Kevin Johnson

Erkka put up a nice diagram of the oil passages and depths in the bedplate a while back. The 2/6 path is the closest to the main feed and has a smaller diameter, ergo pressure reduction which allows compressed entrained air to evolve.

Rest assured that if you could change that the failure would occur in another location. The oil galleys are not the problem. They are an advanced design.

Dead stop. Yes, you can blame the oil quality with respect to the amount of entrained air.


Dead stop. No, not necessarily. The Corvette has a factory drysump that can be overwhelmed by too much aeration. Things are not so straight forward.

The 10psi per 1000rpm was/is a heuristic attempting to overcome entrained air. Priority feeds to the mains is a way to keep this pressure up and entrained air bubbles small and uniformly distributed.

ew928

Anyone frothed up some hot engine oil in a blender and tested to see which oil is best at shedding the bubble/foam? Or was it covered already.

mark kibort

I had the Hoosiers A6s this weekend, so that blows the more grip will cause issues . 2 full races, no issues. no cooler, no accusump, no baffle, no breather problems, near redline shifting on all shifts, 250-260 degree oil temps, and Amsoil!

Kevin Johnson

I would add the obvious third, the windage control system I designed and that has been tested over several years now. It certainly works up to a reasonable G-level. I have heard of three engine failures; all owners admitting that the failure was not due to the system: 1) one involving a rare factory mismatched cap with matching serial numbers -- if the rod had been resized this should have corrected it; 2) one involving a fatigue fracture of a piston skirt that then bounced around in the engine; 3) a failed timing belt.

I have to mention 3 because it seems that the system is imagined to confer a cloak of invulnerability on all other parts.

I remember people mentioning both dry sumps and drilled cranks allowing the 2/6 rod failure.

Kevin Johnson

I heartily suggest doing this. It should be a published spec for oils. Good luck with that.

Kevin Johnson

Yawn. The engine was designed to be raced at 7200 rpms. I mean let's get real here.

Race the car the way it was meant to be run. Its a P O R S C H E

Mein Gott.

ptuomov

Do you have a link to materials on this? I'd love to learn about the Mazda BF/B6 and BP crank designs. If you have something that is not on the web, please post it here or email it to me at <my RL username>"@"<name of the email service by google>"."<first three letters of word commercial>.

Kevin Johnson

http://cgi.ebay.com/ebaymotors/MAZDA...Q5fAccessories

The pic is helpful. The visible opening on the rod journal passes through to the opposite side. If you're serious about it you should snag a junk one. I learn a lot about engines by having them in front of me to study.

ptuomov

I am a big believer in examining a wrecked engine before working on a working one. I bought a fire-damaged '89 S4 engine just to take it apart and see what's inside before opening a working engine. Learned a couple of things already that are better learned on a wrecked engine.

So, to follow up on the topic. There's a couple of ways to combat the problem you are focusing on. Please correct me if I have misunderstood this:

First, whatever air there is in the oil should stay evenly distributed in the oil. Removing anything that causes separation of oil and air in the oil passages helps.

Second, whatever air there is in the oil should be somehow separated in the wet sump/pan. Any mechanism that separates air and oil before the oil pickup in the pan helps.

Third, anything that prevents air mixing in the oil in the first place helps.

Is this basically it? Or have I misunderstood something here?

Continuing on the first topic, is the "Taylor driller" crank as diagrammed in Dennis Kao's photos the best way to do it? Is the Taylor path design the same as the Mazda path design? See the diagrams here: http://gallery.lasttenth.com/main.php?g2_itemId=1440

mark kibort

Lets get real here. You dont know what you are talking about. (racing, and getting the most out of a 928 engine) Have you seen the HP curve for not only the holbert engine, but the stroker engine I race?
If you shifted at 7200rpm, I would be running all over you! You know why? HP curve shape and breadth. 4500rpm to 6500rpm gives me the highest ave HP possible.( HP-seconds maximized) Any higher or lower and you LOSE!!

But, if you just like to beat up your equipment like many of my competitors that do lose engines after a season or two ,or less, then knock yourself out. (I count on the misread of most of my competitors HP curves to win races with a lesser car!)

I have one comment. 1:37.5 at Laguna seca. 1:37.8 with a stock engine with a set of headers. Still think Im not driving the snot out of it?

Watch the last race video, then comment!

http://www.youtube.com/watch?v=xYbFeIai2Ng

mk

ptuomov

MK --

So, if someone would give you big cams for free, would you put them on? And if you would put them on, would you harvest more hp-seconds by racing it at a higher rpm or would you choose to save the engine? Decisions, decisions, although hypothetical...

My point being is that getting the most hp-seconds out of any (normally aspirated) engine means making choices during the engine building stage that lead to an engine that will produce those hp-seconds at high revs. To reconcile your difference with KJ, one could say that you are talking about racing the engine that you have in the car and KJ is talking about building up an engine to get the most hp-seconds possible.

This is not just hypothetical. You could have your S3 cams reground to more aggressive profile, for example by Elgin/Morton.

Best, Tuomo

Charley B

Holy Crap!!!! Two of my favorite people at each other's throat's. Now who do I root for?????

mark kibort

I get it loud and clear and you are right. Kind of analogous to running my engine with stock transmission because I know if I run it with the power I have now,it wont blow. To your point, yes, if I could have andersons HP curve and a transmission to support it, you bet-cha! Then, and only then would I be thinking about coolers, baffles, accusump, drysumps, etc. I do think the drilled crank is a great idea and Have one as well, BUT, the Holbert car motor didnt have it drilled and its in fine shape after 106 race days!

I only said something back because you said I wasnt driving like it was ment to be driven. according to the HP curves of both. I am.



PS: as a side note, I wonder what the reground cams would do on my engine now. Of course Ill end up doing it someday. Hopefully, on the big motor, and not the old 5 liter like dennis'.

Stan.Shaw@Excell.Net

In a 928 with a dry sump, who? Has to be a pretty short list of 928s with dry sumps.

ptuomov

If you get me your engine specs now with a dyno graph, I might come up with a simulation model for it. If I can match your current engine, then I can give you hypothetical power curves using different cam durations and lifts (assuming S3 lobe separation angle and some reasonable cam advance/retard). From those, you can choose what you want and then talk to Jim Morton and Dema Elgin about what is achievable and at what cost.

How about it, you post your engine mods and dyno curves here and I'll try to model them with EAP?