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Old 02-29-2012, 10:56 AM   #41
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Question on the 2618 alloy. Since it has a higher rate of thermal expansion, and thus requires larger clearances, doesn't this mean that on a "daily" engine, were the engine spends a significant amount of time in cold condition, the cylinder walls will wear down a lot quicker, promoting an oval-like shape and losing compression in no time at all?

This seems like an alloy ideal for racing applications, where you don't actually expect an engine to last more than 10,000-20,000 racing miles.
Not to mention the seriously short piston height/skirt contributes to that.

maybe a block heater is your best option...
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Old 02-29-2012, 11:42 AM   #42
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Originally Posted by Reverant View Post
Question on the 2618 alloy. Since it has a higher rate of thermal expansion, and thus requires larger clearances, doesn't this mean that on a "daily" engine, were the engine spends a significant amount of time in cold condition, the cylinder walls will wear down a lot quicker, promoting an oval-like shape and losing compression in no time at all?

This seems like an alloy ideal for racing applications, where you don't actually expect an engine to last more than 10,000-20,000 racing miles.
2618 pistons do tend to be noisier. We use JE and Wiseco 2618's in some of our race engines but try to stick to the Supertech 4032 for everrything, especially the street only engines. One exception is my daily driver 95R which got Wiseco's because they were the only piston in the exact size.cCR combination we needed. I can hear them every morning for the first mile or two on the way into the shop.

The 2.0L race motor we just built with Supertechs is silent.
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Old 02-29-2012, 12:24 PM   #43
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Emilio and Sav, I understand you both have done extensive sonic measuring of the BP blocks. I would like to know if boring to 85mm would be acceptable in a turbo build if boost pressures were kept to about 18-20 psi. How thin were the readings at 85 mm? Did they vary much block to block? Did one year of engine block happen to be better than another?
Thanks
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Old 02-29-2012, 01:52 PM   #44
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More geeky deets, this time on the JE pistons. FSR, yo.

http://blogs.insideline.com/roadtest...the-house.html
What design considerations were made wrt oil control with the factory oil squirters?
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Old 02-29-2012, 02:01 PM   #45
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Originally Posted by 2manyhobyz View Post
Emilio and Sav, I understand you both have done extensive sonic measuring of the BP blocks. I would like to know if boring to 85mm would be acceptable in a turbo build if boost pressures were kept to about 18-20 psi. How thin were the readings at 85 mm? Did they vary much block to block? Did one year of engine block happen to be better than another?
Thanks
They vary significantly from block to block, so you really need to measure yours.
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Old 02-29-2012, 03:51 PM   #46
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The 2.0L race motor we just built with Supertechs is silent.
My Supertech 8.6:1 is silent too.
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Old 02-29-2012, 05:42 PM   #47
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Originally Posted by Reverant View Post
Question on the 2618 alloy. Since it has a higher rate of thermal expansion, and thus requires larger clearances, doesn't this mean that on a "daily" engine, were the engine spends a significant amount of time in cold condition, the cylinder walls will wear down a lot quicker, promoting an oval-like shape and losing compression in no time at all?

This seems like an alloy ideal for racing applications, where you don't actually expect an engine to last more than 10,000-20,000 racing miles.
Isn't almost all forged pistons in 2618, ST use 4032 which is harder and have lower thermal expansion (but maybe too brittle for extreme power).
Cast pistons are probably not a bad idea for a long term DD .
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Old 02-29-2012, 05:54 PM   #48
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My Wesico's are silent.
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Old 02-29-2012, 08:08 PM   #49
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Quote:
Originally Posted by Reverant View Post
Question on the 2618 alloy. Since it has a higher rate of thermal expansion, and thus requires larger clearances, doesn't this mean that on a "daily" engine, were the engine spends a significant amount of time in cold condition, the cylinder walls will wear down a lot quicker, promoting an oval-like shape and losing compression in no time at all?

This seems like an alloy ideal for racing applications, where you don't actually expect an engine to last more than 10,000-20,000 racing miles.


