much ado about CETANE NUMBER..

**rsnald** · October 8th, 2003 03:01 PM

got this info from an article I downloaded while continuing my research on biodiesel... Just want to share this w/ all you DC.org comrades

to quote the article in verbatim...

"...both too high and too low CN can cause operational problems (in case of too high CN, combustion can occur before the fuel and air are properly mixed, resulting in incomplete combustion and smoke; in case of too low CN, engine roughness, misfiring, higher air temperatures, slower engine warm-up and also incomplete combustion occur), most engine manufacturers designate a range of required CN for their engines. In most cases, this range is around CN 40-50. "
- tech publication by Gerhard Knothe, Robert O. Dunn and Marvin O. Bagby Oil Chemical Research, National Center for Agricultural Utilization Research, Agricultural Research Service, U.S.

so, as Doc Diesel and I have been trying to point out, going very high CN (cetane number) does not necessarily mean better engine performance. what this essentially says is, kung ano yung Cetane rating na recommended ng engine manufacturer for your ride, that's the best fuel for you. Fuel ignition within the engine will depend on the design of your fuel injection system.

Hope this helps.

**turk182** · October 8th, 2003 06:19 PM

according to my Patrol GU owner's manual, the recommended diesel fuel for the ZD30DDTi is at least 50 centane. That means I really have to use Pure Diesel (CN 52-53) with it.

**jackaroo** · October 8th, 2003 09:21 PM

Agree that the best cetane rating to use is what the engine was designed for- just like in gas engines. What i don't get is why high cetane can be bad for the engine?
quote "....in case of too high CN, combustion can occur before the fuel and air are properly mixed, resulting in incomplete combustion and smoke" ...end quote
If we are to compare cetane to octane, the higher octane number means that the fuel will not ignite prematurely. The quote above is talking about premature detonation which is contrary to high octane/cetane behavior.
You get premature detonation if the timing is to advanced for the fuel rating but there's no harm if you use a higher rating than needed, it's just that you spent more money but don't get any additional power. A higher cetane would mean the fuel has the capacity to resist early detonation, IMO.