Take the situation where the engine is running at a steady speed and torque, and the vanes are then quickly rotated to a more closed position. The following steps describe the immediate transient effects in sequence:

1. The minimum flow area of the vane channels decreases by a large amount (say, 1/2 the original area) as the vane angle is made more shallow.

2. Immediately after changing the vane angle, the exhaust mass flow rate through the reduced area VNT vane channels does not change significantly, due to increase of the exhaust gas density and velocity. Exhaust gas density is increased due to increased exhaust manifold pressure, and gas velocity is increased by gas acceleration in the vane channels.

3. Increased exhaust gas acceleration in the vane channels is due to the increase of pressure gradient caused by increased exhaust manifold pressure.

4. The pressure in the exhaust manifold increases because the cylinders continue to empty into the exhaust manifold at nearly the same mass flow rate. The exhaust mass flow rate out of the cylinders is reduced slightly due to the increased density of residual gas in the cylinder displacing some air on the intake stroke.

5. The exhaust manifold gas pressure, temperature, and energy density are increased due to the increase of piston pumping work during the exhaust stroke. Piston pumping work significantly affects the engine power output, and is also affected by pressure during the intake stroke.

6. The exhaust manifold takes time to accumulate the additional mass of exhaust gas that increases the exhaust manifold pressure. Exhaust manifold pressure is typically higher than the intake manifold boost pressure at most conditions.

7. The exhaust gas accelerates through the VNT vane channels due to the VNT vane channel geometry (decreasing in area like a nozzle) and due to the increased energy density in the exhaust flow provided from the exhaust manifold (being at at higher pressure and temperature). However – the process of the gas flowing into the turbine wheel at possibly over Mach 1 (1600 mph or 2300 ft/s, @ 1600F – that’s as fast as a bullet!) is not a significant contributor to the generation of torque on the turbine wheel, as the wheel blade tip speed is similar to the gas speed.

8. The pressure of the gas exiting the VNT vanes is typically not far above atmospheric pressure. As the gas flows into the turbine wheel channels, the turbine wheel blades turn the flow to be at an angle to the rotational axis opposite to the entry angle and also act as nozzles. This process results in most of the torque generated by the turbine wheel.

9. The increased turbine wheel torque causes the turbocharger rotor group to accelerate, and the compressor wheel speed increases on the intake side. Increased compressor speed results in increased intake manifold boost pressure. Engine intake airflow increases due to the increased manifold boost pressure. Fuel is increased to maintain A/F ratio and the engine power output begins to increases.

10. On the exhaust side, increased exhaust flow into the exhaust manifold results in a further increase of exhaust manifold pressure and temperature and therefore energy available to the turbine. Energy feedback is obtained causing further increase of the rotor speed until the power developed by the turbine balances the power absorbed by the compressor and bearings. The turbocharger speed can be over 200,000 rpm (3300Hz) for a small displacement automotive engine.

11. When the rotor power is balanced, the engine operates at a higher state of intake and exhaust manifold pressure and engine airflow and consequently power output, depending on how the throttle is operated.

What to check after visual checking wires and fuses both apear ok
where to get electric dignostic tree information. I hope to trouble shoot this issue

Where as in VTT I’m told that turbine blades are movable.

Please Clarify.

My Honda B18b aircraft engines retard intake camshaft to

dynamically lower the compression ratio . This precisely controls

Turbo boost , at all altitudes .

Its an amplified effect , a slight retard of camshaft will drop boost quickly .

On takeoff , at 200 HP / 7500 rpm , a 5 degree retard will drop

H.P. to 170 .

Thanks a ton, Paul

- u wanna rectify ur phrase or sumthin? variable valve timing and variable turbo are totally different parts..

btw paul, this is an essential info to me.. thanx a lot.. wanted to know how it works since the 911 debut..

fuyo , da koreans is tryin sth new long time ago .

Germans talk crap. VW is showing off everyone that they made a supercharged turbo engine for their polo but in fact Nissan did that in 1989 in their Nissan March using K10 engine.

VTG, VNT, VATN are all the same thing like how VVTi, Vanos, CVTC, DVVT or whatever you want to call it.

there has been VTG petrol powered cars before this, but in limited runs like 500 units.

Anyway, its great of you to illustrate what Porsche(or Borgwarner) have done to the turbocharger. If you look at how it works, it is actually almost commonsense way to wring out more energy from the turbocharger and in fact it has been used for some time now in aerospace but only now Porsche has managed to introduce it in the 911.

So, no, I don't think it is present in any other car, particularly in a Sorento!

Paul it seems that the excess boost is controlled by the vanes. My guess is that once the engine speed drops the vanes are kept wide open so the turbine spins more slowly. Then the vanes close base to assume low rpm profile.

http://www.f1technical.net/forum/viewtopic.php?p=…

there's a nice gif animation of vtg in action here.

These dudes are mental……