Spec944 #143 Posted June 22, 2009 Share Posted June 22, 2009 Can anyone with a cross drilled crank tell me the oil pressure they see on a stock gauge at full throttle? I have an early car with the stock gauge. b Before the cross drilled crank and the lindsey gate the oil pressure at full throttle with hit 5 bars. now it hits only 3.5 to 4 bars. I am wondering if the extra oiling creates lower pressure than a non cross drilled crank? I have my mechanic checking the oil pressure relief value to make sure it isn't stuck open. thanks for the help Quote Link to comment Share on other sites More sharing options...
chris_venturini Posted June 22, 2009 Share Posted June 22, 2009 funny you mention because I had the same thing when I rebuilt my 88 engine with an 83 cross drilled crank. I used to be at 5 bar, now its at 4 hot. I asked Dave Dirks (944 MoterWerks) and he seemed to think it was fine. 2 race weekends and so far so good. Quote Link to comment Share on other sites More sharing options...
944-Spec#94 Posted June 23, 2009 Share Posted June 23, 2009 Mine runs 4 bar hot full throttle. 3.5+ on really hot day (racing in 100F) with oil temps over 250F, but is otherwise fine. Quote Link to comment Share on other sites More sharing options...
Weston Posted June 23, 2009 Share Posted June 23, 2009 Yeah, I see around 4 after it gets up to temp, more when it's cold. Quote Link to comment Share on other sites More sharing options...
schwank Posted June 24, 2009 Share Posted June 24, 2009 That would be encouraging to me... if my idle pressure was not suffering as well. When hot it is very scary low, to the point of triggering the warning light. Quote Link to comment Share on other sites More sharing options...
Spec944 #143 Posted July 20, 2009 Author Share Posted July 20, 2009 well I made it through a very hot day with the engine intact. It was showing 3-3.5 close to 4 bars cold but at the end of a session it was 2.5-3.0. The weather was over 100 and my oil temps where 240-250 degrees. My water temps was close to 210 degrees. I think my gauge is a bit off as the accusump was coming on at different readings on the gauge. I am looking for an early style gauge if any one has one or if anyone knows of a plug and play new aftermarket gauge please let me know. Quote Link to comment Share on other sites More sharing options...
Chuck T. Posted July 20, 2009 Share Posted July 20, 2009 Just ran Matt Moore's new car around today and same deal about 1 bar less than "normal" oil pressure. 87 engine with a '83 crank . Quote Link to comment Share on other sites More sharing options...
944-Spec#94 Posted July 20, 2009 Share Posted July 20, 2009 well I made it through a very hot day with the engine intact. It was showing 3-3.5 close to 4 bars cold but at the end of a session it was 2.5-3.0. The weather was over 100 and my oil temps where 240-250 degrees. My water temps was close to 210 degrees. I think my gauge is a bit off as the accusump was coming on at different readings on the gauge. I am looking for an early style gauge if any one has one or if anyone knows of a plug and play new aftermarket gauge please let me know. What oil are you runing? With AMSOIL 20w50 Series 2000 racing oil. I never see lower than 3.5 hot even with oil temps at 250F at the bottom of the pan. This is racing in 100F. I was consistantly seeing 1/2 bar less with Mobil 1 years ago. That is why I switched. Quote Link to comment Share on other sites More sharing options...
Spec944 #143 Posted July 20, 2009 Author Share Posted July 20, 2009 castrol TWS 10-60w. It came recommended from an motorsports shop in SLC. I am thinking of switching to valvoline VR1 due to costs. The TWS is very expensive and the valvoline has positive results and costs halve. what does the amsoil cost and where can you get it? Quote Link to comment Share on other sites More sharing options...
944-Spec#94 Posted July 20, 2009 Share Posted July 20, 2009 castrol TWS 10-60w. It came recommended from an motorsports shop in SLC. I am thinking of switching to valvoline VR1 due to costs. The TWS is very expensive and the valvoline has positive results and costs halve. what does the amsoil cost and where can you get it? Amsoil is about $9 per Qt. So pretty expensive. I buy it in 4 one gallon jugs direct from Amsoil on line. I am a preferred customer. I get a discount off list, but costs me $20 per year. I make that up in one order. Yes it is expensive, but I believe it as good as it gets for my motor. I have run Valvoline VR1 in my stock 944 Turbo S street car. However on the track in high RPM hot conditions I don't feel it does as good as the AMSOIL. Quote Link to comment Share on other sites More sharing options...
