Turbo/wastegate test

[Larry3570]

I noticed no adverse symtoms. Of course part of that is the penalty one pays for being 30 feet distant. I believe with a stuck shut wastegate the worst thing would be possible damage from overboost.

I always look and poke extensively when I'm in rarely visited areas of the coach, so when I was hanging down from the under-bed access port to oil the PacBrake I grabbed the wastegate linkage and it felt like it was welded.

I'm guessing the wastegate shaft is not meant to be lubricated due to high heat. However I shot some PacBrake oil on/around the shaft in a "can't hurt; might help" excersise. Clearly this is a high-temprature-tolerant lube. I will put this on in the future when lubing the exhaust brake.

[chasfm11]

Quote:

Originally Posted by Larry3570 I noticed no adverse symtoms. Of course part of that is the penalty one pays for being 30 feet distant. I believe with a stuck shut wastegate the worst thing would be possible damage from overboost. .

I'm hoping that by monitoring boost while things are working OK, I'll be able to pick up on that if it happens. I'm getting a pretty good feel for the relationship of engine load and boost. One can assume that there opportunity for an overboost condition is climbing a steep hill in a lower gear with the engine RPMs near maximum. If the boost started to climb above the norm then, I'd want to quickly look at why. I frankly didn't expect a stuck wastegate as one of the problems that could develop. I'm much more worried about Charge Air system leaks and the low boost pressure that could result from that. I agree that a stuck open wastegate would give you about the same symptom.

[Flagelpater]

I just got my PacBrake reinstalled from my son's reconditioning. He took it completely apart. It was seized do to my committing the ultimate error by running the engine weekly without getting it up to normal operating temperature. All external joints were seized! The butterfly shaft would not turn after the actuator was disconnected. He completely disassembled the valve and cleaned and lubricated all of the outside location. He did not need to clean the inside because it was still OK. He lubricated the unit with Loctite C5-A, good to 1800 degrees. PacBrake told me that they use Loctite of a lesser temp anti-seize/lube during initial assembly. I coated all external parts that were initially seized with the C5-A as well prior to reassembly. I did use the PacBrake lube on the actuator shaft and put some inside the actuator. Used shop air and cycled the actuator many times to insure lube dispersion. The unit moves smooth as silk by hand. Now I have installed the valve and will let you know how it works later. I also plan on installing the BrakeSwitch after I confirm the proper operation of the PacBrake.

Question: Do all turbo units have a waste gate?

[BigSkyBob]

Flagelpater, the newer Cummins engines and others I suppose, use VTG, Variable Turbocharger Geometry, that changes the angles of vanes where the exhaust gases enter the turbo. As engine demands change, the angles of the vanes change to either direct more or less exhaust gases into the turbo impeller blades. This action is controlled by the ECM thus no waste gate is required. VTG is also used to some extent as an exhaust brake albeit not very effective.

[Flagelpater]

BigSkyBob; Thank you for your reply. I felt all around the Turbo and could find no linkage to make changes. The Turbo experience I have is in Army aircraft, they did have a wastegate, automatic operation only. I am familiar with that type of operation but had not seen it mentioned it the literature for my coach. The blades on my turbo feel like they are fixed pitch, very small impeller! I monitor the boost gage for an increase in boost as I increase demand for power and no boost when I have little demand.

[BigSkyBob]

Flagelpater, the impeller blades in the turbo are a fixed angle and won't change, but the vanes that direct the exhaust gases are on the back plate of the turbo housing and these are the vanes that change position as engine demands change.
Google Image Result for http://images.paultan.org/uploads/2006/08/vtg_diagram_

[Flagelpater]

Thank you BigSkyBob, That was a great link. My experience is completely different. It modulates the exhaust gas to the turbo via the waste gate. I was looking for something similar, wrong. I assume the only thing I would see is an air hose leading to the actuator port, or nothing at all due to internal porting? I have a ISC 330 Cumins, 2005.

[Shanwick]

The turbo in newer Cummins engines still has an actuator to operate the variable vane or sliding shroud ring. I have a 400 ISL in my 2007 Travel Supreme, and the actuator stopped working properly. The symptoms were loss of power, slow acceleration, some smoking, low turbo boost, and loss of about 1.5 to 2 mpg.

I took the coach to Cummins Coach Care in Elkhart for repair (supposedly under warranty). Cummins said that there was evidence of corrosion, so it wasn't a manufacturing defect, and they would not cover the repair. They would, however, be happy to sell me a complete new turbo, as they don't stock just the actuator anymore. Interesting to note that there was no evidence of moisture or corrosion anywhere in the engine compartment, and this engine is probably only about 3.5 to 4 years old with 20,000 miles. To make a long story short, the tech at Cummins was able to locate a rebuilt actuator, installed it, and saved me a few thousand dollars. The repair cost me $309, and now the engine runs fine.

[Happycarz]

Here's a link to the Holst VGT used by Cummins. Scroll down the page to view animation and hit refresh if the animation stops.

http://www.holset.co.uk/mainsite/files/2_5_1_5-VGT.php