I am a truck guy. I have been driving trucks ever since I’ve learned how to drive--from Pajeros to Stradas to Hilux to D-Max to Kia kc2700 to various surplus dropsides. I use vehicles for work; I haul people and things from Cebu City to the provinces. I make around 300km a week of truck driving.
Last May, my best friend finally decided upon my constant lobbying for him to buy a diesel Mitsubishi Montero Sport. You see, I've always believed a diesel-fed vehicle is superior to a gasoline-powered one. Anyway, since I have always projected myself as a diesel know-it-all, my friend approached me last month with a question. Apparently, he stumbled upon some fellow who offered to install a turbo delay timer in his vehicle. I said no, and explained who needs a turbo delay timer and who does not. The last time I saw a truck with one was nine years ago somewhere in Nevada on an F350 with a 6.0-liter diesel powerstroke hauling 35-foot speedboats on a fifth wheel across states. I told my friend that normal driving conditions even at 35 degrees of Philippine weather will never bring your engine over 800 degrees. Those guys hauling boats, motorhomes and other over-a-ton equipment would make their turbos run red hot. I have hauled close-to-a-ton things across Region 7 with a 1992 turbocharged Pajero without a problem.
Because he is spoiled rich, he bought one anyway. Recently, my uncle did the same. Just last night my other friend also had one installed!
It seems I am losing my touch. No one is considering what I say. I need someone other than me to clarify the real truth about turbo delay timers. I really do feel that the guys selling these are just fantastic at marketing and nothing else.
All the best,
In the past when turbochargers were still relatively new in automobiles and cooling systems were not as efficient as they are today, most drivers (particularly of high-performance cars) with turbocharged vehicles usually let their rides run on at idle for a minute or two to cool down the engine oil to normal operating temperatures.
This was to done to indirectly prolong the life of the turbo itself as, back then lubricants weren't as good as they are now and shutting down the engines with the engines "hot" would "cook" the engine oil that remained on the turbocharger's moving parts, which needed lubrication (oil). Consequently, the residue of the "burnt" oil would slowly grind away the turbocharger's center shaft and seals, leading the way to premature turbocharger repair or replacement among other things.
Somewhere between then and now, turbo timers were developed to help avoid that from happening in case the driver forgot and shut off the engine while having just driven the vehicle under full load or hard enough to elevate the exhaust gas temperatures. As you already implied, anything under 800 degrees is nothing to worry about. You are also correct that under most urban or highway driving conditions that the EGTs won't usually go that high.
Since that time a number of things have changed. Now, you've got synthetic oils that can handle higher temperatures better than ever. Engines are also more efficient in several aspects including heat management. There are also other developments, which nowadays further reduce the need for turbo timers.
Here's something to think about. To get the turbo to the state that would require a cool-down period would mean that the vehicles would need to be driven at full load for an extended period of time. This entails the driver to be driving at full throttle and stay at high rpms for the duration of his journey.
That would not be normal for most of the driving that many drivers will ever subject their vehicles to. Even the most spirited of drivers would ease of the throttle just when they're about to arrive at their destination (say as you turn into the corner of the street where you're going to), that brief 30 seconds or so that you ease off will usually be enough to cool down the turbocharger and consequently, the oil temperatures, that you can just shut off your engine when you've arrived and are ready to get out of your car.
Having said all that, some people still want to have the extra "insurance" of having a delay or turbo timer fitted for "peace of mind."
P.S. I don't have a turbo timer fitted to my turbo car either.