PDA

View Full Version : Detroit Diesel 8V92 Discussion


GSrdr
09-20-2010, 01:57 PM
This is an interesting, if lengthy, discussion regarding the two-stroke 6V92 & 8V92 engines. It may be focused on marine applications but remains appropriate for the use in Newells too.

http://www.yachtsurvey.com/comparing_diesel_types.htm

Some points I took from the article are as follows:

DD engine is left with certain advantages such as more immediate power delivery and higher power at lower speeds. This is one of the things that has made these engines more popular with the commercial boat industry. The four cycle engine has to throttle up to a higher RPM before a similar amount of power is delivered.

The fuel systems are both very different and yet similar. The DD has no fuel injector pump, but rather each injector is itís own fuel pump. An injection pump is sort of like a small engine with 6 or 8 cylinders and pistons that pump and supply fuel to the injector which, in a four cycle engine is nothing more than a spray nozzle like on the end of a garden hose, albeit a bit more refined. On a DD engine, each injector is operated by the dual underhead camshafts that are immediately below the head.

A Detroit Diesel uses its fuel as part of the cooling system to the cylinder head and injector. It returns a LOT of fuel back to the tank, and it is very hot. Thus, a DD has a fuel oil cooler, whereas the four cycle does not. With Detroits, you have to worry about the state of fuel return to the tank when, for example, you decide to run off of one tank only. Detroits for the most part are self-priming fuel system. Woe to the captain who gets air into the fuel system of a four cycle engine system. You got to get that air out, or it will not run.

The one critical feature should be the hp/displacement ratio of not more than 110% or so.

In the hot rod class, I'll take the 6V92 at less than 550 hp while being prepared to follow the maintenance guide religiously.

The 8V92 would fall into the same category, except that the modifiers try to squeeze too much power out of these blocks. A good deal at 735 hp and below. A poor choice above that.

fulltiming
09-20-2010, 02:14 PM
Interesting read. One of the downfalls of the V92's is the large amount of heat they generate in over the road vehicles and the rear mount radiators used by Newell until the Series 60. In marine applications, you have a tremendous volume (the lake or ocean) of water available to cool the engine. The radiator gives you 20 gallons of cooling capacity through a radiator that can easily become covered with oil and grim being blown through by the fan. Cooling is the horsepower limiting factor on coaches. Put a 700 hp v92 in a Newell and you will cook the engine on the first long hill as there is just not an adequate amount of cooling available. Power = heat. More power, more heat.

Secondly, the engine on a coach is very easy to lug whereas not so much on a boat (although you certainly don't want to idle around all day every day in a v92 powered boat unless you like engine damage.

Keep the radiator clean and rodded out, don't lug the engine, change out the radiator and heater hoses on an old coach, watch your temperature gauge, take care of any leaking gaskets so it doesn't drip oil and you should have a great engine in a great coach.