Leon Speed

I am guessing the reasoning would be that with the step when the pickup gets air, air would flow on top of the oil and enter the passage to the 2/6 feed. Oil would flow more to the main bearings because there is no step there. So removing the step would spread the oil/air mixture over all bearings evenly. So how about blocking the top of the passage to the 2/6 feed? That would deviate air towards the main bearings, but they can handle it better I assume then the 2/6 bearings. So it sounds like a reasonable fix. That doesn't eliminate air entering the oil pick up of course, and short of a dry sump there is no solution yet for that right?

vwdmc16

hey brain at least you got out better than that 4.9 maserati engine in our office did

the rods are goners too

Andre Hedrick

Please do not scare us with Italian carnage

I just had breakfast and saw the above.

So you keep blocks in the office?

Marine Blue

How many miles and what kind of maintenance on the Maserati engine?

dr bob

That engine was driven a while with some serious noises. Either the driver was deaf or the stereo was up enough to mask all the banging noises. In my limited experience, the oil pressure drops off significantly as soon as the rod bearing shell moves and starts to gall. Most drivers only look at that gauge after the banging starts.

I guess if the engine was under warranty still, I'd grit my teeth and let it continue until I was sure I'd get a new engine vs some local amateur at-the-dealer refurb. But it would cause later nightmares for me, letting all that damage happen on purpose.

Back to th 928 discussions...

Kevin Johnson

The pickup does not get air, it gets aerated oil. An abrupt step causes more of a localized pressure change than is necessary. At localized pressure drops compressed air and dissolved air can coalesce/come-out-of-solution. Once coalesced, when the mixture enters the crank it is further stratified.

The simple and logical solution is to hinder the air being mixed into the oil in the first place. This is the idea behind the dry sump. A passive solution exists for the wet sump too up to quite high levels of performance and RPMs.

At extreme G levels a wetsump needs active transport of oil against the prevailing acceleration. This solution exists as well. BMW used it in the M3 (S50 Euro engine). Porsche uses a version of it in their newer Cayman engine, Toyota uses a version of it in the UR V8. Use a dedicated scavenge pump to transport trapped oil back to the sump well. Suitable electric pumps are available for about $300 dollars. Plumbing and fittings would add substantially but it is less than a dry sump.

vwdmc16

do not know the maintence, but being maserati i doubt i was neglected untill the end, the car was in decent shape.

now the miles, well im not sure its accurate. but....















yeah 775K probably a world recored for a quattrapotte. sadly it died in a pick n pull yard.


and we only store sexy engines in the office.

AO

With a top speed of 85, who would want to drive one of those...

GlenL

A serious problem on these cars is that under acceleration the oil rolls out of the sump and doesn't flow down the pan.

I've thought about doing what Kevin suggests. Use a 1-stage pump, like a rear end pump, and suck the oil from the rear of the pan into the sump. Tap a line vertically into the pan between the starter and the clutch slave cylinder and return it to the sump through the top of the "toe" section.

Possibly route the oil first to a small can or tank that would gravity feed back into the sump. That would allow some separation and a bit of storage for the oil. Under hard acceleration it'd just circulate the oil but at least it'd be removing the oil.

If you're wondering, the pan is so slightly sloped that a 300HP 928 at WOT is accelerating hard enough to prevent oil from flowing down the pan in 1st, 2nd, 3rd and 4th gears. This is a critical design flaw in the engine.

Kevin Johnson

I had a chance to look at a wetsump for the Nissan RB26DETT. The witness marks in the sump indicated that there was long term pooling of oil in the rear of the pan. The factory had engineered a slight forward slope and apparently the mounts on the engine or transmission (or loading of the car, wheels, tires, etc.) allowed the engine to tilt back a bit.

This came up as an issue in a Honda D15 pan as well (transverse). I am sure it is a common problem.

mark kibort

Thats it, im reving to 7000rpm and Im going to put a quart of slick 50 in!

Kevin Johnson

It is worth noting another issue that came up from closely studying a number of Nissan pans. The torque converter bolt access hump that became a corporate signature really disrupts the windage flow by creating high pressure disturbances. The RB26DETT has a girdle and the hump projects into the girdle. Looking at the witness marks you could see that it disrupted the flow in a triangular pattern for the length of the engine.

I think the uneven projection upwards of the rear pan floor in the 928 creates a secondary flow pattern with respect to the bay to bay transfer of pumped air. The secondary pattern would be clockwise when looking down at the pan with the front of the engine closest to your feet. This pattern would also tend to trap oil in the rear corner of the pan where it would be churned. Probably at different rpms levels the pattern fluctuates from an axis centered between the last two bays to an axis between the first and second pairs of bays.

Porsche later put windows in between the mains to try to shift some of the bulk of this transfer higher in the block and away from the floor as well as reduced the outer counterweight diameter to stop their projection past the main cap portion of the bedplate. I just looked at a customer's Mopar hemi (RB) and the outercounterweight diameter is at 7" -- this puts it even with the center of the cross bolted caps in the hemi. When you look at a good number of different engines you can see trends of engineering and recurring higher order problems.