Originally Posted By: Ben99GT
Originally Posted By: CATERHAM
If you know the HTHS vis of an oil, the KV100 spec' has no useful meaning in terms of how thick or thin an oil is terms of it's operational viscosity.
Some of the Comp Eliminator guys would disagree, as oil drain-back is a big part of the reason they run 10-weights instead of 20-weights. I read an interview with John Mihovetz some years ago where he described the oiling issues with his high high-rpm Ford 4.6 4V 2500 HP drag car. He installed glass windows on the timing chain cover and cam cover to observe oil flow, and at high rpm the timing chain was acting as an escalator from the pan to the right cylinder where the oil was backing up in that cylinder head, simultaneously causing oil starvation concerns and a frothy mess (parasitic losses) in that cylinder head's valve-train. A big part of the fix here was to use a 0W-10 oil.
In drag racing the oil rarely if ever gets anywhere near 100C oil temperatures. Heck, you're often lucky to see 40C, hence the popularity of RL's 5wt (KV40 22cSt) and 2wt (KV40 11cSt) drag race oils. Or better still RP's XPR 3.6 (KV40 3.6cSt) which is virtually kerosene I suspect with a boat load of anti-wear additives.
Originally Posted By: CATERHAM
If you know the HTHS vis of an oil, the KV100 spec' has no useful meaning in terms of how thick or thin an oil is terms of it's operational viscosity.
Some of the Comp Eliminator guys would disagree, as oil drain-back is a big part of the reason they run 10-weights instead of 20-weights. I read an interview with John Mihovetz some years ago where he described the oiling issues with his high high-rpm Ford 4.6 4V 2500 HP drag car. He installed glass windows on the timing chain cover and cam cover to observe oil flow, and at high rpm the timing chain was acting as an escalator from the pan to the right cylinder where the oil was backing up in that cylinder head, simultaneously causing oil starvation concerns and a frothy mess (parasitic losses) in that cylinder head's valve-train. A big part of the fix here was to use a 0W-10 oil.
In drag racing the oil rarely if ever gets anywhere near 100C oil temperatures. Heck, you're often lucky to see 40C, hence the popularity of RL's 5wt (KV40 22cSt) and 2wt (KV40 11cSt) drag race oils. Or better still RP's XPR 3.6 (KV40 3.6cSt) which is virtually kerosene I suspect with a boat load of anti-wear additives.