John Veninger

A 928 that sees extensive track use on sticky tire needs an accusump and a drilled crank. It's a $1k insurance policy when building a motor.

A DE once in a while with street tires needs a good oil and shifting at or below 6K seems to keep them alive much longer.

GlenL

Yep. Grenaded the engine. The last one was three years ago, for those keeping track.

I was planning to post some pictures and still might. I've got the whole thing apart and the reults are clear. The rods for 2&6 both broke and the shards broke those pistons and beat the block and cylinders badly. The block is a loss. The crank is scarred and likely too much cost, hassle and risk to fix. There's one obviously bent exhaust valve but the heads look good otherwise.

As to the source, two bearing halves, likely from one rod, are worn down to the copper over most of the surface. This looks to be the failure source. The other bearings picked from the wreckage look "ok" while those on the other 6 pistons look great.

Seems it wanted to fail hard and not just give some knocking. It all let go at about 6300 RPM.

The crank scraper was intact and all nuts an such were still tight. The fingers for 2&6 were jammed down and away. None of that stuff got in the way until it was too late.

To Kevin's question there was no sign of detonation. I'll check things over again but the piston tops and head chambers show no sign of detonation. There were no broken rings or lands. I didn't explicitly check but nothing fell apart.

I'll have more to say later but here's a few hindsight items:

Replace the bearings whenever it's easy and at least every Winter if you're going to track it hard.
Get oil analysis done.
Keep it below 6K RPMs
Get an accusump.
Get a dry sump.

Foam leads to failed bearings. Foam leads to oil ejection. If you've got one then the other is lurking.

mark kibort

Im still lurking! that sucks. wonder what the common denominator now is.

I think redline is close to the same as amzoil in my unscientific research. (what have read on the advertisments!)

i guess i have been real lucky to have over 70 race days on the Holbert chassis and engine with no issues. Im shifting at near redline every shift in the races and times on tight high G turn tracks like Sears, almost 3 seconds faster than anderson when he was first there on the same kind of DOTs in year 2000 with 100 more hp but a newbe to the track. (still knocking hard . "knock , knock")

There maybe a drilled crank in the Holbert car and some anti windage things, but i doubt it. my other 5 liter part euro just had a stock 85 bottom end.

I wonder if there is any kind of driving style thing that could also contribute.

Glen, sorry to hear of the grenaded engine! major bummer!!

MK

GlenL

Yes. Major!

As for driving style, here's a snippet of mine:

Floor it through third, floor it through fourth. Wait 'till the last instant and brake the Hawk Blues at the threshold. A bit of trail braking and then roll on the gas ASAP and get it to the floor! Repeat!

In other words, I'm driving it as hard as I can. MPSCs at the corners but just S4 rims. My boy remarked at the local club race "you're within three seconds of most of them." That's an eternity in racing, but you get the point.

John Veninger

I don't doubt it.

Carl Fausett

First race on this new motor with the 2nd generation windage scrapers and tray installed is Saturday Aug 26th.

Currently, I have 400 miles on the motor and am pleased with the results - I can take 3rd gear to about 80 MPH at WOT with 6-7 psi of Boost showing on the gauge and then lift and engine brake back down hard and not fill the catch tank. That's NEW.

Still, interstate playing around is not racing - we'll see what she does.

Here is the list of the oil control mods we have running in combination on this boosted race motor (this is a 1988 5.0 liter block wearing a 1984 16v Euro top hat)

>Total Seal Piston rings to reduce blowby
>Low-Expansion alloy pistons fitted to 1/2 of factory piston-to-wall clearance to reduce blowby
>Ishihara-Johnson full crank scrapers with 2nd generation oil return troughs
>Ishihara-Johnson full windage tray over sump with directional screening
>Oil Pan installed with 2 stacked oil pan gaskets to lower oil away from rotating assembly (required a custom clutch slave hydraulic line)
>928M Improved Oil Separator modifications (available at our website)
>Custom baffled crankcase vent pick up - (sort of like Tony's, but a little simpler to make)
>Snorkeled front oil drain tube (see pictures above in this thread) to prevent loading the separator on hard braking and
>Restrictor installed in front oil drain tube to prevent loading the separator on hard braking
>Crankcase vented to oil separator/catch can with top exhaust (the Mahle oil separator did not work and has been retired)
>Cranckcase pressure reduced by venturi nipple welded into header collectors and plumbed to suck out crankcase
>Canton/Accusmp EPC electric valve installed to eliminate accidental Accusump discharge and to reduce re-charge tiime of Accusump
>Oil Scavanging pump (available at our website) is plumbed to bottom of catch can - switch on the dash - I can put the oil back in the engine if I want or need to should catch can become full. That is a safety precaution - so far I have not needed to do that.

Anyway - we'll see how it runs on Sat and report back. 400 miles is really not the best to start racing at - I do not believe the rings are completey seated yet, so I do expect a some catch-can filling on race day just from the short break-in period.

Even should that occur - I will still be able to tell if we are on the right path to control crankcase vapors on a boosted 928 under race conditions.

