Recommended oil & oil handling for track/race 951S
03-10-2004, 10:42 AM
#1
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Recommended oil & oil handling for track/race 951S
I know that both of these questions have been asked but much of the responses are rather dated so I wanted to check and see if any new wisdom was available.
I'm progressing on preparing my '88 951S to run in E Stock - hopefully we'll have it racing by the middle/latter part of the summer. The engine is exactly as it came off of the dealer's floor except for a Lindsey 3" exhaust.
- What's the best oil to run in this vehicle? For it's entire life (18k miles) it's had Mobile 1 but given some of the comments I've seen on the boards I'm not convinced that's what I'll use going forward. I've seen pro & con comments regarding Redline, Amsoil, Kendall, etc... What are current recommendations & reasons for this car?
- It's probably a healthy paranoia but I'm really concerned about oil starvation how to keep the #2 bearing from becoming a real problem. I've seen various posts about the Accusump, various baffle modifications, etc. but wanted to see what people have used with good success.
My goal for the engine is max reliability and minimal maintenance.
Thanks much.
Rick
I'm progressing on preparing my '88 951S to run in E Stock - hopefully we'll have it racing by the middle/latter part of the summer. The engine is exactly as it came off of the dealer's floor except for a Lindsey 3" exhaust.
- What's the best oil to run in this vehicle? For it's entire life (18k miles) it's had Mobile 1 but given some of the comments I've seen on the boards I'm not convinced that's what I'll use going forward. I've seen pro & con comments regarding Redline, Amsoil, Kendall, etc... What are current recommendations & reasons for this car?
- It's probably a healthy paranoia but I'm really concerned about oil starvation how to keep the #2 bearing from becoming a real problem. I've seen various posts about the Accusump, various baffle modifications, etc. but wanted to see what people have used with good success.
My goal for the engine is max reliability and minimal maintenance.
Thanks much.
Rick
03-10-2004, 11:08 AM
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I only use Redline 20W50 in my car. The oil pressure I saw with Mobil 1 15W50 on track was scary. I'll never use that stuff again. No complaints about Redline, not even the price. I order it online www.autochic.com and its at my house overnight!
In a pure racecar you could go with one of Redline's straight weight oils , but I have no experience with them.
In a pure racecar you could go with one of Redline's straight weight oils , but I have no experience with them.
03-10-2004, 11:30 AM
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Mike,
Thanks very much for the insight; I'm a bit curious as to your thoughts on their racing oils - is there a reason why you're not using one of those oils?
Thanks again,
Rick
Thanks very much for the insight; I'm a bit curious as to your thoughts on their racing oils - is there a reason why you're not using one of those oils?
Thanks again,
Rick
03-10-2004, 11:56 AM
#4
Race Director
I use Amsoil Series 2000 Racing 20w50 in my 944-spec. I had a similar oil pressure drop from Mobil 1 15w50. I know another 944-spec racer that really likes it. He ran a 2hr endro with an minor oil leak. Forgot to top off the oil at the pit stop. Ran the race with no issues. After the race oil level was BELOW min with No damage to the engine. He was sold on it too. Personally at my last race I was having oil pressure relief valve problems. It was staying open and I had zero oil pressure on start up. Lasted for about 30-40 seconds and then came up. Not fun, but I made it through the weekend with flying colors. Now it is time for new bearings, but it was also time (I have 20+ plus races on the motor anyway).
I did not try Redline racing oil, but will assume that is as good as Amsoil. A friend tried Redline street oil and was not impressed as pressure dropped just like Mobil 1. I do not like mobil 1 in these cars.
I did not try Redline racing oil, but will assume that is as good as Amsoil. A friend tried Redline street oil and was not impressed as pressure dropped just like Mobil 1. I do not like mobil 1 in these cars.
03-10-2004, 12:47 PM
#5
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While I only run DE's, and have a 944S2 and not a 951, here's my $0.42:
Accusump seems to be the way to go. A friend of mine who has a monster track 951S (it's for sale, BTW) had an accusump installed AFTER oil starvation caused a spun #2 rod bearing in the Bowl at Pocono. He's never had a problem with the engine since then. (What's that saying, hind-sight is 20/20 vision). I believe an accusump system is a far better solution vs. baffling.
