Ok, I know what Octane means and does for a gasser. What does Cetane do for the diesels?

 

the exact same thing

the higher the cetane rateing the more energy the fuel has. #2 has a higher cetane rateing than #1, yet #1's cloud point is around -20F yet #2's cloud point is around 10-0F. in the northern states alot of fuel stations will mix #1 with #2 to lower the cloud point and keep the fuel from jelling.

all this mixing #1's and #2's sounds gross

 

I thought it was the opposite of octane rating???

i.e. higher octane rating has a decreased ignitability point for gas and higher cetane has an increased ignitability point for diesel.

The higher the octane, the more compression or boost the engine can be run at and not detonate prematurely.

Diesel doesn't have that problem, so the cetane rating allows it to ignite easier.

I've been wrong before, I'll surely be wrong again.

 

Diesels can detonate prematurely, if the timeing is set too high

Rich, with gassers the higher the octane the slower and more evenly the fuel burns, and yes, it takes a bit more spark energy to detonate 93 octane as opposed to 87. and with anything the harder it is to ignite, or the more energy you have to put in to start the reaction, the more energy you will get from the resulting reaction. this is basic chemestry, with any fuel you want it to burn slow and even. if you get an instant burn you have alot of unburned fuel that is going out the tail pipe.

 

Man, I was just trying to keep it simple, but Mr Drew took us to school.

That's always one of the things you have to take into consideration when Turbo or Supercharging a gasser. When I dropped the supercharger on my Chebie 5.3, I always had to run premium gas with octane booster to keep the engine light from coming on. That was with a boost-a-pump and 42 lb injectors. Running anything more than 8 to 1 compression with a blower on a gasser makes pre-det kinda inevitable without seriously retarding the timing. Without a custom tune, it's an even bigger PITA.

I eventually sent my Superchips in with all the specs on the truck to get it set up right. Ran like a raped ape after that.

But yeah, compression + low octane gas does not equal a good time.

 

Drew, If I am reading this and understanding it, You are saying the engines efficiency is greater @ 87 octane vs. 91 octane ? If that is what you are saying than would it be safe to say the same about cetane? And if the ansewer to that is yes, Than the next ? would be for me is would it be better to run the cetane rating as is for better MPG?

 

no, the engine is more efficient with higher octane/cetane. the fuel burns more evenly produceing more energy throughout the pwoer stroke instead of a huge increase in pressure and most of the energy bypassing the rings in some cases.

you get more power and more mileage when the fuel burns slower and more efficiently. 93 burns more efficiently than 87, and the same with #2 when you add Power Service or anything that increases cetane levels.

Higher cetane rateings works the same way as higher Octane levels.

 

OOOOOOOH, I was back *** words[&:], Thanks for the explanation........