JET951

Here are some interesting notes we have made on the interesting subject of 944 / 951 / 944S2 / 968 con rod bearings .

Note } Over the years we have seen & heard of people having trouble with conrod bearings / destroyed engines with the above mentioned Porsche's & 928 series as well , however we do not , even running wet sump on the track with racing slicks

First of all some background info }

Sean has been competing in the PCNSW ( Australia) SuperSprints( Race track) & Motokahana ( Auto X ) since 2006 in his 1986 951 and has won the Drivers Championship twice & the Motorkhana Championship twice and is the current Open Class winner

The car itself is a full road going car , full carpets , full sound insulation , Excellent A/C system , four speaker stereo , electric sunroof , full steel panels & factory glass , in fact its Sean 's only means of getting to & from work .

Since going into Open class( up against GT3's etc) just over a year ago Sean installed a in house custom 8;1 compression modified 3.0L 944S2 Turbo engine running a Vitesse stage 5 and at the track runs E85 fuel ( 85% ethanol )& on the road as well most of the time
Note } the E85 allows us to reduce the knock count & in turn run higher ignition advance as opposed to running 98 or 100 octane petrol ( gas USA speak)


Over 440 BHP this car is the fastest Porsche on the track with Licence plates in the PCNSW championship , no other GT3 that is road registered can keep up with it , not bad for a 26 year old Porsche 4 cylinder daily driver

Basic Engine details }

*Wet Sump ( yes it competes on the track with racing slicks)
*Large engine oil cooler ( I mean large)
*Custom crankcase breather system ( in house designed & made), this is extremely important
*Vitesse Stage 5 ( would not use anything else )
*Standard ignition system ( Bosch standard cap & coil & standard Beru Leads )
*Custom Pistons , standard Porsche Alusil bores / crankcase
*Standard twin cam head & cams
*custom exhaust system ( Sean made it )
*Speedforce custom inlet manifold + some extra bits
*Custom 104 metal head gasket
*Custom conrods
*Standard Glyco road going conrod bearings & main bearings
*Standard Porsche 951 sump & standard baffle.

Like previous years we set a predetermined schedule to check certain items for wear etc , and in the case of the conrod bearings we just remove the engine sump ( in car) once a year to inspect & replace no matter what or put another way no matter how little wear .

Why little or no wear ?
Answer = we run a minimum viscosity Racing oil of 25w-60 , this is the absolute minimum viscosity racing oil we use for these engines ( ours & customers)

Do not use anything less in viscosity for the track , because with high core temps , the thinning engine oil ( read lower oil pressure at any RPM) will allow( increased risk) air bubbles to enter the main crankcase oil gallery & for some reason no 2 conrod oil feed gets this in a bad way , so how do we reduce this risk ?

Easy, just up the oil viscosity as per the owners manual Printed by Porsche that came with the car , be it 944 , 944S , 944S2 , 951 , 968 , and for the ambient temp rangers of minus 10 deg cel to unlimited high temps = 20w-50( for the street) , so for being flogged at the track then you must up the viscosity a bit further , and it must be a racing oil with very high oil film strength

Question }
How do you increase oil film strength in engine oils ?

Answer , there are two ways

A) increase oil viscosity , say from a 10w-40 to a 20w-50 ( where both oils have the same theoretical levels of ZDDP AW additives )
Note } AW = Anti wear

B ) increase the levels of ZDDP , remembering that racing oils are exempt from the ACEA emission protocols , so that means racing oil are allowed to have higher levels of ZDDP AW additives

So if you add the two together( higher Vis + ZDDP) then you get a high oil film strength & this high oil film strength is the last line of defence if the oil pressure is dropping( even a little) in say no 2 conrod journal

Now how do you help the viscosity at high core temps ?
Answer = run a very large oil cooler( do not allow the oil to go over 125 deg cel ) , I know it seems a simple thing , but its the simple things that work, oil pressure must be maintained with high core temp

If the 951 is doing events like Sean's , then schedule once a year checks & replacements of things like conrod bearings & head gasket , this can all be done in car ( do not leave it for two seasons).

Change the Racing oil & filter after every event

Remember the above events mentioned are just Porsche club events for people to have fun , but that's the point , its not fun seeing other people having a very sad premature ending to their track day with a blown engine that did not have to happen , I just do not want to see any more human inflicted unnecessary damage to these great engines , so if this helps a few out there then that's good enough

Regards
Bruce Buchanan

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Paulyy

Thanks Bruce for all that information!

Like i and a few other people have said, there should be a thread linked to all these threads like this one with very good information

Thom

Thanks, that is great 1st hand feedback, and congrats to you and Sean for running reliably the fastest car in these events

When you mention that a peak oil temperature of 125°C should not be exceeded, where do you measure it at?

reno808

nice feed back very true

JET951

Hi Thom , we have a VDO oil temp sensor screwed into the side of the standard alloy engine sump ( down low in the side of sump ) and we have a VDO oil temp gauge in the centre console ( just below the radio CD player ).

Regards
Bruce
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Reimu

pics of the breather system?

67King

There is a lot more to oil film than just ZDDP and viscosity. There's some info in this thread: https://rennlist.com/forums/racing-a...synthetic.html

The graphs show oils that are all 50 weight oils (10/15/20W50). Some of the WORST performers have the highest levels of ZDDP. It isn't a case of more is better, it is very much a case of optomizing everything that is in the oil.

