... we dont seem to get much out of heavily modified counterweights...
Who is the "we" and where are these "examples"? The whole reason for me posting this topic was to find any such real world examples. (I don't consider knife-edging, etc. "heavily modified", compared with a full-circle configuration). I would truly appreciate being directed to any such examples. Thanks.
Back in the 90's I had access to bhp/tq numbers for 350/358 cubic inch Cup engines. This was the period when Nascar engine development left wet sump technology behind. I do not recall the year Nascar finally allowed dry sump equipted engines. Needless to say, a lot of dry sump development took place ahead of that time.
Although I am still bound by a non-disclosure clause, and can't quote total numbers, I will list bhp differences between spec types.
For everyones edification, real world dyno test stand numbers/examples: (note: bhp numbers varied slightly from pull to pull, +/- 2 bhp approx.)
1/ Swinging door wet sump pan, no windage tray, std crank/rods X bhp
2/ As above, with windage tray X+10 bhp
3/ As above, add knife edged crank with "small c'weights" X+20 bhp (Small dia c'weights used tungsten inserts.)
4/ As above, add complicated crank scraper/windage tray X+30 bhp
Fully round c'weights (ala motorcycle cranks) were never used on any of the test mules I was aware of.
BTW, 10bhp = approx. 1.5% at this point . . . . . .
The problem with all of this is that on banking or in turns, etc, oil contained in the pan sloshes around and up into the spinning mass of the assembly, at the cost of power and reliability. Add ons like an "Accusump" system help reliability, but they temporarily add oil to the crankcase, costing power.
Every driver I've ever worked with hasn't been too keen about a "temporary" loss of bhp while racing door handle to door handle with another team . . . . . . . .
5/ First dry sump iteration, off the shelf parts, cranks as above, very close tolerance "scrapers" X + 80 bhp
6/ Dry sump iteration, circa 2003, including very complicated mods to "minimize" oil in the engine,
-15" (H2O) vacuum in
engine, ALL parts mfg'd "in house", other internal mods to assembly to take advantage of changes:
X + 125 bhpBhp gain, from #1 to #6: approximately 21 bhp/litre. Also note: that some of the gains were only related to the oil system in that the changes to the oil system permitted changes to be made elsewhere in the engine for useful bhp gains . . . . .
And just for a frame of reference, the approximate development cost was:
1.3 million dollars, parts only. I was never made aware of the salary or facility costs, but I know they weren't cheap.
IMHO, anything you can do to get the oil/air out of the engine, (not just the crankcase), and create a vacuum, will serve to benefit your purpose. The only caveat I would add is that certain parts, (valve springs, exhaust valve stems, cylinder walls, piston skirts, etc) are cooled/lubricated by "flung off" oil. You want to be sure that your oil removal process doesn't "starve" a component for cooling/lubrication. Trust me on this one, it is an issue.
Most of this may be moot for LSR, I don't know, I have very little LSR exposure. But like drag racing, oil in a wet sump pan HAS to surge to the rear during launch. Once that oil is entrapped in the spinning mass, I doubt that it might be "flung off" during the high speed portion of a run.
Hope this helps.
Fordboy