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Old 05-24-2020, 05:50 PM   #1
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400 ISL

Has anyone upgraded their 400ISL for HP and torque, other then a programer??. I have a 2007 400ISL that I want more power out of. Curious what the options are?? Can I get more HP/TORQUE by having the engine built?? Any suggestion?. I think it's a pig in my Monaco 38PDQ. Any suggestions please...and go..
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Old 05-24-2020, 06:30 PM   #2
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If you get your engine model, p/n, and s/n, or whatever numbers they need, than call a Cummins repair center they can tell you about that sort of thing.
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Old 05-26-2020, 08:25 PM   #3
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Quote:
Originally Posted by Scot B. View Post
Has anyone upgraded their 400ISL for HP and torque, other then a programer??. I have a 2007 400ISL that I want more power out of. Curious what the options are?? Can I get more HP/TORQUE by having the engine built?? Any suggestion?. I think it's a pig in my Monaco 38PDQ. Any suggestions please...and go..
I recently had my ISL 9 380 HP uprated to 450 HP by Cummins. For the most part I don't notice any difference as the 380 always seemed adequate going down the road. However, I do notice a difference if I need to accelerate quickly or when climbing a steep/long grade. The $350 I paid to Cummins for the upgrade was well worth it.
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Old 05-28-2020, 10:07 PM   #4
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I have a ISC-350-CAPS and have been very pleased with my Ag-Diesel Power Module #12100. I recommend you call them for more information and to find out what part number is right for your engine.

https://www.agdieselsolutions.com/

Your engine may or may use a different type of power module. I think it depends on your injection system type; and I think 2004-2006 ISL motors typically came with HPCR fuel systems. And since 2007 coaches usually have 2006 motors I don't know if you have HPCR or a HPFR system? ...Either way, I bet Ag-Diesel can help you.

Your turbo maybe a VRT (Variable Rate Turbo) and IDK what you can do to change manifold boost pressures. Note: You really don't have to do anything if Ag-Diesel can get you all the HP you want, but in our older turbos we can lower EGTs by adding more air (higher boost).

Another consideration to adding more boost is what with that do (if anythin) to your Charge Air Cooler... should be able to add another 5-8 PSI?

So be sure to ask other people: Can I lower my EGT by boosting my MP? ...And then let us know what you find out?

If you do not know what type of injection system you have, you can call 1-800-CUMMINS with your engine serial number and they will tell you.

SUGGESTION: It's a very good idea to add an EGT-pyrometer to your engine. I'm doing this next month to my ISC and the part cost is about $175 using Amazon.

If you have an ALLISON 3000MH tranny, that may be a limiting factor when it comes to how much more HP you can add to your already "beefy" ISL-400.

I.e., I don't think you want to go above 450HP (maybe 460HP) wtth an Allison 3000MH tranny, because after that you will be getting dangerously close to the max input torque for that tranny. However, if you have a Allison 4000MH then no problem!

What is the weight of your coach? I have 32,000 lbs and my ISC is now putting-out 420 HP and I love it over my stock 350HP numbers.

So you will like your 450-460HP even more if you are in this same 32,000 weight class? ...Just don't try to fly over steep grades unless you have an EGT to keep you operating safely.
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Old 05-29-2020, 06:41 AM   #5
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Is your ISL a EPA 07' engine? EGR and DPF?
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Old 06-01-2020, 09:21 PM   #6
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I think it's a pig in my Monaco 38PDQ.
I find that surprising. I owned a 2005 Holiday Rambler 40PDQ with the 400 ISL and I thought it performed very well.

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Old 06-02-2020, 10:44 PM   #7
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I had a 330HP CAT and a 22,000 National 38' RV that weighed 22,000 (GVGR). This HP/Wt ratio equals 0.01500.

Then I upgraded to a 32,000 lb 2004 Itasca "Horizon" 40AD and I thought the problem (poor performance) was my Cummins ISC-350.

I then started to think my CAT had better “off-the-line-performance” vs. Cummins, because that’s what people said. (This was incorrect, but I believed them nevertheless.)

I expected better performance because I had 20 more HP, but I did not take into consideration my 40' RV weighed 10,000 more.

Now I understand that performance always comes down to HP vs Weight... and my 40" Itasca has HP to Weight ratio of 350/32,000 =0.010937

So now I see why my National has more acceleration. I.e., their 0.01500 ratio is higher than my 0.010937 Itasca HP/Wt ratio.

So I added an Ag-Diesel Power Module to boost my HP to 420 and now my HP/Wt ratio is 420/32,000=0.01312 and now my coach performs much better.

My conclusion is that if your HP/wt ratio is not at least 0.013 then your coach is a "DOG!" ...Ergo it's no wonder "godbee's" 2005 Holiday Rambler 40 foot RV meets his expectations... even if he does not know why? (I'm guessing?)

