HP question on a Cummins 8.3

[LongWeekends]

So our DP sold and we are shopping for our "upgrade". Engine size is one of the things we want to improve. I see the following in an ad:

"THE 8.3 LITER CUMMINS 360 HP ENGINE HAS BEEN RE-RATED TO 425 HP AND GETS 2 MPG BETTER FUEL ECONOMY. "

Can anyone shed some light on this? What is done to magically change the HP other than some creative typing?

As always, thanks in advance.

[LongWeekends]

DSDP Don wrote:
"LongWeekends".....You sold a 2004. If you just buy a year newer, Monaco started putting the ISL 400 in the Diplomat/Endeavor line, and up, in 2005. I wouldn't mess with chipping the 8.3. I'm guessing you saw those numbers in a another forum, possibly "Mr_D" in his old Newmar. Those numbers were NOT from a dyno.

Thanks for the feedback! I saw it in the ad itself, not a forum. It didn't sound right to me so I came here to confirm it. 🙂

[DSDP_Don]

"LongWeekends".....You sold a 2004. If you just buy a year newer, Monaco started putting the ISL 400 in the Diplomat/Endeavor line, and up, in 2005. I wouldn't mess with chipping the 8.3. I'm guessing you saw those numbers in a another forum, possibly "Mr_D" in his old Newmar. Those numbers were NOT from a dyno.

[supercub]

JetAonly wrote:
FWIW we have an 350 HP 8.3 in our Dynasty. We weigh 33k down the road. Without towed my 20k mpg was~8.3 with a 1500 Silverado 4x4 and 500 lb motorcycle in the bed over 10k mile we averaged 7.2. Plenty of HP with out towed. With towed it is adequate. Over Eisenhower tunnel at 11k ft we were about 30 mph. We are about 39k with towed.

The 8.3 was offered in versions to 380 HP from the factory. The transmission is the limiter on most of the 8.3 drive trains. We have the Allison 3066 which is rated to 350 HP and 1050 TQ. The ISL is an 8.3 block with a bigger stroke. It is also a fine engine. The ISL has some years with a bad wrist pin. There is a list of ESN's on this site.o

On my Revolution at around a CGW of 34,000lbs I've average 7.8 mpg in the 14,000 miles I've driven it, all in the western states. It will pull a 6% grade, like the Grapevine north of Los Angeles at +/-45mph and that's without the pedal massed to the metal. I usually back off just a little from full power when pulling a grade, I typically set the cruz for around 57mph.

[LongWeekends]

Thanks for the feedback!

[JetAonly]

FWIW we have an 350 HP 8.3 in our Dynasty. We weigh 33k down the road. Without towed my 20k mpg was~8.3 with a 1500 Silverado 4x4 and 500 lb motorcycle in the bed over 10k mile we averaged 7.2. Plenty of HP with out towed. With towed it is adequate. Over Eisenhower tunnel at 11k ft we were about 30 mph. We are about 39k with towed.

The 8.3 was offered in versions to 380 HP from the factory. The transmission is the limiter on most of the 8.3 drive trains. We have the Allison 3066 which is rated to 350 HP and 1050 TQ. The ISL is an 8.3 block with a bigger stroke. It is also a fine engine. The ISL has some years with a bad wrist pin. There is a list of ESN's on this site.o

[WILDEBILL308]

Ivylog wrote:
If you want 425 HP, look for the 8.9L ISL. Without changing the injectors and the turbo a 8.3 is already pushing it's max at 360. In PU's much of the mileage increase by a chip is done by increasing the tire size in the computer... making it LOOK like you've gone more miles than actual.

Where do you come up with this ssstuf. First I have never seen a 8.9 in a pick up. #2 Who would be so stupid not to check their mileage by using mile marker or GPS.
Bill

[Blaster_Man]

gswcgi wrote:
I've had 3 Cummins, a CAT and a MB diesel. If the manufacturers wanted more HP or torque or whatever they would have designed it that way. I personally would never buy a DP which the owner messed with the design!!! Just my opinion.

I agree, I've had a Duramax, a Yanmar (in a boat), a Cummins and a Detroit Diesel. They work fine as they come off the assembly line, I would not change one, or buy one that had been altered.

[gswcgi]

I've had 3 Cummins, a CAT and a MB diesel. If the manufacturers wanted more HP or torque or whatever they would have designed it that way. I personally would never buy a DP which the owner messed with the design!!! Just my opinion.

[Ivylog]

Sorry, but the 8.3 is not known as a million mile engine at 360 HP... Closer to 600K. If you could get 450 with just a chip it would still last long enough for most.

[Tom_Barb]

prstlk wrote:
Chipped rigs can also be worth less on trade in or outright sale. Some of us have concerns about reliability. I'd take a box of donuts to your local cummins dealer and ask some questions 360 to 425....thats sounds to good be true.

When you have any engine that is well known to go way past 1 million miles, you can turn the horse power up, and it will still last 500K. ever see a coach go past 500K?

[prstlk]

Chipped rigs can also be worth less on trade in or outright sale. Some of us have concerns about reliability. I'd take a box of donuts to your local cummins dealer and ask some questions 360 to 425....thats sounds to good be true.

[barmcd]

I don't think an 8.3 can reliably put out 425 hp. That doesn't mean this particular engine might be unreliable. It might not be putting out 425 hp.

[tinkerer]

One thing to remember when you do anything to increase the hp of your motorhome you will increase the heat the engine produces and if the radiator remains the same size you could overheat your engine which can be detrimental.

[sch911]

Ivylog wrote:
If you want 425 HP, look for the 8.9L ISL.

Another vote for the ISL. Ours is rated per factory specs at 400HP, but can be chipped easily to 450HP.