So 100 cetane rating would not hurt with ignition timing controlled engine- I am living in db2 world. Sorry.
And with modern diesels that are di, it still is ok for the new engines.
I will post a video from Bell Performance that sells cetane booster - so they want to sell it and won’t talk about the rare issues that can occur.
How is too high cetane bad for idi with alcohol added fuels? To early detonation in the precup of cetane before full compression is reached. Imagine piston coming up and at 14:1 ratio(really pressures are key but this is easier to explain) - the actual cetane in the fuel ignites. Then as it burns the heavy long chain of the diesel hasn’t lit but now the alcohols ignite and burn as the piston continues up as you get into 18:1 pressures. Finally at the top of the stroke the actual diesel is now burning.
Yes you will get a more complete burn of the fuel in the cylinder so less emissions and less visible smoke. But this burn just occurred several degress earlier in the cycle.
With modern diesels the computer reads the O2, compensates timing, and life is happy.
Does the ds4 get it’s timing retarded by too much O2? If so- great The db2 does not.
Same issue in the idi Ford and Mercedes.
The high cetane simply move the ignition point foreword- aka advancing timing. But also causes flame burn separation. This is a rare issue. It is known best in gasser world in the Hemi engine because the chamber spread is so big. Having the precup has same effect.
So pre ignition is no biggie- a timing bump, right? Why do tractor pulls have a ton more fuel spewing out the stack rolling coal than needed? Heat. All that wasted fuel helps drop egt a lot. On this forum we don’t have the roll-coal climate. But do some reading and you will see one after another person showing lower egt when rolling. Unburned fuel is simply colder than ambient temperature outside. Spraying out an injector it works like an orifice tube in a/c and the pressure differential causes cooling as the fuel absorbs the heat. Then the now heated liquid fuel gets pumped out the exhaust valve and through the turbo taking heat out the tailpipe with it.
Rolling coal in an idi does not lower egt, it raises it. Why? Because you are cooling the precup and stoping the misting of the fuel in the precup when there is too much liquid. Basically the first fuel coming out mists well, but then more liquid fuel sprays on the misted fuel ahead of it and causes it to condense. We need that high sustained heat of the inside of the precup. The way the precup affect the burn of fuel before it burns on the piston top completely alters that event. Same thing with he flame front not burning all the fuel as it goes and leaving nothing behind the flame front. but flashing the fuel in precup and atop piston at same time means you are creating two flame fronts that crash into each other. Light one end of a football field afire and when it is done all will be burned out except maybe little patches. Light both endzones afire and still same grass gets burned. So a complete, even more complete burn occurs. But multiple flame fronts in a cylinder means over heated piston tops.
How did I learn these details? Well, I didn’t just jump from regular diesel to nitro propane without trying middle ground fuel. Wanting to burn all the fuel for every ounce of power while working at an oil/ fuel company where one of the guys in my racing team was a fuel engineer... yeah I learned a bit. Haha.
Yeah if you retard timing a hair- even idi could deal with it.
The funny thing is, more power and cleaner burn the higher the cetane- why is it they mandated ulsd but not cetane a lot higher. I promise you, many tests have been and still are being done. EU requires higher cetane than here in the name of cleaner exhaust. But still only a few points. When they first did it they mandated cetane up at 75. Reasearch why that went away and they are back down at 50 if still convinced no negative effects ever occurs.
Here is a descent description, but remember- he sells the stuff and is not going to talk about some outlayer obscure engine that they don’t even know exists anymore.
