Race Engine Forum UK

Well here is my take on the subject, the crank does not dip into the oil so the shape on it is purely aerodynamic, as you pointed out this means that the leading edge must be blunt but rounded and the trailing edge is sharper and longer like the classic teardrop shape. The rule in aerodynamics is not only how you cut into the air but how you leave it behind that matters.

Hi it does depend, the crank does not dip into the oil but depending on the engine the air might be very unlike air. For instance a BMC series engine which has a sump/gearbox sharing a common volume of oil. this should be just about the worst setup.

in that case the air would be more like a very dense oil mist/froth

I have not tested it myself but powergains by using a spash shield/ windage tray in this setup seems fairly low (maybe 1-2%) judging from what is written.

I have fitted a tray nontheless as i like to keep the oil where it is supposed to be ..and it just feels like the right thing to do

i doubt regular aerodynamics would fully apply as it it a medium consisting of a multitude of very different particles.

maybe a look at propellor designs for surface drives (as in a semi submerged propellor for speedboats) would be a starting point for counter weight design

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I think it's important to separate the crank from the oil as much as possible. On the Peugeot S16/GTi6 engine, I add a 15mm spacer between the sump and block, then extend the pickup by a similar amount. This engine also has nice windage tray as standard, which fixes to four special extended main bolts.

Interesting link.

I was - maybe still am - looking to install a dry sump system to my TC engined Monte. However, after referring Guys book that describes the advanced sump design on the Monte, I wonder if a dry sump or Accusump will add any noticeable value.

My engine lubrication system is quite standard with the exception of an added oil cooler with an in-line oil thermostat (See images). I have taken this car on some fast tracks to max RPM and never had so much as a flicker from the oil pressure lamp or the pressure gauge, even on some of the bigger sweeping bends, such as Gerrards at Mallory Park it¢ž¢s fine

My only observations of the effects during track use is the higher oil consumption and evidence of increased crankcase pressure ¢‚¬Å“ oil blowing past the oil cap. But in the circumstance both issues are understandable. The dry sump would eliminate the increased crankcase pressure but what other benefit could I noticably expect?

I am tempted to just initially fit a second, better quality, oil pressure gauge and also install an oil temperature gauge and continue to monitor the situation

Any comments would be appreciated

Regs, Geoff

How about adding a crank scraper ??? I brought one form America (can't think of the company name but I'll find it if you're interested. .). You can get a basic one or one with extra baffles which bolt above the scraper between the block and the journals and between the scraper and the sump (as it was designed for a Fiat, I chopped them around a bit to fit the Montecarlo one). It came to about 60 UK notes - a basic one is roughly half this.

Photo in the Turbo Cylinder Head thread

http://guy-croft.com/viewtopic.php?t=17 ... sc&start=0

Here's a photo of the scraper on my Montecarlo sump. It came from Ishihara-Johnson crank scrapers in the good 'ol US of A.

The baffles on the top go between the bearing caps and the block, you can just make out some on the other side that go between the scraper and the windage tray in the sump. These were for a Fiat sump - and had to be cut to fit the Monte one - I think I ended up making one of the bigger ones.

The long tube going in is the oil return from the turbocharger. This is threaded so it can be screwed into the sump over the oil pick-up foot after it's been bolted to the engine block

Julian wrote:I was always taught that oil scrapers were just one of two options for preventing creep and drag. The main purpose is to keep the oil in the bottom of the sump and as such is actual more baffle than the normally envisaged comb. Where the crank is knife-edged you shouldn't use a scrapper anyway...

I am not sure how the crank being knife-edged is a contra-indicator for a scraper. I assure you top level engines with knife-edged cranks run scrapers. They are more trouble to fit that's all.

Wallace,

Bernice in California kindly sent me a Scorpion sump and oil pump. I am just completing a dedicated design for it that includes a full directional screening windage tray and scraper.

I really like the sump. I don't like the broad smooth expanse (mostly)
of the windage tray. I understand that these are always a compromise but the smooth design allows oil to bounce off and be struck again by the rotating assembly.

Wallace wrote:Here's a photo of the scraper on my Montecarlo sump. It came from Ishihara-Johnson crank scrapers in the good 'ol US of A.

The baffles on the top go between the bearing caps and the block, you can just make out some on the other side that go between the scraper and the windage tray in the sump. These were for a Fiat sump - and had to be cut to fit the Monte one - I think I ended up making one of the bigger ones.

The long tube going in is the oil return from the turbocharger. This is threaded so it can be screwed into the sump over the oil pick-up foot after it's been bolted to the engine block

That is a nice Toyota S series sump (my guess). One improvement you could make is to add a suspended layer of directional screening over the smooth windage tray area.

Moroso makes great sumps -- I like them a lot. I was recently asked to make a screening insert for this type (not this specific pan) after very careful dyno testing showed it raised the oil temp rather than lowered it.

cantfindausername wrote:This is the moroso sump I'll be running on my car.

