The #8, and why it failed. An inside look.
4/19/14, 06:21 AM
#21
Bullitt Member
This one I don't see being a big deal:
1. Knock Sensor Retard Rate - This is how fast the Knock Sensor function can pull out timing when a event is triggered. In the SCT base file, this value was increased from .5 to 1 for 4k and up. What that means is that it now takes 1 crank cycle to remove timing, compared to the half crank cycle as before.
One crank cycle = 4 cylinders firing vice only 2. Why would this be so critical?
1. Knock Sensor Retard Rate - This is how fast the Knock Sensor function can pull out timing when a event is triggered. In the SCT base file, this value was increased from .5 to 1 for 4k and up. What that means is that it now takes 1 crank cycle to remove timing, compared to the half crank cycle as before.
One crank cycle = 4 cylinders firing vice only 2. Why would this be so critical?
Bingo
More advance equals more power but it can be a double edged sword.
In the Old days we advanced the timing as much as possible until we heard spark knock (pre ignition or detonation) then we would back off the distributor 2-4* and set it.
The PCM does the same thing but many times a second and for each individual cylinder. As RPM increases more timing is added. BITD it was called centrifugal advance and we controlled this with weights and springs in the distributor. PCM's add timing per cylinder based on several variables Speed, RPM, Load, Octane, Temp etc...
The idea is complete combustion all the time.
By slowing the retard rate they leave the engine open to detonation for a longer period. Half cycle vs full cycle may seem small but think of the effects over time. I would rather error on the side of safety then be tuned to the ragged edge for maybe an additional 5 HP
Sorry for the history lesson.
As far as the `15 5.0 it was my understanding from the articles I've read it is a hybrid of Boss forged rotating assembly with better flowing (not Boss) heads Cobrajet cams and a revised intake but no DI.
4/20/14, 01:59 AM
#22
Bingo
More advance equals more power but it can be a double edged sword.
In the Old days we advanced the timing as much as possible until we heard spark knock (pre ignition or detonation) then we would back off the distributor 2-4* and set it.
The PCM does the same thing but many times a second and for each individual cylinder. As RPM increases more timing is added. BITD it was called centrifugal advance and we controlled this with weights and springs in the distributor. PCM's add timing per cylinder based on several variables Speed, RPM, Load, Octane, Temp etc...
The idea is complete combustion all the time.
By slowing the retard rate they leave the engine open to detonation for a longer period. Half cycle vs full cycle may seem small but think of the effects over time. I would rather error on the side of safety then be tuned to the ragged edge for maybe an additional 5 HP
Sorry for the history lesson.
As far as the `15 5.0 it was my understanding from the articles I've read it is a hybrid of Boss forged rotating assembly with better flowing (not Boss) heads Cobrajet cams and a revised intake but no DI.
More advance equals more power but it can be a double edged sword.
In the Old days we advanced the timing as much as possible until we heard spark knock (pre ignition or detonation) then we would back off the distributor 2-4* and set it.
The PCM does the same thing but many times a second and for each individual cylinder. As RPM increases more timing is added. BITD it was called centrifugal advance and we controlled this with weights and springs in the distributor. PCM's add timing per cylinder based on several variables Speed, RPM, Load, Octane, Temp etc...
The idea is complete combustion all the time.
By slowing the retard rate they leave the engine open to detonation for a longer period. Half cycle vs full cycle may seem small but think of the effects over time. I would rather error on the side of safety then be tuned to the ragged edge for maybe an additional 5 HP
Sorry for the history lesson.
As far as the `15 5.0 it was my understanding from the articles I've read it is a hybrid of Boss forged rotating assembly with better flowing (not Boss) heads Cobrajet cams and a revised intake but no DI.
Tuning is a completely and totally different world than just providing and fabricating parts. I'm sure Matt, who has tuning experience, knows what I'm talking about.
Just a few tidbits of information I think everyone should know about.
4/21/14, 03:51 AM
#24
Mach 1 Member
No. Most production engines from the carburetor era used a standard cast aluminum piston and those are less fragile than hypereutectic We'll pound for pound anyway.
Today's modern engine uses pistons with thinner ring landings, shorter piston skirts, just generally less material than the slugs that were used in engines of the carburetor era. It all means less weight and less rotating mass. Meaning the engines of today are less forgiving.
Also keep in mind that today's engines are making way more power than the engines you speak of. They are already very close to the ragged edge. Today's cylinder heads are also made of aluminum which is also not as forgiving as those old cast iron heads back in the carburetor era.
