Wastegate Actuator Adjustments-- Cummins C Mechanical Engine

[mike-in-sky]

Hi,

Im relatively new to the FMCA. I own an older class A motorcoach. It is a 95 Monaco Dynasty with a Cummins C8.3-300 mechanical engine.

Recently on a trip home to Connecticut from New Hampshire, I lost all my turbo boost. Downhill and on the flats I could cruise at speed. But hit even the slightest uphill slope and the speed dropped drastically. I think I upset a lot of folks that day. What a long trip home that turned out to be. When I got home I researched what might be a cause. Being a very mechanical person, I quickly grasped what I was reading. Based on my coaches symptoms and the information I read, as a starting point, I decided to remove the wastegate actuator and bench test it. It turned out that the diaghram was ruptured and leaking very heavily right out where the actuator rod comes out. So I contacted Cummins parts and ordered a new replacement. Today I installed it exactly as described by the Cummins directions being sure to get the preset correct. Yea!!! I have boost again.

This brings me to my topic. While researching my problem, I read a few peoples comments on ways to increase turbo boost by making slight adjustments to the actuator rods linkage. Has anyone tried this? If so, what was the outcome? was it worth doing?

Right now going up a decent hill not pulling anything behind me. I'm seeing around 20 - 22 lbs. of boost. I've heard people say to stay away from the 30's. may cause problems. I would like to see close to maybe 28.

Any advise, suggestions, would be great.

Thanks,

Mike

[desertdeals69]

The way I do it is to unhook the diaphragm hose as hook up a regulator on an air supply. Adjust the rod so that it starts to move a 30 psi. That should give you 28 lbs of boost. I set mine a 32 and get 30 lbs.

[DaveAtherton]

Mike,

Maybe I can answer your question on turbo boost..first of all understanding just how turbo boost works. The turbo charger has a wastegate and a wastegate actuator. Your engine has Max boost pressure at idle with waste gate in the closed position. When engine speeds up the wastegate will start to open (note: the air / fuel and boost pressure sensor control opening of the waste gate)

The wastegate has a preload spring set for each different H.P. engines. For the ISC engine opening for wastegate is 23 psi.

What happens is as you build up boost pressure the wastegate on engine will open and dump excess exhaust out the exhaust pipe. By a preset value set on the wastegate and opening of wastegate at said value this controls the speed of engine.

Note: as explaining above increasing the wastegate setting above engine spec's a person will not increase power but lose power because wastegate is opening wider and dumping more exhaust from turbine on the exhaust outlet.

Adjustments made to the actuator arm to keep more pressure on wastegate from opening above engine spec's again will only
cause damage to your engine.

Dave Atherton Retired Cat Mechanic

[desertdeals69]

The waste gate does not start opening when engine rpm starts to increase. It stays closed until set boost pressure is reached then it opens. It will only open when boost set pressure is reached. Boost pressure is not always reached with wide open throttle, it depends on rpm and load.

[wildebill308]

1,"What happens is as you build up boost pressure the wastegate on engine will open and dump excess exhaust out the exhaust pipe. By a preset value set on the wastegate and opening of wastegate at said value this controls the speed of engine."

Boost pressure has no direct control over engine speed.

2, "Adjustments made to the actuator arm to keep more pressure on wastegate from opening above engine spec's again will only
cause damage to your engine."

Perhaps if you went crazy. But how do you explain that Cummins uses higher boost pressure to make more hp on some applications with no damage. I think 40 psi is the upper limit. Above that you would need a bigger CAC to cool the air or you don't get the benefit of the higher boost.

Bill

[dickandlois]

Mike,

Call Cummins with the engine serial number and ask what the specification is for the boost and what the maximum pressure could be set at.

Then with the pressure setup described by Desertdeals one can set the boost level.

Rich.