Engine Bearing Failure

[Dessertrunner]

We don't want to hijack Toms engine thread so I figure we need to start one specific to this topic.

My comments, checking the good book it says that the filter will be bypassed above 23psi. Idle pressure is 14psi so in short 1,200 rpm and you have no filter as its bypassed.
Pump relief comes in at 85psi so we should have plenty of pressure.
My calcs say at 7,500 rpm the pump is pumping 84l per min.

A final comment thicker oil may raise increase oil pressure but this will reduce flow and if pressure goes over 85psi the oil will just go around the pump in a loop.

We need guages as Matt has suggested to know what is happening in the engine.
Tony

[dynomatt]

Thanks Tony,

Having now lost two big ends, one definitely heat related, and one of unknown, we are keen to chase some improved options now that we are pushing the motors more than Subaru intended.

It would also be helpful if the experienced folk offered some roadmaps for bottom ends. I know some generic stuff, but SVX specific (if you've got anything) would help.

Like...NA - 7000 rpm = do nothing
NA - 8000 rpm = light weight rods and good cast pistons
NA - 9000 rpm = etc etc etc

Anybody know the weight of the stock piston and rods?

[Dessertrunner]

Just sent Matt a text explaining his issue may have been cold oil. He told me the outside temp was -2 C. Remember he is not using a thermostate so the engine would remain cold. What I said to Matt was I have seen other engine have oil problems in cold weather.

The good book says below 0C to use 5W 30 oil.

This is of course is just a suggestion.

Tony

[Dessertrunner]

read this

http://www.circletrack.com/enginetec..._pressure.html

[SilverSpear]

Originally Posted by Dessertrunner

Just sent Matt a text explaining his issue may have been cold oil. He told me the outside temp was -2 C. Remember he is not using a thermostate so the engine would remain cold. What I said to Matt was I have seen other engine have oil problems in cold weather.

The good book says below 0C to use 5W 30 oil.

This is of course is just a suggestion.

Tony

So basically Tony, is it healthy for the engine to constantly change oil grading during the year? I mean following weather temperature?

If the weather is variable between 0 and 35 degree during the year, shall we use one universal grade oil? or two grades at different stages?

[Dessertrunner]

That is pretty normal range so the good book says 10w30 were I am it gets really hot so I run 10W 40.

[Trevor]

Centrifugal force increases with RPM and is an important consideration in respect of big end bearings. Think on this while examining the cross section and routing of the oil ways in the crankshaft. The length and cross section of passages leading outwards should equal those running inwards, so that there is a balance. However in any event, friction is increased due to substantial inertia and in particular, any abrupt changes in cross section result in increased resistance.

All in all this is probably the most critical section of engine in regards to oil flow/pressure, hence the first to give trouble. It must be remembered that the oil is a major and vital dissipator of localised heat, as well as being a lubricant. An added efficient oil cooler must surely be essential when the engine is being subject to above normal stresses.

[bazza]

Good stuff, DIY:

http://performanceforums.com/forums/...p-construction

[Dessertrunner]

The one concern in the back of my mind is what is the maxium oil flow that can be pumped through the motor.
My logic for asking you about the different pressure at different revs would tell us the amount of oil that can be pump throught the existing system.

In simple terms if you find the point at which the oil presuure fails to increase inspite of increase reves then using that rev number we can calculate the amount of oil the system can handle.

Also don't know if we have all agreed but it seems that high clearance on the bearings is far better. Is that accepted or not?

Tony

[oab_au]

Originally Posted by Dessertrunner

The one concern in the back of my mind is what is the maxium oil flow that can be pumped through the motor.
My logic for asking you about the different pressure at different revs would tell us the amount of oil that can be pump throught the existing system.

In simple terms if you find the point at which the oil presuure fails to increase inspite of increase reves then using that rev number we can calculate the amount of oil the system can handle.

Also don't know if we have all agreed but it seems that high clearance on the bearings is far better. Is that accepted or not?

Tony

I think that is the crux of the matter Mate. It is the flow that gets to the big end slipper that is the main point.
If the flow is reduced as it flows through the gallery and the holes through the crank, then the pressure won't help. There has to be enough flow to cool and lube the big end.
Increasing the bearing clearance will be detrimental if the flow can't keep up the supply, the oil will fling out of the shell faster that it can be supplied.

Look at the way the oil has to flow from the gallery, to the main bearing cap groove, into the main journal, through the crank to the big end shell, it's not just a pipe!

Harvey.

[Dessertrunner]

Have done the DXF of the sump plate for the dry sump so if anyone wants one let me know.
Tony

[Dessertrunner]

Here is draft sump pdf itss #D so double click and you can rotate to see the under side. As I say its a draft so all input appricated.
Tony