Do I have a low boost problem?

[CountryB]

Accordign to the build/test sheet on my 2005 C13, the boost was 48 psi when the engine was tested.
Today driving up the hills in NC, my ScanGauge D shows engine load at 99% and boost at 31.48 psi.

Should I be getting closer to 48 psi at max load?

[JNSNWT]

I’m not a diesel guru but I wonder if the change in elevation is a possible cause of your lower boost psi

What was your elevation when you saw the low psi?

What psi do you see back home in Florida?

[discovery39s]

Has it decreased over time or is this new? Are you now just able to read the boost pressure? 45 Lbs. sounds right.
Before spending $$$ I would pressure test between the turbo compressor tube to the head. May have to rotate the crank to avoid valve cross over.
I pressure test @ 25 psi. Pressure drop should not be more than 1 lb. every 3 seconds. If it drops immediately then turn the crank to get off valve cross over, retest.

Next detailed test is to remove and plug the tube at manifold inlet. You are now testing the hoses, tubes and CAC. Providing your plugs don't leak you should not see any leak.
If you do then start spraying soapy water at each joint and your CAC. Bubbles don't lie.

Be careful pressure testing with plugs. IF the plug is 4", for example, the force attempting to dislodge the plug is 314 lbs. of force. Careful!!!!!

[CountryB]

I have owned the coach about 18 months. I did not have the ScanGauge D until recently so there was no way to read boost before. Engine runs great and no engine codes.

I don't think the elevation was that great (elevation is 2,000 ft according to Google) to reduce turbo boost much (it's a twin turbo C13). I was heading to Ashville NC on I-26. But I have been watching the bst pressure since leaving and on any hill (where engine load says 99%) the max boost is 31.5.

In FL I don't recall ever seeing engine load at 99%. I'll be heading back to FL next week so I'll check again.

Maybe ScanGauge doesn't read/display any higher than 31.5 (doubtful, but I don't know the ScanGauge parameters).

So, if I should be seeing numbers in the 40's I'll need to do the CAC leak test. I'm just not sure what is normal boost reading (the "engine report" boost was probably on a test stand/dyno - maybe that is not a boost number one could ever reach in a motor coach).

[slemnah]

Did you set up scan gauge for higher pressure? My VMSpc has a low pressure and a high pressure set up. Low pressure set up works as you describe. I run around 42psi when pulling hard on my C13

[CountryB]

Originally Posted by slemnah

Did you set up scan gauge for higher pressure? My VMSpc has a low pressure and a high pressure set up. Low pressure set up works as you describe. I run around 42psi when pulling hard on my C13

I didn't know there was a setting for that.
I'll pull the ScanGauge manual and give it a read now.
Thanks

[discovery39s]

You could just T off your boost sense line with an analog gauge, run it into the coach and have someone watch the gauge to verify. Simple, low cost method.

[CountryB]

On the C13 there is just an electronic sensor (no boost port) which is how the ScanGauge reads boost.
I thought about adding a Boost gauge, but went with a pyrometer instead since the ScanGauge can read the boost via the ECM data stream.

[CountryB]

I read through the ScanGauge D manual, and there is no low/high boost psi display setting. So what I'm seeing is correct (assuming engine boost sensor is good). I'll need to test the CAC for leaks when I get back home.

[discovery39s]

Country,
Have you checked your air inlet temp when your boost appears to be low?
Can you see that on your scan?

[CountryB]

I monitored air inlet temps, and they were running about 95 to 120 degrees.

I think the ScanGauge is not setup to read/display above the 31.5 psi I'm seeing (I need to call them to confirm)

In the ScanGauge package there is a form I can send in to provide additional features/scan-data. I'm supposed to write down all the "PID" codes and send to ScanGauge, then they send me a custom update file. At least that's how I interrupt the form. I have not done this.

[discovery39s]

Country,
My coach runs right around 20-22f differential. (ambient to air inlet temp). This is relative to engine load. Not sure what ambient you recorded this against but sounds right for 90-95f.
George

[discovery39s]

Forget to mention. I looked at my inlet manifold and there are two plugged ports. Not sure if your engine has them but you could access a port to measure the pressure.
Good luck!

[CountryB]

I called ScanGauge today and they said the boost pressure max's out at 31.5 psi. I need to copy the PID codes and they will provide an update (i.e. X-Gauges) that will display the full boost values (to 48 psi) for my engine.