Are rings really that much harder than the cylinder walls?


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My Supertech 8.6:1 is silent too.
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My Wesico's are silent.

My Weisco's squeak when hot. Or kinda moan.
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Old 03-01-2012, 02:38 AM   #50
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The biggest thing is you lose oil control when the gudgeon pin intersects the oil control groove like that. Thats why FM has everyone delete their oil squirters on their stroker kits. I don't really feel like checking the difference in g-loading, but a longer rod should theoretically only reduce piston G's by maybe 1 to 2 percent by increasing the amount of dpistondisplacement/dtheta around TDC. This also theoretically increases engine breathing by a small amount by allowing more time for intake valves to open before the piston begins traveling down the bore.

Maximum gain? 1% higher RPM limit? 2-3% in output, but not exceeding previous knock limits?

Innovation is good, but value is calling. Then again I could be missing something. Who knows?

4032
  • 2.68 g/cc
  • 52ksi yield
  • 16ksi fatigue
  • 38ksi shear
  • 10.8uin/in F* CTE

2618
  • 2.76 g/cc
  • 54ksi yield
  • 18ksi fatigue
  • 38ksi shear
  • CTE 13.4uin/in F*
The higher CTE of 2618 is what makes you run the larger clearances. Something like 24% larger then 4032.
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Old 03-01-2012, 11:07 AM   #51
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The significant advantage is the 5.2% decrease in cylinder wall side loading. That's going to reduce wear and egg-ing due to skirt to wall force, and thus increase cylinder sealing and power. Some.
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Old 03-01-2012, 07:08 PM   #52
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Quote:
Originally Posted by Reverant View Post
Question on the 2618 alloy. Since it has a higher rate of thermal expansion, and thus requires larger clearances, doesn't this mean that on a "daily" engine, were the engine spends a significant amount of time in cold condition, the cylinder walls will wear down a lot quicker, promoting an oval-like shape and losing compression in no time at all?

This seems like an alloy ideal for racing applications, where you don't actually expect an engine to last more than 10,000-20,000 racing miles.
I spoke with the JE doodz specifically on this. In their experience, using 2618 instead of 4032 doesn't manifest itself as wear, just noise (piston slap) during cold operation. Also not talking huge differences in clearance here -- 2618 wants 0.001 to 0.0015" more clearance than 4032 in pistons this size.

Historically, the slap noise really has been the biggest driving factor on whether to use 2618 or not, and that's why they designed the FSR forging to accomodate pin offset if so desired. Pin offset essentially preloads the major thrust side skirt so that it doesn't rock over and slap. The tradeoff to pin offset is a bit more side loading.

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What design considerations were made wrt oil control with the factory oil squirters?
Quote:
Originally Posted by TravisR View Post
The biggest thing is you lose oil control when the gudgeon pin intersects the oil control groove like that.
Pin in groove shouldn't affect oil control. In the cases where this is observed it is possibly because said piston also has very short compression height, which makes the oil control ring's job harder esp if ptw clearance is on the large side.

Last edited by JKav; 03-01-2012 at 07:24 PM.
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Old 03-01-2012, 08:52 PM   #53
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The only reason I said that I said is because of my experience with 347 V8 Ford strokers. Every kit that intersected the oiling groove burnt oil. Every kit that didn't controlled the oil. This is the actual reason FM has you delete the oil squirters. The additional oil is not able to be controlled by a compromised oil groove.

Quote:
The belief that every stroker engine uses oil is a myth. There are several factors to consider when building an engine in order to have proper oil control. But it's especially critical with stroker engines where the lower oil ring is in the wristpin hole.

Read more: http://www.mustang50magazine.com/tec...#ixzz1nuqA0HSN
Its well known within the V8 community that compromising that ring groove makes life hard.

