jpitman2

Sometimes apparently complex issues can be solved by simple means. Look up the solution to Spitfire Merlins (carburetted) coughing under negative G loads where ME109s (injected) etc did not . A lady in the drawing office suggested a washer restrictor somewhere in the carb that fixed the problem (surging?). it was known as Ms Shilling's Orifice.
Can anybody advise the idea behind the thick sump gasket please? 8m is a VERY thick gasket IMHO.

jp 83 Euro S AT 50k, not going near 6600, much less 7k

Doug Hillary

Hi,
these references may be of some interest (I hope they work);

http://www.tytlabs.co.jp/office/elib..._044suzuki.pdf

http://www.aa1car.com/library/2003/eb50331.htm

As well, note the reference to lubricant aeration and oil analysis as a preventive tool

Regards

SwayBar

Kevin's I-J crankscraper system addresses this issue with machined cups which fit over those holes which exit from the block at crank-level on the driver-side, and funnels the oil from the head down into the sump away from the rotating crank. It is so cool!

As I reported before, I have the complete I-J crankscraper system in my new wet-liner engine in my GT race car. As a testament on how well it works, after coming in from a 20-minute session at Road America, the Accusump was barely warm, 80-ish degrees on a 65-degree day; we were flabbergasted it was so cool!

That crankscraper works so well controlling the oil that the Accusump hardly ever cycles which is borne-out by the Accusump's low temperature after a hard session. Before the crankscraper, the Accusump would be 210-degrees after a session.

And let me tell you, that crankscraper is a piece of 'Auto Art'; it is simply beautiful to behold, and very complex. Todd who built my engine was literally beside himself admiring what a nice piece it is.

So the bottom-line is, if you are tracking your car and do not have a dry-sump, then it would be prudent to drill the crank (..my new engine's crank is drilled), and install Kevin's I-J crankscraper system since it obviously works.

GregBBRD

944 GTRs used cranks that were surfaced drilled so that the oil didn't have to go to the center of the crank to get out to the rod (like a Chevy crank). They tried a bunch of different crank designs before they solved the rod bearing issue.....go figure. They supplied rod bearings with more bearing clearance, also. They also spun these engines to 7600.

Abby Normal

Mine's going together next week with all of the hardware you mention

Vilhuer

I-J scraper is complex aftermarket solution which is fine for aftermarket. Its hard fo me to imagine factory using similar in production car or even coming up with same setup other than for racing engine. GTS and late 944 oil pan paffles demonstrates this well. They are very very simple compared to Kevin's scraper. I don't mind using $$$ for it and already have it in garage for GTS. Factory would view need for such setup as total failure of original engine design.

Abby Normal

What if it was a "factory" racecar?

SwayBar

Just so you know, Todd told me the crankscraper install was tricky and took some time to get the required clearances right, but to me, it is all money well-spent, especially after finding out how well it worked at Road America.

Abby Normal

The scraper shipped direct to the shop. Are there some instructions or guide included for the install?

SwayBar

Errka, excellent post as usual.

Mike Simard

No motorcycle crank with the journal size or oiling of a 928 is going to live over 6-7000 rpms. I also believe that a 928 with stock oil passages will soon fail at a steady 7000 rpms even on a dyno with virgin oil fed to the pump, the rod bearings will starve while the pressure gage looks good.
If the journal is a large enough diameter and the rpms high enough and the oil has to reach the center of the crank before it can go up to the rods, the centrifical force will be greater than the supply pressure at a certain point. In a 928's cross drilled crank the force of the oil in that channel will cancel out the supply pressure somewhere within high rpms ranges, I would guess by 7000 rpms. At that point the oil column going to the rods will cavitate and no more oil will reach them until rpms drop. Aeration of the oil within the crank's oil passage's is probably happening too before the critical pressure cancellation point, and that can be with a perfect supply of nice oil.

marton

Also compensates for the gasket shrinking over time; my sump bolts come loose at regular intervals - assuming they did not take this shrinkage into account in the original design....

marton

GlenL

Yes. I wore out a bastard file getting the scraper clearances right. Plan for 6-8 hours to get it all in there and trimmed correctly.

A trick is to attach the drain-back fingers (left side) loosely to the long plate while fitting them.

I-J will email the instructions if you ask them nicely.

Be very careful with the bits and don't overtorque the little nuts. I used a small bending beam-style torque wrench to avoid the "just a bit tighter-Snap!" syndrome.

Ah yes, the "angle of repose." I suppose I'm boring some of y'all by now with this but the spreadsheet calculates a bunch of stuff including how much oil is in the pan during acceleration:

http://home.earthlink.net/~morecowbell98/BenchRace.xls

The up-shot is that for WOT runs the oil flows out of the sump, back across the pan and right into the crank. This depends on how much oil is in the sump and how hard the car accelerates, of course. Maybe not a problem for street cars as a 6 sec blast isn't followed immediately with another. Being at the track is another issue entirely. This is why most track cars are run with the oil low on the stick. That first 1/2 quart or so would be frappe'd and ejected on the first hard 2-3-4 run.

Also, the oil doesn't run back down along the pan until 5th gear or lifting. This depends on the car, of course.

Mike Simard

I'm a bit confused about what you're saying in that post. I understand you want to promote your scraper and are keen on the aeration in the crankcase but I'm not sure if you're discounting the crank's oil passages as a concern or in agreement with the idea of cross drilling being a problem. Since this is a crank drilling thread, here's something from another similar thread discussing the term "cross drilling".
http://www.rehermorrison.com/techTalk/51.htm
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Abby Normal

Thanks! Can't wait to see the results