Why we need to idle before we shut off a turbo charged car Just a few basics.
I am assuming we all know how turbos work. Contraption bolted onto the exhaust manifold. Exhaust gases turn turbine which is connected to compresoor with a shaft, anf therefore puts in more air, allowing more fuel to be fed into engine, resulting in more power and big smile on face.
Now, since the turbo runs on exhaust gases it gets seriously hot, very seriously hot and it is virtually impossible to keep them lubricated with any self contained substance, because it would have a tendency to dry out and seize. Therefore in order to keep temperatures down, oil (for lubrication also) and water are used to keep turbo's cooler.
Now, when we really slam our vehicles, turbo's, like i mentioned earlier, tend to get fantastically hot, to the point that they even might burn up the oil that is being circulated thru it. As a result this burnt oil tends to crust up. This phenomenon is called COKING (pleae dont misunderstand for something that some late politicians son did, as a resul of which his insides needed to be washed out). This problem is accelerated further if after a spirited run the engine is shut off before it is suffciently cooled down. This crust is very abrasive and will spell the death knell for your turbo charger.
The basic construction of a turbo is directly related to the amount of friction within it's components which again results in the build up of heat. I am no expert but according to me, following might be some of the reasons why modern day turbo charged vehicles do not require idling before shut off: -
1) Older turbos used to use bushes, modern ones use ball bearings. These bearings are also fed with oil (design) and therefore are less starved of lubrication therefore resulting in less heat build up and therefore reduced chances of coking.
2) Most modern cars also use synthetic oild which vastly improve lubrication and cooling.
3) Some modern cars come equipped with Oil cyclers which continue to provide / pump oil into th turbo even after shut off.
4) Vast improvements to engine cooling components.
Insite of all of the above I personally would still idle my turbo vehicle before shut down. After all these are mechanical components and there is a chance of failure.
Appologies for the long post.
Last edited by Sideways : 24th September 2006 at 15:15.
|