Diesel fuel. What about it? Well as some of you know we build engines for FIA European truck racing and as for this year we have to run on HVO fuel only so what are the differences and consequences?
Ok lest start with the basics. Normal diesel fuel as a density of about 841,8 Kg/m3,15g HVO has 780,8 Kg/m3,15g.
Now only the fun part. What energy dos it carry? Normal diesel has about 42,86 MJ/kg and HVO has 43,45 MJ/kg so that more energy so that always better? Well your not injecting MJ/kg but MJ/litter so as HVO has less Weight you need more fuel for the same Weight so where do we end up with?
Normal diesel has about 36,08 MJ/litter and HVO 33,91 MJ/litter so now we are down more than 6% on power running HVO injecting the same fuel quantity.
So 6% down on power. Easy fix you think. Well yes on some engines we build we can @ 6% more fuel but on most engines the fuelpump runs on 95% capacity also to reduce power take off losses. Simple a bigger pump needs more power from the engine to run.
Now something you never read about on diesel fuel. Diesel can be compressed more than you think. 15% for normal diesel @ 2000Bar is normal due to impurity of diesel. So if you compress normal diesel @ 841,8 Kg/m3 with 15% you get 968,07 Kg/m3.
HVO and even GTL diesel fuel is more pure so it will compress less so estimation is in total we will lose 2% engine power running HVO running the same Lambda numbers on a modern last generation diesel engine as these are build to burn old fashion crappy diesel fuel with a lower cetane number. So how come? Well hi quality of injection makes smaller diesel droplets easier and faster cleaner combustion. Also if we run GTL we get more EGT temp on the exhaust indicating less engine efficiency as well so GTL or HVO dos not help with a hi cetane number that will improve faster easy combustion on older diesel engines.
So next question could be what will happen to combustion pressure running HVO it seems to burn faster? I expect that combustion pressure build up will not chance a lot as long as your not increasing fuel pressure to shorten duration on injection giving more energy per time frame and faster combustion pressure increase. If this is what you want better retard start of injection a bit depending on
CR of your engine not to hurt your engine.
So we have to run HVO fuel on the race engines and we will get the data in on performance so maybe we can run lower lambda numbers maybe gaining some power even on low inlet manifold pressure. Also the game is on building some hi efficient
CR fuel pump for max engine power and torque.
2e Engine back from the machine shop.