Engine power level and piston construction

...In terms of design, I guess more critical is the magnitude of required heat displacement from the crown, which will be largely be dependent on material i.e. If its a forged alloy part, a higher heat transfer rate is experienced so a cooler crown often follows...
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One would also think that the amount of material too has an effect on transfer path as well.

Charles Fayette Taylor states with aluminum trunk pistons first quote is apparently for small bore unsuprcharged engines...
For this type of cooling aluminum is desirable, with generous sections for heat conduction from the center of the piston head..... Heat conduction to the cylinder walls is promoted by small skirt clearances. Rings run cooler as the top "land" (distance from the top edge of the piston to top ring) is increased.
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Now a few sentences later in the next paragraph about supercharged and diesel engine pistons about the oil speed in the gallery of the crown...
For oil cooled pistons the rate of oil circulation must be high enough to avoid breakdown of the oil into cabronaceous deposits
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Food for thought. Though most think oil cooling galleries in pistons are there to keep the crown of the piston cooler, and they do to some extent, they are really there to protect the top most ring and land. If and when the oil does not fill the cavity, the gallery becomes a thermal break between the topmost part of the piston and the skirt causing a huge increase in temperature.
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Going back to my thought, in this situation the piston mass position would provide a more efficient heat-mass-movement (even if it requires a good amount of energy to do it) in the way of least resistance? if the rings had more 'meat' around them the rings would seem to be running at a lower temperature, so they aren't or can't be scorched. If we proceed down to the skirt we have 2 areas that won't absorb heat quickly just because of material differences and not being integral, the rings which are already mentioned and the wrist pin which can be hollow or solid although solid is generally heavy duty commercial. Since we have good manufacturing compared to yesteryear, quality aluminum, forged or cast pistons could have the same efficiency of heat transfer.....

IMO so far, cooling a piston with a liquid seems to be a more efficient way of reducing and maintaining an adequate operating temp of a piston in addition to our conduction process.

I tried looking for piston weights for the 5.9L or any other light duty mill, didn't find much after a quick browse but came across this article from, again Diesel Power. Mahle mentioning, in some applications, the Monotherm can be around 100 grams lighter in weight. Maybe I did not use the precise words in my initial search. Good enough for starters on establishing piston weight discussion anyways.
http://www.dieselpowermag.com/tech/1204dp_mahle_unbreakable_pistons_piston_of_the_future/
 
Material is a very open discussion, steel can be consider an alloy. Articulated pistons where developed to reduce weight with an aluminum skirt and a steal crown for strength. This came with the CR ISC,L and the later ISM.
 
Lenahan should have a good build since he seems to have a great grasp on engines. 1100 and 1200+ weights, comparison, how much quicker would the engine rev up, only practice will show along with other portions being tuned. 1 pound = 453.592 grams for those not aware.

Material is a very open discussion, steel can be consider an alloy. Articulated pistons where developed to reduce weight with an aluminum skirt and a steal crown for strength. This came with the CR ISC,L and the later ISM.
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Articulated pieces are also develpoed to reduce ring seal interruption when the rod has changed directions during the direction at TDC compression.

From reading some of the thread Fingers has over on a Dmax forum on his piston of discussion, one person had mentioned his design alteration changed the exhaust note of the engine as well. I wonder what has changed with his change of the crown that gave the exhaust note a different tone, if it created a more agreassive but smooth burn cycle or just a smoother cycle in all. High speed photgraphy would be great in seeing whats going on with that piston as well as the monitoring thermocouples that could be employed.

Material used itself, I have yet to read on. Do we really need a nickel-chrome top ring insert when you rebuild? Do we need a oil cooling gallery if we design the piston correctly to reduce/maintain temps just by oil jets at the underside? The material used and the design is beginning to point that, any piston configuration, and mass position could change where and when heat is absorbed and how it is absorbed.

I hope everyone's weekend went well. :pop: Anyone know the material grades most diesel pistons are made of?
 
Most after market forged pistons I believe use a 2618 T61 alloy(very tough, but requires large piston to cylinder clearance). High silicon forgings such as mahle produces would use a 4032 or MS75 alloy I suspect(more brittle but favorable growth characteristics). As for the cast stockers, I would think they they would be some sort of hyperutectic alloy.
 
Welp got destroyed by my thermodynamics final exam this morning, can't tell ya much except moose drool brown ale is a fine beer.

Stupidity aside, I wouldn't hesitate to use steel pistons and I think they will become standard on medium duty diesels soon enough. The fatigue endurance limit alone will extend far far beyond aluminum, hence their use in big rigs. Less thermal expansion for accurate tolerances, heat resistance, less skirt area, stable heat behavior at the ring lands, blah blah blah. I'll get in the lab within a couple months and do some heat analysis with aluminum and steel pistons if I can get the geometry specs from you guys.
 
