Reputable links for horsepower from windage tray/crank scraper

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Re: Reputable links for horsepower from windage tray/crank scraper

Post by MadBill »

And an aerodynamicist can show the math to prove a bumble bee can't fly..
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Re: Reputable links for horsepower from windage tray/crank scraper

Post by ptuomov »

MadBill wrote: Sun May 26, 2019 10:18 pm And an aerodynamicist can show the math to prove a bumble bee can't fly..
And, after predicting it can’t fly, sell a wing scraper kit that allows it to fly safely!
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Re: Reputable links for horsepower from windage tray/crank scraper

Post by Kevin Johnson »

ptuomov wrote: ...
The whole idea of oil hanging on to the crankshaft at 5000 rpm is ridiculous. It doesn’t happen. You don’t have to be a physicist to understand that a 5000 rpm crankshaft immediately throws any oil on it. Not saying you claimed this, just making a point.

What a scraper or whatever you call it should try to do is to prevent the oil that is immediately and inevitably thrown off the crankshaft from bouncing back off the crankcase wall or pan back to the crankshaft. If it does that prevention well, then it’s potentially worth having it there.

For a large displacement cross plane V8s, you need to keep that “scraper” pretty far away from the rotating assembly because otherwise you’re trading off a marginal oil rebound reduction benefit against a major cost of piston pumping pulses robbing power and/or preventing oil drain from the heads.
Again:

When I first started making scrapers I talked to many race shops and they found empirically that the closer the scraper ran to the rotating assembly the larger the reduction of parasitic losses. They made iterative copies to get the scraper closer and closer.

At high rpm some percentage of the oil is entrained in the windage cloud. It is trivial that the rotating assembly quickly sheds oil -- no-one was claiming that it does not. It has been discussed previously on the forum as a type of atomizer. See the research from Ricardo Laboratories.* Simulations often model the entrained oil as higher density gas. A link was provided to a thesis that mentions this in this thread. Technical support to that author was supplied by Fiat Chrysler Automobiles.

* I believe this is the third time I have cited this free full-text research paper from Sir Harry Ricardo Laboratories on this forum. That facility would be analogous to https://web.mit.edu/sloan-auto-lab/research.html

http://www.ilasseurope.org/ICLASS/ilass ... RS/097.pdf

https://www.brighton.ac.uk/business-ser ... ghton.aspx

Okay, so now lay off poor Smokey. #-o #-o #-o :roll: :roll: :roll:
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Re: Reputable links for horsepower from windage tray/crank scraper

Post by Raybo »

Im intrigued by the gas flow argument. the newest trend in engines I deal with is to drill and tap heads to vent them directly back to the pan.
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Re: Reputable links for horsepower from windage tray/crank scraper

Post by gruntguru »

Kevin Johnson wrote: Sun May 26, 2019 9:06 amPumping exchanges are a big issue for I4 engines as well. That is why Toyota took the trouble to switch the orientation on the ZZ engines.

If you follow the longitudinal development of Nissan straight fours you can see the pumping problems introduced by a engineering swing -- that is related to, gasp, the ZZ engines.
Hi Kevin. Excuse my ignorance but what is the "orientation switch" you are referring to?
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Re: Reputable links for horsepower from windage tray/crank scraper

Post by Sparksalot »

There is little wonder considering the points made in this discussion that where it is allowed evacuation of the crankcase and dry sump systems stripping out crankcase oil yield benefits. There is no whirling gas (air) around the rotating crankshaft entraining an oil mist cloud acting as a high density cloud to move through for the rotating assembly, there are no pumping losses either.
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Re: Reputable links for horsepower from windage tray/crank scraper

Post by makin chips »

ptuomov wrote: Sun May 26, 2019 10:24 pm
MadBill wrote: Sun May 26, 2019 10:18 pm And an aerodynamicist can show the math to prove a bumble bee can't fly..
And, after predicting it can’t fly, sell a wing scraper kit that allows it to fly safely!
Hey now. Flies can't fly when covered with dog slobber. Maybe you should jump on that crowd, too lmao.

I know this because my dog likes to get up in the window and grab them in her mouth then spit em out lol. Today she drooled on one and it could only walk after that 🤣
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Re: Reputable links for horsepower from windage tray/crank scraper

Post by Kevin Johnson »

gruntguru wrote: Mon May 27, 2019 1:27 am
Kevin Johnson wrote: Sun May 26, 2019 9:06 amPumping exchanges are a big issue for I4 engines as well. That is why Toyota took the trouble to switch the orientation on the ZZ engines.

