From: David W. Lloyd [dwlloyd@earthlink.net] Sent: Thursday, November 08, 2001 9:40 AM To: 928 Subject: [928] Track cars and ZO6's Carlos wrote: > Ed, D. Lloyd, > David Lloyd, how does your 928-hybrid engine compare to the GT's oil > passages. Did you modify anything, or does the combination of parts give > the head oil passage restrictions that the GT's have? I'm using the 2V EuroS heads. The oil return galleys are simply huge passages in the casting, so getting the oil back into the pan isn't a problem. The 4V heads have a check valve affair, I believe, which may be an issue. What IS a problem for SURE, and it seems to afflict both 2V and 4V motors, is aerated oil. The following applies to track situations, so street 928ers need not worry... Sustained high rpm whips the oil into a mist. If the breather venting is to a catch can lower than the outlet (like mine), it condenses and fills the catch can. If the venting is like Don Hanson's, the oil condenses in the lines and drains back into the heads. Ed's failure MAY be related to this, compounded by lateral loading that uncovered the oil pick-up. > Just wondering if any stock pre-87 engines have been blown up this way. If Ed's failure indeed turns out to be the 2/6 rod bearings, oil starvation in the corners can only be compounded by aerated oil in the top end, i.e., less oil in the pan. >Not that I will rest easy until I get my 86.5's crank drilled, and get >some kind of oil sump, but wondering if the S4's/GT's (GTS's?) are more >vulnerable than the earlier cars. The trackmeister, David Lloyd's being >the (repeated) exception, but wondering if the hybrid engine combo >contributes? I'm firmly convinced that the Accusump or dry sump route is mandatory for track use. The redrilled crank is required if you can't keep the right foot from buzzing past 6500...or if you have a cam the WANTS to go there:). >Anyone keeping stats on engine failures? Here're mine: #1 4.5L, scored cylinder wall [must've ingested a 911 part on the track:)] #2 5.0L, first Stuttgart hybrid, rod knock detected on the dyno, saved it. 2/6 was failing. #3 5.0L, second Stuttgart hybrid, built with the 4.5 crank (supposedly less prone to the high rpm oil starvation), no Accusump. Failed at Hallett, 2/6 rod bearings. #4 5.0L, third Stuttgart hybrid, Accusumped and re-drilled, experiencing severe misting. Failed at NHIS when I forgot to activate the Accusump. Saved, but post-mortem not done yet. Re the ZO6 thread, I recently had the EXTREME pleasure of driving one. Taking into account my sordid past (raced a '65, had an LT1 street car), it's an apples 'n oranges deal. Mass produced vs. boutique. But lordy, does that mutha' make some power!!! Best regards, David Lloyd Farmington, CT 79 Euro, Stuttgart hybrid, track car From: Wally Plumley [wplumley@bellsouth.net] Sent: Thursday, November 08, 2001 9:58 AM To: 928 Subject: [928] Re: Track cars and ZO6's At 09:40 AM 11/8/01, David W. Lloyd wrote: >Carlos wrote: > > > Ed, D. Lloyd, > > > David Lloyd, how does your 928-hybrid engine compare to the GT's oil > > passages. Did you modify anything, or does the combination of parts >give > > the head oil passage restrictions that the GT's have? > >I'm using the 2V EuroS heads. The oil return galleys are simply huge >passages in the casting, so getting the oil back into the pan isn't a >problem. The 4V heads have a check valve affair, I believe, which may >be an issue. The oil check valve in the head is in the feed line, to keep the oil in the feed lines from draining back upon shutdown. This reduces the time needed to get pressure to the lifters. Nothing to do with the flow of oil from the head back to the sump at all. Wally Plumley 928 Specialists -----Original Message----- From: Carlos Hernandez [mailto:hernanca@yahoo.com] Sent: Wednesday, November 07, 2001 11:46 AM To: 928 Subject: [928] Re: Status of my GT Ed, D. Lloyd, Ed, would you say you drove your GT on very similar tracks and in the same manner as your 86.5? David Lloyd, how does your 928-hybrid engine compare