Difference between revisions of "Wastegate"
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Porting the wastegate involves boring out the wastegate hole so that it is larger and can therefore release more pressure more quickly. This can be important to prevent overboost when a large bore exhaust has been fitted. | Porting the wastegate involves boring out the wastegate hole so that it is larger and can therefore release more pressure more quickly. This can be important to prevent overboost when a large bore exhaust has been fitted. | ||
| − | One of the first jobs is to remove the heatshields from around the manifold and pre-cat housing. On S2, Fed, some ROW Elans and a handful of SE's, there is an [[Oxygen (Lambda) sensor]] which can sometimes be difficult to remove even after frequent dousing in penetrating oil, heat and using the correct lambda socket. The top heatshield '''can''' be removed without removing the sensor however. First remove the three retaining bolts and [[media:Turbo_top_heatshield_removal_1.jpg|raise the heatshield as high as it will go]]. Gently raise the RHS of the heatshield and the [[media:Turbo_top_heatshield_removal_2+.jpg|gap will widen]] (shown by the red arrows) as the heatshield bends on the PAS mounting bolt (shown by the blue arrow). Eventually, it should be possible to pop the heatshield [[media:Turbo_top_heatshield_removal_3.jpg|over the top of the sensor]]. | + | One of the first jobs is to remove the heatshields from around the manifold and pre-cat housing. On S2, Fed, some ROW Elans and a handful of SE's, there is an [[Oxygen (Lambda) sensor]] which can sometimes be difficult to remove even after frequent dousing in penetrating oil, heat and using the correct lambda socket. The top heatshield '''can''' be removed without removing the sensor however. First remove the three retaining bolts and [[media:Turbo_top_heatshield_removal_1.jpg|raise the heatshield as high as it will go]]. Gently raise the RHS of the heatshield and the [[media:Turbo_top_heatshield_removal_2+.jpg|gap will widen]] (shown by the red arrows) as the heatshield bends on the PAS mounting bolt (shown by the blue arrow). Eventually, it should be possible to pop the heatshield [[media:Turbo_top_heatshield_removal_3.jpg|over the top of the sensor]] and the heatshield will spring back to its original shape. |
==Sticky Wastegate== | ==Sticky Wastegate== | ||
Revision as of 17:48, 31 December 2007
Contents
Wastegate
The wastegate is involved in the release of pressure from the turbo.
Porting the Wastegate
Porting the wastegate involves boring out the wastegate hole so that it is larger and can therefore release more pressure more quickly. This can be important to prevent overboost when a large bore exhaust has been fitted.
One of the first jobs is to remove the heatshields from around the manifold and pre-cat housing. On S2, Fed, some ROW Elans and a handful of SE's, there is an Oxygen (Lambda) sensor which can sometimes be difficult to remove even after frequent dousing in penetrating oil, heat and using the correct lambda socket. The top heatshield can be removed without removing the sensor however. First remove the three retaining bolts and raise the heatshield as high as it will go. Gently raise the RHS of the heatshield and the gap will widen (shown by the red arrows) as the heatshield bends on the PAS mounting bolt (shown by the blue arrow). Eventually, it should be possible to pop the heatshield over the top of the sensor and the heatshield will spring back to its original shape.
Sticky Wastegate
This IS going to happen, sometime. The symptoms can be:
- Lack of boost and power (wastegate stuck open).
- Uneven boost and power delivery (generally sticky).
- Wheel-smoking levels of boost and power (wastegate stuck shut) usually closely followed by fuel cut-off and minimal power for 30 seconds at the most inopportune moment plus illumination of the CEL light and a code 31 - see CEL codes.
Releasing a sticky wastegate
The consensus of opinion on the best way of releasing the wastegate is to remove the actuation capsule. The following pictures were taken of a unit which had been removed from the engine - the turbo does not have to be removed for this operation but it makes for better photographs! The shaft to the wastegate is shown by the purple arrow, the wastegate actuation rod by the red arrow {don't worry about the threaded section, as this is non-standard} and the actuation capsule by the yellow arrow.
This technique simply involves the removal of the 3 bolts (green arrows) that secure the diaphragm bracket to the turbo impeller housing (the shiny aluminium bit).
This then allows you to move the whole diaphragm and rod from side to side (Wiki Wastegate Wiggle), which soon has it running silky smooth. Make sure the wastegate shaft is turned over it's full range as there is often evidence of sticking at the extremes of travel.
There is not a consensus on whether to lubricate the wastegate shaft or not. One strong argument against is that, because of the extreme temperatures involved, most lubricants will degrade rapidly which may cause the wastegate to stick again and may even carbonise which can cause excessive wear. Any expert opinions would be gratefully received. [In the absence of expert opinion you'll have to make do with mine for the time being: CopaSlip type of lubricant is rated to 1500°C which should be adequate - Geoff]
All that remains is to replace the three bolts; the usual problem is getting the thread on the bottom bolt (nearest the wastegate actuator rod) started. Ideally you need to curl your arm right underneath by snaking it down past the water pump. Failing this, due to fingers like pigs' tits, a 12 year old is ideal for replacing this last bolt.
