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Topic: 1990"s 8.3 Cummins 300hp and 325 hp (Read 2179 times) previous topic - next topic

1990"s 8.3 Cummins 300hp and 325 hp

I noticed the same 8,3 Cummins was rated at 300hp in a 34 or 36 foot FT and 325hp in the 40 foot FT model. Anyone know how they get the extra 25 hp on these mechanical pumps and engines in the day
1996 U295-36, Cummins 300hp, 8.3. Build number 4864. Vin number 1F97D536XTNO54271. Purchased October 31, 2019.

Re: 1990"s 8.3 Cummins 300hp and 325 hp

Reply #1 –
I think that 1997 C8.3 engines are all rated 325 hp, no matter what the length. Assume the hp increase was from Cummins spec'ing the engines with stepped up fuel & turbo adjustments. Same engine and components.

Both fuel & turbo can be adjusted for increased boost pressures but is easy to create problems.

Many years ago, Bernd carefully increased our boost and fuel. Our max boost is in low 30psi and coolant & EGT never overheats. Good idea to install boost & EGT gauges before making adjustments.

Re: 1990"s 8.3 Cummins 300hp and 325 hp

Reply #2 –
Cummins labeled the 325hp model as a "fire truck and RV" application. It apparently was primarily available in 1997. In other words, it was a special application  My 98 has a late 97 engine with 325hp and 915 foot pounds of torque. In tractors and other agricultural applications it was sometimes rated at 250hp. You will see the current Cummins 6.7 engine rated down for heavy duty applications. 

I looked at a 96 U270 and it was 315hp. Have no idea what they did to up the ante from 300-315-325.

1998 36 foot U270 Build No. 5328 WTFE, 900 watts solar, Victron controller, B2B, bat monitor, 600 AMPH lithium with 2018 Chevy Colorado toad, SKP #110239, Motorcade #17781, 2021 Escape 17B for when Coach is broken down and campsites are too small, retired and full-timer since Dec. 2020. Part of RV family since 1963.

Re: 1990"s 8.3 Cummins 300hp and 325 hp

Reply #3 –
Quote from: Realmccoy –
Have no idea what they did to up the ante from 300-315-325.
Printed a different decal and stuck it on the engine?

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: 1990"s 8.3 Cummins 300hp and 325 hp

Reply #4 –
Quote from: Chuck & Jeannie –
Printed a different decal and stuck it on the engine?



More likely stronger connecting rods, and maybe a little more cooling oil to the piston crowns. Then more fuel and boost.

Of course, if it was Detroit, you'd put a badge on the side of the car proclaiming 442 with no explanation, unless you asked: Four Barrel, Four Speed, and Dual Traction (Positraction rear axle.).
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.

Re: 1990"s 8.3 Cummins 300hp and 325 hp

Reply #5 –
Not much of a trick increasing the 8.3's hp, just add fuel and the HP along with the boost will go up. This increase is ultra easy and only a small amount of the potential max HP the engine is capable of.

I remember when Detroit's 6V-92TA was limited to 300 hp in the early U300s because of the torque limit of the transmission. When the later 746 transmission was fitted to the U300, a simple firmware update in the ECU raised it to 350. In marine use, another firmware update brought the same engine up to 630 hp but it does not have to pass smog on boats. The same can be seen on pickup trucks today with an electronic box adding fuel until they are "rolling coal" and producing huge HP numbers but also a huge amount of black smoke.

 Not quite the same for mechanical engines as the duration of injection cannot be easily changed so larger injectors must be fitted along with a pump profile change including a possible turbo mapping change. On some pumps, an external adjustment will also add fuel.

The trick is doing it so it will smog. As one of the injection pump manufacturers, Bosch spends a lot of time calibrating the pump and designing injectors so they will put out the HP without the smoke. I remember the U.S. smog injector nozzles with a tiny passage all the way through the pintle in an effort to lower emissions. It's always a challenge to get a very fine spray out of the mechanical injector with only about 3000 psi compared to 25,000 psi in a high pressure common rail injection system where the  injection may be up to 5 different stages in 1 millisecond.

diesel smog injector pintle - Google Search

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: 1990"s 8.3 Cummins 300hp and 325 hp

Reply #6 –
Manufacturers of motor vehicles (of all types) are influenced by many factors when "rating" the power of engines.  Often the advertising department ($$$) has more control than the engineers.  "Horsepower Sells" has always been true.  If embellishing the HP rating sells more engines, then that is strong incentive to "cheat" on the numbers.  To further confuse the issue, they rate HP at different points - crankshaft with a "bare" engine, crankshaft with all accessories, and rear wheel power.  They fiddle with the atmospheric "conditions" under which power is rated.  They specify different fuel formulas to "adjust" power rating.  Is the engine stock off the assembly line, or a hand built blueprinted example?

How many average motorhome owners are able to perceive the actual performance difference between 815 HP and 825 HP?  Not many, I would surmise.  But the bigger number sure looks better in the sales brochure, and sounds better when bragging to your friends around the campfire.

It's all a big game...and we are merely players.

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"
 

Re: 1990"s 8.3 Cummins 300hp and 325 hp

Reply #7 –
Same thing with the ATV and Side by Side makers,the Honda's are actually 420's but are called 500's,the Razors are in the low
900's but are called 1000's.(talking about CC'S.)
96 U270 BUILD 4810
85 380SL
Drummonds TN.