Hypereutectic actually sit in between a standard cast piston and a forged piston from a durability standpoint. They are similar to a cast piston but have a higher silicone content.
Cast and hypereutectic do have some nice qualities that forged does not have. For example you can get the manufacturing tolerances much tighter with a cast/hypereutectic piston than you can with a forged piston. Forged pistons fit much more loosely when cold and need to heat up and expand for proper fitment. This means they are noisier when cold. Forged are much more durable than the others.
When building an NA engine there really is no benefit to using a forged piston. Hypereutectic will work just fine. IMO
The PCM in today's high tech engine keeps the parts rattling to a minimum. engineers just assume that no rattling takes place. The tunes as Matt described with the safety protocols either removed or diminished were not reacting quickly enough thus allowing the pistons to rattle like crazy within the cylinder walls on the way down during the power stroke. Today's modern lighter piston just isn't designed with that in mind as the rattling isn't supposed to take place.
Today's modern engine uses pistons with thinner ring landings, shorter piston skirts, just generally less material than the slugs that were used in engines of the carburetor era. It all means less weight and less rotating mass. Meaning the engines of today are less forgiving.
Also keep in mind that today's engines are making way more power than the engines you speak of. They are already very close to the ragged edge. Today's cylinder heads are also made of aluminum which is also not as forgiving as those old cast iron heads back in the carburetor era.
Hypereutectic actually sit in between a standard cast piston and a forged piston from a durability standpoint. They are similar to a cast piston but have a higher silicone content.
Cast and hypereutectic do have some nice qualities that forged does not have. For example you can get the manufacturing tolerances much tighter with a cast/hypereutectic piston than you can with a forged piston. Forged pistons fit much more loosely when cold and need to heat up and expand for proper fitment. This means they are noisier when cold. Forged are much more durable than the others.
When building an NA engine there really is no benefit to using a forged piston. Hypereutectic will work just fine. IMO
The PCM in today's high tech engine keeps the parts rattling to a minimum. engineers just assume that no rattling takes place. The tunes as Matt described with the safety protocols either removed or diminished were not reacting quickly enough thus allowing the pistons to rattle like crazy within the cylinder walls on the way down during the power stroke. Today's modern lighter piston just isn't designed with that in mind as the rattling isn't supposed to take place.
Last edited by 2014GHIGGT; 4/21/14 at 03:56 AM.
4/21/14, 09:10 AM
#25
Now, have these been resolved? Yes, most all major tuners (Steeda, etc) have adjusted the proper values. I have even caught wind of SCT revising their base value files this year
Best Regards,
TJ
4/21/14, 01:42 PM
#26
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I miss the days of TMS having more technical/mechanical informative threads.Your comments are like what Doug posted early on 7.20.12:
https://themustangsource.com/f800/my...1/#post6401142
However, the questions that remain unanswered - when the fault is stated to only be with the learning curve of the tune - is why did Ford redesign 5.0 pistons for 2013 forward? They not only switched to a coated piston, but also redesigned the oil control ring and eliminated the oil squirters. Why would Ford make these changes if the tune issue was resolved and allegedly the only cause for #8 failures in the 11/12 5.0?
It makes me think the coating (phosphate?) was to harden the pistons or to prevent carbon buildup but I have not read the reasons.
As for the change of the oil control ring with more drain holes in the lands, that makes me think that the oil squirter solution was not providing enough upper cylinder oiling during high load. Or perhaps even an oil starvation issue with the squirters at high rpm/during windage even with the tray. Leading to a momentary overheating issue of the piston crown.
Although some pics show the failure was not so much at the crown as it was at the lands:
<QUOTE=fdjizm>
https://themustangsource.com/f800/tu...4/#post6067451
It was also mentioned that the hood vents were added to the 13 forward at the same time:
<Overboost: Something else interesting, the 2013 GT and Boss have vents on their hood...coincidental? I think not. >
Both of which lead me to believe there were more issues than just the tune. Any info on the reasons for the piston re-design?
Thanx!
<Pics posted by MARZ>
https://themustangsource.com/f800/co...4/#post6280407
4/21/14, 06:03 PM
#27
Mach 1 Member
A coating is not going to stop a piston from rattling under mis-detonation. No coating in the world will prevent that from happening. It's the rattling of the piston on the way down during the power stroke that causes breakage like this. As i stated above Hypereutectic pistons are more durable. Hypereutectic does come at a cost of being more brittle.
