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BMC (Bluebird Motor Coach Unique Issues) If you have a unique issue with your BMC coach and it can't be answered in one of the other forums here, then this is where you can list it.....List your BMC Parts here too.

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  #1  
Old 06-14-2010
AC7880 AC7880 is offline
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Default BMC Cummins 8.3 low boost problem

A while back I had a problem where a fitting broke off the boost line from the intake to the P7100 pump and to the wastegate. When I repaired that fitting I had no boost (2 psi max). After much other troubleshooting I blew 32 psi of air into the fitting, intake, P7100, and wastegate, then I had boost again. All this was discussed at: http://www.wanderlodgeownersgroup.co...ead.php?t=6341

I have pulled my first grades since all this ocurred. I used to get 32 psi max boost. I now get 24 psi max boost. 24 sure beats the 2 psi I was getting after the fitting broke, but 32 psi would give me lot's more power.

No black smoke, egt is fine on the pyro.

I have some type of remaining problem from the break before. When I pulled the fitting to do the repair, there was pipe dope on the threads, and some of it may have fallen into the P7100. I guess what I will do next is to try blowing 40 or so PSI into all areas and see what happens. May have a turbo problem, or a wastegate problem, or a P7100 problem that was caused back when the fitting broke.

So, now seeing 24 psi max boost instead of the 32 psi I had after I installed the number 10 fuel plate.
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  #2  
Old 06-15-2010
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24 -25 is all i have seen also

now how far south did you move
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  #3  
Old 06-15-2010
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Hey Woody,

We've been traveling pretty slowly this spring. We have a Thousand Trails membership that has annual dues of $611. With it we can stay up to 3 weeks (for $0) in any TT, then straight to another one if we want to. So to make sure we get value for the $611, we've been doing some 2 and 3 week stays along the coast where there are a bunch of the TTs. So far in 2010 we have 52 days in TT. Now we figure it came out to $11.75 per camping day for our 2010 membership even if we don't use it more this year (which we probably will).

There won't be so many TTs along the way as we move further south and east.

Yesterday we moved east 85 miles to Eugene Oregon where we are in a nice county park w full hookups, 50 amp, and cable tv. We'll stay here 1 week then probaly head south a short ways on I 5.

This morning we are heading over to LineX of Eugene to get LineX coating on the bottom front cap.

Eventually I'll figure out why I'm now only getting 24 pis boost, when I was getting 32 psi before. 24 sure beats the heck outta 2 psi though....

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Originally Posted by rwoody View Post
24 -25 is all i have seen also

now how far south did you move
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Old 06-15-2010
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Dan,

I have no help on your pressure/boost problem. FYI: My Banks Stinger system does provide 32 - 34 lbs of boost under full load. Normal boost is usually 32 but I have seen 34 at times. I think stock original was 24 lbs according to Cummins.

I would very much appreciate before and after pictures on the Line-X application and your comments on it when completed. Perhaps how much it cost if that is OK.
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Old 06-15-2010
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hot weather and bad air will affect boost pressure.
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Old 06-16-2010
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Brad - I just posted the LineX info at: http://www.wanderlodgeownersgroup.co...ead.php?t=6527

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Dan,

I have no help on your pressure/boost problem. FYI: My Banks Stinger system does provide 32 - 34 lbs of boost under full load. Normal boost is usually 32 but I have seen 34 at times. I think stock original was 24 lbs according to Cummins.

I would very much appreciate before and after pictures on the Line-X application and your comments on it when completed. Perhaps how much it cost if that is OK.
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Old 06-16-2010
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Hi Randy,

Temp was about 70 with around 45% humidity, just above sea level. Good air, so I still have some type of boost limiting problem that is likely left over from when the fitting broke, and when I had only 2 psi of boost after repairing that fitting.



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hot weather and bad air will affect boost pressure.
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Old 06-16-2010
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Quote:
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Hi Randy,

Temp was about 70 with around 45% humidity, just above sea level. Good air, so I still have some type of boost limiting problem that is likely left over from when the fitting broke, and when I had only 2 psi of boost after repairing that fitting.

I could use some of that air today!!!!
your right,that was almost perfect air..
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  #9  
Old 06-17-2010
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I think everything is fine on the coach and the boost. I will be sure on Monday when we move on again. When I had no boost I had moved the boost sensor past the waste gate fitting elbow from Diesel Performance.

Once I freed up the AFC on the P7100 to get boost again, the boost gauge was indicating boost - but likely on the low side due to the elbow fitting. The elbow fitting reduces pressure from real world so that the waste gate opens later - at the lowered pressure.

In other words, I "think" the turbo is producing 30-33 psi, and the P7100 is getting 30-33 psi at the afc, then the elbow to the waste gate reduces that to 22-24 psi where the waste gate opens (and where I had relocated the boost sensor, thus I was reading 24 psi max boost at the gauge).

I did some testing with air pressure on the waste gate - and it is starting to open at around 20-22 psi, fully open at 24-26 psi.

I re-read Woody's posts on where he would tap for the waste gate and for the boost gauge sensor. I checked the air output of the turbo that feeds to the CAC, and it had 2 allen wrench pre plugged taps. I removed the plugs, and put the boost gauge sensor in one tap, and on the other I put the elbow fitting to feed to the waste gate. I then plugged the opening on the P7100 that used to feed to the waste gate.

Now the factory intake fitting to the AFC on the P7100 does only that job - no line to the waste gate.

Should solve all the remaining problems, and the boost gauge will show turbo output air pressure to the intake (thru the CAC), versus pressure to the waste gate (which is lower by design of the elbow from diesel performance).

Woody, to get your boost from the current 25 psi up to the 32 psi Brad and I get, I think all you need is the elbow with the porting from diesel performance or elsewhere.
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  #10  
Old 06-17-2010
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Interesting Dan I look forward to your report.

Have you looked into the turbine housing that Banks installs as part of their stinger system set up? I assume that it does not give more boost as you are getting the same boost as me now. I wonder if it helps spool the turbo up sooner and or quicker.

What kind of exhaust temps are you seeing at 32 lbs of boost during a long climb and also what was the ambient temp?

Good luck Dan.
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