Black Smoke.....power or waste?

I didn't say a V8 couldn't be built to be efficient with today's understanding of torque and a low engine RPM. What I was saying is, the old V8's in trucks weren't built to utilize this theory in the 70's to early 80's.

I don't know the specs on an R730, but I'd bet that it has a long stroke with a small bore dimension.

The older V8s were all big bore with a shorter stroke when compared to a inline 6 cylinder engine in that era. A 3408 has a shorter stroke when compared to a 3406. It isn't dimensional the same bore and stroke, even though they are both 3400 series engines built by CAT. The bore dimensions stayed the same, but the stroke was shorter. This moves the real world working RPM range of the engine higher in the RPM band, which is less efficient. As engine RPM increases the piston dwell time at TDC decreases this gives the slow burning diesel fuel less time to burn completely. Also with a longer stroke engine the cylinder pressures rises at TDC this is why the long stroke engine has a torque advantage over the short stroke engine of the same cubic inch displacement and design.

 

The 903 or do you mean the 9-0-nothing as it was refereed to back in the day.

The engine had a very short stroke compared to the NTC. The bore was the same, but the stroke was 4.75" compared to the NTC at 6.00". All they did was make noise. I think they were used by the military with an automatic transmission to keep them in the working RPM range. The only ones I've ever actually seen in the real world was in a boat, which again is a higher RPM application. I can't even tell you the Hp ratings of these engines, but the 903 does refer to the cubic inch displacement. The NTC, 1693 and 3406 of that era produced much more torque for a smaller cubic inch displacement.

Why do you think the engine failed as a commercial truck engine if it was so good in fuel mileage?

 

My PDI fortified ISX with no egr or dpf makes no smoke

 

It also has a mechanical advantage in that the pressure imposed on the big end journal is further from the central axis of the crank giving it more leverage , thus more rotational torque with the same amount of pressure imposed through the conrod.
The down side is that because of less area on the piston crown surface you need higher pressures to get the same level of pressure imposed through the conrod.
So from a mechanical point there is a trade off.
The burn rate of the fuel seems to be the decider.
With high performance gas engines the bores are often over square with the bore being larger than the stroke.

 

A VT903 was a very strong engine when tuned correctly. A non-turbo 903 was a dog that only produced noise. Every VT903 I drove was getting 5.6-6 mpg when the norm for a small cam Cummins was getting 3.8-4.5.

I owned one VT903 that turned 3300 rpm with 4.44 rears. It would stay with, or out run most any Cat 3406A of the day. I ran back from Chicago with a nice Pete running a 380 Cat that was really embarrased that my first series Road Commode and it's 903 could out run him in speed and out pull him on the hills.

The downfall of the 903 was it had lots of oil leaks, was somewhat heavy, would not hold up as well, had too many moving parts, and finally emissions.

Holly Farms had a fleet of them, and Wyle E Saunders (I think, it was a southern fleet with white trucks) had a fleet of them up until they went out of production. The later 903s were a lower rpm engine called the Formula 903.

 

My apologies mr Haney , I didn't word the original question very well, my question was regarding the egr, the v8's don't have it while the 6 cyl does, in theory the smaller hp 6 cyls should be better on fuel, do you think the egr is soley responsible for this? I just wanted a definitive answer from someone who knows what he's talking about.

That r730 is a 16.5 litre engine and shares the same bore as the 15.6 litre so you are right it's a longer stroke .

And thank you mr Haney for taking the time to respond to my question.

 

Not sure if the trailer's loaded or not- but I laughed myself to sleep last night thinking about a driver doing that burnout on the State scale in California.

Could you IMAGINE the commotion that would cause at a scale house??

I can't stop laughing while thinking about it..!

 

I don't know anything about your emission regulations to be able to answer this question.

As hp and the cubic inch displacement increases the regulation may change to the point that the EGR system isn't needed to comply with the emission standard for that hp size engine

I don't know anything about these two engines and the manufacturer may have used a totally different fuel delivery system between them, along with an after treatment of the exhaust to comply without having to resort the EGR in one while not in the other.

 

I guessing it was by the uphill takeoff and all, but that is just sick power to smoke all those drives that bad with all that weight, kinda embarasses muscle cars! Simply amazing either way though. If you did that in Cali they'd all have heart attacks, heck you could probably be fined for farting out there!

 

Ahh no problem, thanks for taking the time, gentleman!