Old engines in the past that had a standard cast piston that had more meat to it that would actually fair a bit better under mis-detonation than the modern Hyereutectic however the cylinders would wear prematurely. Meaning due to the rattling on the way down of the power stroke the cylinders would wear much more at the bottom of the bore they they would near the top. so the cylinders would be tapered from top to bottom.
Same issue just a different result. As you can see the piston landing broke not the head of the piston. The Hypereutectic held up to the heat from the mis-detonation. It just didn't hold up to the rattling (which is the pinging you hear). Look at those coated piston skirts. They are scraped up badly. Again this is caused from the rattling from side to side on the travel down.
Pistons over the years have become lighter, thinner, thinner ring grooves, thinner ring landings, thinner rings, etc. This is all done to improve economy with less rotating mass and less frictional loss. The trade off is a piston with less material that does't like to handle the abuse of mis-detonation.
Forged pistons as i stated above have their own set of problems. Have you ever had a forged piston failure because it was over hardened and was too brittle? I have seen it. For no reason a big hunk of piston will break away. No mis-detonation, no block machining issues, just an over hardened piston coming off the production line.
Any way you slice it. Pinging is bad and thinner lighter pistons don't like it.
Unless I have the pictures mixed up. The piston landing on the later 13/14 pistons appear to have less material (if it is the picture on the right). That said I would assume that they would be more prone to breaking under mis-detonation.
This stuff is so interesting. I love discussions like this one.
Old engines in the past that had a standard cast piston that had more meat to it that would actually fair a bit better under mis-detonation than the modern Hyereutectic however the cylinders would wear prematurely. Meaning due to the rattling on the way down of the power stroke the cylinders would wear much more at the bottom of the bore they they would near the top. so the cylinders would be tapered from top to bottom.
Same issue just a different result. As you can see the piston landing broke not the head of the piston. The Hypereutectic held up to the heat from the mis-detonation. It just didn't hold up to the rattling (which is the pinging you hear). Look at those coated piston skirts. They are scraped up badly. Again this is caused from the rattling from side to side on the travel down.
Pistons over the years have become lighter, thinner, thinner ring grooves, thinner ring landings, thinner rings, etc. This is all done to improve economy with less rotating mass and less frictional loss. The trade off is a piston with less material that does't like to handle the abuse of mis-detonation.
Forged pistons as i stated above have their own set of problems. Have you ever had a forged piston failure because it was over hardened and was too brittle? I have seen it. For no reason a big hunk of piston will break away. No mis-detonation, no block machining issues, just an over hardened piston coming off the production line.
Any way you slice it. Pinging is bad and thinner lighter pistons don't like it.
Unless I have the pictures mixed up. The piston landing on the later 13/14 pistons appear to have less material (if it is the picture on the right). That said I would assume that they would be more prone to breaking under mis-detonation.
This stuff is so interesting. I love discussions like this one.
Last edited by 2014GHIGGT; 4/21/14 at 06:06 PM.
4/23/14, 12:56 PM
#29
Mach 1 Member
Thread Starter
I dont think that any tuner knows how timing is calculated. (The actually flow of functions). So they rely on what SCT tells them, and removing the safety limits (what the limit is at the end of calculation) is a no no.
Similar to putting your water heater on highest setting, and removing the pressure relief valve... The wait begins
No, but you are about 3 strategies behind. ZFK3 is the latest calibration.
-Matt
4/23/14, 02:06 PM
#32
Mach 1 Member
Thread Starter
I dont think it was ever thought that tuners would ultimately disable this protection.
So are the 13/14 pistons less susceptible to knock/detonation? Yes. Are they tuner proof? No.
-Matt
4/23/14, 03:02 PM
#35
Cobra R Member
I'm curious, does anyone have any data for how many tuned engines failed due to poor (or too aggressive) tuning? Even better if the tuning company was known for each case...
Basically, is this a significant issue, or is it just something that happens to folks who try and take the tune too far?
Basically, is this a significant issue, or is it just something that happens to folks who try and take the tune too far?
4/23/14, 03:21 PM
#36
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In the beginning it was thought that money could be saved with a conservative piston design. Of course when you make a weaker piston more protection logic would need to be implemented in the Engine management routines.
I dont think it was ever thought that tuners would ultimately disable this protection.
