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Old 11-07-2018, 06:04 PM   #1
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Cummins Diesel Performance Upgrade

Question for those out there that have experience with Diesel engines. I have a 360 HP Cummins in a 40 ft Class A motorhome. It has no power to get up and go as well as terrible mileage. (about 7 miles to gallon full or empty. I have been told that PDI (Performance Diesel) is the only service which can increase power and subsequently improve mileage by tuning up the performance computers. Cost is approx. $2500. I have no idea if my leg is getting pulled here.
Does anyone have any experience with this type of tuning and is this worth the money?
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Old 11-07-2018, 06:11 PM   #2
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7 - 8 mpg is about average for a DP. I used 7.5 when figuring fuel cost on our '02 DSDP 40' with 350 ISC and Banks kit. Very few people realize any major fuel mileage increase with a tuner.
Present rig is running 7.6 mpg but it's heavy and has more HP than most.
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Old 11-07-2018, 06:13 PM   #3
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Don't know what year your rig is... I would take it to Cummins and have them hook it up to their diagnostics to see if there is an issue before I did anything else... IMO
7 MPG is about par...., I got 7 on my Monaco 40 with a 400HP, and get 7 on my 600HP current rig... Economy is driven by how aggressive you are as a driver... I am very aggressive and like to "drive it like I stole it".... LOL
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Old 11-07-2018, 06:15 PM   #4
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I'm suspect you don't have a real power issue. Low or leaking turbo boost, fuel filters or fuel supply restriction, air filter restricted etc....or a number of other things that cause low power.

Have you taken it to a good shop and had it looked at for low power?

I have a 1999 40ft American Eagle ISC Cummins 350hp that will run with most everything on interstate. I don't baby it.

Anyrate, before adding some magic "tuner" bandaid, I'd be sure all engine components are at 100%

Be awful to burn 2500 bucks and still have a low power issue due to a boost leak
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Old 11-07-2018, 06:16 PM   #5
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Possible adjustments to the valves? That does need to be done based on age and mileage. How many miles on it?
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Old 11-07-2018, 06:30 PM   #6
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Quote:
Originally Posted by Sparqee1 View Post
Question for those out there that have experience with Diesel engines. I have a 360 HP Cummins in a 40 ft Class A motorhome. It has no power to get up and go as well as terrible mileage. (about 7 miles to gallon full or empty. I have been told that PDI (Performance Diesel) is the only service which can increase power and subsequently improve mileage by tuning up the performance computers. Cost is approx. $2500. I have no idea if my leg is getting pulled here.
Does anyone have any experience with this type of tuning and is this worth the money?
I have the same motor and a 36 ft. I get high 7's for mpg.

Cummins has been around for years - you'd think by now that they would have adopted anything that would give more power PLUS better mileage.

Yes, your leg is being pulled.

Most "super tune" "whiizz-bang addon" "Hyperflow coriolis venturi tornado boosters" are all snake oil.

You can't get both more power and better mileage while keeping street legal.

There are ways to flash your ECM on the motor and transmission so everything shifts more aggressively - and several of those companies claim you can get better mileage - but, the way they do that is to give the operator a gauge so they can monitor their DRIVING HABITS and learn to drive smarter.

I think we all bought the wrong rigs if we really wanted a drag racer.

And now for everyone to reply with..."but, I {did something magic}"
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Old 11-07-2018, 06:39 PM   #7
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An ISB 6.7 L Cummins pushing a 40 ft motorhome around is asking a lot from a little diesel found in pickup trucks. If it is pre-08, you can have a Banks system installed that will increase the HP by 40 or so and boost torque to around 1000 lb/ft.

My suggestion, learn to drive it within its capabilities. You can easily cruise at 62 mph on flat ground and get around 7.5 to 8.5 mpg. When you hit the hills, you will be in the right lane enjoying the scenery slowly passing by.
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Old 11-07-2018, 07:01 PM   #8
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Get up and go?!?! Can you out run a Greyhound Bus? I mean, you got a 40' bus, so....


7mpg? That's half the story. What speed? If you're getting 7mpg at 55 mph, you may have a problem. If you're getting 7mpg at 85mpg, slow the heck down, but your milage is good! And where did you get 7 mpg, from your computer or by doing the math. NEWSFLASH: Computers lie.


A guy who sells hammers only sees nails, your PDI buddy will obviously say "Buy my stuff and your get better power and performance which I will NOT guarantee in any way."


I get 8-8.5 outta my 40' DP with a 350hp CAT C7 at about 65mph.
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Old 11-07-2018, 07:08 PM   #9
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Quote:
Originally Posted by Sparqee1 View Post
Question for those out there that have experience with Diesel engines. I have a 360 HP Cummins in a 40 ft Class A motorhome. It has no power to get up and go as well as terrible mileage. (about 7 miles to gallon full or empty. I have been told that PDI (Performance Diesel) is the only service which can increase power and subsequently improve mileage by tuning up the performance computers. Cost is approx. $2500. I have no idea if my leg is getting pulled here.
Does anyone have any experience with this type of tuning and is this worth the money?
That is an accurate statement. I have a PDI tune on my Kenworth. My mileage increased by 20% and power was night/day difference. Big block CAT engine.
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Old 11-07-2018, 07:09 PM   #10
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I am a true believer in PDI performance products. They do work and they work well.
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Old 11-07-2018, 07:15 PM   #11
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Depends on your engine, if the 6.7 cummins, many options. Go to supermarket and buy "Diesel Power Magazine" or any other of the diesel truck mags for suggestions on increasing power and mileage. These guys are highly regarded by the Cummins guys. https://www.bankspowerproducts.com/B...mmins-s/35.htm
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Old 11-07-2018, 07:47 PM   #12
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Our family recently acquired a 2018 Newmar Dutch Star with the 8.9 Cummins, 450 hp, 1250 torque...of course it has all the emissions bullcrap on it. While under the remainder of warranty I will leave it a factory specs and settings....but if the emissions crap starts raising hell after the warranty is out....I will not hesitate to put a PDI tune on her and get rid of all that crap. And let her roll!!
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Old 11-08-2018, 12:23 PM   #13
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Quote:
Originally Posted by Sparqee1 View Post
Question for those out there that have experience with Diesel engines. I have a 360 HP Cummins in a 40 ft Class A motorhome. It has no power to get up and go as well as terrible mileage. (about 7 miles to gallon full or empty. I have been told that PDI (Performance Diesel) is the only service which can increase power and subsequently improve mileage by tuning up the performance computers. Cost is approx. $2500. I have no idea if my leg is getting pulled here.
Does anyone have any experience with this type of tuning and is this worth the money?

Hi ! Welcome to IRV2! We're sure glad you joined the gang!

Can't help with the questions but noticed that you are kinda new on IRV2 and wanted to say hello! Have fun and keep her between the ditches!

Good luck, happy trails, and God bless!
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Old 11-08-2018, 03:08 PM   #14
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I am a true believer in PDI performance products. They do work and they work well.
I totally agree.

.....But only on a engine that has no other mechanical or electrical power issues. Just adding a tuner will not fix a engine that was already down on power.
Hopefully OP will chime back in and fill in the blanks.
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