944ja väntvõll ja kepsusaale probleemid

Porschede mootori- ja veermikuprobleemid.
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joonas
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Re: 944ja väntvõll ja kepsusaale probleemid

Postitus Postitas joonas » 15 Apr 2009 12:36

Paar huvitavat arvamust õli temperatuuri kohta
http://forums.rennlist.com/rennforums/9 ... crank.html

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Re: 944ja väntvõll ja kepsusaale probleemid

Postitus Postitas joonas » 28 Apr 2009 18:39

Juttu kas accusump aitab või ei. Linnalegendid jätkuvad ...
http://forums.rennlist.com/rennforums/r ... ation.html

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Re: 944ja väntvõll ja kepsusaale probleemid

Postitus Postitas joonas » 30 Apr 2009 11:07

Rick,

Ok, here is the real reason rod bearings (mostly #2) fail in 944s.

In 1985, when we won Firehawk Grand Sport, we had to run on Firestone S660 tires. The bottom end of the engine was never disassembled and we never had a bearing failure. At the end of the year, the engine was disassembled and the rod bearings were great. Why? The tires had no stick. Cornering never exceed .96G, we didn't hit curbs, drive off the track, and braking didn't exceed .98G. We shifted at 6400 rpm because the rev limiter cut in at 6500.

Here's why the rod bearing fails. There isn't sufficient oil at the rod bearing to lubricate and cool it. Bearing cooling is one of the most important functions performed by lubricating oil.

Why isn't the oil supply sufficient? There are a number of reasons. The first is the oil pump design and the oil pump supply. The gerotor pump design should never be driven faster than 70% of crankshaft speed. On the 944, it's locked to the crankshaft. At high revs, air can be drawn through the oil in the oil pan when the oil covering the pickup is marginal and enter the oil system. When this air reaches the oil pump, there is an instantaneous loss of oil pressure until the air is compressed. When the air reaches the oil gallery, it is mixed with oil and traveling at quite a velocity. The oil inlet port to the main oil gallery is opposite the oil supply to #1 main bearing. #1 main bearing supplies oil to #1 rod bearing. Oil has considerably greater mass per unit volume than air so oil goes to #1 main bearing and air displaced and forced down the gallery to #2 main bearing supply. #2 main bearing supplies oil to #2 rod bearing. Main bearings can live with marginal lubrication much longer than can rod bearings. Rod bearings fail rapidly when subjected to air and oil mixed. This is the total reason.

What can be done about this? 0. Run tires with no grip 1. The oil pan can be baffled better than the factory baffling to keep the oil level higher at all times. 2. The oil pickup can be modified to reduce the ability for air to enter. 3. Air can be removed from the oil before the air gets to the engine. 4. Bearings can be coated with an oil retaining film that makes the bearings more durable when supplied insufficient oil. 5. Modifications can be done to the oil pan to remove more oil from the crankshaft (may not be legal in PCA) and return this oil to the deep part of the sump. 6. Use an accusump with an anti-backfeed one way valve to keep the instantaneous pressure loss from occurring (I feel this is the least important but OK with the rules makers). 7. Never run the oil level over full as this allows the crankshaft to whip more air into the oil. The question here is just what is full? Try checking the oil level this way and run it half way between the full and add line. Engine fully up to temperature, remove the dipstick and plug tube with finger. Rev engine to 5000rpm and hold for 15 sec. Switch off engine. Immediately after crank stops turning, insert dipstick and remove, reading level.

Hope this helps

Jon

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Re: 944ja väntvõll ja kepsusaale probleemid

Postitus Postitas Raceboy » 30 Apr 2009 12:26

Ja kõige olulisem jäeti mainimata: kuivkarter, mis on tegelikult ainuke õige lahendus probleemile.
'83 924 2.6 16v Turbo 570 hj
'67 911 hot-rod 2.4S
'78 924 Carrera GT projekt
'84 928 S
'90 944 S2 Cabriolet
'91 944 S2 [müüdud]
'82 924S/931 "Gulf" 2.0 Turbo [müüdud]
'84 924 2.0 "Turbo" [müüdud]

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Re: 944ja väntvõll ja kepsusaale probleemid

Postitus Postitas joonas » 30 Apr 2009 13:20

Raceboy kirjutas:Ja kõige olulisem jäeti mainimata: kuivkarter, mis on tegelikult ainuke õige lahendus probleemile.
Võibolla tead mingit linki, kus on hea kirjeldus 944 kuiva karteri kohta. See kuivkarteri soovitus on ka igalt poolt läbi käinud. Vastustes ei ole seda vahest selle tõttu, kuna klassid, kus osaletakse, ei luba sellist modifikatsiooni.

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Re: 944ja väntvõll ja kepsusaale probleemid

Postitus Postitas joonas » 30 Apr 2009 13:55

928 ja Devek accusump-i propageeriv leht
http://jenniskens.livedsl.nl/Technical/ ... Tip780.htm

There are two issues with 2.6 oiling failures.....oil galley flow and oil pickup starvation.....unless you are revving over 7K, the later is the only one that applies to the common 2.6 failure.