Regarding oil weights: While I use Mobil 1 15W50, I too have noticed that on hot days on the track, my oil pressure will drop significantly. During a fall DE at Lime Rock, I had to come off the track HOT without a cool down (insturctor needed to use the potty!
) In that case, the pressure dropped so far that the "!" light activated. (Moral of the story: use the cooldown lap!!) I may switch up to a 20W-50 weight this season.
Another important thing to consider is that rod-bearings should be replaced every 2 or 3 years on a track driven 944. Maintenance is always cheaper than repairs!
Just my $0.42,
-Z.
Accusump seems to be the way to go. A friend of mine who has a monster track 951S (it's for sale, BTW) had an accusump installed AFTER oil starvation caused a spun #2 rod bearing in the Bowl at Pocono. He's never had a problem with the engine since then. (What's that saying, hind-sight is 20/20 vision). I believe an accusump system is a far better solution vs. baffling.
Regarding oil weights: While I use Mobil 1 15W50, I too have noticed that on hot days on the track, my oil pressure will drop significantly. During a fall DE at Lime Rock, I had to come off the track HOT without a cool down (insturctor needed to use the potty!
) In that case, the pressure dropped so far that the "!" light activated. (Moral of the story: use the cooldown lap!!) I may switch up to a 20W-50 weight this season.Another important thing to consider is that rod-bearings should be replaced every 2 or 3 years on a track driven 944. Maintenance is always cheaper than repairs!
Just my $0.42,
-Z.
03-10-2004, 01:45 PM
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I would also suggest an oil cooler, or two. I used one big cooler which went in front of my radiator, but it wasn't helping the radiator at all. So I would suggest two smaller coolers on each side of the radiator.
With the one big cooler, I was seeing temps in the 190 degree F range during normal driving at the hottest point, and about 260 degrees F during hard track driving at the hottest point (I know!). Unfortunately I did not have any readings pre-oil cooler but I can only guess that it was hotter than 260.
This was in an 87 951 which was otherwise stock except for running 19 psi boost. Ran great for 3 years or about 50 track days until I had about 50% leakdown in 2 of the 4 cylinders. At that point I sold the car (for other reasons).
I did run Mobil 1 15-50 and was pretty happy except pressure was kind of low when it was really hot, especially at idle which is to be expected.
Good luck,
With the one big cooler, I was seeing temps in the 190 degree F range during normal driving at the hottest point, and about 260 degrees F during hard track driving at the hottest point (I know!). Unfortunately I did not have any readings pre-oil cooler but I can only guess that it was hotter than 260.
This was in an 87 951 which was otherwise stock except for running 19 psi boost. Ran great for 3 years or about 50 track days until I had about 50% leakdown in 2 of the 4 cylinders. At that point I sold the car (for other reasons).
I did run Mobil 1 15-50 and was pretty happy except pressure was kind of low when it was really hot, especially at idle which is to be expected.
Good luck,
03-10-2004, 02:07 PM
#7
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I started a thread on rod bearings & such on here a while back.
The bottomline was that there seemed to be no bulletproof solution to rod bearings.
What you did need to do was to maintain a good supply of oil to the rod bearings to prevent damage.
Things inhibit that are
1) Insufficient oil supply - Due thing such as
Uncovered oil pick-up tubes due to cornning and/or low oil levels
Broken pick-up tubes
2) Poor oil properties
Oil with low operating temp viscosity (Too thin)
Oil that is too hot cause viscosity breakdown
3) Too much Many RPMS
Too many RPMs or Time at RPM... This creates more heat and more strain on the oil
Windage in sump causing air bubbles in the oil
4) Old or worn MAIN and ROD bearings
Oil supply for Rods comes from the mains. Large gaps at mains will limit supply to rods. Mains will survive, but rods are starved.
So you really need to combat all these issues and you still may not be immune. I don't really thing cross drilling helps. I am not sure that accusumps work, but they don't hurt. Oil pan baffles are cheap and can keep the pick-up tube coverd. If it sucks air you ARE in trouble. Then again check the oil before each track seesion to ensure it is just a hair over the full mark. Don't go too far over as this can cause crankcase windage and air bubbles in the oil. Oil coolers can lower the oil temps which is good. Good quality oil is important since the area is sensitive and lower pressure at operating temp means lower viscosity. That is really bad at the bearings if it goes too low. Don't just change the rod bearings as you have done only 1/2 the job. Keep RPM's down. Use the stock redline. More RPM's for more time just mean more loading and puts further strain. On stock motors there is no added power beyond 6k so don't bother reving there lap after lap.