Spec944 #143 Posted July 20, 2009 Author Share Posted July 20, 2009 joe- how often do you change your oil? Do measure it units of track days or sessions? Tim Meyer in vegas changes his when it is black. I change mine every 2-3 events and have had a ton of issues. he uses VR1 and swears by it. Quote Link to comment Share on other sites More sharing options...
944-Spec#94 Posted July 21, 2009 Share Posted July 21, 2009 joe- how often do you change your oil? Do measure it units of track days or sessions? Tim Meyer in vegas changes his when it is black. I change mine every 2-3 events and have had a ton of issues. he uses VR1 and swears by it. I change mine every 2-3 events. More often in summer any less often in winter when oil temps run cooler. Always at least 2, but up to 4 events or 8 track days. Quote Link to comment Share on other sites More sharing options...
Weston Posted July 22, 2009 Share Posted July 22, 2009 VR1 is good stuff. I've been using 20w50 VR1 for years with great results. I had tried regular Castrol 20w50 early on, but it didn't hold very good pressure like the VR1 did. Chris and I both decided to try Rotella T Synthetic 5w40 at our last event, since that's what Dirks and others are using... It's loaded with ZDDP like VR1 is, and the thinner oil should give us slightly better power. It was a very hot day, so I can't make any big conclusions from this yet, but we both saw 1 bar less pressure than before. At 6000+ RPM, I only had 2-3 bar, and it was only at 1 bar total when I came off the track and let the RPM's drop, causing the oil warning light to come on. This is with a 951 oil cooler too. That didn't exactly inspire my confidence in that oil, but as I said, it was a very hot day... my coolant temps were quite a bit higher than usual and I was overheating the entire race. I'm on the fence if I want to keep using this stuff or go back to the peace of mind of VR1... I think I'll give it another try at our next event, assuming that the outside temperatures aren't crazy high again. Quote Link to comment Share on other sites More sharing options...
Spec944 #143 Posted July 23, 2009 Author Share Posted July 23, 2009 DISCLAIMER- I am by no means an expert on oil. I did some reading on bob is the oil guy.com and what seems to be true is you just can't say I like oil X as it has a lot of ZDDP. This is due to the fact they are consistently changing the formula for emissions. It seems you have to look at the API (American petroleum Institute or something) rating on the bottle. If it is SM it the newest requirements and may or may not have the ZDDP content you think it does. The API rating of SJ is the oldest and is more likely to have the ZDDP. Not sure if it true but seems be true as every “motorsport” oil I have checked on the shelves of the local shop was SJ. I was the one who told Dirks about Rotella – I learned about it from BIOG.com website. It has more ZDDP since it is diesel oil but even diesel oils are now being forced to reformulate for emissions. So check the API rating on the bottle. Note sure it the above is correct but seems to be. The Castrol oil I am using is a motorsport developed for M5s and M3s seems ok just expensive. It was 100+ the other day I a still have 2.5 to 3.5 bars of oil pressure after the race at idle and a full throttle. When I am through with the case I have I am going to try the Amsoil that Joe recommends. Even expensive oil is cheaper than building motors and I have built three. Quote Link to comment Share on other sites More sharing options...
Weston Posted July 23, 2009 Share Posted July 23, 2009 I don't think an "SM" API rating is necessarily bad, as many say it is, but just that it's not actually required to have all that much ZDDP in it... Both VR1 and Rotella T are marked SM, and advertise that they exceed the Zinc levels of SM and meet or exceed various other standards. My last batch of VR1 is marked SM and says it exceeds SM/SL/CD. Numbers I've found around the Internet put it at 1200-1300 PPM of ZDDP, and their FAQ says it has 75% more ZDDP than SM oil: http://www.valvoline.com/faqs/motor-oil/racing-oil/76 Rotella T synthetic is marked CJ-4/SM and says it meets CJ-4, CI-4 Plus, CI-4, CH-4, CG-F, and CF/SM. The current formulation is supposedly 1300 PPM of ZDDP, while the old stuff was 1600. Their website also says it meets SL, SJ, SM... http://www.shell.com/home/Framework?siteId=rotella-en&FC2=/rotella-en/html/iwgen/leftnavs/zzz_lhn2_4_0.html&FC3=/rotella-en/html/iwgen/products/product_rotellasynth.html Mobil 1 15w50 is marked SM and has 1300 PPM of zinc, but many other weights have less... http://www.mobiloil.com/USA-English/MotorOil/Files/Mobil_1_Product_Guide.pdf My concern with Rotella T is just that it's a 40 weight and is obviously thin, which resulted in lower oil pressure. That's better for performance, but the viscosity is wrong for our engines in these conditions, so we're basically trying to balance that out by loading it up with stuff like ZDDP. If you look at the Mobil 1 "Racing" oils in the above PDF link, they seem to do the same kind of thing, but take it further... even thinner oils for more power, and tons of anti-wear additives. If that works for Rotella T and really does protect our engines adequately, then that's great, but I'm not convinced of that yet... Quote Link to comment Share on other sites More sharing options...
