How to tell if turbo is going bad?

[JohnEd]

Dallas,

My apologies.  I had no idea it was that complicated.  Thank you for taking the time.  Sorry if I put you on the spot.

Lost,

That is exactly the procedure I was refering to.  Find out what it is now doing and compare future readings.  The remote sensor for air pressure is far more spendy that the trierd and true air line to a conventional gauge mounted at the driver.  I am really interested in the boost you are getting from what engine and how it is equiped.  I feel certain you can't reference all the info that Dallas mentioned in determining min performance readings for boost pressure, but I think you could reference the salient ones.  1,800 rpm, full throttle at load, muffler spec, after cooler, altitude at test.  What is your "norm" reading"?  I found your comment that there is no apparent lag for a pressure reading really good news as that was the only consideration I had for installing a line to the engine bay.  Thank you very much for the "good news" on our ability to collect and use this information.

Sincerely,

John

[lostagain]

All I did was install the Airesearch (Garrett) specified for my engine in the service manual (4-71 DD). Put in the newer oil seals in the blower and a bigger exhaust (5"). Same injectors (N65's). I even kept the old oil bath air filter which works quite well. I haven't done a air to air intercooler yet, but thinking about it. I get 7 to 8 psi of boost at full load. I was expecting more like 15 psi, but it has made a very noticeable difference in power anyhow. I now go up hills one gear higher than before so I'm happy. My engine is set at 2375rpm no load, with advanced timing (it should be set to normal timing for turbo) but you'd have to have the engine out of frame to get at the timing gears. Bigger injectors would be possible, but that would involve a bigger rad for cooling, and lousy fuel mileage.
Just see how much boost you get at full load on the governor, so you know. Then if one day you don't get that, you'll know a charge air hose came loose or something else packed it in. Keep it simple in you mind. Don't sweat the details too much, just drive it.

[JohnEd]

Lost,

Thank you thank you.  That is exactly what I would want to hear and you kept it simple.  8 psi at full load for a stock 4-71.  That plugs that hole.  I couldn't agree more that knowing what it did is a great troubleshooting tool.  I think that historic data would come in handy if you replaced your turbo and the new one only did 4 psi.

Thanks again,

John