Concerns about Supertech pistons
08-17-2009, 03:13 PM
#1
Elite Member
Thread Starter
iTrader: (15)
Join Date: Dec 2007
Location: San Antonio, Texas
Posts: 4,847
Total Cats: 27
Concerns about Supertech pistons
Well, looks like my 'expensive' built motor is coming BACK out of the car 
Long story short, I cracked the #1 piston. No pictures yet as I have not removed the head yet. But it damage was confirmed with a VERY NICE $6000 borescope, by a knowledgeable technician, and seen by me first-hand. Motor still runs, but the piston is a time bomb and has to come out.
The damage is right at the edge of the piston, where the recessed pocket for one of the intake valves intersects the flat portion right at the edge of the piston (at the bore). See the yellow circle area on the image below.
So here is my question/concern. Do I replace this piston (or all of them) with ANOTHER set of Supertechs (maybe even lower compression) or go with Wiseco?
So as some of you probably know the Wiseco is made with 2618 Aluminum, and the Supertech is made with 4032. The advantage of 4032 is it has a lower CTE, about 15% less than the 2618. So, the bore clearance can be a little tighter, and/or there is less chance of overexpansion and seizure/scuffing.
BUT, there is a downside. The 4032 is less ductile, much less. Its elongation is only 4% elongation at break, versus 10% at break for 2618. This is significant, given that I have had a piston failure due to what looks like a fracture, and not due to a melt-through for example, from overheating.
The other differences are that the 2618 has a higher tensile strength and ultimate strength than the 4032 does:
Yield (Mpa) Ultimate (MPa)
2618 372 441
4032 331 359
2618 is 12% stronger in yield, and 22% stronger in ultimate.
I have now seen some anecdotal warnings against Supertech pistons on the interwebz due to problems with cracking. This is consistent with my experience. Though who is to say that the wiseco would not have suffered the same fate under the same conditions? But, being prone to cracking would be consistent with lower ductility. This is the classic tradeoff normally present with metallurgy in general.
Now, my best guess is the crack was due to detonation. I did think I heard some recently when under acceleration, though I got off the throttle when I thought I heard it, and immediately backed the timing down (via the tuning laptop) by 3 degs across the board just to be safe. But, the other pistons, though not also borescoped, were showing no signs of problems, and, all of the plugs, including the plug in this one, did not show the usual signs of heavy detonation, like damaged electrodes. The bore, cylinder head and valves all look OK in the damaged piston cylinder as well.
So... I am hoping this will spur some additional discussion and bring in some experienced voices on the matter. I need to decide very quickly what I am going to do on the pistons as I need to get the motor out of the car, repaired, reinstalled, and tuned, in less than a month. I want to buy the pistons by the end of the week at the latest.
I also want to give you guys a heads-up so you would be informed. I am NOT saying at this point to stay away from Supertechs, rather just sharing what I know so far for further discussion.
By the way, this is supposedly a common area for pistons to fail in. The area over the top compression ring is basically cantilevered and therefore can break off when subjected to extreme pressure, like with detonation. Plus, if you look at the area where it failed, there is not a lot of material in that spot due to the valve pocket, not to mention the stress risers due to all of the intersecting geometry features.
Long story short, I cracked the #1 piston. No pictures yet as I have not removed the head yet. But it damage was confirmed with a VERY NICE $6000 borescope, by a knowledgeable technician, and seen by me first-hand. Motor still runs, but the piston is a time bomb and has to come out.
The damage is right at the edge of the piston, where the recessed pocket for one of the intake valves intersects the flat portion right at the edge of the piston (at the bore). See the yellow circle area on the image below.
So here is my question/concern. Do I replace this piston (or all of them) with ANOTHER set of Supertechs (maybe even lower compression) or go with Wiseco?
So as some of you probably know the Wiseco is made with 2618 Aluminum, and the Supertech is made with 4032. The advantage of 4032 is it has a lower CTE, about 15% less than the 2618. So, the bore clearance can be a little tighter, and/or there is less chance of overexpansion and seizure/scuffing.
BUT, there is a downside. The 4032 is less ductile, much less. Its elongation is only 4% elongation at break, versus 10% at break for 2618. This is significant, given that I have had a piston failure due to what looks like a fracture, and not due to a melt-through for example, from overheating.