Fahlin Racing said:
Lenahan should have a good build since he seems to have a great grasp on engines. 1100 and 1200+ weights, comparison, how much quicker would the engine rev up, only practice will show along with other portions being tuned. 1 pound = 453.592 grams for those not aware.



Articulated pieces are also develpoed to reduce ring seal interruption when the rod has changed directions during the direction at TDC compression.

From reading some of the thread Fingers has over on a Dmax forum on his piston of discussion, one person had mentioned his design alteration changed the exhaust note of the engine as well. I wonder what has changed with his change of the crown that gave the exhaust note a different tone, if it created a more agreassive but smooth burn cycle or just a smoother cycle in all. High speed photgraphy would be great in seeing whats going on with that piston as well as the monitoring thermocouples that could be employed.

Material used itself, I have yet to read on. Do we really need a nickel-chrome top ring insert when you rebuild? Do we need a oil cooling gallery if we design the piston correctly to reduce/maintain temps just by oil jets at the underside? The material used and the design is beginning to point that, any piston configuration, and mass position could change where and when heat is absorbed and how it is absorbed.

I hope everyone's weekend went well. :pop: Anyone know the material grades most diesel pistons are made of?
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I wish I could post some of the pictures I grabbed from work. Being too big, I’ll have to figure out a way to resize them.

From the depths of my memory modern piston design also have an offset pin for noise control and crown rocking during operation. This was supposed to help with ring wear and combustion sealing.

Wonder if it’s possible to install Dmax pistons reversed?

Also 03-04 vs. 05-06 5.9l Cummins sound different. Both different pistons designs but I’m ignorant on the difference in tuning...
 
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CurtisEmery said:
Most after market forged pistons I believe use a 2618 T61 alloy(very tough, but requires large piston to cylinder clearance). High silicon forgings such as mahle produces would use a 4032 or MS75 alloy I suspect(more brittle but favorable growth characteristics). As for the cast stockers, I would think they they would be some sort of hyperutectic alloy.
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Interesting, thank you Curtis. I have never seen 2618 T61 alloy until you posted. I hope to bring up more material grades soon on both Steel and Aluminum. I wonder what the underside of the pistons made with the 2618 material looks like since you say the expansion rates are higher. From reading wiki I guess hypereutectic means the aluminum alloy contains more silicon which allows the expansion to be lower and its strength higher as well.

If anyone is interested I was tought this process on measuring taper of the piston, if the piston has taper or if the piston is cam-ground. Generally, with cam-ground pistons (old tech), areas with more clearance at startup is on both 'sides' of the piston matching the wrist pin end positions. We have the 10,2,5 and 7 o'clock postions with the actual piston thrust zones in between 10 & 2 and 5 & 7 looking at the piston from the top. As you measure move down the piston crown to skirt. The newer stuff is most likely not going to be cam-ground or tapered, once the scraper ring you should notice the taper forming.

Now the total height of the piston we all know can affect stability within the cylinder, but with light high speed diesel mills how short of a piston can we really play with without jepordizing wear rates and ring seal quality. Granted the wrist pin and ring package location will be the deciding factors how short we could go. But also could we shape the piston's skirt in a similar fashion as short compression height gasser pistons. Right now the diesel piston is cylindrical from crown to piston skirt bottom, could there be weight shedding possibilities without effecting the heat transfer path and efficiency without causing an over heating of a piston.

Straight 6, when you tested the different injectors, did you have a open chamber crown or a lipped re-entrant chamber? I will have to look for the Moose Drool, I just had some of the Dragon's Milk brewed up in Michigan. I can try to get some geometry info here soon, not sure what piston it will be on though.

If there is a difference in sound on the 5.9L Cummins you listed HeTheAethry! do you think that the timing and injection system is different or maybe some piston designs may be changed just enough to quiet the engine that much?
 
The under sides look like your typical turbo piston. Being a forged design there is no oil gallery in the crown. I have heard that the Ross and Arias pistons(2618) run .010-.012" clearance. The higher silicon forged pistons like Mahle produces run anywhere from .003-.006" clearance. A good test on some junk pistons if you have some laying around. Place each piston in a vice and strike the skirt with a hammer. Observe what happens to the cast piston vs the forged piston. I am not saying one is better than the other. Each has its advantages. Steel pistons on the other hand seem to have all the desirable traits of both the cast and forged aluminum designs IMO.
 
