On Wednesday, December 8, 2004, at 12:04 PM, Stephen F. Doherty wrote:
> If I may branch off and address viscosity:
>
> One of the comments that is commonly made about Rollie Free
> is that he ran a very low viscosity oil, like 10 wt (or
> maybe less?), and one also hears about racers pre-heating
> the oil, to avoid running the engine for a time to get
> the oil up to temp. I also suspect Rollie wasn't concerned
> about getting hundreds of flat out miles from the engine,
> just enough miles for that year's meet.
>
> This raises a few questions.
>
> How significant of a power loss difference is there between
> running lighter or heavier weight oil?
> The Vincent, having roller bearings on the crank and relying
> on oil flow, not pressure, is this a more favorable environment
> to run a lighter oil, ie can a plain bearing motor cope with
> such a light wt oil?
>
> What weight oil would you say (guess?) is the 'norm' for land
> speed racers, either overall or separating out bikes from cars?
>
> For whatever reason, I had this perception that all, or most,
> land speed racers were running as light a weight oil they could,
> and this comment of running 50 wt stood out.
>
> SFD
I run Red Line 10W40 in my race bike.
Approx. 10% power increase from first dyno run (on a "relatively" cold
engine, i.e. warmed up but certainly not at full temp, maybe 160 F
water temp) to full normal operating temp. (200-205 F water temp) run.
Same tuneup, same day, same dyno, same operator, same weather.
No data for different oil viscosities.
I make sure the engine is toasty-warm before a run. That 10%
additional power sure comes in handy. . .
Jon Wennerberg
Seldom Seen Slim Land Speed Racing
Marquette, Michigan
(that's 'way up north)
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