Viscosity Affects Piston Rings

[buster]

http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=4;t=000419

Motorbike posted this and I'm wondering if the reason certain racing oils such as Mobil 1 R and 76 NASCAR oil are on the "thin" side and only have a HT/HS of 3.0-3.2, is that because the film strength will be higher with a light weight oil at the ring area, versus a thicker viscosity oil? Very few if any run 20w-50 in NASCAR engines anymore. Most qualify with a 0w-5 (Q is one of them) and run the entire race with a 0w-30 or less (Joe Gibbs racing oil is a 5w-20 made by Lubrizol). And with AEHaas, he notice DECREASED oil consumption with a 20wt oil vs Shell 5w-40. On top of that HP is gained. The 5w-20 UOA's have remarkably good. Thoughts?

Direct link to source: Shell Study

[ February 22, 2005, 02:31 PM: Message edited by: buster ]

 

[MGBV8]

view from Silkolene on thin and hp

http://www.silkoleneoil.com/techtip6.htm

 

[thedawk]

Interesting comparison there. I wonder why they didn't throw in another run with their motorcycle specific oil since they were using a motrcycle for their test bench. Things that make you go Hmmmm . . .

 

[cryptokid]

the reason nascar use thin oil is because it frees up horsepower, at the expense of engine life however. most of the nascar engines only life to be 500 miles old before they are worn out.

think of this, a 0w5 oil is ONLY used in qualifying. why not the entire race? because the engine wouldnt last, thats why. those engines running on 0w30 are basically worn out at the end of the race, many engines dont even make it to the end of the race and blow up befor then.

if they ran a 50w or some other thick oil, the engines would last alot longer, but they would lose enough hp to be no longer competitive. therefore, a 0w30 has to be used, even if it is at the expense of the engines life.

 

[Gary Allan]

Correct me if I'm wrong here (yes, please correct me!! Help!!) but wasn't the assertion of greater film strength evidenced by decreased measured wear??


As far as NASCAR engines ..they use a whole different set of rules for oil flow. They use a high volume/low (relative) pressure theory that uses oil for a coolant as much as a lubricant. This has been the trend from the big engine builders for a few years.

I don't know if you can retro-engineer too much from their usage.

 

[1sttruck]

What is commonly used in Paris-Dakar or even LenMans ?

 

[Doug Hillary]

Hi,
it is my understanding that in the longer events a heavier viscosity oil is used

Castrol's "R" 10w-60 and Motul & Repsol have the same. Shell tailor make their race oils on the spot with ambient, humidity, geography and etc along with race distance and circuit layout (time at low/high revs etc) all playing a role
In OZ the V8Supercars (600+hp) were using M1 15w-50 (special blend not sold here) but now use M1R as required

Regards
Doug

 

[427Z06]

quote:

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Originally posted by Gary Allan:
I don't know if you can retro-engineer too much from their usage.

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My sentiments exactly.

 

[1sttruck]

For peak performance in physical conditioning 'specificity' is all important, which is why marathon runners have different builds and train differently than Olympic lifters. Using the same anology in racing if you're only interested in peak power and aren't concerned about long term wear then see what the 'sprint racers' are using, which in my opinion includes anything less than a 24hr race. An oil suitable for high power output over a longer time starts to suggest what works for low wear.

 

[Doug Hillary]

Hi,
I forgot to mention too that one reason for the higher viscosity used in longer events (LeMans etc) is fuel dilution

As others have mentioned the race brews are indeed "doctored" for a specific application

Regards
Doug

 

[buster]

These are all good points. I'm comparing apples and oranges here a bit, but I am thinking that with the new additives, better flow, reduced cooling and great UOA's provided so far here on BITOG.

Doug, good point about the fuel dilution, makes sense.

 

[oilyriser]

high RPM, racing --> thin oil is ok

low RPM, lugging --> thick oil

 

[1sttruck]

Most motorcycles seem to use heavier oil, even though they're typcially even more competitive than other vehicles regarding engine output, and rev higher to boot. 13 to 14 grand is common, and even the bigger bikes often run at 10 grand. In Europe heavier oils are the norm, in spite of extended high RPM runs in lots of vehicles. Lighter oil seems to be used in shorter distance races and in US vehicles.

 

[Leo]

quote:

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Originally posted by Doug Hillary:
Hi,
I forgot to mention too that one reason for the higher viscosity used in longer events (LeMans etc) is fuel dilution

---

Thats pretty much what Motul says about their 300V oils; fuel dilution during events is one factor in determining which viscocity of 300V to choose. Check their website..

 

[JohnBrowning]

I do not think that the film strength is going to be any differnet in the ring area then any place else on the engine. THe film strength is set by the make up of the base stock and VII's! I think the RING MOVEMENT and OIL FLOW PATERN around the rings and piston are what was significant in the study posted by motorbike!

The problem with the study was the information that was missing!! WHat type of wear was takeing place on the cam, followers, lifters, rod bearings, oil pump drives etc?????? An engine is a complex mix of metalurgy adn parts. You have to ballance wear across the entire engine. The fact that the study did not mention any of this is what troubles.

Cams, lifters, followers, oil pumps/drives, and timeing componets are all more prone to fail prematurely due to oil viscosity. Rings are more affected by total miles of piston travel,corrsion and RPM then they are by oil viscosity in my opion.

Since NASCAR went to the one engine rule how sure are we that they are running 0W5 to qualify? Seems like 0W30 would get the job done just fine. They used to do all kinds of silly stuff for qualifying that they can no longer do like run light weight rotor.