Godbee: What's your HP/Wt ratio?
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Old 06-02-2020, 11:15 PM   #8
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I've always heard and read that the rule-of-thumb for comparing engine power before you buy is that the weight to HP ratio should be NO MORE than 100lbs per HP. If you think about it, it makes sense. The more a single horse has to push/carry a heavy rider plus weighted saddle bags up a hill, the more it gasps for air, stumbles, slows.

Extending that to the examples in the above post,

22,000lbs/350HP=62.9 lbs per horse. Pretty good. Should be easy for the horses.
32,000lbs/350HP=91.4 lbs per horse. Tough hall for a horse going up a hill.
32,000lbs/420HP=76.2 lbs per horse. Much better. And easier to climb hills.

Just saying that the examples shown might be easier to understand using the horse analogy. At least it is for me. Plus I like horses.

My RV is 27,000lbs/330HP=81.8 lbs per horse. The lower the weight per horse, the better. I am pleased with my Cat's pulling (or rather pushing) power up a hill and don't expect to ever boost it. I rarely pass anyone anymore (I'm retired and not in a hurry) so can't speak to passing power with my ratio.
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Old 06-02-2020, 11:30 PM   #9
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So to "normalize" the HP/Wt ratios that "Jim_HiTek" is trying to change, and confuse us all, or me at least, is that his coach has a ratio of 0.01222 if you do the math. And as I said, in my book this is a "Dog" number, because it's less than 0.013.

...Nothing personal Jim_HiTek! Okay?

And Jim know this, because like he says: ...I rarely pass anyone anymore. I'm retired and not in a hurry.

...And I think that's the goal we all should aspire to! ...But it's also true he has no choice!

So the real purpose of pointing all this out is so you:

1) You know where you stand in simple terms of know your HP/wt ratio is either under or above 0.013; which is an arbitrary number I have set based on 4 Diesel RVs I have owned...

and...

2) You learn to not worry about passing anyone, because you do know the difference of a 4 hour trip is only 20-30 minutes between traveling at 60 vs 65MPH... if, and only if, you can do it without stopping.

...Besides, personally, I have to stop anyway for a potty break; so in my case, why would a 5-10MPH make a difference in my schedule? ...I'm retired too!

On the other hand I'm not that old, and sometime I do like cruising at 70MPH; and whenever I accelerate and merge into highway/freeway traffic I will tell you it's much easier and safer with more HP. So "yes" more HP is nice to have.

So in my book, if you want more HP... do it for fun! ...Just do it safely and if you can't keep your lead foot off the peddle then you should install an EGT-pyrometer.
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Old 06-04-2020, 07:23 PM   #10
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Godbee: What's your HP/Wt ratio?
That Rambler weighed about 34,000 according to the manufacturer. That gives a ratio of about .00117. Obviously it was a dog.

As it was my first motorhome my only point of reference is the large trucks I've driven. Going up steep mountain grades I would whiz past those same trucks like they were standing still, so from my point of view the performance was acceptable. If I had driven nothing but passenger vehicles I would have been very disappointed, so it's a matter of perspective.

My King Aire works out a slightly better at .012 but still a dog.


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Old 06-04-2020, 10:42 PM   #11
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Right out of the Winnebago factory they have been providing ISL-400HP motors in 40 foot diesel pushers since ~2002. These coaches typically had a CVGR of 32,000 lbs. so that makes there HP/Wt ration equal to 400HP/32,000= 0.01250; and that's pretty good performance for a stock motor. ...I certainly would not bother adding more HP.

Most ISC-350 coaches shipped in the same weight class, only yields a ratio of 350/32,000 = 0.01094. (Bow-Wow!)

...And because most ISC coach motors can handle 400-420HP easily; now you know you can add an Ag-Diesel Power Module, and install it yourself, for ~$700.

Godbee: Please share your HP and weight ratio for that magnificent King Aire you are touring around in? ...And is it a 42' coach? ...And maybe what you don't get in running the numbers your engine makes up for in torque!??! ...I would be curious to know what sort of "beast" you have?
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Old 06-05-2020, 12:11 AM   #12
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If subject to the wrist pin issue, I don't think I'd consider changing it.

Imho. Ymmv.
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Old 06-10-2020, 11:16 AM   #13
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Radiator and Transmission cooling are the two areas that are limited and have to be observed closely climbing long grades or mountains

In the past on trucks/tractors Radiator cooling capacity was usually my limiting factor but doable
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Old 06-10-2020, 01:41 PM   #14
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I think they do the same miserable sales things they have done for vehicles for years. Start at the lower hp and then simply re-program in the next years line up etc. My 400 isl has put out far more power than that with a simple inline device. I have been told by factory folks they can output lots more but they will not go over certain criteria based on transmissions etc. I don't think cooling would be any issue. I had mine dynoed and it was doing a great job and never heated.

However, I had to endure a new DPF early on and blame that on bad fuel. They re-flashed the ecm with several updates and I suspect based on the dumpster full of DPF filters that they were tweaking the ECM and trying to find their way. And we customers paid for their learning curve.
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