89 replies to this topic

[malbear]

atomic conrod



friends please give me your opinnion as to how the pin is pressurised if there is an efective squirter hole on the top side to squirt at the piston?

[24gerrard]

Thanks malbear, I seem to remember posting that we used this idea back in the 1970s on some Ford engines.
I was told it would not work.
Looks like it does.

[24gerrard]

There can also be a hole through the gudgeon pin bearing and the top of the rod directed at the inside crown.

Most of the oil coming up the rod is to lubricate the gudgeon pin.
With a fully floating pin, without the rod oil feed drilling the pin relies only on oil splash.
The drilling oils the pin bearing surfaces both in the rod and the piston.
Excess oil comes out into the piston at the level of the gudgeon pin and will be thrown against the piston crown as the piston does down.
At least this is the theory. How effective it is needs to be confirmed.
IMO it works fairly well but would not be sufficient to be sure enough to reduce piston weight beyond conventional cooling methods.
I still think that most piston crown cooling is from conduction into the cylinder wall and through air in the crank case. IME more cooling can be obtained by opening up better breathing to the crankcase and increasing the water cooling in the engine block and head.
Teflon coating the crown works well, as does allowing more scavenging air into the cylinder through careful cam design.

[cheapracer]

friends please give me your opinnion as to how the pin is pressurised if there is an efective squirter hole on the top side to squirt at the piston?

It's not, I'm sure the spiel means that it's lubed/fed directly by the pressurized system rather than being actually pressurized per say?

[cheapracer]

IME more cooling can be obtained by opening up better breathing to the crankcase

All modern racing engines worth their salt run highly sealed crankcases with very effective evac systems (commonly a large scavenge pump as part of the dry sump oil system) to give very low crankcase pressures to control oil windage more effectively.

[kikiturbo2]

aren't pistons most effectively cooled by oil squirters at the bottom of the block?

I can't see how the top hole in this rod will provide any sort of adequate oil flow for cooling...

[Tony Matthews]

aren't pistons most effectively cooled by oil squirters at the bottom of the block?

I can't see how the top hole in this rod will provide any sort of adequate oil flow for cooling...

I was thinking the same, but wasn't confident enough to post it. Certainly the Ferrari 049 V10 had oil squirters at the bottom edge of the block, aimed at the underside of the piston.

[kikiturbo2]

I was thinking the same, but wasn't confident enough to post it. Certainly the Ferrari 049 V10 had oil squirters at the bottom edge of the block, aimed at the underside of the piston.

I somehow think that a little oil that goes trough the big end bearing and trough a small hole in the rod shouldn't be anywhere near enough to cool a piston...

on a normal road engine oil squirters are placed in the main oil line that feeds the main bearings and have a small valve that opens at a predetermined pressure (to stop flow if the oil pressure gets too low)

[malbear]

I somehow think that a little oil that goes trough the big end bearing and trough a small hole in the rod shouldn't be anywhere near enough to cool a piston...

on a normal road engine oil squirters are placed in the main oil line that feeds the main bearings and have a small valve that opens at a predetermined pressure (to stop flow if the oil pressure gets too low)

I am currently looking at the inside of a Suzuki TL engine . It has oil squirters aimed at the underside of the piston and a hole about 2mm diameter up from the big end on the conrod on the side between the struts of the I beem quite close to the big end. the big end shell only has a hole in it communicating with it . the crank has two oil supplys at 10 and 2 on the clockface so to speak. so this small squirter only recieves volume twice a crank revolution.
what I am trying to get a handle on with the help of you cretons is should I pressure feed the pin by delete the small side conrod squirter, drill to the pin ,and add the small hole at the top of the conrod or delete the small hole as it might reduce the pressure available at the big end.
I am making new conrods as I am shortening the stroke and increasing the bore.
thankyou malbeare

[Tony Matthews]

cretons

Is that cretins, as in idiots, or croutons, as in small cubes of fried bread added to soups or salads? I think we should be told. You could just leave out the con-rods...

