Thanks Ben, but I could not get the new box to work. The new box does not put the trans in to limp mode, but when I hit the lock/ unlock button it does nothing. I do not have time to mess with it.
Piston Bowls
- Thread starter Fingers
- Start date
Great thread! I have a few thoughts to share.
I wonder how much difference there is in the thermal maps and how the heat absorbed is moved out to the rings and cooled underneath the crown compared to the stockers. Since the others cracked like you guys have said, is it because of changing the materials position around or is it possibly because of lack of material? or even lack of quality heat transfer properties of the piston design and material?
I wonder how much difference there is in the thermal maps and how the heat absorbed is moved out to the rings and cooled underneath the crown compared to the stockers. Since the others cracked like you guys have said, is it because of changing the materials position around or is it possibly because of lack of material? or even lack of quality heat transfer properties of the piston design and material?
The mechanism for cracking the piston top via thermal is ring stress. Hot expanding center and cool contracted outer edge. It is why these pistons are domed in the middle. I don't think it is a major player here though.
As far as how oval changes the thermal map on the piston surface, I only have crude calcs on that. That is because the heat source is not evenly distributed across the crown of the piston stock or oval. A critical component of that is the exposed surface area of the crown. More area, more heat absorption. Ovals have less exposed area for a given CR.
As far as how oval changes the thermal map on the piston surface, I only have crude calcs on that. That is because the heat source is not evenly distributed across the crown of the piston stock or oval. A critical component of that is the exposed surface area of the crown. More area, more heat absorption. Ovals have less exposed area for a given CR.
So, then the oval design has less capacity for heat absorption/transfer? Then where will said heat go? To the turbo? Cylinder walls? The head? Just curious. This is a very interesting thread, btw.
Fingers it would be pretty interesting to see the difference in temp from the central area to the crown area towards the circumference of the piston in the crevice area. Thanks for starting this thread!
All surfaces involved HotCoCoal,
Crown down to your top compression ring
Lip or edge in the crown (heat absorbs quickest and dissipates the quickest in these types of areas too)
Top ring
Bore wall
Gasket fire ring or just fire ring
Valve chamber faces
Cylinder head fire deck
If our heat transfer can be properly controlled by the materials & dimensions used in the engine our torque production can be contained to a point, however with producing good parts at a cost effective quality, sometimes things will at some point say bye at an expensive price if things aren't good enough during operation.
All surfaces involved HotCoCoal,
Crown down to your top compression ring
Lip or edge in the crown (heat absorbs quickest and dissipates the quickest in these types of areas too)
Top ring
Bore wall
Gasket fire ring or just fire ring
Valve chamber faces
Cylinder head fire deck
If our heat transfer can be properly controlled by the materials & dimensions used in the engine our torque production can be contained to a point, however with producing good parts at a cost effective quality, sometimes things will at some point say bye at an expensive price if things aren't good enough during operation.
Static heat absorption is fairly easy to do across the crown of the piston. Unfortunately, that is not how the heat is produced in a diesel. The fuel plume from the injectors localize the heat initially along the plume then all heck breaks loose as the chamber fills and grows as the piston moves down.
From what research I have done, the toroidal bowl of the stock piston tends to keep a "ring of fire" in the bowl while the piston is near TDC. The "quench" area along the flat of the piston is aptly named since the combustion in this area is snuffed out initially. So near TDC essentially all the heat is generated in the bowl of the piston, and all the initial absorption is from this area. Considering the highest chamber temps happen within the first 20 degrees of TDC, (from my measurements) I would tend to use that as the worst case state for heat absorption by the piston.
What I don't know is when the quench area becomes active. The proximity of the "cool" piston, cylinder wall, and head keep the charge temps below the fuel's flash point for an extended time.
Now introduce a bowl design that is essentially two interconnected bowls like my oval design.
So, as I said earlier, the thermal analysis of the chamber is non-trivial. At least it is outside my ability to fully solve.
From what research I have done, the toroidal bowl of the stock piston tends to keep a "ring of fire" in the bowl while the piston is near TDC. The "quench" area along the flat of the piston is aptly named since the combustion in this area is snuffed out initially. So near TDC essentially all the heat is generated in the bowl of the piston, and all the initial absorption is from this area. Considering the highest chamber temps happen within the first 20 degrees of TDC, (from my measurements) I would tend to use that as the worst case state for heat absorption by the piston.
What I don't know is when the quench area becomes active. The proximity of the "cool" piston, cylinder wall, and head keep the charge temps below the fuel's flash point for an extended time.
Now introduce a bowl design that is essentially two interconnected bowls like my oval design.
So, as I said earlier, the thermal analysis of the chamber is non-trivial. At least it is outside my ability to fully solve.
Not sure if this will be a good reference or not but here it goes. Its been found that in gassers the quench region is generally set to a norm of .035 - .040" without abnormal combustion to create adequate squish action. Anything around .060" and above allows fuel to be consumed.
Could the region become active around the same once the crankshaft has moved enough to create the .060" and above gap? What is the usuall deck height of the Duramax when it has been assembled? plus the quench clearance in addition?
I may be able to help you locate someone to help you with the thermal analysis if you want to try Fingers.
Could the region become active around the same once the crankshaft has moved enough to create the .060" and above gap? What is the usuall deck height of the Duramax when it has been assembled? plus the quench clearance in addition?
I may be able to help you locate someone to help you with the thermal analysis if you want to try Fingers.
My truck is under the knife right now and we are going to be installing a set of these pistons in it. I will keep you all posted on it.:thumb: Goal is 1,000hp single pumped fuel only with twins so we will see how close I can get!
This just happened to me.. http://www.duramaxdiesels.com/forum/showthread.php?t=44191
Looks nice jon
This may be a stupid question and it quite possibly was already answered in the past 26 pages of this thread so forgive me if thats the case but..
Injectors spray in a "flower/star" type pattern which is more or less similar to a circle correct? With the oval pistons I assume the spray pattern is still confined into the bowl even with the smaller oval shape impeeding on the sides of the bowl.
So why not make the bowl round but use the smaller diamater across the bowl?
Injectors spray in a "flower/star" type pattern which is more or less similar to a circle correct? With the oval pistons I assume the spray pattern is still confined into the bowl even with the smaller oval shape impeeding on the sides of the bowl.
So why not make the bowl round but use the smaller diamater across the bowl?
I was thinking that as well but besides from the compression "issue" It would probably be an even stronger piston..even if that difference was negligible.
Personally, I don't see high compression as anything but a plus in a built motor application... I mean how many built motors do we see failing due to chamber pressures? besides those with stock pistons?
Personally, I don't see high compression as anything but a plus in a built motor application... I mean how many built motors do we see failing due to chamber pressures? besides those with stock pistons?
The narrow width of the oval is as wide as a stock bowl. So the injectors do not spray over the edge any more than stock there. The long way in the oval is ~3/4" longer than stock.
In short, the shape was selected because it provides the best strength. Circular chambers do not.
piston cost
Hi there!
So, how much for a set of your oval pistons for stock bore for an LBZ?
Thank you.
Jason
Hi there!
So, how much for a set of your oval pistons for stock bore for an LBZ?
Thank you.
Jason