WTF bearing fretting

[Einspritz]

26 minutes ago, jimk said:

I thought the throttle was downstream of the compressor.  If so how does the compressor side develop vacuum unless there is a severe restriction in the air filtration system?

It is downstream.

 

The way I see it the air filter is a restriction point as well as when the pistons move downward creating a vacuum (not in the surge or critical zone or when producing boost) as it is with a naturally aspirated engine. So, the engine is pulling a vacuum not just in the plenum downstream of the butterfly, but all the way back to the compressor and filter. Right up to the point that the turbo is producing enough to overcome the vacuum------the surge zone----- and then transition to boost.

 

Not to be condescending, but the gauge is a vacuum / boost gauge.....in general terms,the white zone is vacuum, the green zone is boost. Of course the take off point is at the plenum, so the vacuum measured is behind the throttle plate. Even so, there is still vacuum until you open the throttle and it varies as you modulate the butterfly. Remember too that as far as the engine is concerned, at about 85% opening and above is the point at which the maximum amount of air that will pass under "non boost".

 

If anyone has the map of the turbocharger, then you can figure out how much air is being produced at any RPM. Compare that to the needs of the engine and the difference is vacuum or boost, right?

 

I have a parallel gauge in numeric form; idle sees about 15in. Hg IIRC.......and then 9 Lb. boost. But I don't watch it much.

 

If you want to lower the filter restriction there are alternatives to the Purolator.

 

Of course, refreshing the seals on the compressor "should" eliminate the passage of oil into the intake path....

[jimk]

8 hours ago, Einspritz said:

The way I see it the air filter is a restriction point as well as when the pistons move downward creating a vacuum (not in the surge or critical zone or when producing boost) as it is with a naturally aspirated engine. So, the engine is pulling a vacuum not just in the plenum downstream of the butterfly, but all the way back to the compressor and filter.

Not enough to be consequential to draw oil.  Tap in and put a map sensor or gauge that reads vacuum between the compressor discharge and the throttle.  Reading of vacuum will be minor, 3-5 kP.  The turbo rotor is turning all the time but not necessarily enough to build boost.  The tubing between the compressor discharge and the throttle can be above atmospheric before the intake manifold is showing boost due to the throttle position.

(I studied and installed turbos in the late '70s)

[Einspritz]

2 hours ago, jimk said:

Not enough to be consequential to draw oil.

 

Perhaps, but shouldn't the oil pressure forcing oil through the bearings be of consequence, or is it at that point little or no pressure?

 

3 hours ago, jimk said:

(I studied and installed turbos in the late '70s)

 

Great, a learned perspective.

 

Remember Doug Frasier Racing Engines' setup in Hugh McInnes' book?

[jimk]

20 hours ago, Einspritz said:

Perhaps, but shouldn't the oil pressure forcing oil through the bearings be of consequence, or is it at that point little or no pressure?

Oil is metered by the small oil passage (orifice) inlet to the bearing block.  Often can be seen when the oil supply line is removed and examine the bearing block inlet.  The bearings are not pressurized but rely on flow.  Oil exiting the bearing drains by gravity all the way to the pan, so that is why the drain tube can't have any dips in it.  Turbo is mounted low on the M10 and good drainage can be difficult.  I realize it is factory design.  If the drain tube connection at the pan is disconnected and oil drains out it's a sign of oil pooling, that can make oil back up into the bearing block and push out the seals.  Will get lots of smoke if the drain isn't right.

 

The discussion turbo has been recently been rebuilt, but is is important to use an oil with a high flash point temperature rating to avoid coking in the bearing block oil passage.  I have an ASME paper from the late '70s that tested turbos for that problem and has sectioned bearing blocks showing the issue.  I realize oil is better today but still a concern.

[m6smitten]

There was a thread about oil types being used by Turbo owners. Jim, have any suggestions for oil?

[Einspritz]

1 hour ago, jimk said:

The discussion turbo has been recently been rebuilt, but is is important to use an oil with a high flash point temperature rating to avoid coking in the bearing block oil passage.

 

I figure then that it is unfortunate that the compressor seals are not doing their job unless due to the design of the day "they all do that".

 

I have two units, one recently refurbished using an NOS kit and the other which is apart but has about 40 K miles, of which at least 10K on track. The bearings are not coked nor is there any carbon buildup; I have always used Mobil 1 20W-50 at 4000 mile intervals and let the engine cool for a few minutes after hard running.

 

I know about the service bulletin regarding oil change interval, but that was before more "modern" synthetic oils. I don't want this to get into an oil discussion....because, well, how many miles do you drive your Turbo a year?

 

[dlacey]

On 9/25/2019 at 11:35 PM, Einspritz said:

It is very important to note that the Turbo pump, unlike the tii pump which delivers fuel as a function of engine speed directly, meters fuel as a function of engine speed AND vacuum or boost.

 

The turbo kugelfischer pump is a mechanical marvel: it responds to engine speed, throttle position and manifold pressure. A 3 dimensional fuel map inside a mechanical device....

[Einspritz]

7 hours ago, dlacey said:

The turbo kugelfischer pump is a mechanical marvel: it responds to engine speed, throttle position and manifold pressure. A 3 dimensional fuel map inside a mechanical device....

 

And altitude compensation!

[jimk]

21 hours ago, Einspritz said:

I have always used Mobil 1 20W-50 at 4000 mile intervals and let the engine cool for a few minutes after hard running

To find out how well the product in use fairs in engine deposit formation protection, see how the results from the industry standard test that simulates turbocharger operation, which is the test called TEOST 33C, ASTTM D6335.  The test is "designed to predict the high temperature deposit forming tendencies of an engine oil"   The test is required to meet API SN and ILSAC GF-5 oil specs.

A passing grade is 30mg or less of total deposit formed.  Mobil 1 Extended Performance came in at 28.2mg in results I have seen, and is ok.  The best of the group came in at 7.0 mg (4x better).

[Einspritz]

...And the others are?

[m6smitten]

Drove the car hard today and it pulled well but boost wouldn't go Green. Prior owner "adjusted" the blow off mechanism so , I have no way to know if that's the problem.

No obvious exhaust leaks. I will check pipe connections for leak and recheck nuts after clocking the turbocharger.

Edited September 30, 2019 by m6smitten

[Einspritz]

Are you able to tell if the engine went lean ?

 

Will the engine only pull to a certain RPM or will it go to redline?

 

Check to see if the gauge is reading correctly. it may be at full boost, but not showing.

 

Check the chamber on the back of the pump to see if there is oil there.......could be hydro locking and not letting enough fuel.

 

Start there....

 

HTH

[jimk]

On 9/29/2019 at 4:44 PM, Einspritz said:

...And the others are?

Believe it or not, Royal Purple came in no 2, No 1 withheld due to conflict of interest.

[m6smitten]

Pulled it all apart and found the issue. My buddy "helped" me swap the turbo and didn't tighten all four of the nuts on the turbo to manifold.Car boosts fine now.

Appreciate all the input and advise has gone into my files for future reference. 

[Einspritz]

I hate when that happens. :)