[Grumbles]

I'd assume that the croutons at Suzuki knew what they were doing when they added the mystery oil hole. So I'd duplicate their work as closely as possible with the new rod, and change nothing apart from the length.

I'm not sure what's worse Tony, to be called an idiot or fat and crusty?

Edited by Grumbles, 16 April 2011 - 23:03.

[24gerrard]

Hmmm, fat and crusty now that rings a bell, must reduce my intake.

[kikiturbo2]

in some cultures, fat and crusty might be taken as a compliment..

[Tony Matthews]

I'm not sure what's worse Tony, to be called an idiot or fat and crusty?

Fat crusty idiot, probably...

[cheapracer]

what I am trying to get a handle on with the help of you cretons

What engine configuration/layout are you looking at Mal?

Tony obviously he meant "Kryten's" in reference to obvious high intelligence.

[Magoo]

I am currently looking at the inside of a Suzuki TL engine . It has oil squirters aimed at the underside of the piston and a hole about 2mm diameter up from the big end on the conrod on the side between the struts of the I beem quite close to the big end. the big end shell only has a hole in it communicating with it . the crank has two oil supplys at 10 and 2 on the clockface so to speak. so this small squirter only recieves volume twice a crank revolution.
what I am trying to get a handle on with the help of you cretons is should I pressure feed the pin by delete the small side conrod squirter, drill to the pin ,and add the small hole at the top of the conrod or delete the small hole as it might reduce the pressure available at the big end.
I am making new conrods as I am shortening the stroke and increasing the bore.
thankyou malbeare

If there are piston squirters in the block as you seem to be saying, there should be no need to change anything. If you don't have them I'd add them. They work much better at oiling the pin and cooling the piston than drilling the rod. A hole through the top of the rod is ineffective compared to a current piston squirter setup. You also seem to be describing a hole through the big end of the rod to the outside of the beam. If so, that's for oiling the cylinder wall and I'd keep it.

[malbear]

What engine configuration/layout are you looking at Mal?

Tony obviously he meant "Kryten's" in reference to obvious high intelligence.

Hey Im Australian , If I call you a bloody old Bastard or idiot or creton then thats a term of endeerment ( Interperate dear Close friends)
If I said Deceptively evil, deviously cunning, Machiavellian, predatory, vindictive, psychopathic, habitually lying. above all a cane toad neck parasitic schoolyard bully. then that may be serious.

Engine Layout 1000cc L. V twin 90 degrees capable of 15000 rpm so you can guess a stroke of around 2 inches
Normally such a layout would prove difficult from a combustion efficiency viewpoint as the combustion chamber shape would be all in the valve pocket cutouts in the piston .but with different heads should be good.
Im a big fan of Red Dwaf
malbeare

Edited by malbear, 17 April 2011 - 09:40.

[Tony Matthews]

Im a big fan of Red Dwaf

Do you mean your Prime Minister?


I tried to add a little colour to the squirters, just to cheer the drawing up and help any crouton to locate them, but my limited software wouldn't cooperate...

Edited by Tony Matthews, 17 April 2011 - 10:54.

[24gerrard]

Bl--dy Colonials
They will be wanting their own Parliament next.

Webber drove a brilliant race by the way.

[Lee Nicolle]

Bl--dy Colonials
They will be wanting their own Parliament next.

Webber drove a brilliant race by the way.

Currently it is a kindegarten in Canberra

[cheapracer]

If there are piston squirters in the block as you seem to be saying, there should be no need to change anything. If you don't have them I'd add them. They work much better at oiling the pin and cooling the piston than drilling the rod. A hole through the top of the rod is ineffective compared to a current piston squirter setup. You also seem to be describing a hole through the big end of the rod to the outside of the beam. If so, that's for oiling the cylinder wall and I'd keep it.

+1 on that lot.

I asked about configuration as I suspect you may have a horizontal cylinder and if the thrust is on the upper side you may want to aim your squirter to that wall/side of the piston, gravity and crank throw will do the other side well enough. Some V8's and V6's are setup to do the same on the far bank thats effected in the same way

Do you mean your Prime Minister?

I laffed hard!

Edited by cheapracer, 17 April 2011 - 12:49.

