Crank windage

[DaveB]

JimL, thank you for that bit of insight. Oftentimes decisions are made for reasons that are not apparent but that does not necessarily make them bad decisions. Apparently the V10 had a bit of that going on.

[JimL]

Times and places have jumbled a bit, in my memory, so I cannot remember what year it was....I was in a contract shop looking at a row of beautifully forged and machined V12 crankshafts destined for GMs luxury line.  I believe they were abandoned in view of the pending OBD2 regs, perhaps before the Misfire cylinder allowance was proposed.  I am not for certain, but I think maybe about '89-90?

It may have been canceled due to cost or market issue for some model that would be limited sales potential. 

So.....before it seems we run too far off the crank windage issue; one of the biggest improvements comes with shortening the stroke and pulling the counterweights inboard.  It has an unmentioned side affect of reducing the pumping VELOCITY beneath each piston.  That is a tremendous benefit.

Need proof?  Many of the new "longer stroke ratio" production engines are resorting to ported main bearing webs to get control of the higher velocity lateral pumping in the crankcase.  It turns out the air isnt just whirling around with the counterweights in a nice neat circle!  Maybe that is why we dont seem to get much out of heavily modified counterweights.

Longer strokes are so violent that some new 4-cylinder engines now require dedicated oil separation chambers, in the side of the blocks.  This to keep themselves alive with thinner oils and tighter HC emissions.  Interestingly, this whole windage/oil vapor control issue gets better as the number of cylinders goes up.  I have no idea why.

As usual, those sharp engineers are ahead of us on this one, also....

JimL

[Rex Schimmer]

We have discussed this before but isolating each piston bay and then having each section have its own dedicated section of the dry sump scavenging pump and if you make the scavenging sections very large or large and instead of being a gear pump it is a two lobe pump you can actually lower the pressure in the engine case low enough that the air density drops considerably and drag is proportional to air density so drag on the crank, rods and piston is reduced accordingly. All NASCAR, F1 etc are doing this now and per Roush Racing it is worth about 40 hp on a NASCAR engine at 9500. Part of that increase is supposed to be credited to improved piston ring sealing due to the case vacuum.

Large generators have their internals flooded in hydrogen, low density, to reduce aero drag on the rotating armature. Good for 2-3% efficiency increase.

Rex

[Koncretekid]

What about full circle steel flywheels with mallory weight on the sides opposite the throws?  Heavy, but so what, it's not a drag race.  Would the the extra weight dampen out harmonics?
Tom

[Milwaukee Midget]

Seeing as you're running a V-8 crankcase and a custom 4 cylinder crank, all bets are off as to finding anything other than your own creation on this.

But because of the long throw and the cavernous air space that the Poncho block has, a scraper and any baffling you can devise to get your oil to a pickup would be prudent, even if it didn't give you a single pony.

I just started the order process for mine today -

http://crank-scrapers.com/

[JimL]

Rex, looking at this "internal crankcase", which surrounds my crank tightly, do you think I can just close the rod access windows and scavenge that area safely?  This is both cylinders into one case, with no way to separate them because the rods run next to each other on a single pin.  There are no other openings, just two cutouts to access the rod nuts (what a pain to take pistons in and out!) and the right side piston oiler hole, seen in photo.  The left side is a closed bearing plate, kind of like an Offy, with the piston oiler for the back cylinder built in.

The right block-case area is a big hole with just the oil pump in it.  I may have room to add an additional stock oil pump to scavenge that small "internal crankcase".  It would be easy to close the rod-nut access holes with simple sheet metal plates.

The rest of the question....can I just have the second oil pump pickup whatever it can get and dump it right back into the sump, or must it go to an oil separator externally?

Thank you, and anyone else with an opinion, for looking.

JimL

[fordboy628]

Fordboy,
Your use of the units “pounds/feet” is puzzling.  It seems to be intended to indicate stress levels, and the numerical amounts discussed seem to correlate with stresses expressed as “pounds/square inch”, but “pounds/feet” has me stumped.

Interested Observer,

It's the result of an imperfect and aging brain.   My apologies to all reading this thread.

Instead of referencing Lb/ft; the correct reference should be using Lbf, pounds of force.   These numbers can be referenced from Critical g Load values typically applied to the reciprocating parts of race engine assemblies.    This is a pretty typical reference method for software used to model/analyze con rod strength, ring flutter, etc.

Most race con-rod manufacturers can give a prospective purchaser an idea of the maximum load in pounds their con-rod styles can withstand.   This is useful information, but you have to ask nicely for it.    And it helps make intelligent decisions about the mass/weight of other components.

 
Fordboy

[fordboy628]

"should refer to: Volume 2, 'The Internal-Combustion Engine in Theory and Practice', pages 298/305 for self-gratification."


If I do -- will hair grow on my hands and I'll go blind?

SSS,

That's exactly what I meant . . . . . . .     Why do you think most racers wear glasses?
 
F/B

[fordboy628]

Times and places have jumbled a bit, in my memory, so I cannot remember what year it was....I was in a contract shop looking at a row of beautifully forged and machined V12 crankshafts destined for GMs luxury line.  I believe they were abandoned in view of the pending OBD2 regs, perhaps before the Misfire cylinder allowance was proposed.  I am not for certain, but I think maybe about '89-90?

It may have been canceled due to cost or market issue for some model that would be limited sales potential. 

So.....before it seems we run too far off the crank windage issue; one of the biggest improvements comes with shortening the stroke and pulling the counterweights inboard.   Yes, very effective.    It has an unmentioned side affect of reducing the pumping VELOCITY beneath each piston.  That is a tremendous benefit.   The best racing engine engineers are aware of this and design to take advantage of this benefit, although this is not the primary reasoning behind short strokes.

