n4rf wrote: ↑
Thu May 18, 2017 7:15 am
godlameroso wrote: ↑
Tue May 16, 2017 6:23 pm
etusch wrote: ↑
Tue May 16, 2017 4:10 pm
There must be standart oil and fuel
From what I can gather, there is no restrictions on the oil type, there are restrictions on the fuel composition, however there is still development in the fuel. I'm curious as to what they can develop in the fuel, how do they tailor it to the combustion concept? Do they use lower or higher octane, or special anti-knock additives, or what?
It's not that simple, really. The big problem with most turbocharged engines, especially the current F1 engines, is not knocking but rather pre-ignition. The difference being that knocking occurs after the spark in the still unburned zones of the cylinder, in general after TDC, and pre-ignition occurs before the spark and before TDC. Pre-ignition is usually a much more serious problem than knocking, which can be tolerated to quite a degree, depending on the needed engine-life and piston material.
Pre-ignition is as of yet not completely understood. The process itself is much better understood than the influence of different fuel characteristics. There's some serious research going on in trying to identify something like the octane number for characterising the pre-ignition tendency of different fuels. As of now, this research has not come to a proper conclusion. This also fits to how the fuel development seems to happen at the teams. It appears to be a very iterative process, where a lot of stuff is tried. If one fuel component helps with pre-ignition, a lot of tests are run with this component. However, it is my understanding, that no one knows a priori, which component will help to what extent (general tendencies can be observed, but nothing major).
This is actually a field where there might be a direct transfer from F1 to road cars, because pre-ignition is quite relevant for highly boosted gasoline engines on the road as well. Hence the research into pre-ignition behaviour of different fuel types.
Pre-ignition in Forced induction DI cars is bit different than normal NA engines. Sometimes the worst instances of it occur at surprisingly low rpms. In road cars, the phenomenon is calls LSPI (low speed pre ignition) and is a relatively mundane 2.0 Liter for a family sedan, I have seen LSPI create in cylinder pressures as high as 3x4 times pmax (max cylinder combustion pressures) and in some cases, much higher! 30 to 50MPa is not uncommon. Under these severe conditions, connecting rods buckle, piston ring lands are obliterated, piston skirts crack, oil films on bearing are squished away completely. Basically, things break, catastrophically.
Now that I think about it....... I wonder if Alonso's engine blowing up on the 3rd turn of practice, while he was still warming up, was a result of this... kinda lugging around,, not hammering on it,,, but holes out the side of the block... as I think about it, almost text-book LSPI failure???
As for causes, if i recall correctly, in road car engines, we had seen strong correlations with LSPI and oil particles getting past the rings as a source of ignition. I few hot tiny drops of oil making their way into the combustion chamber caused the autoignition, and BOOM!! test stopped, engine destroyed.....