[Canuck]

Deceptively evil, deviously cunning, Machiavellian, predatory, vindictive, psychopathic, habitually lying. above all a cane toad neck parasitic schoolyard bully.

You could have saved yourself all that typing and just said politician.

God I love this forum. Thanks Tony.

[kikiturbo2]

I tried to add a little colour to the squirters, just to cheer the drawing up and help any crouton to locate them, but my limited software wouldn't cooperate...

do I see 2 squirters per piston?

[bigleagueslider]

malbeare,

The wrist pin bushing mostly operates in boundary type contact conditions, so having a pressurized feed is not really beneficial. Its oil flow requirements are for cooling, but due to its low-speed oscillatory motion not much heat is generated. Using a drilled conrod beam to deliver oil to the bushing is not generally an efficient approach, since the flow area past the rod bearing is limited, the flow pressure drop is high, and the oil mass in the drilled passage is subject to inertia forces.

As others noted, if the piston crown itself requires oil cooling flow, a better approach would be jets located in the crankcase. These jets deliver a directed and metered amount of oil flow. Of course, using oil sprays to cool the piston crown using simple impingement is also an inefficient process. The impinging oil mass does not stay in contact with the crown underside long enough to transfer much heat, so the oil mass flows required to achieve a given heat rejection are usually much higher than one would expect.

Wrist pin and bushing life could best be improved by creating some sort of dynamic condition or kinematic geometry at this joint that caused the pin to constantly rotate.

regards,
slider

[malbear]

malbeare,

The wrist pin bushing mostly operates in boundary type contact conditions, so having a pressurized feed is not really beneficial. Its oil flow requirements are for cooling, but due to its low-speed oscillatory motion not much heat is generated. Using a drilled conrod beam to deliver oil to the bushing is not generally an efficient approach, since the flow area past the rod bearing is limited, the flow pressure drop is high, and the oil mass in the drilled passage is subject to inertia forces.

As others noted, if the piston crown itself requires oil cooling flow, a better approach would be jets located in the crankcase. These jets deliver a directed and metered amount of oil flow. Of course, using oil sprays to cool the piston crown using simple impingement is also an inefficient process. The impinging oil mass does not stay in contact with the crown underside long enough to transfer much heat, so the oil mass flows required to achieve a given heat rejection are usually much higher than one would expect.

Wrist pin and bushing life could best be improved by creating some sort of dynamic condition or kinematic geometry at this joint that caused the pin to constantly rotate.

regards,
slider

Thank you slider. It may be better to ditch the conrod side squirters and provide a seperate flow to squirters aimed at the other side of the piston not served by the original two.
I have looked at the underside of Nissan GTR pistons and they seem to have a false floor or chamber to presumably hold the oil from the squirters for a period to aid cooling.
malbeare

[24gerrard]

malbeare,

The wrist pin bushing mostly operates in boundary type contact conditions, so having a pressurized feed is not really beneficial. Its oil flow requirements are for cooling, but due to its low-speed oscillatory motion not much heat is generated. Using a drilled conrod beam to deliver oil to the bushing is not generally an efficient approach, since the flow area past the rod bearing is limited, the flow pressure drop is high, and the oil mass in the drilled passage is subject to inertia forces.

As others noted, if the piston crown itself requires oil cooling flow, a better approach would be jets located in the crankcase. These jets deliver a directed and metered amount of oil flow. Of course, using oil sprays to cool the piston crown using simple impingement is also an inefficient process. The impinging oil mass does not stay in contact with the crown underside long enough to transfer much heat, so the oil mass flows required to achieve a given heat rejection are usually much higher than one would expect.

Wrist pin and bushing life could best be improved by creating some sort of dynamic condition or kinematic geometry at this joint that caused the pin to constantly rotate.

regards,
slider

Thank you slider, very informative.
I was always dubious about the effectiveness of the drilled con rod or for that matter oil jets.
I do not think it advisable to rely on either in any tuned engined.
Sufficient oil flow from jets would result in to high oil windage.
Your comments do point to a preference for a fully floating gudgeon pin and a design to result in offset load paths to promote rotation is interesting.
Can you expand this a little?
I cannot see a piston being designed with any worthwhile size of pocket for oil retention, the changes in piston mass would be a negative result of this.