The other differences are that the 2618 has a higher tensile strength and ultimate strength than the 4032 does:
Yield (Mpa) Ultimate (MPa)
2618 372 441
4032 331 359
2618 is 12% stronger in yield, and 22% stronger in ultimate.
I have now seen some anecdotal warnings against Supertech pistons on the interwebz due to problems with cracking. This is consistent with my experience. Though who is to say that the wiseco would not have suffered the same fate under the same conditions? But, being prone to cracking would be consistent with lower ductility. This is the classic tradeoff normally present with metallurgy in general.
Now, my best guess is the crack was due to detonation. I did think I heard some recently when under acceleration, though I got off the throttle when I thought I heard it, and immediately backed the timing down (via the tuning laptop) by 3 degs across the board just to be safe. But, the other pistons, though not also borescoped, were showing no signs of problems, and, all of the plugs, including the plug in this one, did not show the usual signs of heavy detonation, like damaged electrodes. The bore, cylinder head and valves all look OK in the damaged piston cylinder as well.
So... I am hoping this will spur some additional discussion and bring in some experienced voices on the matter. I need to decide very quickly what I am going to do on the pistons as I need to get the motor out of the car, repaired, reinstalled, and tuned, in less than a month. I want to buy the pistons by the end of the week at the latest.
I also want to give you guys a heads-up so you would be informed. I am NOT saying at this point to stay away from Supertechs, rather just sharing what I know so far for further discussion.
By the way, this is supposedly a common area for pistons to fail in. The area over the top compression ring is basically cantilevered and therefore can break off when subjected to extreme pressure, like with detonation. Plus, if you look at the area where it failed, there is not a lot of material in that spot due to the valve pocket, not to mention the stress risers due to all of the intersecting geometry features.
Reply
0
0
08-17-2009, 03:20 PM
#2
Elite Member
Join Date: Mar 2008
Location: Enschede, NL
Posts: 2,053
Total Cats: 12
Why did you investigate? What made you think something was wrong? Just curious.
Here in Europe not many have heard of Supertech and it sounds a bit like Wachiwucchi or your average China brand. The Wiseco, J-E, et. al pistons are much more well know.
Here in Europe not many have heard of Supertech and it sounds a bit like Wachiwucchi or your average China brand. The Wiseco, J-E, et. al pistons are much more well know.
Reply
0
0
08-17-2009, 03:30 PM
#3
Elite Member
Thread Starter
iTrader: (15)
Join Date: Dec 2007
Location: San Antonio, Texas
Posts: 4,847
Total Cats: 27
Here is a closer look at #1. No signs of detonation damage I can see, just the dark coloring.
The rest of the plugs all looked like this one
So, wondering WTF, I began some diagnostic work:
Compression test showed #1 at 165 psi. The rest were all at 190-195 psi. Uh oh...
Then I did a leak-down test. #1 was at 10-15%. The rest were all at about 5% or less. ****..
Then I did the borescope check, first with a cheap Chinese one, then the nice one, and that is when I saw, then confirmed the damage. ****!!!
I'll post up more pictures when I get the head off and look at the damage. The camera for the borescope was not available.
Last edited by ZX-Tex; 08-17-2009 at 03:49 PM.
Reply
0
0
08-17-2009, 03:47 PM
#5
Tour de Franzia
iTrader: (6)
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,085
Total Cats: 375
did you use det-cans to rule out detonation? Plug one looks like its blasted by detonation. #1 electrode looks rough, the other looks smooth.
edit: look at the insulator...its covered in metal. Lets see a picture of that piston. I'm sorry to see this misfortune.
If I didn't score the crazy deal I would go with Ross, Wiseco, or JE.
Who tuned this car? Do you have a knock sensor (as if they even work)?
This thread really drives home why I'm tuning on 91-octane then running 93 for headroom, running low compression, and running the large turbine housing.
edit: look at the insulator...its covered in metal. Lets see a picture of that piston. I'm sorry to see this misfortune.
If I didn't score the crazy deal I would go with Ross, Wiseco, or JE.
Who tuned this car? Do you have a knock sensor (as if they even work)?
