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01-21-2021, 06:53 PM
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#1
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Member
Join Date: May 2017
Posts: 36
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400hp ISL turbo boost questions
How much boost is your 400hp ISL making?
Mine doesn't seem to run as well as I think it should, in fact my previous 325hp larger slightly lighter coach ran much better.
I have done all normal maintenance and power has not improved. The things I have noticed is my boost guage seems higher than I would have expected. At idle I see close to 5psi, reving motor in neutral will rise near 22psi, driving it often goes well over the 30psi max on the guage. This is a mid year 2004 non emissions Monaco so I doubt its an exhaust restriction like you'd expect from a plugged cat? You can also hear the turbo whistle at idle from the exhaust which seems unusual?
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01-21-2021, 07:15 PM
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#2
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Member
Country Coach Owners Club
Join Date: Jun 2010
Posts: 84
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My 2008 which is a 425 hp produces max about 32 to 33 pounds.
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08 Allure 470 37 Sunset 31597 Cummins 425
2014 GMC Sierra M&G braking
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01-21-2021, 07:45 PM
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#3
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Senior Member
Winnebago Owners Club Fleetwood Owners Club Holiday Rambler Owners Club
Join Date: Dec 2011
Location: North East Florida
Posts: 1,300
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Sounds like your boost is pretty normal. How heavy is the coach?
__________________
2019 Horizon 42Q
Cummins L-9 450 HP
Maxim Chassis / IFS with Tag
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01-21-2021, 09:38 PM
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#4
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Senior Member
Join Date: Apr 2018
Posts: 1,091
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I never see more than 23 on a non emissions 2004 isl. Been the same for 3 years, checks out with the manual iirc.
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01-21-2021, 09:42 PM
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#5
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"Formerly Diplomat Don"
Newmar Owners Club
Join Date: Apr 2005
Location: Moorpark, Ca.
Posts: 16,840
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It's been a long time since I had the 400 ISL, but if I recall, it was right around 30 psi. My 450 ISL (L9) will max at 34 psi.
"shootist".....you either have a bad gauge or turbo issues!
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Don & Mary
2019 Newmar Dutch Star 4018 (Freightliner)
2019 Ford Raptor
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01-21-2021, 09:47 PM
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#6
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Senior Member
Join Date: Jun 2012
Location: NorCal
Posts: 2,387
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If I remember right my 500 ISM is about 25 psi
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Outbound
2002 Monaco Executive 500 ISM
2004 GMC 2500HD 4X4
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01-22-2021, 12:40 AM
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#7
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Senior Member
Join Date: Apr 2018
Posts: 1,091
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CAPS, with non vt turbo should be 23.8 ideally. I believe a waste gate adjustment sets it. I could be wrong on the wastegate as I've never actually worked on one. The variable turbos have increased boost pressures from what I've read. Non egr, non vt, caps you would be high. Either common rail or vt has higher boost.
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01-22-2021, 10:47 AM
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#8
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Senior Member
Join Date: Jan 2018
Location: Capistrano Beach, California
Posts: 2,800
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Quote:
Originally Posted by shootist
CAPS, with non vt turbo should be 23.8 ideally. I believe a waste gate adjustment sets it. I could be wrong on the wastegate as I've never actually worked on one. The variable turbos have increased boost pressures from what I've read. Non egr, non vt, caps you would be high. Either common rail or vt has higher boost.
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This is important^^.
The OP has a "mid year 2004". That means he could have the CAPS or the Common Rail, depending on year of the engine itself. We need to know the year of the engine to assess whether or not his boost is correct.
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Larry, Eileen, and Finley
2004 Alpine 36FDDS
Third motor home, first Alpine, no need for another.
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01-22-2021, 11:31 AM
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#9
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Senior Member
Newmar Owners Club Spartan Chassis
Join Date: Apr 2015
Location: Dallas, TX area
Posts: 485
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I called Cummins and asked what they show for the max boost for my ISL400.
They said that it should be 26#. That is what I get for a reading on a ScanGuage D. The throttle position indicator is close to 100% at the 26# reading.
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Don and Marilynn
'04 Newmar Dutch Star 4010
Spartan Chassis/Cummins ISL 400
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01-22-2021, 12:05 PM
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#10
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Member
Join Date: May 2017
Posts: 36
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My engine was manufactured in March of 2004, hope that helps
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01-22-2021, 12:54 PM
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#11
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Senior Member
Join Date: Jan 2018
Location: Capistrano Beach, California
Posts: 2,800
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Quote:
Originally Posted by bearscat
My engine was manufactured in March of 2004, hope that helps
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I believe that makes it a Common Rail engine (others can verify), and so would have the higher boost rating. Your engine serial number will confirm, or a picture of your fuel pump.
__________________
Larry, Eileen, and Finley
2004 Alpine 36FDDS
Third motor home, first Alpine, no need for another.
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01-22-2021, 01:12 PM
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#12
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Registered User
Monaco Owners Club
Join Date: Mar 2018
Location: Blairsville, GA & WPB, FL
Posts: 3,993
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24 for a 03 CAPS ISL 400 and 32-34 for 04 common rail.
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