Edited by 24gerrard, 18 April 2011 - 11:19.

[Tony Matthews]

Sufficient oil flow from jets would result in to high oil windage.

Didn't seem to be a problem in a V10 turning over 17,000 RPM.

[24gerrard]

Didn't seem to be a problem in a V10 turning over 17,000 RPM.

You would need to be more specific about the flow used and the reliability and power output in service.

[Tony Matthews]

You would need to be more specific about the flow used and the reliability and power output in service.

I don't have to be more specific, it worked.

[24gerrard]

I don't have to be more specific, it worked.

It was used,
Whether it worked is another question.

Edited by 24gerrard, 18 April 2011 - 17:26.

[Tony Matthews]

It was used,
Whether it worked is another question.

As far as I know the Ferrari 049 V10 was a reasonably successful engine.

[Magoo]

Piston oil sprayers are the unsung innovation of 21st century engines. I have to believe that every new engine in the last decade has them, or is at least protected for them. It would be foolish not to. The benefits are great and aside for a tiny bit of manufacturing cost, there are no real drawbacks.

[24gerrard]

I think you will find that the main benefit of oil jets is to lubricate the cylinder walls to replace the oil mist taken away by dry sump pumps.
The effectiveness of piston cooling is debateable.

[Tony Matthews]

I think you will find that the main benefit of oil jets is to lubricate the cylinder walls to replace the oil mist taken away by dry sump pumps.
The effectiveness of piston cooling is debateable.

That must be why they point at the underside of the piston crown then. Over and out.

[Magoo]

That must be why they point at the underside of the piston crown then. Over and out.

Exactly. Greater CR and higher boost levels. A pretty sweet deal.

[Lee Nicolle]

For the most part the oil spraying from the conrods lubricates the cylinder walls, plus the general oil mist in the engine, even a good dry sump does not suck all of that out.
Drilling a conrod is a potential strss riser. Done properly it should be ok but really there should be enough oil there in the first place to lubricate the pin.. Just another oil leak and more oil to try and control.
I have never had anything to do with so called hi tech race engines, just old school pushrods grunters that usually out perform and are more reliable anyway.
But spraying oil on the cylinder walls defies logic to me as it is more oil for the poor old rings to try and control. That is why for decades a windage tray [of many styles] has been no1 in engine prep.
And trying to cool the piston with oil is pretty dubious as the volume needed is going to make a huge mess of oil to clean up. Probably off the road behind the car!!
If an efficient cooling system cannot cool the piston adequatly back off on the horsepower.And unless you are spending a million bucks a year the KISS principle is totally valid.
Most turbo racers, street or track should remember that as they melt another set of pistons regularly, and even toy diesels used in some passenger cars and light commercials have a similar problem. Especially when people up the boost to try and get a bit of performance out of them!!

[gruntguru]

There have been a couple of posts stating that oil-cooling of the piston underside is dubious or won't work and that flow is insufficient. Based on what? Every example I have heard of block-mounted piston squirters has been stated to be a piston cooling device. How much heat is removed?

Cooling = Massflow x Specific-heat x delta T(oil).

- delta T could be pretty big since the oil in is around 100*C and the piston underside perhaps 200*C +. Say oil out = 150*C then delta T(oil) = 150 - 100 = 50*K
- Specific heat approx 2 kJ/Kg.K
- flow = say 10gram/s (3 teaspoons)

Cooling = 0.01kg/s x 2kJ/kg.K x 50*K = 1 kW. That's a lot of cooling! Adjust wherever you wish.

Edited by gruntguru, 19 April 2011 - 00:21.

[Canuck]

Don't be introducing all that confangled math and logic trickery here. We all know that a lever is a lever except when it's not (when is it not again?)!

[cheapracer]

That must be why they point at the underside of the piston crown then. Over and out.

I've also seen some of the pipes near hit the underside of the piston crown at BDC they extend so far into the piston area.