944-Spec#94 Posted July 23, 2009 Share Posted July 23, 2009 ...Even expensive oil is cheaper than building motors and I have built three. I hate to spend money on overpriced crap, but this EXACTLY why I run this stuff. It is far cheaper for me to run this oil than run cheaper oil and risk it breaking down under high temps and high loads. My take is oil pressure drops at temperature due to the oil thinning. The lower viscosity is good to a point since it improves flow. However that also means it runs like water and oil that is too thin does not have film strength to support loads. At the rod journal you have oin flowing through the gap and you have load being applied. Simply put bearing spings when the oil can no longer support the load from the rod. Then they contact and bad things happen very fast. So oil that is has greater ablility to support load is a benefit to preventing crank & rod contact. A few years ago I did some light engineering analysis on hydrodynamic bearings and came away with the idea that oil quality is important. ZDDP is not factor for the rod bearings like it is for the valve train. However oil weight is. Too thin and it wont support a load at 260F or higher given the local heating of the journal due the rotational friction. Of course too thick and it won't flow which is bad too. So that is why keeping the oil cool is important since viscosity is maintained at lower temps. This also why I run thick oil. The key is good high temperature performance as you need to maintin enough local flim strength to float the bearing. If you don't you have contact and almost instant failure. So running thin oil you may get by for abit, but all you need is one disruption to oil flow and you can have an issue as it takes more flow from thinner oil to support the same load. Now when you look at weights you see 2 numbers. The first is cold flow and the second is hot. The farther the spread the more additives they put in the oil to make it "act" thicker at high temps. It is those additives that can suffer when pushed very hard. Plus not all oils work the same at 250F temps even if they all have XXw-50 ratings. When I saw mobil 1 15w50 losing pressure as a track session went from 15 min to 20 min to 30 min I started looking for alternatives. AMSOIL was one I tried and instantly I maintained hot pressure better. So I used that figuring that this was a single I was mainting greater viscosity at the temperatures I was running the oil at. Both oils were XXw-50 rated so in theory had the same hot rating. However like brake fluid hot means different things on the street vs the track. Quote Link to comment Share on other sites More sharing options...
944-Spec#94 Posted July 23, 2009 Share Posted July 23, 2009 I.. If you look at the Mobil 1 "Racing" oils in the above PDF link, they seem to do the same kind of thing, but take it further... even thinner oils for more power, and tons of anti-wear additives. If that works for Rotella T and really does protect our engines adequately, then that's great, but I'm not convinced of that yet... Well two things to consider with that. 1) Our engines are 20+ years old. That means they were designed in early 80's with differnet concepts for internal tolerancing. The current trend in engines is tight clearances and very thin oils. Plus our engines have 20 years of wear. We might have new bearings and new rings, but most of other parts are old. Who is going to buy a $3000 new crank? Nope we get $80 used ones and make the best of it. 2) Pro "Race" motor are disposable. This means you build them to make XXX power for xx hours. After that you rebuild. Making power is key and rebuild are part of the game. So you will natually take some longevity loss to make more hp. We are different. We want good solid hp, but most will not try to gain 3 hp at the risk needing to rebuild every 6 months. I personally want to my oil to protect the motor and reduce rebuilds rather than increase their frequency. So given that I am not certain I buy into the Mobil Racing oil concept. I want racing oils geared to durability. Quote Link to comment Share on other sites More sharing options...