Rick Carter

Carl,
Nice to see progess. Do you know if oil coats your intake?

Carl Fausett

No - not on this car because I am not re-breathing crankcase fumes like you would on a street vehicle.

The PCV gases are drawn off to the catch-tank/separator, and not allowed back into the intake. This is referred to as an "open system"

On most street-blown cars I have seen that employ a closed system (PCV gases drawn back into the intake and burned) then yes, of course, you are going to see some oil film into those tubes.

In my experience, I have not seen any problems caused by a small quantity of oil film on the tube walls other than perhaps the need to change spark plugs a tad more often if they are fouling (especially because it is popular to go one plug colder on SC cars, and then the spark plug cannot burn off oil as well and it forms into deposits).

A larger amount of injected oil in the intake stream though, will lower the octane rating of the charged mixture and can lead to detonation. This is more so if mineral oils are being used, less so if synthetic.

Rick Carter

Carl,
I have an open system, venting both cam covers to catch cans but there was a film of oil in the intake just before the SC. I'm puzzled as to source.

Rick Carter

Kevin,
I don't think it's the rebuilt SC. Thanks for the link, he charges $250 for porting lower than the $400-$450 quotes I've had. If I had a guarantee it would give me 35+ rwhp I would do it this winter.

GlenL

Carl,

Forgot to mention that I tried the bit you sent. No difference. I also tried adding a second oil separator (2" PVC contraption) that drained back into the pan. (Tee'd into that Al piece. Thx.) Again, no difference.

Something that this showed was that the problem could be that the lower end of the fill tube was getting uncovered as the oil sloshed away on hard acceleration. That'd allow air to go up the tube and disrupt the stock separator. It might also be carrying foam up the tube.

I was lookng for a 1-way valve before it blew. Also looking into extending the fill/return tube to the bottom of the pan. I'm also thinking about venting from the heads and blocking the block-top exit.

Carl Fausett

Rick - perhaps you are using a oiled cotton air filter (aka K&N) ?
Oil in the tubes BEFORE the SC should not be too hard to find - there isn't much else it can be if there are no PCV hoses routed up there.

Glen - I'll let you know how it all turns out. Did your second separator have a pump to move the oil into the motor?

Please rememeber that any "return" line back to the engine will never work without some sort of pressure differential... a "push". Simply put, the drain from the bottom of the catch can to the cam tower (or wherever you put it) will have crankcase pressure on both ends of the hose - and the oil will not flow.

If the catch can has a vented top (open system) there is actually MORE pressure in the motor than the catch can - then ESPECIALLY the oil will not flow in against the air trying to get out.

You must pump oil from the catch can or separator into the motor - it will not flow by gravity alone.

Carl Fausett

Forgot to mention - I am also trying the new Canton Accusump EPC valve.... seems that they have improved the Accusump remote electric valve by adding a pressure switch to it.

Several of us have mentioned how it seems the Accusump unloads at in-opertune times - then I am suddenly over-full and pumping the first quart up into the catch tank. This gets blamed on the 928 engine design - but may actually be an Accusump error.

The old electric valve (which I have had until tomorrow) had a slow recharge rate... so if the Accusump unloaded into your oil system, once the G's straighten out and you do not need the extra oil anymore - the extra 2 quarts will get thrown into your catch tank faster than it will get pushed back into the Accusump to recharge it.

The Accusump engineers tell me that the recharge time on the 3 qt Accusump with the traditional remote electric valve could be as long as 90 seconds on a 3 qt Accusmp. Hell, I have burped my 1 qt catch can (which I measured actually holds a pint) by then.

Solution? They have now added a Hobbs-type pressure switch just past the valve... and it does two things.... it makes accidental discharge of the extra oil into the motor less likely, and it greatly increases the up-take or recharge rate of the Accusump.

My hope is that the Accusump will actually refill now before my catch can throws it overboard. It is called the "Accusump EPC valve"

John Veninger

I ran a two cans on my old EuroS motor. This was done after spending to much time after ever track session emptying oil form the catch can! Throwing money into the recycle container!!
The first was a separator with one small -4 drain line back to the pan were the stock oil tube use to be, no pumps. There were two -8 lines from a custom oil fill off the top of the motor to the separator. Another set of -8 lines from the separator then feed a standard catch can w/ a breather via two -8 lines. No issues at all.
I could run a PCA Club Race for 45 min. on the track and get a few teaspoons of oil in the catch can. Was running the standard accusump electrical setup.

GlenL

The "push" is the weight of the oil itself. As the block-top vent is pretty big the difference between external and internal pressure should be low. Then the return oil will flow down the tube. That's the way the existing system is supposed to work with the oil going back down from the filler/separator.

Having the tip of the return below the oil surface will improve the flow down that path. With the return from the second separator piped into that I expected it do drain some oil but there was no improvement at all. That tells me there's a basic assumption wrong like there's airflow up that tube.

Does point up that if the airflow through the main opening is restricted then the blow-by will overly pressurize the crankcase and will pump the oil up into the filler. I recall you demonstrated this.

Maybe one day I'll pull the hood at the track so I can watch what goes through the clear tube.