Cummins ISL 400 estimated mileage

[YC1]

Originally Posted by Party Barge

I saw on one of your old posts you had installed a DIGI CR chip. I had also installed that chip back in 2016.
I have been working on the coach and reviewing how everything is running at a little over 100k.
I am running the chip on the A setting. I think I started at the 9 setting, moved it once and have left it there for the last 5 years.
I think I read that you ran your coach on a dyno, with 52 add HP. That's about what I was looking for.
I was told the sweat spot for the DIGI was between 9 and C setting.

What was your experience?

RAB

YC! here with a 2008 Endeavor.

I installed the chip years ago and had it dynoed. Amazing hp and torque improvement. Cummins man told me they get 800 hp out of that engine in the marine environment.

Mine could never be run above the 8 mark and began going into the limp mode at even lower levels. I love the chip. I got better mileage when I kept my foot out of it and it was a rocket as Don mentioned.

Later had a dpf filter issue. Not many miles on the rig at the time. Maybe 25K miles.

I ultimately gave the chip away but would love to have the power back.

A hp "Uprate" was done recently. From 400 to 450 hp. The power is noticeable but nothing like the chip gave me.

As Don did, I too changed my fixed pitch engine fan to one from Source Engineering. The difference in acceleration was dramatic. I did lose some downhill (braking) because the fan is not as resistive.

With the chip and fan I could easily get 8mpg at the time. With the chip long gone and the HP uprate along with several flash updates (probably do to the tremendous amount of problems with the dpf filters), my mileage is rarely much above 7.

[Wild Card]

Originally Posted by momcat

I have a '07 allegro bus, 40' with the 400 isl. I drive between 60 and 65 mph. Pull a jeep wrangler toad. Check mileage with pen and paper and screen. Very similar. 6.2 to 6.4 is all the mileage I get w/o the gen set. Would I be able to hear a cracked manifold? I would love to get 8mpg. I could use some help too. Thank You...MOMCAT

Pre 07 emission engine? that's about right. get some tuning and it will come up 1mpg

07 emission engine you're short, unless you are in the hills all the time then that's not bad.

my 07 emission engine got the same pulling an F150 7mpg, mostly flat ground.

look for soot around your manifold and yes you can hear them as well. Whats your peak boost? Also lets not forget you can loose boost from the CAC or interconnecting piping.

another thing to look at is does your fan cycle? Alegro Bus, side rad? I bet your fan is always running some and dragging hp from the engine.

[momcat]

Thanks for the info. I really don't expect "good" mileage, but I would like to get what other people are claiming....or close. I see or hear no evidence of a manifold leak, and all my connections look good. I am ok with the mileage until I start reading these 8, 9, 9.5 mpg claims. Thanks again. I will just live with it and continue to enjoy what I have. I don't mind spending money.....But I don't like throwing it away. MOMCAT

[tropical36]

Originally Posted by Tiffin0542

I have a 2005 tiffin with Cummins isl 400. Pushing 32,000 lbs. with C-RV tow.
I am consistently getting right at 5.6 mpg. Running at 65 mph at 1700 rpm. Not heavy footed by any means. Everyone seems to be getting better fuel mileage. Any suggestions as to what i could do better. 97k on engine.

That's kinda of low for sure. I'm at 16tons also and my CAT has averaged 6.2 over a 14yr period. Still don't know if the ECM readout is including the genset or not.
I run at 57 - 58mph and find that best for staying in top gear and for having a relaxing drive.
So, how are you calculating this?
I agree that you should probably slow down a little and for getting there a few minutes later.
Funny thing I've noticed a lot is for those who drive really fast, sometimes take more or longer breaks, cuz I've seen the same coach pass me as much as 3 times in any given day.

[rssnape]

Here is my mileage on 40 ft MA with 400 ISL. Some towing, some not. I’ve had days that calculated 13 and some sub 5. I always take out 1/2 gal/hr for the Genny before I calculate mileage. So that may skew the mileage calculation a bit higher.

[HEPHAESTUS]

I'm joining this convo because I feel something is wrong. 2006 Newmar Dutch Star 4320, tag, 400 ISL. Driving like a complete granny, accelerating almost imperceptibly, 65 top speed, 5.8mpg is the best I can get towing my VW or not. If I drive like a normal person it goes down to 5.2. Dash readout is very close to hand calcs. I feel something is wrong and am looking for suggestions. 40k miles on engine.
There is no soot around my manifold. I love the coach but the mpg is terrible enough that it affects how much we use it. I'd be ecstatic if I ever saw 7. I'd be in heaven to see 9.

[n2zon]

Originally Posted by HEPHAESTUS

I'm joining this convo because I feel something is wrong. 2006 Newmar Dutch Star 4320, tag, 400 ISL. Driving like a complete granny, accelerating almost imperceptibly, 65 top speed, 5.8mpg is the best I can get towing my VW or not. If I drive like a normal person it goes down to 5.2. Dash readout is very close to hand calcs. I feel something is wrong and am looking for suggestions. 40k miles on engine.
There is no soot around my manifold. I love the coach but the mpg is terrible enough that it affects how much we use it. I'd be ecstatic if I ever saw 7. I'd be in heaven to see 9.

What kind of roads are you driving on? 5-6 mpg is about normal for surface streets with traffic lights.

On the highway, though, you should probably average 7 or somewhat better unless you are perpetually driving into a headwind. We've had trips like that, where the wind changes and the mileage is worse than normal. (Once in a while the gods smile upon us and give us tailwinds for most of the trip and we see 8+ mpg. Woo-hoo!!!) Highest I've ever seen combined favorable winds with negative elevation change. We got something like 9.2 on that leg.

We get up to speed quickly (foot to the floor on on ramps), then settle down to cruise speed (normally 62 to give us a few mph to play with because the CR-V has a 65 mph limit). On really flat ground we'll go 65 and lose a couple tenths off the mpg if we're "in a hurry."

I don't bother to count genset or AquaHot hours for travel legs. The coach burns almost 9 gph at 62. 5% here or there doesn't move the needle much. Wind, stopping and starting, and elevation change matter more. If we camp where we have to use the genset or the heat we'll factor it in, but otherwise we just ignore it.

Stopping and starting really kills mileage. If you stop at every rest stop, you can easily drop 1-2 mpg overall. It can take 100 miles or more for our mileage to top 7 mpg after fueling.

[znt1186]

Just finished an 1800+ mile trip averaging 7.8 to 8.0 according to my ScangaugeD. It weighs about 32,000 lbs. and tows a 2013 Ford Edge. Most of it was in relatively flat terrain through Florida. I don't worry about it too much. I just want to know if something changes a lot. I use 7.0 as a planning number for fuels stops, etc.

[jacwjames]

Road and weather conditions can make a huge impact on mileage.

Last month took a trip out west and driving through Kansas the winds were terrible, my steering wheel was at 1-2 OClock all the time and I could feel the gusts. My mileage dropped below 6mpg.
Driving through the mountains of CO really dropped it.

But I average ~7.1mpg the trip. My Windsor is pretty heavy and I was pulling a Jeep Grand Cherokee.



Back in 2009 we took a trip to AK, did not pull a vehicle. I kept a log of expenses including fuel and mileage. For the +14K mile trip we averaged 8.3mpg which included any generator use. Not bad.





FWIW, I drive the speed limit up to 70 mph but out west the speed limit was as high as 80mph which I don't do.

[HEPHAESTUS]

Originally Posted by n2zon

What kind of roads are you driving on? 5-6 mpg is about normal for surface streets with traffic lights.

Nearly 100% flat i-10 through Florida.