to the GT's oil passages. Did you modify anything, or does the combination of parts give the head oil passage restrictions that the GT's have? Just wondering if any stock pre-87 engines have been blown up this way. Not that I will rest easy until I get my 86.5's crank drilled, and get some kind of oil sump, but wondering if the S4's/GT's (GTS's?) are more vulnerable than the earlier cars. The trackmeister, David Lloyd's being the (repeated) exception, but wondering if the hybrid engine combo contributes? I love going to redline, but haven't (much) since my 4K vibration developed . Anyone keeping stats on engine failures? Carlos Hernandez 86.5 928S 5-Speed, 150K Miles Gran Prix White / Black Leather From: Jim Bailey [jim@928intl.com] Sent: Thursday, November 08, 2001 5:32 PM To: 928 Subject: [928] Re: Status of my GT Carlos , the early 928 was redlined (CIS with a centrifugal rotor) cut out at 6,300 + - 200 prm , 1980 USA at 6200 + - 150 by electronic cut off of fuel pump , 1985-86 USA cars cutoff at 6,400 , S-4 cutoff at 6,600 and the GT at 6,800 rpm , then the GTS for some reason was put back at 6,600 rpm . So the GT has a higher rpm cutoff and is a 5 speed manual which allows the driver to hold it in a lower gear near redline while cornering ... the automatic transmission cars sensing part throttle would upshift and drop rpm . The oil return passages cast into all the engine blocks are eight rectangular passages about 3/4 inch square . They match up to the bottom lower edge of the cylinder heads . The heads mount to the engine at a 45 degree angle ( engine is a 90 degree V-8 ) . Oil pumped into the heads drains down a 45 degree slope then falls into the eight 3/4 by 3/4 passages down to the oil pan . The drain passage area 8 times .75 square inches is about 6 square inches that is a rather large amount of drain potential . Theoretically , excessive windage (oil being beaten by the crank rods and movement of the piston) coupled with blowby (combustion gasses leaking past the rings ) might pressurize the crankcase and push oil / foam up the 3/4 inch passages . Remember the oil separator screened can used from 78-84 where you add oil) was eliminated for 85 > and no longer has a hose running from the separator down to the top of the oil sump pan to return liquid oil . For reasons known only to Porsche with the GTS they added additional vents on the left cam housing cover . Stroker engines moving the piston up and down some 95 mm have more air moving around under the piston than a GTS at 85.9 mm or the standard 78.9 mm stroke of the 4.5 to 5 liter . Additionally the piston must move faster to maintain the same RPM adding to windage problems as well as wear on the rings from traveling farther , roughly 20 percent per revolution . Think of the piston at top dead center it stops moving up and starts down (the opposite at the other end of the stroke) but half way up or down and the crank shaft journal is at a 90 degree angle and the piston is moving at top speed . At 6,000 RPM the piston is going up and down 100 times per second !! GTS blocks have added windows at the bottom of each cylinder to help allow air to get away from the bottom of the pistons . There has been previous mention of oil consumption and smoking from 928s being tracked particulary the 32 valve engines including GTS which seems to be the stock crankcase venting system allowing oil to be sucked into the intake to be burned by the engine . Don Hanson has replumbed his system to eliminate much of this problem . Mark Anderson the "White racecar " runs a drysump system , fabricated oil pan , and large oil seperator , reservoir. A seperate belt driven oil pump sucks all the oil from the oil pan and dumps it into the reservoir . The stock oil pump is fed by a direct line from the bottom (liquid oil) of the oil reservoir . The reservoir is small diameter but rather tall to minmize the side to side movement of the oil under cornering forces . Jim Bailey 928 International Jim@928intl.com www.928intl.com (714)632-9288