Thread: VNT Turbo Setup??

Originally Posted by 1103.9TDI

......or increase the wing camber (profile) of course this is why a VNT is always going to be more successful at gaining boost in the first place. The lift of an aerofoil is also directly proportional to its surface area.

Parsitic drag is directly proportional to its surface area. lift is "camber (profile)" and angle of attack

Originally Posted by Dougal

Or increase the angle of attack.

true, but this increases drag, reduces speed, and things can compound in thin air. the canbria when used by the poms on photo recon over E germany. there problem was getting the bird down from 50K feet +.

to slow and stall. couldnt close the throttles or the jets ( pure) would flame out, had to maintain 90% power. solution was push the nose up< angle of attack. this would slow the bird and she would decend untill the air got a bit thicker.

in responce to an older post

back in the day we would weld a nut with a bolt to limit the amout the waste gate could open. this eliminated a surging problem. where the Hot gas pressure droped to far, the responce time of every thing else was to slow

Originally Posted by 85 county

in responce to an older post

back in the day we would weld a nut with a bolt to limit the amout the waste gate could open. this eliminated a surging problem. where the Hot gas pressure droped to far, the responce time of every thing else was to slow

That was what the original Dawes valves (the non-TDI version) were used for.

Unless the turbine or turbine housing A/R is large enough, restricting the amount that the waste gate can open will compromise turbo operation at high speed and full load.

For performance applications it is usual to use an external waste gate, which gives you more control and overcomes the problem of internal waste gates being too small.

Sorry for going off the topic of VNT turbos, but I always like (though sometimes hold back) to take opportunities to draw attention to the often overlooked exhaust side of turbo systems, whether that be waste gates, variable turbine nozzle, or staged turbos.

[quote=85 county;1884614]Parsitic drag is directly proportional to its surface area. lift is "camber (profile)" and angle of attack[/quote

I don't know where parasitic drag comes into the equation, that's just something that sticks out into the airflow, maybe like an aerial. Bugger all chance of seeing one of those inside a turbo.

[quote=1103.9TDI;1884944]

Originally Posted by 85 county

Parsitic drag is directly proportional to its surface area. lift is "camber (profile)" and angle of attack[/quote

I don't know where parasitic drag comes into the equation, that's just something that sticks out into the airflow, maybe like an aerial. Bugger all chance of seeing one of those inside a turbo.

wrong, parisitic drag is the friction between a surface and the airflow, nothing to do with some thing stick out. remove all the aerials and you still have drag

Originally Posted by Bush65

That was what the original Dawes valves (the non-TDI version) were used for.

Unless the turbine or turbine housing A/R is large enough, restricting the amount that the waste gate can open will compromise turbo operation at high speed and full load.

For performance applications it is usual to use an external waste gate, which gives you more control and overcomes the problem of internal waste gates being too small.

Sorry for going off the topic of VNT turbos, but I always like (though sometimes hold back) to take opportunities to draw attention to the often overlooked exhaust side of turbo systems, whether that be waste gates, variable turbine nozzle, or staged turbos.

so a Dawes valve is a proportonal valve ??

[quote=85 county;1885055]

Originally Posted by 1103.9TDI

wrong, parisitic drag is the friction between a surface and the airflow, nothing to do with some thing stick out. remove all the aerials and you still have drag

Wrong again, you're getting very confused with skin friction, the resistance which is set up when relative motion exists between the surface of a body and the air contact between the two gives rise to a layer of retarded air in immediate contact with the surface over which it is passing. We were origially talking lift not drag. Even the Collins Dictionary gets it right: the part of the drag on an aircraft that is contributed by nonlifting surfaces, such as fuselage, nacelles, etc Also called: parasite resistance or drag.
Better go back and read your manual or simply do a Google search, Mr 85 county.