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turbo waistgate and acuator


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hi can anybody explain how the actuator works ,what does it do to the injection pump and what is the waistgates function? its just that i carnt understand how diafram in the injection pump has enough pressure to open the waistgate actuator or does it work the other way around and the turbo activates something on the pump?

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The compressor side of the turbo is connected to both the injector pump and the wastegate actuator. When the compressor is high enough - it opens the wastegate and also injects more fuel into the engine (boost). The actuator opens the wastegate which spins the turbo even faster. That's my take on it anyway - bit technical for me :)

Les.

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borrowed from Wikipedia ---------- http://en.wikipedia.org/wiki/Turbocharger#Wastegate

Wastegate

Main article: Wastegate

By spinning at a relatively high speed, the compressor draws in a large volume of air and forces it into the engine. As the turbocharger's output flow volume exceeds the engine's volumetric flow, air pressure in the intake system begins to build. The speed at which the assembly spins is proportional to the pressure of the compressed air and total mass of air flow being moved. Since a turbo can spin to rpm far beyond what is needed, or of what it is safely capable of, the speed must be controlled. A wastegate is the most common mechanical speed control system, and is often further augmented by an electronic or manual boost controller. The main function of a wastegate is to allow some of the exhaust to bypass the turbine when the set intake pressure is achieved. Most modern passenger car engines have wastegates that are integral to the turbocharger, although some earlier engines (such as the Audi Inline-5 in the UrS4 and S6) have external wastegates. External wastegates are more rugged and can handle higher boost levels than internal wastegates (but are also more expensive to implement), and are generally found in racing cars.

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The compressor side of the turbo is connected to both the injector pump and the wastegate actuator. When the compressor is high enough - it opens the wastegate and also injects more fuel into the engine (boost). The actuator opens the wastegate which spins the turbo even faster. That's my take on it anyway - bit technical for me smile.gif

Les.

what do you mean a bit technical for you lez ? you are MR technical. the reason i ask is that my turbo has burnt out its seal so its burning oil when the turbo kicks in i have just got a turbo from fleebay with no play . do i use the actuator thats set for my engine or do i use the one that i got from fleebay that i know nothing about its settings or history?

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no reason why you cannot swap your known good wastegate actuator unto the replacement turbo. or just use the actuator that came with the replacement & check/adjust the setting of the operating rod as shown in the workshop manual.

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no reason why you cannot swap your known good wastegate actuator unto the replacement turbo. or just use the actuator that came with the replacement & check/adjust the setting of the operating rod as shown in the workshop manual.

i would but i dont have a pressure gage . i think il just change it as i havnt got a clue what im doing anyway . whats the worst that can happen. wile your typing can you tell me how to upload picks on to a post?

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without a gauge, re-use your existing actuator, at least you know it is right & works for your engine,

info on how to upload photo's is in the pinned thread at top of Defender forum topics list, or use the 'Use full editor' button below the reply text box 7 you can upload direct from your own PC, provided the upload limit is not exceeded.

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without a gauge, re-use your existing actuator, at least you know it is right & works for your engine,

info on how to upload photo's is in the pinned thread at top of Defender forum topics list, or use the 'Use full editor' button below the reply text box 7 you can upload direct from your own PC, provided the upload limit is not exceeded.

thanks western ill give it a go next time i need to.

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Hi everyone,

Whilst (I think) I understand how the turbo wastegate operates, I was wondering if it's possible for the wastegate to get stuck open? I'm pretty certain my turbo is performing as it should - plenty of power most of the time - every now and then I'll lose all power. I'm investigating all options - and it did occur to me that it could be turbo-related. By just looking at the turbo, is it possible to ascertain whether the wastegate is open/closed? How can I ensure the mechanism isn't sticking from time to time?

Thanks in advance,

Ian.

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Hi everyone,

Whilst (I think) I understand how the turbo wastegate operates, I was wondering if it's possible for the wastegate to get stuck open? I'm pretty certain my turbo is performing as it should - plenty of power most of the time - every now and then I'll lose all power. I'm investigating all options - and it did occur to me that it could be turbo-related. By just looking at the turbo, is it possible to ascertain whether the wastegate is open/closed? How can I ensure the mechanism isn't sticking from time to time?

Thanks in advance,

Ian.

at the end of the waistgate actator there is a rod whitch goes in and out if you think its sticks open you can undo the clip that holds the rod and open and close the wastgate by hand it should move freely. if you are losing loads of power it could be something like a crushed air intake hose whitch only crushes when the turbo cuts in and creates more suction . i had that happen last year and it turned out it was the air hose in the wing.blink.gif

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When you buy a new turbo - it generally doesn't come with a wastegate actuator (that's another £100 please sir smile.gif ) As long as you don't adjust the operating rod length, then it's just a straight bolt on and connect job.

You can buy repair kits for turbo's, which include the bearing and seal. Bearing wear or seal leak is the most common reason for turbo problems, and is the cheapest option.

Les.