Personally I had a #2 fail and motor blow-up. I think this was due to a craked oil pick up tube. I believe the tube cracked after a number of races with mis-timed balance shafts. (BTW... I recommend keeping them in stock motor with of course proper timing)
My car is now down for new main and rod bearing as prevetion and may get a new oil cooler. It never sees over 6200RPM on the track.
2)
The bottomline was that there seemed to be no bulletproof solution to rod bearings.
What you did need to do was to maintain a good supply of oil to the rod bearings to prevent damage.
Things inhibit that are
1) Insufficient oil supply - Due thing such as
Uncovered oil pick-up tubes due to cornning and/or low oil levels
Broken pick-up tubes
2) Poor oil properties
Oil with low operating temp viscosity (Too thin)
Oil that is too hot cause viscosity breakdown
3) Too much Many RPMS
Too many RPMs or Time at RPM... This creates more heat and more strain on the oil
Windage in sump causing air bubbles in the oil
4) Old or worn MAIN and ROD bearings
Oil supply for Rods comes from the mains. Large gaps at mains will limit supply to rods. Mains will survive, but rods are starved.
So you really need to combat all these issues and you still may not be immune. I don't really thing cross drilling helps. I am not sure that accusumps work, but they don't hurt. Oil pan baffles are cheap and can keep the pick-up tube coverd. If it sucks air you ARE in trouble. Then again check the oil before each track seesion to ensure it is just a hair over the full mark. Don't go too far over as this can cause crankcase windage and air bubbles in the oil. Oil coolers can lower the oil temps which is good. Good quality oil is important since the area is sensitive and lower pressure at operating temp means lower viscosity. That is really bad at the bearings if it goes too low. Don't just change the rod bearings as you have done only 1/2 the job. Keep RPM's down. Use the stock redline. More RPM's for more time just mean more loading and puts further strain. On stock motors there is no added power beyond 6k so don't bother reving there lap after lap.
Personally I had a #2 fail and motor blow-up. I think this was due to a craked oil pick up tube. I believe the tube cracked after a number of races with mis-timed balance shafts. (BTW... I recommend keeping them in stock motor with of course proper timing)
My car is now down for new main and rod bearing as prevetion and may get a new oil cooler. It never sees over 6200RPM on the track.
2)
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03-10-2004, 10:19 PM
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In case anyone's interested, here's the response I got from Redline...
If I read the PCA rules correctly the Accusump isn't permitted if I want to keep my car in E Stock - is that correct?
The viscosity I would recommend in your engine for track use would be the Red Line 30W Race Oil. The 40W would be an option, the higher viscosity might not quite move away from the pick up as fast though I wouldn't expect there would be a big difference.
I would think of looking into an Accu-Sump or similar product for oil pressure back up.
Regards, Dave
Red Line Oil
I would think of looking into an Accu-Sump or similar product for oil pressure back up.
Regards, Dave
Red Line Oil
03-11-2004, 02:00 PM
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I'll throw my hat in the ring with a few comments and anecdotes;
Porsche recommends Mobil 1 0w oils for the Cup cars.
My car? 84 944, approximately 150,000 miles, of which about 20-25k are track miles I'd guess off the cuff. No internal engine work, EVER. I use Mobil 1 15w-50. I get 60-70psi under load at all times, and no lower than 15-20 full hot idling after a run in the pits. In case you were inclined to wonder, the car is NOT babied. I always run the car 1pt over-full, and usually get a little nervous in those long high speed turns where cavitation is most likely to occur. No problems yet.
My experience makes me wonder what is wrong with the cars of those who lose pressure with Mobil 1?
Regarding temps, I have never gotten around to plumbing my temp gauge. Always figured I'd do it when I had to drop the pan, but the damn thing won't quit, so... You will start to see HP losses when oil temps start to head North of 230-240. Best to keep it around 200 if possible.
You might be tempted to go to multiple coolers for space reasons and such. However, the downside of this is not just plumbing expenses, but you REALLY have to make sure that this added plumbing does not create any restrictions in the oil system. This is most acute for 911s, but I would not ignore this thought it in ANY car. I would suggest going no smaller than -12 lines, and -16 really gives you high flow volume.