You can drill your cranks any way you like, but it will not solve the under 7000 rpm 2/6 oiling problem. We thought that this was a partial solution long ago, but further research indicated that there were other forces at play...no pun intended.

Only an accusump, properly installed will do the trick. Porsche AG recognized our solution years ago and bought our Racing Accusump kits for their racing customers.

We identified the problems and developed the solutions long ago, and have proven it to work time and time again on sub 7K rpm racers with non-drilled cranks!

Marc
DEVEK
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Väljavõtted Deveki kirjavahetusest
http://www.nichols.nu/tip682.htm

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Re: 944ja väntvõll ja kepsusaale probleemid

Postitus Postitas Raceboy » 01 Mai 2009 08:12

Mis linki siin anda on, kuivkarter on lihtne ju....Pace ( http://www.paceproducts.co.uk/" onclick="window.open(this.href);return false; ) pakub bolt-on komplekti 924/924 Turbole umbes 20 000 krooni eest, ma pole kursis kas nad 944 mootoritele ka pakuvad, aga kuivkarteri süsteemi tegemises pole midagi rasket, tuleb lihtsalt osta korralik pump, rihmajam paika panna, õlivann ümber teha, õlipaak osta/teha ja voolikud Dunlopis/Hydroscandis teha lasta.

Endal on see plaanis järgmine või ülejärgmine talv, hetkel pole viitsimist ega eriti raha ka mitte.
'83 924 2.6 16v Turbo 570 hj
'67 911 hot-rod 2.4S
'78 924 Carrera GT projekt
'84 928 S
'90 944 S2 Cabriolet
'91 944 S2 [müüdud]
'82 924S/931 "Gulf" 2.0 Turbo [müüdud]
'84 924 2.0 "Turbo" [müüdud]

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Re: 944ja väntvõll ja kepsusaale probleemid

Postitus Postitas joonas » 01 Mai 2009 18:26

928 õlituse kohta

Oiling facts:

1 during a test at laguna in 1995/96, using mobil 1 at factory recommended fill volume, turning 1:44's laps, showed repeated fluctuations - drops in oil pressure using a stock crank running at 6000 rpm.

2 dyno test to 8,000 rpm for 30 seconds using a stock crank and modified chipset using factory filled crankcase showed fluctuations in oil pressure at 3-6 seconds

3 disassembly of the above engine showed unusual wear patterns on 2/6 rod bearings vs other journals. all journals had "rpm" related wear

4 same laguna test #1 performed with drilled crank..same oil pressure drops

5 same test as #2 performed, same drops

engine not disassembled, oil tested ok

6 install devek race accusump system

7 #1 laguna test performed, no oil fluctuations

8 # 2 test performed again, oil fluctuations occurred later in test 10-14 seconds

9 engine disassembled and bearing checked....some wear on 2/6 bearings

10 two known 2/6 rod failures in GT by driving at or above 5500 rpm for over 100 miles through sweepers. engine oil level unknown.

11 many 2/6 rod failures in track driven 928s

12 known failures using an accusump...one not turned on and the others not installed correctly and too small a capacity...now you know why we choose the 3 qt vs a smaller size.!

13 Porsche AG purchased DEVEK race level accusump for 928 racers after repeated failures of customers racers....no recorded failures since installation

Conclusion:

2/6 failure at normal rpms is due to oil starvation, not crank oiling pattern

the hotter the oil, the faster the onset of starvation

if you are spinning it ot over 7K rpm, drill the crank

DEVEK 3 qt accusump system will allow for more time before onset of oil starvation. If you are using slicks, use the race level system.....

dry sump will eliminate starvation forever, regardless of crank, unless you exceed 7000 or so rpm, then you need revised oiling pattern...also, a well designed dry sump will add 7 or so hp per liter...hmm, in a 6.5 that makes close to 50 hp...

Porsche designed an excellent street engine......the reason why GT and GTS fail "more" often is the average revs are higher, thus more oil is pumped and "aerated", and less is available to be pumped to the bearings.......And in Germany, running at 170 ish on the bahn, the revs are high, the oil level in the crankcase is low and up comes a high speed high "g" corner...and a potential oil starvation situation.....a condition they did not take into account.....well enough.

Things you can do to minimize the situation:

1 keep the oil cool
2 run high grade synthetic...cost more, but change less...amsoil, redline, etc.
3 if racing, use race level accusump
4 if building a racer from scratch, use dry sump and gain hp

maybe more on crankcase venting later...