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When you buy a new turbo - it generally doesn't come with a wastegate actuator (that's another £100 please sir smile.gif ) As long as you don't adjust the operating rod length, then it's just a straight bolt on and connect job.

You can buy repair kits for turbo's, which include the bearing and seal. Bearing wear or seal leak is the most common reason for turbo problems, and is the cheapest option.

Les.

were can you get them from lez?

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With the small turbos used on vehicles with small displacement diesel engines, a turbine sized to provide good boost pressure at low and medium speeds will be too small for the exhaust temperature/flow/energy at high speed and loads. This has 2 undesirable affects, the pressure in the exhaust ports and manifold will be too high (reducing efficiency) and the turbine can/will overspeed (leading to mechanical failure).

A larger turbine that will not require a wastegate (known as free floating) will not start to produce useful boost pressure until engine speed is high, so drivability will suffer.

A common solution is to use a smaller turbine and a wastegate to reduce the exhaust manifold pressure and prevent the turbine from overspeeding. A better solution, more common with modern vehicles (e.g. disco 3 and later Land Rovers), is to use variable nozzle vanes for the turbine, which allows a larger turbine to be used while still performing well at low and medium engine speeds.

The wastegate has a valve that is opened by exhaust pressure so the gasses can bypass the turbine. The actuator has a spring that holds the wastegate in the closed position, the length of the rod between the actuator and wastegate lever can be adjusted to increase/reduce the pre-load from the spring. The actuator has a diaphragm that pushes against the spring to open the wastegate when boost pressure increases above the set value.

IMHO don't trust the pre-load achieved from an actuator to be the same when it is transferred from one turbo to another.

Edit: a kit to overhaul a turbo from a 200/300Tdi or TD5 are reasonably cheap and common. Although they have different turbos the same kit is used for many different turbos. search ebay for T25 turbo overhaul kit.

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For those interested in the workings of the turbo and waste gate:

The turbo waste gate and the fuel boost diaphragm are two separate systems that are sensitive to the same boost pressure. The fuel boost diaphragm alters the amount of fuel injected to match the increased air delivery from high turbo boost, like adjusting the mixture automatically. The waste gate limits the maximum boost of the turbo to prevent the turbo spinning to destruction or over boosting the engine and cracking the head, pistons or bores by over-pressurising them.

The waste gate works by sensing the pressure of the induction air exiting the compressor section of the turbo charger (or the inlet manifold pressure). It is a diaphragm in a small metal drum that has compressor pressure on one side and a spring on the other. When the turbo's output pressure reaches its maximum, the air pressure on the diaphragm overcomes the spring on the other side, and the actuator pushes a rod to open the waste gate. This allows exhaust gas from the exhaust manifold to bypass the turbine section of the turbo charger, regulating the amount of energy the turbine delivers to the compressor.

On LR engines, the peak torque is needed at pretty low rpm, so the waste gate starts to open relatively early compared to street cars. The size of the unit is also chosen to bee small enough to be effective at low rpm while not restrictive at the max rpm (fairly low at 4250 for Tdis).

The position of the waste gate is controlled only by the compressor output pressure on Tdis, though TD5s and other ECU controlled engines have electronic inputs. However, the waste gate will generally try to maintain maximum rated output compressor pressure. It is not engine rpm or throttle governed, though those controls will affect the waste gate position - in essence, any time the exhaust gas temperature goes up from the engine having a large demand placed on it, the turbine will spin up and the compressor will deliver more pressure. As soon as the max pressure is reached, it will be maintained by the waste gate modulating to allow enough exhaust gas to bypass the turbine. Any drop in compressor output allows the spring to overcome the the air pressure, moving the waste gate towards closed and diverting more exhaust gas through the turbine to keep it spinning fast enough to provide the maximum set pressure.

In practice, floor the pedal and the EGT shoots up from the increased fuel burn; the turbo will spin up and command the fuel pump to thrown in even more fuel, further increasing EGT and turbine speed, and thus compressor pressure. When the max pressure is reached, the waste gate will open to stabilise turbine rpm and the boost pressure. Take your foot off the pedal and the fuel injection is reduced; EGT drops and the turbine rpm follows, dropping the boost pressure. As the boost pressure reduces, the waste gate will close to ckeep the turbo providing as much boost as it can.

One of the tuning mods that is done is to increase boost pressure by shortening the rod between the waste gate actuator and the waste gate operating arm so that the diaphragm has to travel further against the spring (higher pressure) before it starts to move the operating arm and thus open the gate. This means that more exhaust gas is routed via the turbine instead ob bypassing it, increasing the energy delivered to the compressor and increasing air charge. It's a reset of the target pressure for the turbo charger.

Swapping the actuator and rod from one turbo unit to another could lead to slight variations in compressor performance to to the slight differences in the distance between the aft face of the compressor housing (where the actuator bolts on) and the waste gate shaft due to manufacturing tolerances, but I think these variations would be well within LR's operating tolerances. The big thing is to make sure you have a rod and actuator that haven't been tampered with to increase boost - look for the yellow paint on the locking nuts.

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