Some on the piston height above the wrist pin from Taylor's ICE in Theory and Practice Vol 2 book, page 481

Height Above Pin
The ratio of this height to bore is given in the design-ratio tables. Where possible, it would seem desirable to locate the pin in the middle of the skirt-bearing surface. However, successful engines have been produced with pin locations near the rings and also near the bottom of the skirt.
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The design ratio table of Piston proportions just before what I quoted from pin height in the best way I believe I could post it.
Length/bore (l/b) - Max. 2.36 - Min. 0.64
Height from pin center to top of bearing surface (h/b) - Max. 0.97 - Min. 0.25
Pin Diam/bore (p/b) - Max. 0.48 - Min. 0.20
Number of compression rings (Nc) - Max. 6 - Min. 2
 
JQmile said:
I know people (including me) who have beat the snot out of non-intercooled pistons. How much heat gets into the rings/ring land is also a big deal, because that's what gets the rings to expand and score the cylinder wall. Many have run non i/c stuff at 1600-2000 deg EGT in racing for years without problems. EGT can also be controlled at virtually any power level with water, so there's that, also.

IMG00187-20111204-1448.jpg
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JQ, have you measure the positions of each ring land from the top of either of those pistons before? Would you happen to have any crown pictures of those too with the soot or burn pattern on them?

Earlier when Fingers posted this ....
Fuel/air mix in the space just above the ring is quenched the further down towards the ring they get. The proximity of the cool piston and cylinder wall reduces the temp of the gas below the ignition point
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How far up can we move them is another question, Smokey Yunick did numerous dyno runs with different ring and locations until what he said they wore out a good set of wrenches doing it once they came up with the closest, optimal top ring position.

With raising ring positions we can also look into lowering the compression height of the piston hoepfully as well. However with a diesel we endure more heat within the chamber and with lowering the compression height of the piston we reduce, or can reduce the total length of the piston in turn reducing weight of one variable effecting our engine operation speed. What I can see as of right now if we reduce the length of the piston we also reduce piston mass, if we do that we also are changing the material mass densities with the structure of the piston which what I believe will alter our heat transfer paths and cooling methods. If we move the wrist pin closer we introduce that to more heat from combustion. Would a full floating pin or press-fit to the rod, floating in the piston retained by snap rings be sufficient?

Still working on finding more alloy information.
 
Food for thought. Though most think oil cooling galleries in pistons are there to keep the crown of the piston cooler, and they do to some extent, they are really there to protect the top most ring and land. If and when the oil does not fill the cavity, the gallery becomes a thermal break between the topmost part of the piston and the skirt causing a huge increase in temperature.

Coming back to Fingers' thought here, does the size and geometry effect the cooling?

More area allows more to be transfered, but can a more tubular shape change the transfer rates compared to a another, but like Taylor states the rate of flow also influences heat movement and as you say Fingers, a break in flow will alter flow. That leads one aspect of engine oil selection, which viscosity to use that will flow the greatest at operating temperature.

Could the geometrical shape and CSA of the cooling port directly relate to how the density of the crown resulting in a thicker or thinner crown design?

Since the high power levels produce more heat, does that necessarily mean 100% that our piston either is produced with more material or choosing a different material that resists strength reduction due to heat exposure?

:pop:
 
I've often marveled at how little attention is paid to the squirter nozzles.

On the one hand there's nothing to them, on the other hand it has to be aligned very well to put most of the shot in that hole X many inches away. I've always wondered if there were trucks out there with nozzles that weren't hitting the hole for one reason or another.

I did some experimentation long ago with normal 15-40 oil heated to operating temp pushed through the squirter, and it should be like a birdbath inside the block (it shoots far further than one would expect). Maybe some pistons are getting all of the shot right in the hole and some may be getting partial hits or whatever and/or just drowning the back side without really hitting the gallery.
 
nwpadmax said:
I've often marveled at how little attention is paid to the squirter nozzles.

On the one hand there's nothing to them, on the other hand it has to be aligned very well to put most of the shot in that hole X many inches away. I've always wondered if there were trucks out there with nozzles that weren't hitting the hole for one reason or another.

I did some experimentation long ago with normal 15-40 oil heated to operating temp pushed through the squirter, and it should be like a birdbath inside the block (it shoots far further than one would expect). Maybe some pistons are getting all of the shot right in the hole and some may be getting partial hits or whatever and/or just drowning the back side without really hitting the gallery.
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Great point and "should" be part of a engine blueprint when being rebuilt, While not alot i have seen certain squirters off by .250" and hitting pistons...along with them plugged up or bent.
 
Squirters

I have had mine plugged for a long time. No need in a race only motor. I should say no need with piston that doesn't have a oil channel. Stock type pistons I would run the squirter. Then again I don't think a race motor should have stock type piston.
 
Would anyone have thoughts as to using a oil passage in the crown and using a squirter without using water injection, or, would that not have a large enough effect to not include a water injection system for temperature maintenance on higher heat producing engines?
 
Pistons

How would you inject the oil in? You would have to have higher pressure at the oil supply than you have in the cylinder.
 
If the cooling effect of both the cocktail shaker and the squirter from the bottom of the bore, without increasing our oil pumps power consumption, dry-sump electric powered pump doing the work, or would that be too much? However, if we spray large amounts of oil, we are creating windage but I doubt it would be that great of an acceleration loss.
 
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