If you're driving your turbocharged car from one point to the other in full throttle, you may need to let your engine cool down. But in most cases, new vehicles don't need this process. Read on for a detailed take.
We at IndianAuto.com come across questions from owners whether they should let their turbocharged diesel vehicles cool down after a long drive? The simple answer is no you don’t need to, but we will talk about this topic in detail so that you can understand better. A turbocharger is a simple device, consisting of individually enclosed turbine blades mated together by a common shaft. This shaft “floats” on a thin film of oil which also acts the turbo’s lubricant and keeps things moving smoothly. The “drive” side of the turbo is powered by exhaust gases leaving the engine. These hot gases spin the turbine side of the turbocharger to drive the compressor side. In doing so, the compressor pumps air to the engine at a higher pressure, which the engine would've received at around atmospheric pressure in turbo's absence. When added with the appropriate amount of fuel, the added air means a turbocharged engine makes more power than a naturally-aspirated engine of similar size.
The speed of rotating parts of the turbocharger can exceed 80,000 rpm, in some cases going up to 150,000 rpm at full throttle. Under these conditions, the turbine housing can get so hot that it will glow orange. However, the heat generated isn’t always from the turbine running at high rpm, but rather it is from the elevated temperatures which is a byproduct of the combustion process when the engine is at full bore. Under full throttle, the exhaust gas temperatures can reach anywhere between 650 to over a 1,000 degrees Celsius. Some of this heat will be transferred to the metal components of the turbocharger and the engine oil.
Subjecting engine oil for such long temperatures will see it attaining its flashpoint ( which can be as low as around 180 degrees Celsius for petroleum-based oils and above 225 degrees for most synthetic-based oils) and will start burning. When that happens it stops lubricating or protecting any of the engine’s moving parts. In the case of a turbocharger, the rotating shaft gets damaged due to a lack of lubrication to eventually fail in its entirety. In the old days, when materials weren’t as advanced as it is currently, it was common for people to allow the engine to cool down by letting it idle for a few minutes before shutting it off.
Nowadays, you should allow your engine to cool off if you drove your car from point A to point B on full throttle. Otherwise, there is no need to follow the practice anymore as modern material will easily cope with normal driving loads.