dmdirks Posted July 23, 2009 Share Posted July 23, 2009 My concern with Rotella T is just that it's a 40 weight and is obviously thin, which resulted in lower oil pressure. That's better for performance, but the viscosity is wrong for our engines in these conditions Weston, The oil pressure in our cars only dropped to 3.5 bar hot this past race weekend, which is over 50psi. Therefore a 40 weight oil may only be wrong for your engine in these conditions. The properties of R.T. Synthetic are comparable to most other higher priced, higher viscosity oils and it is available everywhere. Oil temperatures will typically be 10F lower with 40 wt compared to 50wt oil, however the pressure will be slightly less. In your case you should run 50wt if your pressure is substantially affected, which it sounds like it was, perhaps due to your water temps being too high. When I changed Michelle's rod bearings over the winter after a full season, they looked fantastic. That was good enough for me to keep using it. So I'm not trying to start a pissing contest about motor oil here, just throwing in our experience. Quote Link to comment Share on other sites More sharing options...
Weston Posted July 23, 2009 Share Posted July 23, 2009 That's good to know. I figured that my pressure of 2-3 bar was a bit lower than what it should be in those conditions. I'm not quite ready to give up on Rotella T yet, but it sounds like I need to find a way to get better pressure if I continue using it... I think there are some things I can do to help the oil cooler, as well as the radiator... Quote Link to comment Share on other sites More sharing options...
AvantAddict Posted July 23, 2009 Share Posted July 23, 2009 My concern with Rotella T is just that it's a 40 weight and is obviously thin, which resulted in lower oil pressure. That's better for performance, but the viscosity is wrong for our engines in these conditions Weston, The oil pressure in our cars only dropped to 3.5 bar hot this past race weekend, which is over 50psi. Therefore a 40 weight oil may only be wrong for your engine in these conditions. The properties of R.T. Synthetic are comparable to most other higher priced, higher viscosity oils and it is available everywhere. Oil temperatures will typically be 10F lower with 40 wt compared to 50wt oil, however the pressure will be slightly less. In your case you should run 50wt if your pressure is substantially affected, which it sounds like it was, perhaps due to your water temps being too high. When I changed Michelle's rod bearings over the winter after a full season, they looked fantastic. That was good enough for me to keep using it. So I'm not trying to start a pissing contest about motor oil here, just throwing in our experience. My Dirks motor also never dropped below 3 bar with oil temps over 240 while running the Rotella Quote Link to comment Share on other sites More sharing options...
chris_venturini Posted July 23, 2009 Share Posted July 23, 2009 I used Rotella this last race weekend for the first time and I did drop a tick below 3 bar but I also kept blowing a fan fuse every race. I did experience some massive lifter tick less than halfway through both main races that I have never experienced before. My engine temps were pegged on the stock gauge at that point though I've had that before and never heard engine noises like this. I'll be changing the oil here soon, hoping I dont find any suprises. Quote Link to comment Share on other sites More sharing options...
bnewport Posted November 9, 2009 Share Posted November 9, 2009 I'm going to try the Amsoil racing 15w50 for the 9 hour enduro at Road Atlanta in Dec instead of my normal 15w50 mobil 1. I had low oil pressure after an hour or so at Road America Enduro back in May so 9 hours is probably too much but I'm expecting it to be cooler there. I don't have an oil cooler yet so I'm take it as insurance. I ordered 12 quarts for 132 bucks. Quote Link to comment Share on other sites More sharing options...
Tim Comeau Posted November 11, 2009 Share Posted November 11, 2009 Interesting reading guys. I was sponsored by Liqui-Moly starting back in 2004-ish? They offered me their 10-60 fully synthetic racing oil. I sprint raced that oil in ambient temps over 100F and I raced it in several 3 and 4 hour enduros. I've never had low oil pressure. I think it stays at 4 bar even after a hard race. I've never spun a bearing. You have choices out there for sure. I hope you can find an oil that you can trust like I trust my Liqui-Moly! Quote Link to comment Share on other sites More sharing options...
944cer Posted November 11, 2009 Share Posted November 11, 2009 Ok, too many geeks in 944 spec! Or you'all just secretly want to be German engineers! 99% of aftermarket pressure gauges are in psi and the stock gauge doesn't measure in any units, so, what about 15 psi/bar? Quote Link to comment Share on other sites More sharing options...
944-Spec#94 Posted November 12, 2009 Share Posted November 12, 2009 the stock gauge measures in Bar. 1 bar = 1 atmosphere = 14.7 psi. Quote Link to comment Share on other sites More sharing options...
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