Vilhuer

I can't recall seeing this mentioned in here:

http://www.amicale928.org/forums/vie...hp?f=13&t=7951

Google translated version:

http://translate.google.fi/translate...D13%26t%3D7951

Certainly very interesting read for bearing issues data.

dprantl

That's a really cool test and it is very interesting to see aeration effects directly on the oil paths.

Dan
'91 928GT S/C 475hp/460lb.ft

IcemanG17

WOW....amazing test and amazign data.....

Very interesting how the aeration appears to cause significant loss of oiling to #2-6....which of course is the most common failure.... It makes perfect sense.....

So the question remains is WHY is the oil so aerated when it gets picked up by the pump... starvation due to cornering or excessive oil in the heads could do it....

This does explain why my combo of 3/8th spacer + OB pan works so well.....less chance of whipped oil by the crank and the de-aeration effects of the mesh screen + cloverleaf insert...... very interesting

Vilhuer

Early S4 heads have few tenth of mm smaller oil feed holes than later heads. Do they work better than later heads by preventing too much oil going up? Why hole size was made larger? Too much wear on cams or lifters?

In any case block modifications are secondary fix. Real solution is to keep oil in pan and stop aeration.

PorKen

I'd like to know if a vacuum pump (Colin's) would reduce the aeration.

atb

I hereby retract any and all deragatory statements I've ever made about the French (most typically in jest).
That post was awesome!

F451

Wow. Very interesting. Love the creative engineering.

Lizard928

Ken,

I'm not sure, but I think it could prevent the head from packing with oil!

danglerb

Bubbles float to the top, so bubbles in the pickup I think implies a lower level of oil near the pickup.

danglerb

Wow, I am impressed with the Google translation and the study. Some results with oil I think should also be gathered now that the basic test arrangement exists.

GlenL

That's a great experiment.

That foamy oil being sucked in has been identified previously.

The problems are:

A front sump.
Shallowly sloped pan
Pan very close to crank.

On hard acceleration the oil rolls out of the pan and does not flow down into it. It fills the back of the pan and is fed into the crank. That's where all the foam comes form. The small volume inside the block doesn't allow the windage to leave suspension.

No, it doesn't address that at all. And, as we've exchanged, the cloverleaf isn't a demonstrated fix. The spacer is a good thing by moving the pan away from the crank and increasing the volume inside the block.

My car seized the 2/6 bearing with the original (cloverleaf) oil pick-up. Working great with an S4 pick-up and an Ishihara-Johnson windage kit.

NoVector

That is a great thread find, Errka. In addition to the poor flow on 2/6, can only imagine what that's doing to oil cooling and oil breakdown too.

mark kibort

the crank is well above the level of the oil. and it follows a pretty narrow path. of course the falling oil can get near the crank, but the paths do a pretty good job to miss the crank. i think a lot of the splashing around is good for the piston lubrication. i also dont t think that the screens can be too friendly to flow back to the pan. it would be intersting to have an electronic oil level sensor to see what happens at redline, and sustained redline.

again, the pan spacer can only do so much, if the pickup is not extended down to take advantage of the deeper pan. in my use, i would ever be able to use the pan spacer, as it would hit the ground coming down the corkscrew if i did!

also, i think the oil quality and characteristics has a major roll here.

just this week, i was running 20-50 castro GTX in that stroker, and the oil pressure is SO much weaker vs the amsoil that was in it before. (but dirty and it had to go!)

very intesting article though! thanks for posting

IcemanG17

The IJ kit does help turn the oil foam back into oil, just like the mesh screen does in the OB pan.....BUT the IJ kit doesn't have many controls-baffles to keep oil in-around the pickup....like the cloverleaf does in the OB pan....

I understand you blew an engine with an early pan & certainly others have too....but it is a better design than the S4 or S4+GTS baffle......Kevin Johnson himself said so....

I am at 76 hours on track, with about 1/2 on R comps or slicks at a known 928-944 killer track...zero indication of any bearings issues on oil analysis....another "lemons" 928 team is running only an OB pan and have 2 completed races (35 hours) on an extremely old-undermaintained engine running normal dino oil (high zinc diesel oil).....

I think it boils down to this....your opinion is the OB pan is garbage and the IJ+ S4 pan is the way to go & I doubt you will ever change your mind......my opinion-experience is very positive on the OB setup I run....and I will never-ever run a 928 on track with a S4 setup.....been there done that & blown 2 engines...never again

GlenL

Actually, I think the pick-up isn't important to the problem. I went with a later pickup because it has a screen. I also didn't like the look of the spring-loaded rubber pieces on the old pickups that I have. Getting stiff.

The IJ kit has specific features to keep oil in the sump. That's the problem: the oil leaves the sump under acceleration because it's shallow and in the front.

I do wonder about the RPM range used by the drivers of your car and with the auto transmission. Also, with the lower power (4.7 US, right?) it's not accelerating as hard as other 928s.