View Full Version : Forgive my Ignorance

02-04-2006, 08:32 AM

Now dont line me up and have me shot but whats the big deal over this me-109K ata, so my dumb question is whats ata stand for, obviously it has something to do with the engine/atmospheric units????/

02-04-2006, 08:54 AM
The power you get out of an engine depends on the amount of fuel-air mixture you can push into it during the intake stroke. Obviously, you can get more fuel-air mixture in if you force-feed the engine with it. Thus, you add a blower (supercharger) driven by gears or belts by the engine, or a turbocharger, driven by a turbine in turn driven by the exhaust gases.

ATA is a measure of how high the pressure can be in the intake manifold, or how hard you push fuel-air mixture into the cylinders (or just air, when we're talking fuel injected engines).

So, why have an upper limit?

If you have the intake pressure too high, the temperatures and pressures inside the cylinders will become higher than the engine can take. You will end up blowing top gaskets, engine tops or even pistons.


02-04-2006, 01:29 PM
I think the real question Stugumby is asking is, "What the h3ll is ATA?"

I've flown the 109 a lot, but I don't know what the "ATA" stands for either. I do understand turbo- and supercharging. I understand manifold vacuum and boost pressure. WHAT is ATA?

02-04-2006, 01:41 PM
Originally posted by effte:
If you have the intake pressure too high...

You might blow the welds on the intake.


02-04-2006, 02:13 PM
It apears to be the German measure ment of PSI pounds per square inch.



02-04-2006, 02:41 PM
http://www.mindspring.com/~divegeek/altitude.htm (http://www.mindspring.com/%7Edivegeek/altitude.htm)

Atmospheres Absolute (ATA)
The combination (or the sum) of the atmospheric pressure and the hydrostatic pressure is called atmospheres absolute (ATA). In other words, the ATA or atmospheres absolute is the total weight of the water and air above us.

Terms Used to Measure Pressure
We use various terms to measure pressure. HBO therapy involves the use of pressure greater than that found at the earth's surface at sea level. This is called hyperbaric pressure. The terms or units used to express hyperbaric pressure include millimeters or inches of mercury (mmHg, inHg), pounds per square inch (psi), feet or meters of sea water (fsw, msw), and atmospheres absolute (ATA).

One atmosphere absolute, or 1-ATA, is the average atmospheric pressure exerted at sea level, or 14.7 psi. Two-atmosphere absolute, or 2-ATA, is twice the atmospheric pressure exerted at sea level.

02-04-2006, 05:35 PM
I'm a layman at this, but will look into it more seriously, but thinking about it in a logical way.

A/C engine power (like all piston engines)(fuel injection) relies on a certain fuel/air(oxygen) mixture ratio for maximum power output. AFAIK one has to keep this mixture this side of 'Lean' (too much air) for max power, so the higher you go the 'richer' (to much fuel = not all of it burns in the engine = wasted power) the engine mixture becomes and you get exhaust trails of excess fuel.

So with a fuel-injection system you can either reduce the fuel injection with altitude to match the 'thinner' air intake. This will result in less engine power which is not what you want when your life is flashing before your eyes.

Or your can keep the fuel injection constant and 'pump' extra air into the engine, via turbochargers, etc thus keeping the engine power output the 'same' at sea level. Thus giving the power at altitude

All specs are in relation to each other and I suspect the ATA spec is about the engine power at cruising altitude with respect to sea level.

Engine Temps and Pressures:
I take this as a combination of..
1- The higher/faster I go the cooler the engine becomes.
2- The leaner the fuel the hotter the engine (Fuel has a cooling effect)
3- With high temps, comes the high pressures and thus 'goodbye' gaskets and heads

To summarise:
ATA looks to be a optimised sea-level equivalent of engine power at a specific altitude. This altitude is obviously questionable...

I'm really zinging it at this stage, somebody help me ???

02-04-2006, 09:32 PM
You people have no sense of humor. http://forums.ubi.com/images/smilies/mockface.gif

02-05-2006, 07:27 AM
Your ignorance is forgiven (my sun http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif).

02-05-2006, 07:50 AM
German intake pressure boost guages measure in multiples of atmospheric pressure at sea level instead of the American "inches of mercury" or the British "pounds per square in inch". The 1.98ata refers to the maximum boost level on this model of the K4, 1.98 times "standard" sea level atmospheric pressure (sea level being a tad over 14 pounds, this is about 28psi / 60inches boost). I don't recall if German boost guages measured above atmospheric like the Brits or absolute pressure like the American guages.