Marc
DEVEK


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Re: 944ja väntvõll ja kepsusaale probleemid

Postitus Postitas siim » 01 Mai 2009 19:27

Mida rohkem ma taolisi tekste loen,s eda vähem ma tahan rajale minna :?
928
996 C4

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Re: 944ja väntvõll ja kepsusaale probleemid

Postitus Postitas joonas » 01 Mai 2009 19:38

Huvitav 928 karteri tuulutus väljalaske süsteemi.
http://forums.rennlist.com/rennforums/1 ... st101.html

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Re: 944ja väntvõll ja kepsusaale probleemid

Postitus Postitas joonas » 01 Mai 2009 20:10

siim kirjutas:Mida rohkem ma taolisi tekste loen,s eda vähem ma tahan rajale minna :?
Paistab, et rada pole vajagi. Piisab, kui kõrge pöördega, kehva õli ja madala õlitasemega sõita.

Väidetavalt peaks mingi lahendus olema ka peale kuiva karteri süsteemi, kuid see paistab olevat saladus :)

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Re: 944ja väntvõll ja kepsusaale probleemid

Postitus Postitas joonas » 31 Aug 2009 17:29

Leidsin veel ühe "lahenduse" kirjelduse

I am using a different method as suggestd by Greg Fordahl out on the West Coast. They support a lot of ITS 944's out there and though his local contacts with a NASCAR engine builder, was able to use their equipment to come up with a simple solution to the #2 problem.

According to their research, the #2 bearing gets almost no flow ad idle which is the cause of the premature wear. Cross-drilling the crank doesn't improve flow. They used the Nascar engine flow tools to look at a simple ratio of oil being pumped through the system. #1 and #4 bearings were getting 50% more oil than #2 and #3. To even out the flow, they simply installed restrictors in the #1 and #4 oil galleys that provide about 50% restriction. The result was near even flow through all 4 bearings and much-improved flow at idle for the #2. The machine shop that did the crank polish and hole on my engine was familiar with this technique and it cost almost nothing to have it done while the engine was in their shop.

Only time will tell, but Greg assures me that they have tried cross-drilling and other techniques and this one seems to make the engines last the longest.

http://44cup.zeroforum.com/zerothread?id=691

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Re: 944ja väntvõll ja kepsusaale probleemid

Postitus Postitas ndrk » 31 Aug 2009 21:00

nojah...kui ühele juurde anda ei saa sis tuleb teistelt veidi vähemaks keerata...

Mul üks üldine õliteema küsimus: Kas 944 motorile meeldiks 10W60 sünt?(gulf) või peaks kindlasti poolsünt olema (mootoril 320 000 km turjal, lahti pole käinud...väga tõenäoliselt).
R - stands for Racing

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Re: 944ja väntvõll ja kepsusaale probleemid

Postitus Postitas laur4 » 01 Sept 2009 08:45

Pane ikka täissünti ja jälgi igaks juhuks, et õlirõhk piisav oleks. Mina kasutasin 5W40 täissünti 944-l ja ka see sobis küll. Läbisõit oli teadmata.
Õlide kohta oli siin kusagil üks eraldi teema ka.

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Re: 944ja väntvõll ja kepsusaale probleemid

Postitus Postitas joonas » 02 Sept 2009 14:18

joonas kirjutas:Leidsin veel ühe "lahenduse" kirjelduse

I am using a different method as suggestd by Greg Fordahl out on the West Coast. They support a lot of ITS 944's out there and though his local contacts with a NASCAR engine builder, was able to use their equipment to come up with a simple solution to the #2 problem.

According to their research, the #2 bearing gets almost no flow ad idle which is the cause of the premature wear. Cross-drilling the crank doesn't improve flow. They used the Nascar engine flow tools to look at a simple ratio of oil being pumped through the system. #1 and #4 bearings were getting 50% more oil than #2 and #3. To even out the flow, they simply installed restrictors in the #1 and #4 oil galleys that provide about 50% restriction. The result was near even flow through all 4 bearings and much-improved flow at idle for the #2. The machine shop that did the crank polish and hole on my engine was familiar with this technique and it cost almost nothing to have it done while the engine was in their shop.

Only time will tell, but Greg assures me that they have tried cross-drilling and other techniques and this one seems to make the engines last the longest.

http://44cup.zeroforum.com/zerothread?id=691
Saatsin Eric Rupertile meili, et täpsustada, millised need restrictorid on ja sain järgneva vastuse.

Unfortunately, it’s been a long time since that post. What I can tell you is that I raced the car for 3 seasons and won a championship. I then sold the car to another guy. He ran it for two seasons before selling it. As far I know, the engine was still strong after 5 seasons.

The mod was described to me by Greg Fordahl of Fordahl motorsports on the West Coast (Chief Engineer for the Alex Jobs ALMS team and Brumos Porsche Daytona Prototype team). I mentioned to the guy at the local engine shop and he knew exactly what to do. You need to restrict the #1 and #4 galleys by threading in an allen plug then drilling it out to provide 50% restriction. (have to do some math on that one as I don’t remember the diameter of the galley).

Vasta