IcemanG17

With the constant debate over the 928's oiling problems I am trying to find some good pictures that show the oil drain back ports in the head and how they flow into the crank underneath?

Ideally I would like to see a shot straight down through the ports from the top that can see the where the ports drop into the crankcase-crank. Some will pour out onto the spinning crank which is NOT good....and the other side will get oil thrown UP into the other head at high rpm (exactly how high I dunno)....

I would love to get some pictures like Dennis made of the cross drilled crank that show how it works....but with the routing of the oil returns... It will help me visualize what is going on inside the engine better...

IcemanG17

something like this looking down return ports would be great

mark kibort

This has been a circus of presumption and assumptions. There is no flying back of the oil from the crank up to the heads. the crank BARELY can touch the oil in the pan, its flush with the top of the pan, AND, there is no need for any fancy spacers or baffels/scrapers at speeds less than 6400rpm.

the oil drops down, WELL away from the crank to slide into the pan untouched by the crank, which is very distant from the outlets of the return oil passages. they are huge and well protected from any "whipping" issues. driving the oil up though those passages is a long shot IMHO.

take a look. even the block has well protruding structures for the oil to return to the oil pan. There is a wall, to protect that flow back to the pan too . its very isolated from the crank in many ways.

mk

mark kibort

how funny, you posted that picture that I posted a long time ago and I just posted it again.

Kevin Johnson

Hi Brian,

The passages in the block appear to stay constant. It is the passages in the head that vary quite a bit. Look at the pic from the Holbert head (4V) and compare it to the 2v.

Kevin Johnson

Here is a pic of how Ford corrected the problem of oil drains dumping on the crank with the GT engine (dry sumped but it is possible to convert the block to wetsump.

mark kibort

the 928 engine doesnt have that problem. there are wide, separate passages that drop the oil well to the sides of the crank without any intereaction. there is even a separator wall between the outlets and the crank area, besides not even being near the crank.
however, if you add oil while its running, it will drip over the crank.

Mike Simard

Here's my fix for the left side drains that come right out at the crank.

OBehave

That's pretty clever Mike!

mark kibort

I guess if they were under pressure, I would be concerned. certainly this solution doesnt have any downside, and with 1g turns, that oil would be falling at a 45 degree angle at the crank. How many of those outlets are there? If forgot about them. good find and interesting solution!

Mike Simard

I'm more concerned with the effect of the crank windage at high rpms on straights than cornering. That comes from having the left valve cover spew only after long straights.
The right side has it's drains protected by the lower case webbing.

ptuomov

Does it work?

IcemanG17

interesting point......I can't see WHY they would design such windage..BUT they were designing the motor as a fairly low RPM motor with lots of torque.....so maybe they did?

Its also interesting how the shape of the 16V oil return passages are so different in the heads? I wonder why?

I knew Mike modified his engine...& that makes sense!! Great pic

Kevin Johnson

I think they had to put the drains inboard because of the oiling passages in the bedplate. Not enough room for them to pass through there. They certainly could have made plates as Mike has done but it would have required several more machining operations. At the time there was not so much concern over oil dumping on the rotating assembly.

mark kibort

probably, but you would think that with all the scraper systems being used, that ring failure would then be a factor, and I dont think that has happened yet.

I kind of like the fact that the oil is splashed everywhere. so far, its hasnt been an issue for me for many years and engines.

Be interesting to hear the porsche engineers on some of the things we are talking about.

mk