Need proof?  Many of the new "longer stroke ratio" production engines are resorting to ported main bearing webs to get control of the higher velocity lateral pumping in the crankcase.  It turns out the air isnt just whirling around with the counterweights in a nice neat circle!   YES!   And that air/oil mixture has to go somewhere!   Highly pressurized wet sump crankcases can blow out gaskets and seals.   Oil/air "froth" can also be "pumped" back up into the heads or prevent oil/air drainage from the heads to the crankcase.    My experience is: The best situation is if all the "extra" oil/air is evacuated from the crankcase with properly sized scavenge pumps.   Maybe that is why we dont seem to get much out of heavily modified counterweights.   That is the result I saw with wet sumps in "any" configuration and why dry sumps replaced them.

Longer strokes are so violent that some new 4-cylinder engines now require dedicated oil separation chambers, in the side of the blocks.  This to keep themselves alive with thinner oils and tighter HC emissions.  Interestingly, this whole windage/oil vapor control issue gets better as the number of cylinders goes up.  I have no idea why.   Usually the improvement comes from the larger overall crankcase volume.  A larger volume is more difficult to highly pressurize as a result of multi-piston movement.   At least that's what we concluded at the time.  2001.

As usual, those sharp engineers are ahead of us on this one, also....

JimL

Jim,

Still a slow and crappy typist.    A long time ago, in a galaxy far, far away, I did a LOT of development work on dry sump V-8's.    I added my highlighted thoughts to your text, sorry.
 
Fordboy

[fordboy628]

We have discussed this before but isolating each piston bay and then having each section have its own dedicated section of the dry sump scavenging pump and if you make the scavenging sections very large or large and instead of being a gear pump it is a two lobe pump you can actually lower the pressure in the engine case low enough that the air density drops considerably and drag is proportional to air density so drag on the crank, rods and piston is reduced accordingly. All NASCAR, F1 etc are doing this now and per Roush Racing it is worth about 40 hp on a NASCAR engine at 9500. Part of that increase is supposed to be credited to improved piston ring sealing due to the case vacuum.

Large generators have their internals flooded in hydrogen, low density, to reduce aero drag on the rotating armature. Good for 2-3% efficiency increase.

Rex

Rex,

The Nascar engines I know of are running about the equivalent of -15" water to "evacuate" the crankcase.   The power increases typically come from lowered radial tension ring packages.   The top piston ring is then "energized" by the pressure of combustion, creating a friction/drag savings during other portions of the process.

ALL piston rings "work" via the principle of pressure differential.    Creating a higher "differential" by lowering the crankcase pressure allows clever engine builders/engineers to reduce the radial tension for all of the rings.    Thereby saving friction/drag for a net horsepower increase at the flywheel.    It is important to note that this horsepower was always "inside" the engine.    The drag friction of the higher radial tension rings kept it from getting out to the flywheel.

The bhp number you quote is in the ballpark for 358 cubic inch V-8's turning those rpm's.
 
Fordboy

[fordboy628]

Rex, looking at this "internal crankcase", which surrounds my crank tightly, do you think I can just close the rod access windows and scavenge that area safely?  This is both cylinders into one case, with no way to separate them because the rods run next to each other on a single pin.  There are no other openings, just two cutouts to access the rod nuts (what a pain to take pistons in and out!) and the right side piston oiler hole, seen in photo.  The left side is a closed bearing plate, kind of like an Offy, with the piston oiler for the back cylinder built in.

The right block-case area is a big hole with just the oil pump in it.  I may have room to add an additional stock oil pump to scavenge that small "internal crankcase".  It would be easy to close the rod-nut access holes with simple sheet metal plates.

The rest of the question....can I just have the second oil pump pickup whatever it can get and dump it right back into the sump, or must it go to an oil separator externally?   
It will depend on how "frothy" it is coming out of the crankcase.   Heavily "frothed" oil will need to be de-aerated.   All the engines I've worked on want to be lubed with oil Vs. a frothy mixture of oil & air.   IMHO.

Thank you, and anyone else with an opinion, for looking.

JimL

Jim,

See the highlighted note above.
 
F/B

[JimL]

Thank you very much.  Now I have some idea I am going in the right direction.  As you can tell, the block volume, outside the crankcase, is HUGE on this engine, and the crankshaft is far above the sump area.  It was originally designed to have an automatic transmission with the planetary/clutches on one side and the pump/valve body on the other.  It wound up with a 5-speed and a great big hole to match.  This volume may explain why this thing never seems to push oil out of a simple open breather.  There is also a huge, mostly empty, back case attached to the block (vented into the main sump below the crankcase).

This volume deal also makes it sound like Jack Giffords block arrangement could be an interesting advantage compared to typical 4-cylinder engines.

Also...did you ever work with Dave Phillips?  Just wondering.

Thanks again, everyone.  I spent too many years learning emissions and its diagnostics for our techs, and not enough learning this fun stuff.

JimL

[Jack Gifford]

... 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.

[Jack Gifford]

... This volume deal also makes it sound like Jack Giffords block arrangement could be an interesting advantage compared to typical 4-cylinder engines...

I agree. I considered blocking off the unused cylinders, but quickly decided that additional crankcase volume is preferable, if for no other reason than reducing the magnitude of pressure fluctuations in the crankcase.

I suppose I should also ask for opinions about this crucial decision- whether or not to place four sparkplugs in the block-off plate of the unused cylinder bank. A friend (who did body/paint on my "Speed Queen") thinks it would be hilarious during tech...

[fordboy628]

... 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 bhp

Bhp 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