Thank you Mike.

Tuomo, thats a good question. I'm in the shop right now, but should be able to show some pics and provide some small explanations later today. If you search, there is quite a bit on the internet on how crank scrapers work.

 

Crack Scraper sounds gross...

 

We had a custom dry sump pan, with a custom scraper (no names, here) that did this very thing....it would suck the dry sump tank empty when you did any steady state rpm's above 5,000 rpms. EMPTY! And it only took a few seconds, to do this. Of course, as soon as you let off and let the rpms drop back, the tank filled right back up. You had to be looking at the tank, in order to see it do this....or the rod bearings.

Real eye opener to suddenly realize that there is 20 quarts of oil being held above the crankshaft....in suspension....and to think about how quick this can happen with a wet sumped engine with 8 quarts. Of course, there is no sump tank to watch...so you'll never know this is happening...until the rod comes through the block.

 

Based on what I've read on the internet, I would have assumed that the best way to install two scrapers would be as follows:

CrackScraper.jpg

This way, the scraped oil from both scrapers will shoot to the sump.

Now, I understand that scraping is not the only concern with 928. It may be that what that second horizontal scraper is really doing is stopping the oil from surging from that side when the car corners. I don't know. I assume Kevin Johnson had his reasons. However, I am wondering about how the oil accumulating on top of the second horizontal scraper is supposed to find its way to the sump.

 

Yes, I do. Although you have removed the pictures and all reference to the pictures, for some unknown reason, the questions are still the same. Is the knife edge the leading edge, like you say, or is the rounded edge the leading edge?

 

 

He made a mistake when posting about an unrelated topic. **** happens. That's why there is the fantastic edit feature on this board.

Moving on back to scrapers.

How did you solve the problem of cumulating oil above the scraper in your dry-sump example? Only installed a scraper on one side only?

I am looking at your web page at http://www.precisionmtrwerks.com/products/products.htm. These are interesting. Since I haven't tried anything yet amnd you have worked on these engiens for a long time, please consider the below juet as ignorant questions.

The pan spacer has to be part of the solution, because it allows for increased sump capacity. The pickup has to of course also be lowered.

I have one question about the pan spacer, though. With the pan spacer, the fins in the bottom of the oil pan are no longer as close to the crank as they used to be. Those fins are at 45 degree angle, and when the crank rotates (clockwise), the oil hits these fins and presumably gets deflected towards the front of the pan. I believe that this was one of the ideas that the original designer had in mind.



Doesn't installing the pan spacer eliminate this presumably beneficial effect? Would it make sense to install extensions to the fins in the bottom of the pan if used with the spacer?

The same question applies to the windage tray, both your and Kevin Johnson's. Doesn't the windage tray prevent the oil pan fins from doing their jobs?

The whole windage tray is a two edged sword, isn't it? On the one hand, it keeps the oil in the sump from hitting the crank when the car accelerates hard in some direction. That's good. On the other hand, it keeps the oil from draining back to the sump. That's bad. Since people are finding that installing a windage tray helps in many designs, it must be the case that the former effect must dominate the latter.

The following is pure speculation. One would think that for the windage tray to work, one would have to somehow use the energy of the oil spinning with the crank, scrape it off to shoot thru an opening in the windage tray. This opening in turn would have to be in a place that the surging oil can't reach easily from the bottom of the pan.

The whole sump oil flow seems to be all about designing passages thru which the oil only wants to go in one direction.

 

Greg - you are right. The round nose is the leading edge and the chisel-point is the trailing edge. I removed the pictures - no mystery here. I can't sit at the keyboard for long and its faster to remove a picture that raises more questions than it answers.

 

Tuomo,

maybe this will help. I'm going to show two iterations in the current crankshaft scraper and windage tray system.

Keep in mind that the photos at the start of this post are of only parts of this kit -not the whole thing installed as-run. There are many separate pieces that assist with getting the oil down and keeping it down.

These pics represent the state of the scraper and windage tray system when it was here in 2007. Note the open center section. This is when we partyicipated with IJ in a redesign of the system and making new and better patterns for the scrapers.

 

...and here is what that 2007 development produced: the 2008 version.

Note the increased use of unidirectional screening under the crank center. Kevin Johnson's excellent idea. It allows oil to flow thru in one direction easily, not so easily to get back thru the other way.

The four L-shaped items on the floor are diverters that divert the oil coming down from the heads around the counterweights instead of running right into the spinning counterweight like it does OEM.

Also note the hinged gates. They are up-side down in this photo - of course they hang down from the engine when installed.
They allow oil to easily return to the front sump, yet under hard acceleration thay swing shut to prevent oil from climbing the ramp up to the rear of the pan where it will get into the rotating assembly.

The CW on bearings, oil, and entrained air is that main bearings can tolerate as much as 50% entrained air in the oil before they fail, but rod bearings will only handle a max of 30% entrained air in the oil before they fail.

 

two of the fastest and most durable 928 engines around doesnt have a scraper.
Why is that?

 

So, it kind of proves that if this is not designed absolutely correctly, that it could cause MUCH more of a risk than not having one. maybe Doty's motor met this fate. how would he know, unless he has a record of the accusump releasing oil, and what if it wasnt fast enough? could the bearings run dry at high rpm and the oil all being suspended above the crank?

I kind of like the fact that our engines. Mine, Joe's, and others like it, can be beat to snot, and not have any issues in a stock configuration.

why change???? Do we really understand what the real goal is here?

Confused.

 

If Im understanding you, wouldnt the one "scraper" be enough then? the vertical piece looks a little redundant. You would think that it should only be on one side to avoid the oil from being suspended during high rpm.

 

not sure, but how about starting your own thread on your theories surrounding crank scrapers instead of posting in this one.


Carl, I too am thankful for your product development. Although, I'll probably never have need for this, I do benefit from several of your products currently installed on my 928.

 

What does "unidirectional screen" mean? What makes it "unidirectional?"

Doesn't the screen under the center section disable the deflectors in the bottom of the pan?