They are good for cross country performance but poor in maneuverability. That is why you don't see many slick aerobatic platforms.

Drag with appropriate power gives a pilot precise speed control allowing him to reach and maintain his aircraft's design performance speeds quickly.

As a pilot, there is nothing worse than having too much speed and not being able to get rid of it when you need the airplane to maneuver or require maximum performance from it.

[Crumpp]

At first, thx for all the excellent references you are giving on many of your post.

You are most welcome. Thanks for your contributions to the discussion too.

I understand you point on DI vs SPI (single point injection). DI has clearly many advantage and was the panacea at the time.

The technological advantage of DI allowed the German designs to be equal to despite strategic material shortages.

Maintaining equality with inferior materials came at a high cost though.

simpler is.....

Exactly. The main drawback of Direct Injection is the expense and complexity. Germany is just a little smaller than the state of Montana in terms of square miles and had a strategic material shortage even before the war began.

For a resource poor country of that size to take on most of the civilized world in an all out war of attrition, complex and expensive is something to be avoided.

[Viper2000]

Originally Posted by Crumpp

There is no such thing as a direct injection aircraft engine in General Aviation. All fuel injection is single point injection much like the Allied designs of WWII.

Actually pairs of these things fly over my head every day...

Originally Posted by Crumpp

In a direct injection engine, there is almost no variation in CHT or EGT between the cylinders.

CHT is dominated by cooling; EGT is dominated by stoichiometry. CHT variations are an inevitably fact of life for air-cooled engines.

Originally Posted by Crumpp

It is that temperature variation that robs a single point fuel metering system of power.

A perfectly reasonable statement if and only if you are comparing identical intake conditions.

[CaptainDoggles]

Originally Posted by Viper2000

CHT is dominated by cooling; EGT is dominated by stoichiometry. CHT variations are an inevitably fact of life for air-cooled engines

He's not saying that EGT and CHT are equal, he's saying that across the cylinders CHT won't vary much, and neither will EGT.

[Viper2000]

Originally Posted by CaptainDoggles

He's not saying that EGT and CHT are equal, he's saying that across the cylinders CHT won't vary much, and neither will EGT.

I was responding to this:

If you have flown an aircraft with individual Exhaust Gas Temperature Gauges and Cylinder Head Temperature gauges you would know their is a wide variance in the temperatures with any fuel metering system that introduces fuel to the intake.

...

[Crumpp]

He's not saying that EGT and CHT are equal, he's saying that across the cylinders CHT won't vary much, and neither will EGT.

Correct. Thank you.

What I am saying is obvious for anyone who has flown a piston engine aircraft with individual CHT/EGT. You can see the power robbing temperature differences of introducing fuel anywhere in the intake system.

Only by metering fuel with a direct injection system will the cylinders have equal EGT's and CHT's across the engine.

Actually pairs of these things fly over my head every day...

I did not know the DA-42 diesels were direct injection. It figures, diesel is the easiest type of engine to direct inject.

[Crumpp]

I was responding to this:

You misunderstood it.

Of course EGT is not going to equal CHT in an individual cylinder, that is a silly concept. Only in direct injection will the EGT and CHT be equal across the cylinders of your engine.

Fuel introduced in the intake will cause the cylinders to draw different mixture ratios as the firing order is cycled. The different fuel mixture ratio will cause each cylinder to have a different CHT and EGT from the other cylinders in the engine. This is a very common known fact for pilots as you see it every time you fly so you don't get worried when one cylinder has a temperature 100 degrees lower than another cylinder. That is just a by product of introducing fuel into the intake system instead of directly injecting it in the cylinders so the mixture can precisely metered.

[Viper2000]

Originally Posted by Crumpp

I did not know the DA-42 diesels were direct injection. It figures, diesel is the easiest type of engine to direct inject.

In many ways it's tougher because the pressures are higher. However, the alternatives are worse, so injection becomes the route of least resistance sooner.