While we are at it.
Excess heat will damage the engine. This can happen in a general sort of way, by the whole engine becoming too hot; and it can happen locally, by a specific part in the engine becoming too hot.
When the whole engine becomes too hot, the water boils, and boiling water does a lousy job of transferring heat, so now the engine rapidly becomes even hotter, and maybe the head gasket fails, and the head itself can become twisted (warped), and Dog knows what. In the 1970s, I saw a set of piston rings from a car engine that could be twisted like bailing wire. The man had kept driving until the car would. Not. Go. Another. Inch. The heat wiped out the factory heat treatment (hardening) of the piston rings.
Then there is local. What goes first is usually the pistons, which are made of aluminum, which melts at a lower temperature than steel. Where might we have aluminum-melting temperature in an engine? In the combustion chamber. The very flame of the combusting fuel.
How would that happen? Essentially, by burning too much fuel.
That's why we have an instrument called a pyrometer. Pyro means heat or flame or some such. The "official" word for fireworks is pyrotechnics.
The pyrometer measures the temperature of the exhaust fumes IMMEDIATELY after those fumes exit from the combustion chamber. That's as close as we can get. So far, nobody has invented a sensor that can live thru the actual fire in the chamber. Something like 1,200 degrees Fahrenheit in the exhaust manifold corresponds to a safe temperature on top of the pistons.
There is a second spot we can install the sensor for the pyrometer, and that spot is immediately after the turbocharger. Why would we do that, and get a less accurate reading? It's about what is practical.
When I installed a pyrometer in Millicent, I needed to drill a hole for the sensor.
Ideally, I would drill the hole in the exhaust manifold and get the closest reading. But that means that the chips from the drilling would be upstream from the turbocharger, and would ENTER THE TURBO. Turbos are rather finicky about swallowing metal chips, and turbos are expensive.
I could have removed the turbo, and reinstalled it after drilling and cleaning, but that opens the door to all the Oooops Stuff that can happen.
So I drilled the hole in the pipe downstream from the turbo.
The whole point of the turbo is to capture and make use of the energy in the exhaust fumes. So those fumes are cooler when they come out of the turbo. I even telephoned Isspro, the manufacturer of the pyrometer, for advice. Word was, to subtract 250 or 300 degrees from the 1,200. So I use 900 as the max.
When Millicent climbs a hill, I watch the pyrometer. When it hits 900, I either lift my foot, or downshift. Typically, after lifting my foot, I soon need to downshift! The good news is, that higher RPMs allow "more foot".
Why? Well... as I believe I perhaps understand it... more RPM means more air per second, and... while we are now burning more fuel with the additional air, that more air also has a cooling effect as it enters the combustion chamber.
Or something like that.
I have read that a larger turbocharger may also help -- and can contribute to making more power at the same time. But we have now exited my realm of actual knowledge.
Except that... I can mention that there are "heavy duty" pistons with a thin layer of steel on top. This is very desirable. Such pistons are available for the IH DT466, and that's all I know about that.
Annnnd.... I was supposed to be doing something else this evening. Which I will now do.