I had my con rod bearings go while using an allegedly high ZDDP, 20W50 oil. ONly 3 events on them when they went.

JET951

Hi robstah actually }

A) ZDDP is not there just for the top ends , ZDDP is added to engine oil to increase oil film strength , like for example crankshaft thrust bearings ,just in normal street cars alone over the last 15 + years we have seen way too many thrust bearing failures in last century Porsche engines that had been running on very low oil film strength this century low viscosity street engine oils , where as the same Porsche types , same milage, same usage that had been on a 20w-50 engine oil had no wear at all , same goes for piston to cylinders excess wear ( no oil pressure , just splash ) , same again goes for top end wear , same goes for cam lobe pitting, hydraulic lifter face pitting , cam chain sprockets , valve guides , anywhere there is no oil pressure

B) Racing oils are rich in ZDDP for the above reasons , even this century low viscosity racing oils for this century engines are rich in ZDDP , its there to increase oil film strength

C) Sean is the current Open Class Champion , so in other words he won open class with this engine and car last year , which was new for last year. Here are the results from last year. Look for class O. Class O is basically open class where anything goes so long as its a Porsche
http://www.pcnsw.com.au/PorscheClubs...20Placings.pdf
The previous years Sean was running the older 2.5L standard turbo engine with a Vitesse stage 3 , it was in these lower classes , like A , B , D . E etc ( power to weight classes) that have more competitors and the way the points are allocated , the more Porsche's in ones class the more points you get for a win , its a club thing , and because Sean wanted to go faster & he had already won the Drivers Championship when in the lower classes ( points accumulation ) we just thought lets try Open Class , which he won

D ) 8:1 compression is a normal Porsche compression for turbo charging, The 3.0ltr is Seans car has plenty of bottom end, It hits 1 bar boost at 3000rpm and doesn't stop making power until 6400rpm. The car has that much bottom end that it is extremely competitive in Our motokhana series. Your Auto X. This is against cars such as the latest GT3RS's, 996 RS, 993RS, Boxsters Etc.

E ) The 951 & the 944S2 , 968 engines all have a engine oil thermostat , so that means the engine oil only flows to the engine oil cooler when the thermostat opens , but then you know that ?
So that means you can have as big oil coolers on as you like. Our goal is to keep the oil at a stable tempreture which we are capable of doing

F ) The con rods that Sean competed with in the 2.5 L turbo engines were standard Porsche 951 Forged rods & we have only have used stock standard Glyco street bearings & we never ever had an issue with them as we kept the oil viscosity up & the oil film strength up ( simple stuff )
The Con rods Sean has in the 3.0L 16 Valve Turbo engine are off the shelf Wossner rods with standard Glyco bearings ( no issues at all )

Subnote } all our customer 944 engine's also run the same , no issues

G ) After every super sprint event ( high temp heat cycle) we always change the oil & filter , oil is the cheapest part one can put in the engine , if one can not afford 6 litres of oil , then I suggest to buy a push bike

H )Here in Australia , Valvoline Racing only comes in 25w-60 ( not 20w-50 ) as in the States , I am not sure why , maybe Australia is deemed slightly higher ambient temps ?
I only mentioned this as a reference , meaning keep the oil viscosity up & not to run these with low viscosity at the track

Its up to each person to use what they want , I can only give ( for free ) some background info from years of club track info in regards to these engines with no failures at all


Remember , this 951 of Seans's is not a dedicated racing car , its a sports car that drives to work & drives to the track & kicks **** , then it drives home with the A/C on in comfort with the stereo on .
It does't get any better than this


Regards
Bruce Buchanan
Buchanan Automotive
Working on Porsche cars since 1977

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Sean's 944 turbo at wakefield chasing a 2005 996 GT3 RSR
Sean at Eastern creek chasing a 2010 GT3

JET951

OH I just remembered , Sean's the current PCNSW Motokahana ( Auto X ) outright Champion ( as well ), which he won on the new 3.0L turbo engine last year .
So the bottom end torque doesnt appear to be any issue at all .

Peedster

Nice car! What suspension mods are there?

/Peter

kinglenario

Nice driving. Keeping it tidy . Man that thing handles huh? I'd like to know the suspension setup, springs and bars too. Looks super stiff.

Eric_Oz_S2

As a point of reference my supercharged S2 oil temperature sits at around 130°C as measured by a Stack Professional series oil temp gauge mounted in the sump with the standard S2 cooler. This is with an ambient temperature of around 27°C. I haven't had the gauge in long enough to check temps on hot days (32-35°C ambients aren't uncommon here during summer). I run Penrite Sin20 20W60 oil at the moment.

I was looking for an additional oil cooler to fit in front/below the AC condenser. Bruce - any suggestions on a suitable model for these? No room on the left side - the supercharger oil cooler sits there.

PS - still on original rod bearings (the car has been tracked for 8 years now), though planning on changing at end of the year along with stronger con rods (Pauter/Wossner).

Voith

Does anybody have experience with MOTUL 300V Le Mans 20W60 oil?

On paper it seems like it should be great for these engines.

Thom

A friend tried it and found it a bit too thick for all round use.
15W50 seems to be a better choice for all round use.

pontifex4

Bruce, what's a typical ambient temperature? I'm guessing that it's a lot hotter there than it is here.