With todays alloys and amazing production tolerences, oil misting is well and truly sufficient for wall lubrication.

[carlt]

some of those old Ford rods with the oil hole out the side of the big end , just about where they thinned down into the stem , would break at that point every time the rev range was raised above stock
as mentioned above almost a guaranteed stress point

If not fitting oil squirters ,
I have always just filed a couple of small rounded slots [ 2-3mm] one on either side of the rod on the edge of the big end [where it chamfers away from the bearing shell , pointing upwards towards the piston , the theory being that the pressure fed oil to the big end will find the easiest exit which will be the two new slots between crank web and rod .

[Magoo]

The function of piston oil sprayers aka oil squirters is cooling the piston. In fact, that's what a number of mfg'ers call them: piston coolers.

The Chevy LS9 supercharged engine couldn't have been done without them, really. Here's a link to an article on the engine with comments from Jim Cremonesi, the DRE recip. Excerpt:

Integral piston squirters in the crankcase oil galleries were essential in making the LS9 live under prolonged high boost. "Our analytical tools told us early on we would be in big trouble without them," says Jim Cremonesi, DRE (design responsible engineer) for the LS9 cranktrain. "We see a significant drop in piston-dome and pin-boss temperatures. It's the best way we know to pull the heat out of the piston when making this much power."

Full story:

http://www.hotrod.co..._zr1/index.html

This piece also does a fair job of describing what goes into an OE project of this type... how the people are organized, the efforts are focused, etc. If I may say so.

[Tony Matthews]

If I may say so.

[bigleagueslider]

gruntguru,

Your approach for estimating heat rejection via oil impingement is correct, but the oil delta T you note is way too high. The delta T would be something closer to 20degC, not 50degC. And therein lies the problem, with a low delta T the mass flow must be increased.

All turbo engines (gasoline and diesel) use piston oil cooling, and normally these pistons use some sort of oil gallery in the piston that keeps the oil in contact with the piston for a longer period. The result being that the cooling oil flow achieves a much greater delta T and less mass flow is required. The most advanced automotive diesel engine pistons are now forged and inertia welded from steel, in order to minimize the cooling required.

http://www.mahle-aft...6MPHCS671STULEN

slider

[gruntguru]

Thanks for that info slider. So, only 400 W of cooling for 3 teaspoons/sec flow - I'm happy with that!
As I said - Adjust wherever you wish.

[malbear]

some of those old Ford rods with the oil hole out the side of the big end , just about where they thinned down into the stem , would break at that point every time the rev range was raised above stock
as mentioned above almost a guaranteed stress point

If not fitting oil squirters ,
I have always just filed a couple of small rounded slots [ 2-3mm] one on either side of the rod on the edge of the big end [where it chamfers away from the bearing shell , pointing upwards towards the piston , the theory being that the pressure fed oil to the big end will find the easiest exit which will be the two new slots between crank web and rod .

The conrods from the suzi TL have exactly that only two , about 5mm in from the outside struts of the I beam.
The conrod stroke ratio in the TL is 1.86 . 66mm stroke 123mm conrod . my new conrod has a ratio of 2.38 so the side thrust should be reduced . It is shorter than the stock rod but the stroke is shorter by a greater percentage. Exact dimentions are a trade secret but some of you might be able to have a good guestimation. The overall length was dictated by those pesky oil squirters at the base of the block . The barrels or bores are a seperate item in bike engine construction . I have checked out the several TL suzi forums . They all talk about increasing the stroke and bore and clutch mods never reducing the stroke.

[mariner]

More crank than piston but can somebody help me with a turbo boost vs RPM question please?

I know you need a better crank as power goes up ( forged vs cast, non twist vs twist etc. ) but what stresses cranks the most - boost or revs.

So if I take a stock crank with a nominal limit of 6,000 rpm and retune to 7,000 rpm is that more stress on the crank than say going to 1 BAR of boost still at 6,000 rpm? I seem to recall that boost actually eases some stress when the piston is stopped at the top of the stroke but I don't understand all the dynamics of revs versus boost at lower revs.