Taken from the mororso site...
- Kicked-out sumps on each side of the pan increases capacity to 6.5 quarts without restricting ground clearance and helping to lower the average oil temperature
- Solid windage tray with oil drain & dipstick cut out holes prevents oil from splashing back to the rotating assembly, robbing vital horse power
- Trap door baffling allows oil to flow …œone way‚ into the pick-up area during hard acceleration and deceleration, preventing the pick-up screen from starving for oil

I'd like to hear your opinions on this please.





Thanks,
Ant

Hi, I have only just found this topic,
but here is my input if it helps any.
I used to own and fly a microlight, and as such, we were expected to learn about areodynamics etc.
I am NO expert in areodynamics, but what I will say is, it is very easy to confuse this topic with whats been discussed here.
A wing of a plane or the prop of the same, have very specific jobs to do.
A wing must give lift, and leave stable air behind it to keep the plane going in a line. A prop must produce a pulling force etc.
A crank needs to do none of this.
Lets take a crank running in the block, and assume that it does run out of the oil for a given time, as it spins in the confines of the block, the amount of turbulance it creates and consequently the way the air is now moving inside the block is a thing that I feel maybe being overlooked.
If we belive it does run in oil for a given time, then it is here that the most benifits can be had if we try to reshape the crank webs.
I personally beleive that as the crank spins, the air in the block spins with it (whirlling effect)
I would look to the shape of the inside of the block, and reshape where posibble to reduce anything that might cause this whirlling effect to be interupted, all we can hope to do is to keep it all moving freely as one, (Crank and air).

Piero wrote:Hi, I have only just found this topic,
but here is my input if it helps any.
I used to own and fly a microlight, and as such, we were expected to learn about areodynamics etc.
I am NO expert in areodynamics, but what I will say is, it is very easy to confuse this topic with whats been discussed here.
A wing of a plane or the prop of the same, have very specific jobs to do.
A wing must give lift, and leave stable air behind it to keep the plane going in a line. A prop must produce a pulling force etc.
A crank needs to do none of this.
Lets take a crank running in the block, and assume that it does run out of the oil for a given time, ...

Yes, modern wetsumps with positive pressure lube systems have the running fluid level below the swept area of the rotating assembling -- this even holds through a fair amount of inclination. This neglects vehicle movements and the effect of the windage on the surface/body of the oil.

Piero wrote: ... as it spins in the confines of the block, the amount of turbulance it creates and consequently the way the air is now moving inside the block is a thing that I feel maybe being overlooked.

Yes, there is a spinning and also pumping from bay to bay (inline) or across a bay (V configuration). Makes for complex turbulence.

Piero wrote: If we belive it does run in oil for a given time, then it is here that the most benifits can be had if we try to reshape the crank webs.

The turbulence actively draws oil into it that continually comes from a number of sources so there is definitely oil in the path of the crank. More so if the car is driven with heavy acceleration, turning, braking, etc.

Piero wrote: I personally beleive that as the crank spins, the air in the block spins with it (whirlling effect)

Yes, exactly. The pressure differential in the vortex is what suspends the oil.

Piero wrote: I would look to the shape of the inside of the block, and reshape where posibble to reduce anything that might cause this whirlling effect to be interupted, all we can hope to do is to keep it all moving freely as one, (Crank and air).

Because the phenomenon is so complex and varies in nature over the rpm range this is not the best solution in isolation. The pumping of the cylinders which is commensurate with the rpm of the crank, of course, ensures that there will always be forces acting to decelerate at least some portion of the turbulence which the crank and rods must then pass through (friction). Also the beam of the rod will be in the way for much of its path again slowing a portion of the turbulence.

If you disrupt the pressure differential it allows entrained oil to be released axially and radially decreasing both mass and friction. Yes, disturbing the turbulence does cost power in and of itself but there is more energy saved than lost so a net gain over parasitic loss. Disturbing the turbulence for no good effect is not desireable and is why girdle structures can cause a net loss in horsepower. Unpublished research by Nismo indicates the girdle in the SR20 engine costs 5% power -- quite significant.

Reducing the atmosphere present in the crankcase is a better solution but more expensive. Dry sumping does this as well as dedicated crankcase evacuation pumps.

Here is a link to an article by David Vizard detailing how very minor crank profiling and various coatings can save horsepower. I think you can trust this data:

http://www.circletrack.com/techarticles ... echnology/

Some good points there both.

If you're worried about complex things like this - dry-sump the motor.

GC

I have read a few articles on crank scrapers, one written by David Vizard (I have a copy but unfortunately its at my parents so I will work from memory) Smokey Yunick also discusses oil control in his Power Secrets book.

My understanding is that oil clings to the crank in much the same way as egg does when you whisk it. A few pints can be around the crank which can be quite a percentage of the oil in the engine. This oil can also cause drag and power loss, however this is not measurable below 7,000rpm.