And consequently the deletion of the oil squirters increase piston temperature and decrease piston life. The same 2618 alloy at 600*F has just 2030 psi of yield strength. While that same piston at 300*F has 49000 psi of yield strength (a 96% reduction in strength in just 300*F of change). Now considering combustion temperatures can easily exceed 1500F in these high output combos you need every bit of help you can get to maintain the strength of the aluminum in the pistons.
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Old 03-01-2012, 10:55 PM   #54
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So if I recall from back in the day in sport compact car, they did a big shtick on Swain coatings--particularly ceramic piston top coatings.

The intent was to keep heat out of the piston if I recall. I guess both to reduce thermal expansion and help maintain tensile strength. I think they even said they ran slightly tighter clearances too.

I didnt re-read this since I read it originally in print but here's the article:
http://www.modified.com/projectcars/...vii/index.html

edit: I have a minor issue with Swain using a "Jesus Fish" in their magazine ads but there are quite a few other coating companies out there now so it is mostly moot.
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Old 03-02-2012, 01:55 AM   #55
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Originally Posted by TravisR View Post
The only reason I said that I said is because of my experience with 347 V8 Ford strokers. Every kit that intersected the oiling groove burnt oil. Every kit that didn't controlled the oil. This is the actual reason FM has you delete the oil squirters. The additional oil is not able to be controlled by a compromised oil groove.



Its well known within the V8 community that compromising that ring groove makes life hard.

And consequently the deletion of the oil squirters increase piston temperature and decrease piston life. The same 2618 alloy at 600*F has just 2030 psi of yield strength. While that same piston at 300*F has 49000 psi of yield strength (a 96% reduction in strength in just 300*F of change). Now considering combustion temperatures can easily exceed 1500F in these high output combos you need every bit of help you can get to maintain the strength of the aluminum in the pistons.
Not all V8s - the C6 Z06 guys have pin in groove from the factory...

Something else is going on if consumption increases. With a proper support rail for the oil control ring, there's no difference compared to ordinary pistons.

Agreed 100% that deleting the squirters is a horrible idea.

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Originally Posted by y8s View Post
So if I recall from back in the day in sport compact car, they did a big shtick on Swain coatings--particularly ceramic piston top coatings.

The intent was to keep heat out of the piston if I recall. I guess both to reduce thermal expansion and help maintain tensile strength. I think they even said they ran slightly tighter clearances too.

I didnt re-read this since I read it originally in print but here's the article:
http://www.modified.com/projectcars/...vii/index.html

edit: I have a minor issue with Swain using a "Jesus Fish" in their magazine ads but there are quite a few other coating companies out there now so it is mostly moot.
I'm more skeptical of coatings in general than Kojima. Ceramic crowns may reduce piston temp but the heat that doesn't go into the piston is in the chamber on the next intake stroke. Similar "adiabatic" engines always have shitty VE as a result.

That said, I do like dlc coating esp on valve buckets. Nice on wrist pins too, since you can then delete the bushing and save some more rod mass. Spendy, though.
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Old 03-02-2012, 09:52 AM   #56
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edit: I have a minor issue with Swain using a "Jesus Fish" in their magazine ads but there are quite a few other coating companies out there now so it is mostly moot.
You're kidding, right? If that bothers you...
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Old 03-02-2012, 10:32 AM   #57
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edit: I have a minor issue with Swain using a "Jesus Fish" in their magazine ads but there are quite a few other coating companies out there now so it is mostly moot.

I saw that fish on cars for 20 years before I learned what it meant. By that time though, I was already a Satinist.



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Ceramic crowns may reduce piston temp but the heat that doesn't go into the piston is in the chamber on the next intake stroke.
Hmm, so you mean it goes into the valves and the um, valve dome? Wouldn't some of that heat also be pushed out when the valves open?
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Old 03-02-2012, 10:35 AM   #58
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That's why you can't open an oven when you are baking, all the heat is lost and you have to start over again.
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Old 03-02-2012, 10:44 AM   #59
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That's why you can't open an oven when you are baking, all the heat is lost and you have to start over again.


Not sure if you are serious :|
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Old 03-02-2012, 10:46 AM   #60
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im not.
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