Main Journal Bearing Failure [Archive]

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Fulcrum

11-13-2010, 08:49 PM

Could these bearings have failed due to Overheating of the engine ? We unknowingly ran the engine with a very lean AFR during initial dyno runs . Or could this have been caused due to donuts without a dry sump ?

http://i1136.photobucket.com/a...ghsehra/DSC03049.jpg (http://i1136.photobucket.com/albums/n493/indersinghsehra/DSC03049.jpg)

http://i1136.photobucket.com/a...ghsehra/DSC03048.jpg (http://i1136.photobucket.com/albums/n493/indersinghsehra/DSC03048.jpg)

http://i1136.photobucket.com/a...ghsehra/DSC03050.jpg (http://i1136.photobucket.com/albums/n493/indersinghsehra/DSC03050.jpg)

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Inder Sehra
Orion Racing India 2010

Fulcrum

11-13-2010, 08:49 PM

Faterooski

11-16-2010, 07:09 AM

The pictures you posted show an issue with oiling. Just running lean or hot by itself wouldn't cause the heat buildup that those bearings show. Overheating could have thinned the oil out enough so that you weren't making good oil pressure, and inversely you could have been trying to run too much speed/load before the engine was properly warm. You could have been running over the engines advertised redline, which compromises the required oilfilm. Oil starvation also could cause it, be it from a clogged oil rifle/drilling, from a plugged filter, or from long steady-state turns like on a large skidpad. I don't see too many scratches from debris or contaminants in the oil, so thats good. Do you have any record of oil pressure from the last 30 minutes or so that you ran? What caused you to notice a problem and shut the engine down?

atm92484

11-16-2010, 07:17 AM

More than likely the donuts. The oil was probably pinned to the side of the pan and the pick up wasn't able to deliver it to the pump.

Drew Price

11-16-2010, 05:45 PM

What does the crank journal look like?

Ditto. Looks like an oil pressure / delivery problem to me, good thing you caught it in time. Were there a lot of hours on that engine?

Make sure you check the timing chain components, and the camshaft bearing journals too. If you were running an engine oil cooler you should back-flush it with solvent to make sure you get any metal out that may have been washed in.

Looks like it wasn't running without oil pressure, at least very long since you didn't get too much heat and it didn't start to gall up and spin the bearing shells.

Drew

ibanezplayer

11-16-2010, 05:53 PM

Which bearing is this, and are all of the others similarly effected?

Ockham

11-16-2010, 08:06 PM

Running lean will cause elevated coolant temps, dangerous EGTs, and earlier knock, but I haven't heard of it burning main journal bearings. Like the others say, oil starvation was probably the issue. If all the journal bearings are nuked, then the starvation occurred at the pressure pump pickup (AKA, dry sump tank ran dry), or a main gallery was blocked.

Either hoon less (yeah, right http://fsae.com/groupee_common/emoticons/icon_biggrin.gif )or run more oil in the sump tank. What is your system's reserve capacity?

AxelRipper

11-16-2010, 08:16 PM

yeah, that looks like they got a bit hot, most likely from oil starvation as others have mentioned.

Though those dont really look that bad to me. definitely not good, but seen worse

Fulcrum

11-21-2010, 09:01 AM

@Faterooski

We didn't use an oil pressure sensor , just the OEM Oil Pressure Switch . We were running the engine on the stock ECU during the donuts , so I have no record . We used the M400 on the dyno , but never saw a low oil pressure warning . We never ran the engine over 10000 revs on the dyno . The engine ran fine , no problems .

@atm92484

I am in doubt .

@Drew Price

The journal looks fine . I have no photographs of the journal . We had to replace the bearings with brown bearings . Will check the camshafts and flush the oil lines .

Yep caught it in time . There was some oil leaking from the crankcase , so we opened it up and found the center bearing stuck on the crankshaft . Had to wait for the plastigauges to arrive , we don't find them in India . Bearing replacement is a pain !

@ibanezplayer & Ockham
Only the center journal bearing pair and the extreme one on the flywheel side . Why only these bearings , any idea ?

@AxelRipper

Caught them in time ...

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Inder Sehra
Orion Racing India 2010

Drew Price

11-22-2010, 05:45 PM

If it was only one or two bearing pairs I'd blow the oil galley out backwards with compressed air in case there is a bit of grit or a chip or some other obstruction in there, especially considering how much you guys probably paid for that engine and how difficult it will be to get spare parts.

Do you even have a backup engine?

It may just have been abused before you got it, but you never know.

Since you have Plastigage coming check all the bearings while you're in there to make an educated decision about how to proceed.

Drew

Jay Lawrence

11-23-2010, 03:14 PM

The other thing to consider is the balance of your crank. If you have modified internal rotating components directly related to the crank, you may upset its balance, which can cause it to vibrate and operate at variable clearances. This can cause bearing damage due to reduced clearance at certain points during rotation.
If you don't have an oil pressure sensor, GET ONE. Run the M400 on the car and ALWAYS monitor oil pressure. Nothing will stuff an engine faster. You don't need a dry sump to be safe, but the stock sumps are not designed to tolerate lateral loading

Drew Price

11-24-2010, 04:53 PM

Very good point Jay, that would absolutely have an effect if you've had things in there lightened from stock.

Drew

Fulcrum

11-25-2010, 05:51 AM

@Drew
Yep we will flush the oil gallery . Should we do the same to the crankshaft ?
Yes we have backup engines .

@Jay
We use a stock crank with no modifications . Actually we did procure a oil pressure sensor , but it turned out to be a current type sensor . So we used the stock oil pressure switch . We have ordered the voltage type pressure sensor and will use that . Thanks !

-Inder Sehra
Orion Racing India 2010

jd74914

11-25-2010, 03:23 PM

By all means clean the entire engine including all oiling passages (including those in the crank). Just like when welding, during engine building, cleanliness is extremely important; you can never over clean passages.

You can use a current output transducer by putting a resistor inline with the output and measuring the voltage drop across it. If you have a 4-20 mA output device and want a 0-5 V output, just add a 250 ohm resistor to measure across. The only trick is to make sure the resistor is to add resistor accuracy into system accuracy or compensate for it in your ECU/DAS.

Fulcrum

11-26-2010, 10:54 AM

@jd
We always try to maintain cleanliness . But still there is always dirt ! . How do you guys clean the engine ? Any tips ? How do you clean the threaded holes ? Gasket maker somehow enters the holes .

Cant use a resistor as the sensor has a input voltage of 12 to 21 V .. we got a totally wrong sensor ! Will have to get it exchanged .

-Inder Sehra
Orion Racing India 2010