If you follow the longitudinal development of Nissan straight fours you can see the pumping problems introduced by a engineering swing -- that is related to, gasp, the ZZ engines.
Hi Kevin. Excuse my ignorance but what is the "orientation switch" you are referring to?
Bays 3-4 exchange horizontally.
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Re: Reputable links for horsepower from windage tray/crank scraper

Post by ptuomov »

Sparksalot wrote: Mon May 27, 2019 2:33 am There is little wonder considering the points made in this discussion that where it is allowed evacuation of the crankcase and dry sump systems stripping out crankcase oil yield benefits. There is no whirling gas (air) around the rotating crankshaft entraining an oil mist cloud acting as a high density cloud to move through for the rotating assembly, there are no pumping losses either.
I agree that pulling a vacuum would help a lot.

Couple of points:

First, the direct effect of rotating crankshaft on the crankcase gasses is relatively minor for a large displacement V8. The dominant effect is the piston pumping pulses. Management of these pulses determines whether the engine makes better or worse power on a stationary dyno.

Second, thinking about the fluids in crankcase as a high density gas can sometimes be misleading. The oil droplets are large enough that they behave more like stream of bullets in the air and less like part of a homogenous gas. What leads (in my opinion) to the best intuition of thinking oil as ricocheting bullets in the crankcase and the oil control devices as trying to prevent those ricochets from rebounding back to the crankshaft.

There’s a whole thread about these topics here:

https://www.speed-talk.com/forum/viewtopic.ph ... 15#p454674
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Re: Reputable links for horsepower from windage tray/crank scraper

Post by ptuomov »

Kevin Johnson wrote: Sun May 26, 2019 11:17 pm Simulations often model the entrained oil as higher density gas. A link was provided to a thesis that mentions this in this thread.
I don’t believe that the crankcase oiling issues are modeled by car factories in a way that the combination of oil droplets and crankcase gas are considered a single, high density gas. That would by my understanding give a materially wrong result anyway.
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Re: Reputable links for horsepower from windage tray/crank scraper

Post by ptuomov »

makin chips wrote: Sun May 26, 2019 9:44 pm Here's an LS crank scraper. What about that will rob power and prevent oil from draining from the heads? A standard sbc crank scraper is usually even less than that. One rail with well placed edges, usually.

How would that rob power and prevent oil drain?

LS

Image

SBC crank scraper

Image

A crank scraper wouldn't be the thing to do that, one would think. That'd be a windage tray without the proper drainage that would be preventing oil from draining and everything else. Wouldn't it? Or common sense would tell you it would more than a crank scraper ever would.
The device in the first picture might rob power on a stationary dyno because it may reduce the flow area from one bay to another. I say may, as I don’t really know.

The device in the second picture is probably not going to do anything to power in a stationary dyno since it’s in an engine with main caps and ample flow area.

To the extent either does something beneficial to power on a stationary dyno, it’s because it block some of the rebounds of oil spray back to the crankshaft.
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Re: Reputable links for horsepower from windage tray/crank scraper

Post by Kevin Johnson »

ptuomov wrote: Mon May 27, 2019 8:09 am
Kevin Johnson wrote: Sun May 26, 2019 11:17 pm Simulations often model the entrained oil as higher density gas. A link was provided to a thesis that mentions this in this thread.
I don’t believe that the crankcase oiling issues are modeled by car factories in a way that the combination of oil droplets and crankcase gas are considered a single, high density gas. That would by my understanding give a materially wrong result anyway.
First: https://www.google.com/search?rlz=1C1CH ... u3_0k20kys

Second, et alia:
Marco Fogliarino wrote:It has been an intense year, practically a blend of hard
studying at the University of Windsor and tough work at the Chrysler Automotive
Research and Development Centre (ARDC) here in Windsor.
According to [7], the oil particles with diameter smaller than 1 μm are called “micro-oil”,
while particles with diameter smaller than 10 μm are usually called “fine oil”; oil
particles which are visible to naked eye are called “coarse oil”.
The intensity of this windage is directly related to the engine rotational speed and to the
engine sump design: as engine speed increases, also the quantity of oil droplets inside the
cloud increases. According to [26], the quantity of oil which can be suspended in the
cloud due to the rotation at high speed of the crankshaft and counterweights can reach
one quart. The motion of the gas in the crankcase has a negative effect on the oil in the
sump: the gas interacts with splashing oil and, as a consequence, the oil is ventilated. Oil
ventilation (or aeration) can decrease the oil properties, because gas bubbles can appear
in the liquid oil and, when they reach the oil pump, they can cause cavitation and loss of
head, blockage of the filter and loss of precision control (i.e. with the Multi-air system)
[4]. This can also reduce the oil service life. In engine blocks where a short skirt solution
is adopted the ventilated area over the oil level is large and so the oil aeration effect is
great.


