Viscosity, speed and load on bearing friction

[buster]

Link

Quote:
For example an NHRA Pro Stock engine makes over 1,400 HP and uses a 0W-5 weight engine oil. A NASCAR Nextel Cup Engine only makes 850 hp but uses a 5W-20 weight oil. How can a more powerful drag motor use a lighter weight oil? The NHRA Pro Stock motor runs at a cool 100 degrees F. A NASCAR Nextel Cup engine runs around 220 degrees F. Our Joe Gibbs Driven XP0 racing oil is 11.5 Centistokes at 100 degrees F, and the XP0 oil is popular with the NHRA drag racers. Joe Gibbs Racing uses the XP1 in our un-restricted NASCAR Nextel Cup engines, and the XP1 is 9.5 Centistokes at 212 degrees F. As you can see, the operating viscosity of the 5W-20 XP1 oil is lighter than the operating viscosity of the 0W-5 XP0 oil due to the difference in operating temperature.

All material referenced from Lubrication Fundamentals, Second Edition, By D.M. Pirro and A.A. Wessol, Published By Marcel Dekker, Inc., Copyright 2001 Exxon Mobil Corporation

 

[XS650]

It helps that an NHRA pro stock engine turns under 600 revolutions under full load at a time.

 

[lewk]

volume/velocity are the reasons xx20w oils do their jobs so well.extreme temperature variations at either end of the spectrum will increase oil pressure, which is not wanted or is detrimental to the oils objective.At least thats my opinion, I could be wrong!

 

[Curious Kid]

I wouldn't expect much in the way of longevity in the sport of drag racing. With those engines that ingest so much fuel that they are near hydro-locking, have enough energy at the plugs to weld with, etc....yeah, I'll see you at the pits after EACH run IF it all goes as planed. Drag racing is a high cash flow sport, if for no other reason than specialty parts, energetic talent, AND short component life-times. I don't think a sump of oil is used for more than one run down the 1/4.?.

Generate as much power as the set-up can yield, point the thing in the general direction your wanting to go, and get that power down for the lowest ET possible, hoping to see the light of day on the other end!

Take care.

 

[Curious Kid]

Even so, the engine's likely not to take much notice of the "5" weight rating over such a short run, but in those pressure zones I bet the heat does push it to around similar operating conditions as with the 5w-20 in the circuit car. It's been said that temps in the bearings can be 50 degrees elevated under extreme conditions, but I cant recall whether that was in f or c (darn english/metrics). I also imagine bearing surface area is modified, but ???

 

[mitchcoyote]

I recall seeing dragsters blow up and Nascar engines fail. These lightweight oils are a compromise and a gamble......

 

[ProfPS]

Originally Posted By: mitchcoyote
I recall seeing dragsters blow up and Nascar engines fail. These lightweight oils are a compromise and a gamble......


Be careful when comparing a production engine to a competition engine. NASCAR engines are built by select engine builders using alloy parts to save weight, operate at extreme RPM's and other extreme conditions; what's inside them are not the same parts as what's inside engines that are on the dealer's car lots.

You and I will run our cars upto 3-5k RPMs a couple times a day on a 200 hp engine commuting to work, while 700 hp NASCAR engines run upto 10K RPMs once or twice a minute on a short track during a 4 hour race. Race teams spend a lot $$ in engine development and assembly. At the Hendrick complex [as I call it], their engine building is not open to the public; a lot of proprietary stuff going on in each of the team's engine departments to try to have an edge at the next race.

 

[1sttruck]

What oil cars run in 24hr races is more relevant, as the engines are expected to last at least a few thousand miles.

 

[Audi Junkie]

Seems like a race oil specific topic.