The main reason I fit a crank scraper is for oil control. The scraper will take the oil off the crank and dump it in the sump. However there is a risk it can then bounce straight back up, so a wire mesh is placed in the sump to diffuse the oil and prevent the bounce back.

The picture shows my dry sump pan. The trough is offset so it is below the scraper. A fitting and hose is fitted to each end and goes to the scavenge pumps.




In the pan are 2 layers of mesh. The first to stop the oil bouncing back and the second finer acts as a filter to stop any big bits getting to the pumps.




The crank scraper made from 2mm steel and held in place with the sump bolts. If the crank or rods touch this I have other serious problems!




My feeling is the crank scraper can not do any harm and possibly help oil control so I fit them. Now I have a template they are quicker to make.

John

John,

I have visited your site many times and always greatly admired your work. The last visit I was following your rework of some headers and exhaust routing. ;-)

JB wrote:I have read a few articles on crank scrapers, one written by David Vizard (I have a copy but unfortunately its at my parents so I will work from memory) Smokey Yunick also discusses oil control in his Power Secrets book.

One excellent point that Vizard makes is that the crank acts like a crude propeller and distributes entrained oil along its length. This is important to take advantage of in a wetsump engine that is used in performance apps -- the forces present are much stronger than the lateral accelerations that the vehicle is experiencing so having a portion of the scraper over the sump well acts to continuously feed it.

JB wrote: My understanding is that oil clings to the crank in much the same way as egg does when you whisk it. A few pints can be around the crank which can be quite a percentage of the oil in the engine. This oil can also cause drag and power loss, however this is not measurable below 7,000rpm.

I assure you that with a scraper the power curves typically diverge on the dyno at about 2700-2800 rpm. At 7000 there are indeed significant losses to windage -- probably around 8%. I say 8% because that is the level that has been reportedly reclaimed in Formula 1 engines (at great expense). A scraper typically recovers 2-3% of the output of a NA engine. That is just a rule of thumb.

If you look on my homepage at the very bottom is a dyno test run by Ed Peters -- retired Chrysler failure analysis engineer. His dyno cell normalizes the ambient conditions -- holds temperature to within one degree for example. It will register the effect of you walking through the room. This is an order above using correction formulae. I know he scrapped a day of testing because it was raining too heavily and that made it too difficult to control the humidity in the cell. I am fairly sure that this is the level of control that Vizard used in his magazine article data.

That brings up another related issue -- the rpm at which windage effects are significant in an engine. There was a windage study at M.I.T. reported in an SAE paper (2004) with a boroscope observing within the crankcase. At a mere steady 2000 rpm high speed oil droplets flung from the crank can cause very heavy foaming.

This is all confirmed by the massive shift by the OEMs in controlling windage on their stock engines.

JB wrote: The main reason I fit a crank scraper is for oil control. The scraper will take the oil off the crank and dump it in the sump. However there is a risk it can then bounce straight back up, so a wire mesh is placed in the sump to diffuse the oil and prevent the bounce back.

The picture shows my dry sump pan. The trough is offset so it is below the scraper. A fitting and hose is fitted to each end and goes to the scavenge pumps.

Yes, you have an excellent design. A little bird has told me that there are well known aftermarket pans that actually raise the temperature of the oil rather than lowering it because they do not pay the same attention to detail that you do.

JB wrote:


In the pan are 2 layers of mesh. The first to stop the oil bouncing back and the second finer acts as a filter to stop any big bits getting to the pumps.

The earliest example that I know of that utilizes this effect is the Triumph 2000 Mark I sump from the mid 60s. The screening has a dual role in that it also filters the oil prior to the pump pickup.

JB wrote: The crank scraper made from 2mm steel and held in place with the sump bolts. If the crank or rods touch this I have other serious problems!




My feeling is the crank scraper can not do any harm and possibly help oil control so I fit them. Now I have a template they are quicker to make.

John

They definitely help oil control -- there is no question of that at least by the OEM engineers. They do a fantastic amount of research but it is very difficult to learn about it. Kept in house -- sometimes you see references to it in their patents or papers presented at conferences.

Guy Croft wrote:Some good points there both.

If you're worried about complex things like this - dry-sump the motor.

GC

Hi Guy,

I know you're not a fan of scrapers from your other post. One thing you can do with a design like John's is to pin it in place at a few strategic locations around the oil pan rail.

Formula Ford engines have been using scrapers for decades now with good success. The SCCA rulebook has finally caught up with reality and begun to mention them specifically. At many circle tracks they are forbidden because they are too much of an advantage.

Also, very important to note that many dry sumps use scrapers to direct the stripped oil to the scavenge openings. If you see louvers for oil control that is an example of scraper technology.

A current OEM example of a scraper like John's can be found in the pan gasket of the DaimlerChrysler SRT4:



Here's an OEM example of a crank scraper in a Porsche engine:



Porsche is using a scraper design utilized by Ford in its FE engines about 45 years ago: