Wandering Turbo Boost Pressure

[Barryc737]

2009 HR Scepter with Cummins 425 ISL power plant
Usually, under normal driving conditions, my boost pressure max's out at 30-32 PSI when I've got the accelerator floored and climbing a hill. Today, we did some higher elevation driving from Salt Lake City to Torrey, Utah where a couple of passes were on the order of 8,500' MSL.

I noticed that the boost pressure under max power conditions was wandering between 30-24-22-28-30 PSI at random. I did not notice any other instability in RPMs, etc. Could it just be an indication issue? Loose hose? A hole in a hose? Turbo going bad?

Hard to tell if climbing performance was affected as it was our first time towing with a dolly and minivan. Should I expect a mushy climb at altitude?

I do have a ScanGaugeD and will try to find a page that gives any turbo info. Meanwhile, any thoughts?

[WILDEBILL308]

That sounds about right. Electronic engines are constantly changing.
Bill

[Captjake1]

Originally Posted by WILDEBILL308

That sounds about right. Electronic engines are constantly changing.
Bill

I agree. Mine, though a Cat, just had a turbo fail. 40 psi under load and no power.
Prior I saw the boost fluctuate widely. Depending upon the load, grade, etc.

[Mr_D]

On some engines like my ISX the EGR closes at about 7,500 feet which might affect boost pressure.

[Captjake1]

Originally Posted by Captjake1

I agree. Mine, though a Cat, just had a turbo fail. 40 psi under load and no power.
Prior I saw the boost fluctuate widely. Depending upon the load, grade, etc.

I should clarify. I saw no issues with the fluctuation in pressures. Only when it went excessive on the boost pressure.

[twinboat]

Change the fuel filters, if not done recently.

Low fuel supply, low boost pressures.

[CountryB]

Originally Posted by Captjake1

I agree. Mine, though a Cat, just had a turbo fail. 40 psi under load and no power.
Prior I saw the boost fluctuate widely. Depending upon the load, grade, etc.

40 psi is normal boost for some CAT engines (like my 2005 C13).

Can you provide more detail? What failed in the Turbo? Bearing/seal?
Are you saying you were getting 40 psi boost AND the turbo had also failed at that time?

[palehorse89]

Originally Posted by Barryc737

2009 HR Scepter with Cummins 425 ISL power plant
Usually, under normal driving conditions, my boost pressure max's out at 30-32 PSI when I've got the accelerator floored and climbing a hill. Today, we did some higher elevation driving from Salt Lake City to Torrey, Utah where a couple of passes were on the order of 8,500' MSL.

I noticed that the boost pressure under max power conditions was wandering between 30-24-22-28-30 PSI at random. I did not notice any other instability in RPMs, etc. Could it just be an indication issue? Loose hose? A hole in a hose? Turbo going bad?

Hard to tell if climbing performance was affected as it was our first time towing with a dolly and minivan. Should I expect a mushy climb at altitude?

I do have a ScanGaugeD and will try to find a page that gives any turbo info. Meanwhile, any thoughts?

You can set your Scan Gauge D for boost, and it will come right off the ECM, and more stable reading than a dash gauge. Did this just start to happen?, if so I would check all the connection's on the air filter system and to the charge air cooler. Even the Charge Air Cooler might have a small leak......

[Captjake1]

Originally Posted by CountryB

40 psi is normal boost for some CAT engines (like my 2005 C13).

Can you provide more detail? What failed in the Turbo? Bearing/seal?
Are you saying you were getting 40 psi boost AND the turbo had also failed at that time?

Highest on mine is 29 normally. Noticed loss of power and the boost wrapped right up to 40. It is a variable vane turbo. Scanning with computer showed that the vane were not moving. Only common (I am told) with the vvt turbo.

[kketterling]

Originally Posted by Captjake1

Highest on mine is 29 normally. Noticed loss of power and the boost wrapped right up to 40. It is a variable vane turbo. Scanning with computer showed that the vane were not moving. Only common (I am told) with the vvt turbo.

That's a bummer.

[rgl]

I too am having boost pressure issues so very interested in this discussion.

This post on an older coach and therefore turbo, may be of interest:

http://www.irv2.com/forums/f123/low-...isl-93510.html

When monitoring this, is your PacBrake/exhaust break on? (turn off temporarily, to take it out of the scenario)

Not sure if you have an EGR, but this could be affecting steadystate conditions.

Are you in Economy mode while this is happening?

[jimmy braden]

Originally Posted by Captjake1

Highest on mine is 29 normally. Noticed loss of power and the boost wrapped right up to 40. It is a variable vane turbo. Scanning with computer showed that the vane were not moving. Only common (I am told) with the vvt turbo.

The fix for carbon and soot buildup on ISB-6.7 VVT cummins is to drill a hole in the housing and fog with solvent. Not sure if its done while running or not. But it doesnt sound real good to me. G/L..

I like my wastegated old school turbo ;-)

[palehorse89]

Originally Posted by jimmy braden

The fix for carbon and soot buildup on ISB-6.7 VVT cummins is to drill a hole in the housing and fog with solvent. Not sure if its done while running or not. But it doesnt sound real good to me. G/L..

I like my wastegated old school turbo ;-)

What do ya do with the hole then?
Solvents have a high flash point ......does not sound like a good idea ......

[jimmy braden]

Plugged with a brass pipe fitting I think