how a vgt turbo works when mechanicaly controled
#11
05-29-2012, 08:21 AM
Is the Tdi the only engine using VGT?
Diesel and throttle?
Just as info:
Variable geometry turbochargers (VGTs) are a family of turbochargers, usually designed to allow the effective aspect ratio (sometimes called A/R Ratio) of the turbo to be altered as conditions change.
This is done because optimum aspect ratio at low engine speeds is very different from that at high engine speeds.
If the aspect ratio is too large, the turbo will fail to create boost at low speeds; if the aspect ratio is too small, the turbo will choke the engine at high speeds, leading to high exhaust manifold pressures, high pumping losses, and ultimately lower power output.
By altering the geometry of the turbine housing as the engine accelerates, the turbo's aspect ratio can be maintained at its optimum.
Because of this, VGTs have a minimal amount of lag, have a low boost threshold, and are very efficient at higher engine speeds.
The vanes are often controlled by a membrane actuator identical to that of a wastegate, however electric servo actuation is becoming more common. Hydraulic actuators have also been used in some applications.
Diesel and throttle?
Just as info:
Variable geometry turbochargers (VGTs) are a family of turbochargers, usually designed to allow the effective aspect ratio (sometimes called A/R Ratio) of the turbo to be altered as conditions change.
This is done because optimum aspect ratio at low engine speeds is very different from that at high engine speeds.
If the aspect ratio is too large, the turbo will fail to create boost at low speeds; if the aspect ratio is too small, the turbo will choke the engine at high speeds, leading to high exhaust manifold pressures, high pumping losses, and ultimately lower power output.
By altering the geometry of the turbine housing as the engine accelerates, the turbo's aspect ratio can be maintained at its optimum.
Because of this, VGTs have a minimal amount of lag, have a low boost threshold, and are very efficient at higher engine speeds.
The vanes are often controlled by a membrane actuator identical to that of a wastegate, however electric servo actuation is becoming more common. Hydraulic actuators have also been used in some applications.
Last edited by Deezel Stink3r; 05-29-2012 at 08:27 AM.
#12
05-29-2012, 11:29 PM
Is the Tdi the only engine using VGT?
Diesel and throttle?
Just as info:
Variable geometry turbochargers (VGTs) are a family of turbochargers, usually designed to allow the effective aspect ratio (sometimes called A/R Ratio) of the turbo to be altered as conditions change.
This is done because optimum aspect ratio at low engine speeds is very different from that at high engine speeds.
If the aspect ratio is too large, the turbo will fail to create boost at low speeds; if the aspect ratio is too small, the turbo will choke the engine at high speeds, leading to high exhaust manifold pressures, high pumping losses, and ultimately lower power output.
By altering the geometry of the turbine housing as the engine accelerates, the turbo's aspect ratio can be maintained at its optimum.
Because of this, VGTs have a minimal amount of lag, have a low boost threshold, and are very efficient at higher engine speeds.
The vanes are often controlled by a membrane actuator identical to that of a wastegate, however electric servo actuation is becoming more common. Hydraulic actuators have also been used in some applications.
Diesel and throttle?
Just as info:
Variable geometry turbochargers (VGTs) are a family of turbochargers, usually designed to allow the effective aspect ratio (sometimes called A/R Ratio) of the turbo to be altered as conditions change.
This is done because optimum aspect ratio at low engine speeds is very different from that at high engine speeds.
If the aspect ratio is too large, the turbo will fail to create boost at low speeds; if the aspect ratio is too small, the turbo will choke the engine at high speeds, leading to high exhaust manifold pressures, high pumping losses, and ultimately lower power output.
By altering the geometry of the turbine housing as the engine accelerates, the turbo's aspect ratio can be maintained at its optimum.
Because of this, VGTs have a minimal amount of lag, have a low boost threshold, and are very efficient at higher engine speeds.
The vanes are often controlled by a membrane actuator identical to that of a wastegate, however electric servo actuation is becoming more common. Hydraulic actuators have also been used in some applications.