This thread really drives home why I'm tuning on 91-octane then running 93 for headroom, running low compression, and running the large turbine housing.
Reply
0
0
08-17-2009, 03:55 PM
#7
Elite Member
Thread Starter
iTrader: (15)
Join Date: Dec 2007
Location: San Antonio, Texas
Posts: 4,847
Total Cats: 27
- Though they were rebuilt and tested by Witch Hunter about a year ago, I may pull the injectors and have them tested just to be sure #1 is not running leaner.
- Though this is a guess, is that the WI charge is not getting to the #1 cylinder as well as the rest (not sure about that). Makes me seriously think about going to port WI and adding more water/meth.
- Somehow the reroute is causing #1 to run hotter, not sure how it would though. If anything cooling would be more even.
- The fuel rail is not up to the task (feeds from #4 forward to #1) so maybe I need to go to a return-style system. I know this has been debated at great length.
- I am pushing the margin with the 550cc injectors. They are above 85% at 20 psi, 7500 RPM (14+ ms of duration). Might be time to go bigger.
And, the top reason is...
- Hustler scares me with his awesome manliness, so I had to blow up something on the motor to have an excuse to avoid getting ***-raped by him at the track.
Last edited by ZX-Tex; 08-17-2009 at 04:05 PM.
Reply
0
0
08-17-2009, 05:06 PM
#10
Elite Member
Thread Starter
iTrader: (15)
Join Date: Dec 2007
Location: San Antonio, Texas
Posts: 4,847
Total Cats: 27
Do you mean new, or now? New, yes, see top photo. Now, no idea.
Or, do you mean the cylinder walls in the block? No idea yet either, engine is still in the car.
Or, do you mean the cylinder walls in the block? No idea yet either, engine is still in the car.
Reply
0
0
08-17-2009, 05:09 PM
#12
Elite Member
Thread Starter
iTrader: (15)
Join Date: Dec 2007
Location: San Antonio, Texas
Posts: 4,847
Total Cats: 27
No idea. The wall in #1 looked OK on the borescope, except for some scuffing where the piston damage was. The honing marks are still clearly visible. I am going to have all of that checked when I have the motor fixed by the local badass machine shop.
Reply
0
0
08-17-2009, 05:22 PM
#13
Elite Member
Thread Starter
iTrader: (15)
Join Date: Dec 2007
Location: San Antonio, Texas
Posts: 4,847
Total Cats: 27
Does anyone have some good, close-up shots of a 1.8L 9.0:1 Wiseco piston? I want to make some geometry comparisons. A shot from the side, looking down the wrist pin axis, would be ideal.
Reply
0
0
08-17-2009, 05:36 PM
#16
Elite Member
Thread Starter
iTrader: (15)
Join Date: Dec 2007
Location: San Antonio, Texas
Posts: 4,847
Total Cats: 27
I have been guilty of subjective reasoning before, but I am thinking the same thing about the water. Inertia would tend to carry it past the #1 cylinder since it has to turn pretty sharply once it enters the plenum to get to the #1 cylinder, especially with all of the VICS related geometry in the way. After all, it was designed as a dry-flow manifold.
In fact, I think I am going to go with port WI, and might even gut the upper intake (get rid of VICS). No matter how you slice it, I am pushing the motor pretty hard at 300+ rwhp (guesstimate), and the WI system needs to work well in order to restore some knock margin.
In fact, I think I am going to go with port WI, and might even gut the upper intake (get rid of VICS). No matter how you slice it, I am pushing the motor pretty hard at 300+ rwhp (guesstimate), and the WI system needs to work well in order to restore some knock margin.
Reply
0
0
08-17-2009, 05:38 PM
#17
Elite Member
Thread Starter
iTrader: (15)
Join Date: Dec 2007
Location: San Antonio, Texas
Posts: 4,847
Total Cats: 27
But on that note, Supertech goes no lower than 8.6:1. Wiseco goes no lower than 9.0:1. Plus, if compression ratio was the cause, why didn't the other three cylinders get ***-raped as well? Current pistons are 9.0:1. Compression test shows about 190-195 psi.
Last edited by ZX-Tex; 08-17-2009 at 06:05 PM.
Reply
0
0
