903 Cummins performance - In the Day

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Hi All,
Just to add two bob's worth to the 8/71 VS 903 debate, Mitchell Cotts (pommy merchant bank mob who bought E.D & D. Camerons before they in turn sold out to Lindsay Fox (around mid 70's?), ran KW cab overs with GM 871 and O/D transmissions AND ALSO 903 Cummins with DIRECT transmissions. Forget how many they had of each, but used on both relay, change over as well as (towards the end) running Syd-Adel.

What little I can recall of them was that there really wasn't a great deal of difference in performance, perhaps the 903's were slightly better on fuel at the end of the round trip Syd-Adelaide. 871's running @2100 so probably std 318 H.P. 903's running 2600 for probably std 320 H.P.
Plenty of them around, both Wettenhalls and Eastoes running S2's with 903's, but Camerons/ Mitchell Cotts/ Linfox they only ones I had anything to do with where you could probably do a direct comparison.

Be somebody here who can either correct or add to this, stoke the fire a bit , so to speak!

Cheers.

Well I can't really talk of comparison back in the day but I currently have a 903 in a 75 Kenworth and an 8V71N in a Crusader.

The 903 is set up at 3070 settings, I think 285@2600, the 8V71 has N70 injectors, according to my book this is supposed to produce 333hp at 2300.

The driving experience seems to confirm the figures, the GM feels to go better, make more black smoke and use more fuel.

In regards to 180Wannabee comments on the 8V71 turbo, if a mid 1970's engine then the book says 333@2100 with N70, or 350@2100 with N75 injectors. This is the same power as the N version but at lower revs, I guess they also improve the torque through the range and reduce the smoke.

The book also shows settings for fuel squeezer engines, eg 8V71TT and 8V71TTA, 305HP @ 1900, so perhaps some engines were built to theses specs.

I think Cummins did a similar thing with a 300hp turbo 903.

Paul

hello all i know they dont have a long life span but the 903 american tank specs are out there, 6 to 700 horses aren't they???? cheers whale

I think the military ones are generally about 650 HP, with some special versions at around 750 HP.

I'm also lead to believe Cummins had built several prototypes of a 1000 HP + engine, based on a 903, but along with all the good bits, a lot of the extra power was gained from turning up the engine speed.

This brochure: tinyurl.com/lmqpn3u says the Bradleys are at 600hp, but Cummins has the V903 at 850hp "while still retaining all the inherent reliability of the proven engine design"

Paul

Here is the manual for the US Army V903.

tinyurl.com/mwf9n89

Hope the link works.

Paul

...i'm not 100% on this, but the military spec 903 tank engines were good for well over 3500 revs....

...it's not as though these engines can't take it....they had "emergency" settings...and the last thing you would give a bugger about in the heat of battle would be "long engine life"!! :-*

....what truck manufacturers require is suitable HP along with long engine life, and the piston feet per minute of a military 903 would make sure that they were never going to last an overly great length of time...

ahhhh Defective......me thinks you exaggerate the revs....you mention piston speed per ft/min which is ALWAYS the design parameter limitation.....I don't have my formulas in front of me...(but i will check)...but I believe they were more in the 3,200 rpm limit....
was told one time when visiting the Cummins Tech Centre in Columbus Indiana that the expected life cycle of a tank in battle was something like 4 hrs,so the tank version of the VT903 was designed to last 6hrs!!!...flat out....so if they didn't get zapped in battle they could at least get home!!

The horsepower on those mother's was gained by using very retarded timing on huge lift cams and STC style injectors (as used in 444's) and aftercoolers....coupled with huge capacity sumps and plate style oil coolers,plus a nominal rev increase.......when stripped down a tank engine looks nothing like our road going VT400's.

newto

...aaah well Newto .. i s'pose you gotta throw a bit of bait when you're on a fishin' trip! ....cheers mate