Porsche recommends Mobil 1 0w oils for the Cup cars.
My car? 84 944, approximately 150,000 miles, of which about 20-25k are track miles I'd guess off the cuff. No internal engine work, EVER. I use Mobil 1 15w-50. I get 60-70psi under load at all times, and no lower than 15-20 full hot idling after a run in the pits. In case you were inclined to wonder, the car is NOT babied. I always run the car 1pt over-full, and usually get a little nervous in those long high speed turns where cavitation is most likely to occur. No problems yet.
My experience makes me wonder what is wrong with the cars of those who lose pressure with Mobil 1?
Regarding temps, I have never gotten around to plumbing my temp gauge. Always figured I'd do it when I had to drop the pan, but the damn thing won't quit, so... You will start to see HP losses when oil temps start to head North of 230-240. Best to keep it around 200 if possible.
You might be tempted to go to multiple coolers for space reasons and such. However, the downside of this is not just plumbing expenses, but you REALLY have to make sure that this added plumbing does not create any restrictions in the oil system. This is most acute for 911s, but I would not ignore this thought it in ANY car. I would suggest going no smaller than -12 lines, and -16 really gives you high flow volume.
03-11-2004, 02:34 PM
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Rick
If the car has only 18,000 miles are you sure you want to turn it into a racer? I had a low mileage 87 951 that I sold to my brother (kept a very nice car in the family) and used a higher mileage car as the racer.
Just a thought, and I know there are good arguments either way.
If the car has only 18,000 miles are you sure you want to turn it into a racer? I had a low mileage 87 951 that I sold to my brother (kept a very nice car in the family) and used a higher mileage car as the racer.
Just a thought, and I know there are good arguments either way.
03-11-2004, 02:41 PM
#11
Have to admit I was in the 'dino oil only in earlier engines' camp with the 911. Too many horror stories involving synthetics in early [pre-993] engines AND CUp cars that were regularly pulled down.
That said, Eric Steinel is religious about using M1 15W15 in the many 951 track cars he prepares. I bow to experience on this, and use what he suggests. YMMV.
We ran an oil analysis on #11 as part of the PPI. Seems that this can provide a reliable reading on bearing wear state, and a lot cheaper than running to destruction. It wont help with oiling-related failures [starvation, air entrainment etc] but at least it should provide an early warning of acellerated wear. Would be interesting to hear from anyone who has had oil analysis over a reasonable period, to get a better sense of the value of this approach.
That said, Eric Steinel is religious about using M1 15W15 in the many 951 track cars he prepares. I bow to experience on this, and use what he suggests. YMMV.
We ran an oil analysis on #11 as part of the PPI. Seems that this can provide a reliable reading on bearing wear state, and a lot cheaper than running to destruction. It wont help with oiling-related failures [starvation, air entrainment etc] but at least it should provide an early warning of acellerated wear. Would be interesting to hear from anyone who has had oil analysis over a reasonable period, to get a better sense of the value of this approach.
03-15-2004, 09:26 AM
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I emailed Jon Milledge to get his thoughts...here's what his reply which is helpful.
I'd welcome anyone's comments on these various options.
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
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
03-15-2004, 09:49 AM
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After a lot of research, I concluded that Jon speaks only when he knows. I have the hinged trap door in the sump for left hand turns, cross-drilled crank (although by Jon's reasoning this doesn't matter), and the collar around the oil pick-up tube. This is all second best, and Jon said the only fool-proof way to protect #2 is a dry sump system. The other point he mentioned to me is oil pressure: 10 psi per 1,000 rpm, which means 60 psi, or 4 bars, at 6,000 rpm. Mine was dropping to about 3 bar, so I added a MOCAL oil cooler to keep it over 4 bar. I only do DE with 032 R's, so the acceleration forces are lower than some other set-ups. Henri Costa, the mechanic who rebuilt my engine, used to work on the Rothmans Cup cars in the 80's, and they never had the #2 problem either. I'm going to try Amsoil this summer, and then check the rod bearings after this season. (Famous last words?)
03-15-2004, 04:10 PM
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"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)."
I wonder what the benifit of the accusump is?? I was thinking of adding this mod to the list, is it just insurance??
I wonder what the benifit of the accusump is?? I was thinking of adding this mod to the list, is it just insurance??