S-Prihadi

Sharing..........

My M276 3.0 TT has its crankshaft pulley blocked by the aftercooler, so traditional hand spinning the crankshaft to do mild pre-lubing is not possible.
I also would think the speed of hand spinning is too low to do much good.

My usual drill is to use TEST feature in the Engine Computer called Compression Test, which this is a relative compression test to see pistons speed.
So I use this test to pre-lube my engine using 200ish RPM and no firing by spark plugs or injectors. Hence no stress to the engine while the engine oil film may have drained down in the 44 days I been away.
MB does not have the typical US engines Clear Flood Mode, which is cranking without engine starting simply by pressing accelerator pedal to MAX while cranking and no need to use scanner.

I notice something of a good suprise.
On 10 Septh 2022, I replaced the engine oil at 35,685KM. Today I did the Compression Test with mileage at 36,550KM only. So 865 KM and 4 month 13 days old engine oil.

The good suprise is, it seems this very new oil has better oil film retention compared to an older oil with higher mileage. Same Mobil 1 0W-40 for both test.

Lets compare a 9 months oil, but with only 1,105KM. This was after intake valve carbon cleaning. 30 days engine has not run. It was Aug 2022.
First compression test

Almost always Xentry will show some cylinders below 180 RPM if 30 days or longer engine has not run. Thats been my experience so far.


By 2nd Test 4 minutes later, oil has spread around better and lowest RPM cylinder is only at 195 RPM. All tests in this post is with battery charger assist, so battery is fully charged and my battery is super healthy.




Now, lets compare 1st and 2nd test of today. 44 days no engine running, but oil is only 4 months 13 days old and 865 KM old.

1st test above

2nd test below





I usually do 3 compression test before I fire the engine up.

3rd test of the 9 months old oil



======

3rd test of the 4 months old oil




I then fired up the engine for 255 seconds or 4.25 minutes.

The first 5 seconds to see oil pressure build up speed.

At 1.6 seconds ( 9th marker minus 1 ) oil pressure has reached 10 PSI. At 2.8 seconds (14th marker minus 1) full 58ish PSI achieved.
Engine start to crank at 1st marker, not zero. By 0.4 second or marker 1st to 3rd, starter has managed to do the minimum 200 RPM crank for car to start.
Marker 3rd to 5th or 0.4 seconds, that is the engine itself has started. So all it need to start from COLD is 0.8 seconds of cranking + self firing.
This is how fast a healthy engine with a healthy battery should start. No more than 0.8 to 1 second.
My definition of COLD start is no cooler than 18C. Since I did the Compression Test 3 times before firing up the engine, I got my HP fuel pump already primed to 2,700ish PSI.
If HP pump has discharged its pressure over weeks of no running, we need approx 0.1 to 0.2 seconds for it to prime.

Below is the full log file of 255 seconds, starting at 6 seconds ( 59th marker ) to 1,248th ish marker when engine is already OFF seen by oil pressure.
RPM down to zero is not engine OFF, the Banks Gauge retain in its memory last RPM value before engine kill and 5+ seconds later of seeing no real RPM input it will then shut down the gauge.




The Banks Gauge system sees ECM power OFF or no signal for Engine Coolant Temp as -17C temperature value.
Banks own Thermocouple system which is used on the Engine Oil Temp is ON along with gauge being ON, so it has signal already and can show ambient temp of 30C.

4.25 minutes of running produced almost 60C of coolant temp or 30C temperature rise.



This is a 4th Compression Test after 4.25 minutes of engine running and engine oil of 40C temperature has been well spread all over.





3rd vs 4th compression test. For my warm climate. I think 3 times of Compression Test as pre-lubing is good enough.




Hope the information is useful for some.

CaliBenzDriver

pre-lubing is one solid idea that has been used for ages on large engines where oil can easily drain back down (deleted timing check valves... LOL)

You've found the best way to do it through a Xentry compression test mode.
​​​​​​
Correct me if I misunderstood:
When we analyze your test data, you confirm that oil pressure and direct fuel injector pressure rebuild to normal level super quickly. I thought this was a good sign.

lube crank test sequence

Yet there seem to be a significant RPM increase between 3rd and 4th crank, right?

To me this suggest lube was still recovering friction losses ...? no?

S-Prihadi

I think the added RPM at cranking speed between 3rd and 4th is from 2 reasons.

One is oil has spread really well all over the engine within those 4+ minutes of idling
and
secondly, a 40C oil temperature is easier to spread around compared to 30C oil temperature.


When ignition is still OFF, Banks Gauge register no signal from ECM as -14 PSI for HP fuel pressure at rail.
When ignition is ON, the HP fuel pressure at rail was still/already at 2,732 PSI from the few compression tests I did.
So starting is super easy. At 3.8 seconds is when Ignition is ON, but engine has not crank yet.







Att 11th seconds is when I started to crank the engine.
Too bad I can not hook on the Banks Gauge at the same time I run the Xentry, can't have Banks Gauge sharing the OBD/DLC connector with Xentry.
Maybe next time I will do 20Hz logging resolution to see crankshaft speed during Crank-To-Start.
Banks Gauge can do max 20Hz but I do not want to log at such resolution for daily drive, 5Hz is good enough to catch any glitch longer than 0.2 seconds...if any.



Below is the 4+ minutes engine run, for its HP fuel pressure data.