IIRC part of the VNT/VGT control algorithm in the TDI uses the injection quantity, which is read from the 3rd injector (on VP cars). So isn't the throttle position a good way of telling the injection quantity ? Add RPM to the equation and based on the turbine efficiency map you can tell how much boost you can request, to adjust the vanes.
I have a TPS on my IP, even though it's an old VE pump
This is just merely what I have read around, I'm not stating them as hard, indisputable facts
#13
05-30-2012, 03:32 AM
The "throttle" position is not enough. An easy example. You are hitting the pedal at a step uphill climb while towing a heavy trailer.
You demand power but since the load is that heavy the RPM's will not change. CPS is transmitting tghe actual rpm to the ECU compares your "throttle" position with the available air and rpm's and nothing happens because the ECU protects the engine from overfueling.
Another example is the same situation and you run out of air. A rich fuel condition would result in extremely high EGT's.
Now add extreme RPM's to the book. Old style VP' limited the fuel supply via a cenrtifugal limiter inside the VP- this is done now by counting the CPS pulses.
Let me seek for the circuitry plan, showing as an example how many inputs are interefering with the fuel supply and boost conditions.
And the TDI's are known for their huge electronic "network" of sensors and values to be obeyed.
You demand power but since the load is that heavy the RPM's will not change. CPS is transmitting tghe actual rpm to the ECU compares your "throttle" position with the available air and rpm's and nothing happens because the ECU protects the engine from overfueling.
Another example is the same situation and you run out of air. A rich fuel condition would result in extremely high EGT's.
Now add extreme RPM's to the book. Old style VP' limited the fuel supply via a cenrtifugal limiter inside the VP- this is done now by counting the CPS pulses.
Let me seek for the circuitry plan, showing as an example how many inputs are interefering with the fuel supply and boost conditions.
And the TDI's are known for their huge electronic "network" of sensors and values to be obeyed.
#14
05-30-2012, 04:19 AM
I agree with you that throttle position alone cannot be used for VGT control, I never counted on that and that's why I mentioned it as part of the control algorithm
So, a bit simplified, engine load is rpm vs throttle position and you need that to control a VGT turbo ideally?
If that's the case then for an ideal control, mechanical control is out of the question and an electronic control unit is needed, which reads a requested boost map (boost vs rpm vs throttle) and adjusts the vane position so that the generated boost matches the requested boost. This is also simplified (PID loops are one big thing in matching actual boost to requested boost)
So, a bit simplified, engine load is rpm vs throttle position and you need that to control a VGT turbo ideally?
If that's the case then for an ideal control, mechanical control is out of the question and an electronic control unit is needed, which reads a requested boost map (boost vs rpm vs throttle) and adjusts the vane position so that the generated boost matches the requested boost. This is also simplified (PID loops are one big thing in matching actual boost to requested boost)
Last edited by AdrianD; 05-30-2012 at 04:24 AM.
#16
05-30-2012, 04:00 PM
I already have that 
Really haven't had time to read it though.
Anyway, on the matter of VGT control, I will have my sensor reader ready in about a month. RPM, Intake manifold pressure, Exhaust manifold pressure, throttle position and 3 more inputs which are unused at this point. Should be a good base for starting a controller
Really haven't had time to read it though.
Anyway, on the matter of VGT control, I will have my sensor reader ready in about a month. RPM, Intake manifold pressure, Exhaust manifold pressure, throttle position and 3 more inputs which are unused at this point. Should be a good base for starting a controller
#17
05-31-2012, 12:46 AM
#18
05-31-2012, 04:52 AM
#19
06-04-2012, 11:01 PM
Couldn't us CR guys use the signal from the FPR to open & close the vanes? It would be something like the controller used in the duel CP3 setup. The turbo would supply air in proportion to the fuel. When the pedal is pressed and the demand for fuel is increased then the turbo vains will also open for more air.
#20
06-26-2012, 06:10 PM
