Mustang Dyno results for GTR at 4,000ft altitude

[heavychevy]

Yes but since the Turbos act off of exhaust gases and pressure from the Motor anyhting that significantly affects the engine power will directly affect the turbos, though not as much as NA. Car and plane Turbines dont work the same from what I know as auto turbines are completely driven by exhaust gases from a motor and plane turbines have motor that spin them and they work of air speed though them.

Partially educated guess FTW.

[psd1]

Originally Posted by paul cawson

For info

The performance of the turbine improves at altitude as a result of the greater pressure difference between the virtually constant pressure upstream of the turbine and the lower ambient pressure at outlet. The lower air density at the compressor inlet is largely equalized. Hence, the engine has barely any power loss.

Uhmmm...no! Every engine loses power as the altitude goes up. NA cars are just effected more. Try living in Denver or Colorado Springs then driving at sea level...very noticeable, for NA the the % loss is around 3% for every 1K feet in elevation, so at 6K feet your losing 18% of your HP!

Thicker air will bring more power...fact of life, cant fight physics!

[R32 Combat]

This is going to go on.

[moleman]

Originally Posted by psd1

Thicker air will bring more power

That's how I understand it. Dense is good.

[R32 Combat]

Engines use air in 'weight'. Eg 14.7 kgs air to 1 kg fuel.

So if the air is 'thinner', a little more boost will force in the extra 'weight' to compensate.

This is my point, the stock ECU can compensate for altitude to a certain pressure, and I wasn't sure if 4000ft would show much on a dyno.

[paul cawson]

Originally Posted by psd1

Uhmmm...no! Every engine loses power as the altitude goes up.

Thicker air will bring more power...fact of life, cant fight physics!

No and yes, the air in the atmosphere is at its coolest in the 30000 to 45000 ft band, which is why aircraft fly at this height, any higher and it heats up again

[Drifter Steve]

would it be possible that since the gt-r has gps, it could use the gps to calculate its altitude and increase boost accordingly?

[bonzelite]

Oh no, here is yet another "dyno thread" that will elicit all kinds of "I spotted Big Foot" stories and claims that the dyno operator or equipment was faulty, lying, substandard, otherwise doctored.

Talk of millibars and barometric pressures, intake, exhaust, timing, altitude sickness, base camp, sea level, below sea level, vacuum of space, low Earth orbit, distance of Moon from the Earth, tidal locking, sulfuric emissions... all will be thrown around and never agreed upon as being credible or plausible factors affecting horsepower and torque curves.

Yet some will insist they saw Big Foot anyway and carry this out to several pages.

[covak2002]

Aircraft fly high because the stiction over the wing is less therfore the engines run more "cannot spell" economical i have served in the RN now for 12 yrs worked on sea harrier and merlin mk1 so as stated the higher the car the less air yes but the car wont know the turbos spool the same speed and engine wont run as good

[paul cawson]

Originally Posted by covak2002

Aircraft fly high because the stiction over the wing is less therfore the engines run more "cannot spell" economical i have served in the RN now for 12 yrs worked on sea harrier and merlin mk1 so as stated the higher the car the less air yes but the car wont know the turbos spool the same speed and engine wont run as good

I copied this to save a long reply


At higher altitude, the temperature decreases. The colder the air temperature, the better it is for the jet engine as it convert fuel more efficiently at low outside air temperatures. Basically, the efficiency is directly proportional to the temperature differential. The greater that temperature differential is, the more efficient the engine.

Colder air is also good for jet engine operation. Colder mass means more air. Remember the principle of a gas turbine engine - it requires air to be sucked at the front, compressed, combusted then expanded and blasted out through the jet nozzle (a more simplistic explanation - suck, squeeze, blow and go!)

Further, when a plane climb higher, the air outside gets thinner and less dense. This has the effect of reducing the forward resistance.

So we are both right, but I dont agree with the last bit about the turbo, see my first post

[tyndago]

The R35 GT-R has supposedly good compensation for altitude.
Everything I have heard about it, is that it works well ,unlike 99.9 percent of the other cars on the road.

This is my actual real life experience with turbocharged cars. Not a theory in a book, or what happens in an airplane. You can go on and on about theories, and I will tell you realities.

I looked up the highest point in the UK, its 2000 feet. You guys don't have to deal with it.

If you want to try it out Paul , come over to LA. We will run a car at Pomona which is 1200 feet. We will then take the same car, the same tune and go up to Bandimere which is 5000 feet. The car will lose about a second in the quarter mile. If Palmdale was still open, I would show you any car, even a turbo one will lose about 0.4 - 0.6 second , same day, same temp, same fuel, same engine management. Get the same car, on a cold dense day in Baltimore, on a good track, and it will be quicker still.

I'll pay for the trip if you prove me wrong in reality rather than theory.

[JDMist3hfastar]

Guys the fact is that cars just run slower up high. I have a 2002 WRX with a STi turbo and supporting mods and only can put down 250whp and about 265tq at 5800 feet in Boulder, Colorado. Back at home in NY though, with the same tune, it puts down 272whp and 283wtq. The spool time and just general responsiveness of the car is night and day going between altitudes...and its sucks

[R33_GTS-t]

Originally Posted by paul cawson

No and yes, the air in the atmosphere is at its coolest in the 30000 to 45000 ft band, which is why aircraft fly at this height, any higher and it heats up again

He's right to an extent. It's easier to compress a colder less dense gas. The pressure ratio across a jet engine compressor section will be higher, which improves efficiency, and the temperature difference from turbine inlet to ambient will also be higher, which improves power. The net thrust will be lower but the SFC improves, the overall effect being that it performs better. You've got to remember that combustion engines and jet engines are fundamentally different.

Comustion Engine - combustion at constant volume.

Gas Turbine - combustion at constant pressure, therefore trying to squeeze more oxygen into a fixed volume is not an issue.

However, after a point, generating lift becomes difficult due to low air density. You either have to have a high-lift wing design (longer wings), be lighter, or fly faster.

[paul cawson]

Originally Posted by tyndago

The R35 GT-R has supposedly good compensation for altitude.
Everything I have heard about it, is that it works well ,unlike 99.9 percent of the other cars on the road.
I would show you any car, even a turbo one will lose about 0.4 - 0.6 second , same day, same temp, same fuel, same engine management. Get the same car, on a cold dense day in Baltimore, on a good track, and it will be quicker still.

I think the key here is engine management, the after market and older OEM systems are crude at best, the R35 will adapt the fueling more precisely so not suffer the power loss.

Originally Posted by R33_GTS-t

You've got to remember that combustion engines and jet engines are fundamentally different.
.

But a turbo and jet engine are very similar in operation

[R33_GTS-t]

Overall efficiency = {[(Mass flow*Ambient Speed)*(Jet Speed - Ambient Speed)]/mass flow fuel} * (1/Net calorific value of fuel at constant pressure)

Mass flow is down but ambient speed is up (less drag) and SFC is also down.

It's about efficiency rather than power.

From the above equation:

[Mass flow*(Jet Speed - Ambient Speed)] = Thrust for simple jet

Another way of looking at it is to say that the specific thrust increases with altitude, i.e. the thrust per mass unit of air.