So are the 13/14 pistons less susceptible to knock/detonation? Yes. Are they tuner proof? No.
-Matt
I dont think it was ever thought that tuners would ultimately disable this protection.
So are the 13/14 pistons less susceptible to knock/detonation? Yes. Are they tuner proof? No.
-Matt
>>If the tune was corrected back to where it would detect and adjust for knock/detonation as designed, would you still have faith that the 11/12 #8 piston (and the rest) would have normal longevity?
The piston coatings, redesigned oil rings, hood vents (esp considering #8 was the typical failure and is a back [hotter] cylinder), for 13 forward; leads me to believe there was also an upper cylinder lubrication problem, possibly leading to piston overheating (considering the compression ratio), potentially contributing to knock/detonation; that added to the problem of the 11/12 piston's failure to withstand a degree of knock/detonation.
Perhaps squirting oil under the piston just isn't as effective as the more direct oiling of the cylinder wall through redesigned oil ring/lands/drain holes. Esp at high rpm's where there could be a potential oil starvation issue with squirters...
I understand what you have pointed out that if the tunes had kept the safety features intact, the ECU would have adjusted to avoid knock after detection. But that doesn't give me faith that there weren't other contributions to the #8 failures such as I am asking.
Thanx!
Last edited by cdynaco; 4/23/14 at 03:23 PM.
4/23/14, 06:59 PM
#37
Mach 1 Member
OK - let me try this another way... because I'm still wondering if there was an upper cylinder oiling issue (11/12 squirters vs 13+ squirter delete + redesigned oil rings) that contributed to the failure - or if the #8 failures were strictly the tune errors you (and Doug) have described...
>>If the tune was corrected back to where it would detect and adjust for knock/detonation as designed, would you still have faith that the 11/12 #8 piston (and the rest) would have normal longevity?
The piston coatings, redesigned oil rings, hood vents (esp considering #8 was the typical failure and is a back [hotter] cylinder), for 13 forward; leads me to believe there was also an upper cylinder lubrication problem, possibly leading to piston overheating (considering the compression ratio), potentially contributing to knock/detonation; that added to the problem of the 11/12 piston's failure to withstand a degree of knock/detonation.
Perhaps squirting oil under the piston just isn't as effective as the more direct oiling of the cylinder wall through redesigned oil ring/lands/drain holes. Esp at high rpm's where there could be a potential oil starvation issue with squirters...
I understand what you have pointed out that if the tunes had kept the safety features intact, the ECU would have adjusted to avoid knock after detection. But that doesn't give me faith that there weren't other contributions to the #8 failures such as I am asking.
Thanx!
Just google "Piston heat damage" and look at the pictures. You'll see the difference between a piston that melted due to excessive heat and one that broke up like the one pictured above. This issue with our factory pistons is that they are lightweight and brittle. They do not like the pinging or rattling caused by mis-detonation.
4/23/14, 07:32 PM
#38
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The broken piston pictured above did not break up due to heat. It was caused by mis-detonation. The heat could have been a contributing factor to the mis-detonation. but that piston was rattling inside that cylinder. It did not melt or burn away.
Just google "Piston heat damage" and look at the pictures. You'll see the difference between a piston that melted due to excessive heat and one that broke up like the one pictured above. This issue with our factory pistons is that they are lightweight and brittle. They do not like the pinging or rattling caused by mis-detonation.
Just google "Piston heat damage" and look at the pictures. You'll see the difference between a piston that melted due to excessive heat and one that broke up like the one pictured above. This issue with our factory pistons is that they are lightweight and brittle. They do not like the pinging or rattling caused by mis-detonation.
And I understand that restoring the knock sensors and other safety measures would/should prevent knock/detonation/rattle.
However, no one is offering a direct answer to my questions as to why Ford invested in a re-design for 13 forward...
4/23/14, 10:08 PM
#39
Mach 1 Member
Yes - I'm following your previous posts. Great info and makes sense. Thanx! Although the pic of that piston may or may not be typical of the majority of the #8 failures. Haven't seen that many.
And I understand that restoring the knock sensors and other safety measures would/should prevent knock/detonation/rattle.
However, no one is offering a direct answer to my questions as to why Ford invested in a re-design for 13 forward...
And I understand that restoring the knock sensors and other safety measures would/should prevent knock/detonation/rattle.
However, no one is offering a direct answer to my questions as to why Ford invested in a re-design for 13 forward...