CPMEP = {(W(crankcase))/(V)} = 0


From this very simplified model it is possible to conclude that ideally, with an
isentropic process, a crankcase completely closed, with no communication with the
adjacent bays, will results in zero crankcase pumping mean effective pressure. This
is also confirmed by the literature [32], [29].
In any case a null CPMEP is impossible in a real engine with a common wet sump, and
some CPMEP cannot be avoided for many reasons: first, due to the non-perfect symmetry
inside the crankcase, not all the work lost in compression is recovered in expansion; in
the proposed model, the crankcase is simply treated as a volume which is compressed and
then expanded: this is not the real crankcase where there are also rotating elements like
crankshaft, connecting rods, counterweights etc. but just a simplified model. If the engine
has an oil pan, the oil motion has to be considered: the oil agitation will also absorb
energy from the fluid, which will not be given back to the system, and will be lost. Oil
agitation losses reduce engine power and aggravate the work for the crankcase ventilation
system. Furthermore, heat transfer losses and friction of the flow with the hardware of the
crankcase do not allow all the compression work to be recovered in the expansion of the
crankcase.
The ventilating area allows the amplitude of pressure variation inside the crankcase to be
reduced, but induces another problem: the gas flow has to pass through these holes and
resistance is generated; this directly hinders the piston motion. The frictional resistance
which is generated when the gas pass through a pipe causes a drag force to appear and
this lead to pumping work inside the crankcase.
Also the fluid density has an important effect on the CPMEP: if the oil concentration is
high in the windage cloud, the fluid density is high so the CPMEP is great: for this reason
a windage tray is usually adopted, which has the target to limit the oil mist formation
inside the crankcase and reduce the oil aeration, which will affect the lubrication system.
In GT-Power, the solutions are based on one-dimensional fluid dynamics: the equations
used to describe the behavior of the fluids are resolved in one dimension and this
basically means that all the quantities (pressure, temperature, velocity, density…) are
averages through the direction of the flow [35]. The software also computes the heat
transfer and the friction related to the flow in order to give reliable results.
In this and in the following sections the most important parameters affecting the pumping
losses inside the crankcase are evaluated with the results provided from the GT-Power
model.
In an engine with a V configuration each crankcase bay has 2 cylinders facing it; this
means that for a V6 there will be 3 crankcase bays and 4 for a V8.
The computed power loss is quite small because the CPMEP is small when only exhaust
gases are considered as crankcase fluid. In paragraph 5.5 it will be shown how the
CPMEP deeply changes considering also oil vapor and liquid oil in the crankcase.
Moreover, in a 1D simulation, the rotation of the crankshaft and counterweights is not
considered so the flow field generated by their rotation and the drag on that elements is
not taken into account, leading to a low value of power losses.
Burned gases and air are not the only fluids present in the crankcase; usually a not small
percentage of volume is occupied by oil droplets and oil vapors; the crankshaft rotation
whip up the oil from the oil pan, and generally oil is wildly flying in the crankcase due to
crankshaft, counterweights and connecting rods motion. The oil coming from the
bearings of the crankshaft is also trapped in the crankshaft rotation and the common
lubrication of the bottom part of the piston through oil squirters does not improve the
situation. The result is a greater fluid density compared to burned gases only and greater
density means greater power losses.
In order to evaluate this effect, the initial crankcase fluid was modified considering other
two fluid compositions for Case 1; the first one considers 70% mass fraction of burned
gases and 30% of oil vapor, the second 50% of burned gases and 50% of oil vapor. In
Figure 5.5-1 there is a comparison between the three considered fluids.
According to the authors of [37], this mixture can be considered the closest to the real
fluid. The average density is very high because a liquid is considered in the mixture and
this leads to high power losses.

Okay, I am assuming you've read this far. These quotes are just from the first 123 pages of the thesis. Yes, you really have to make the effort to read the whole thing and it is extremely disappointing to me to have to point this out. This really is a waste of my time. A thesis advisor would not put up with this. I had the chance to be a teacher (professor) but I chose not to because among other things I would have precious little patience for this.
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Re: Reputable links for horsepower from windage tray/crank scraper

Post by Kevin Johnson »

ptuomov wrote: Mon May 27, 2019 8:15 am ...
The device in the first picture might rob power on a stationary dyno because it may reduce the flow area from one bay to another. I say may, as I don’t really know.
No, you do not.
ptuomov further wrote: The device in the second picture is probably not going to do anything to power in a stationary dyno since it’s in an engine with main caps and ample flow area.
About 60 years (probably more) of dyno testing disagrees with you.
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Re: Reputable links for horsepower from windage tray/crank scraper

Post by pcnsd »

I have read this thread with interest. Because I make use of a somewhat obscure motor and common performance accessories are few, I am always interested in boiling things down to the practical.

A question for Kevin Johnson if he will indulge me. On an oil scrapper, what clearance distance range are we looking to establish?
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Re: Reputable links for horsepower from windage tray/crank scraper

Post by Kevin Johnson »

One mm or .040" will keep you out of trouble with a steel scraper. That is roughly a ten fold safety factor for thrust bearing clearance variance.

Shops have run steel scrapers much closer than this but it demands consistent periodic monitoring of your engines internals.
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