I would presume the heavier piston for high boost also enters the calculation but I do not know the details.

[carlt]

More crank than piston but can somebody help me with a turbo boost vs RPM question please?

I know you need a better crank as power goes up ( forged vs cast, non twist vs twist etc. ) but what stresses cranks the most - boost or revs.

So if I take a stock crank with a nominal limit of 6,000 rpm and retune to 7,000 rpm is that more stress on the crank than say going to 1 BAR of boost still at 6,000 rpm? I seem to recall that boost actually eases some stress when the piston is stopped at the top of the stroke but I don't understand all the dynamics of revs versus boost at lower revs.

I would presume the heavier piston for high boost also enters the calculation but I do not know the details.

Revs
some physics and math to do with the reciprocating mass[pistons , rods etc] and its acceleration / deceleration

[bigleagueslider]

More crank than piston but can somebody help me with a turbo boost vs RPM question please?

I know you need a better crank as power goes up ( forged vs cast, non twist vs twist etc. ) but what stresses cranks the most - boost or revs.

So if I take a stock crank with a nominal limit of 6,000 rpm and retune to 7,000 rpm is that more stress on the crank than say going to 1 BAR of boost still at 6,000 rpm? I seem to recall that boost actually eases some stress when the piston is stopped at the top of the stroke but I don't understand all the dynamics of revs versus boost at lower revs.

I would presume the heavier piston for high boost also enters the calculation but I do not know the details.

mariner,

There is not a simple answer to your question. The crank is subject to both bending and torsion. The stresses produced in the crank are due to combustion pressures, inertia forces from the reciprocating rod and piston masses, and dynamic forces due to vibration response of the crank structure. As noted, the higher turbocharged intake and exhaust manifold pressures can help offset some of the piston/conrod inertia loads around TDC on the exhaust stroke. But the turbo engine will also have higher peak combustion pressures acting on the piston. And the torsional forces transmitted along the crank will also be greater with the turbo engine.

RPM's tend to be problematic due to the fact that inertia forces increase exponentially with speed. While loads due to higher turbo combustion pressures remain more constant. All other things being equal, increasing the RPM's from 6K to 7K would probably produce more crank rod/main pin bending stress than 1 bar of boost, but the 1 bar boost would produce more torsional stress.

slider

[gruntguru]

Actually turbo motors do not necessarily have higher peak pressures. In many cases the turbo motor will be set up for similar peak pressure courtesy of lower compression ratio and/or later ignition timing.

In addition the turbo motor will have a "fatter", less peaky pressue curve which is better from a crank stress veiwpoint.

Torsional stress is mostly due to torsional vibration. The con-rod loads contribute relatively little - even in a high boost application. You only have to look at a crankshaft to see that it is capable of handling torsional loads several orders of magnitude greater than the engine output.

Edited by gruntguru, 22 April 2011 - 04:19.

[bigleagueslider]

Actually turbo motors do not necessarily have higher peak pressures.........

Torsional stress is mostly due to torsional vibration......... You only have to look at a crankshaft to see that it is capable of handling torsional loads several orders of magnitude greater than the engine output.

gruntguru,

You are correct that turbocharging does not necessarily mean higher peak cycle pressures. But in reality, the point of turbocharging is to increase the BMEP rate of an engine, and thus it would almost always lead to higher peak cycle pressures.

As for torsional vibration modes being the main contributor to torsional shear stress in a crankshaft structure, this is not normally true. Crank trains are normally engineered to operate at speeds and forcing frequencies that are outside of the lower order (most energetic) critical modes of the crankshaft. If there were some crankshaft structural mode identified that would couple with a forcing frequency created by the engine's operation, the stiffness or mass properties of the crank train would be modified to remedy the condition. These corrective actions may involve adding/moving counterweight masses, altering flywheel mass properties, or using tuned mass dampeners.

With the possible exception of pure racing cranks, the limiting factor with crank life is always fatigue. Fatigue life is affected by combined stress levels (both torsion and bending), number of load cycles (N), stress concentrations (Kt), and magnitude of load reversals ®.

Regards,
slider