Lost piston #7 AGAIN
Thread Starter
Drifting
Joined: Aug 2007
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From: Homer Glen IL
Tech Contributor
Joined: Jan 2007
Posts: 19,293
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From: Dyer, IN
They would have to be maxed out (which your tuner would know from the duty cycle). At the horsepower level you are at, I'd be surprised if the injectors were your issue.....at least from a 26 v/s 28 lbs perspective.
Le Mans Master
Joined: Oct 2001
Posts: 5,145
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From: The Motor City
Depends on how big the cam is. My '70 with a TR224/224, stock (unported) LS1 heads and exhaust manifolds I was hitting 80-90%+ duty cycle on 26# injectors. For safety's sake, I replaced them with SVO30s.
Team Owner
Joined: Sep 2003
Posts: 43,084
Likes: 33
From: Raleigh / Rolesville NC
or the 2 plus G Braking that keeps the oil in the heads, again starves the oil pick up ( huge problem in the LS3 and LS3 / L92 heads)
only takes a second or so without oil on that bearing
Other issue with #7 is the coolant galleys are so thin around the cylinder that part of the block OVER heats soo quickly. This was fixed in the LS2 blocks.
ie weakest part of the LS6 block is around #7
LS1 blocks were very poor here. LS6s are better, LS2 blocks better still.
SO it not just the oil flowing but oil volume to prevent problems. an Accu-sump is good or dry sump better.
and 40 psi is NOT enough. Need 10 psi / 1000 rpms. if your running a 6500 red line you need 65+ PSI at red line for race engines.
Last edited by AU N EGL; Jun 13, 2011 at 04:47 PM.
Le Mans Master
Joined: Jul 2005
Posts: 7,121
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From: Shreveport/Bossier Louisiana
St. Jude Donor '08
I'm guessing he meant 40psi at idle.
I will agree with some of the previous statements, this isn't an oiling issue. Oiling issues usually spin bearings. Fueling issues usually cause detonation that results in missing chunks out of pistons.
I will agree with some of the previous statements, this isn't an oiling issue. Oiling issues usually spin bearings. Fueling issues usually cause detonation that results in missing chunks out of pistons.
Burning Brakes
Joined: Jul 2009
Posts: 976
Likes: 53
From: smyrna de
i have always had the assumption the the number 7 cyl got the most air volume, thus made the most power creating a lean condition. the piston failures ive seen from the number 7 cyl indicates high amounts of heat/detonation.. the stock ecu in our cars does not allow individual cyl injector control like other brands do.. i DO know that high horsepower hondas run the middle two injectors about 5% higher duty cycle, cause research has shown the middle two run leaner and hotter.. (i know the CF hates hondas, but lets face it, there leading the way on tuning and innovation). i dont know if any one has done any testing with egt/wideband to determine if the #7 cyl does infact run leaner, which is resulting in the piston failures .. i run my wideband on the drivers side header, hopefully to monitor the lean side..
Pro
Joined: Aug 2010
Posts: 545
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From: Calgary Alberta
I like EGT's, use them on my snowmobile for tuning, but I think wide band O2 sensors are a better bet with computer controled engines. That said I'm all for more information.
Burning Brakes
Joined: Jun 2010
Posts: 812
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From: Metairie Louisiana
If the duty cycle for your injectors are maxed or always close to it you could have a bit more of a safety margin with higher delivery injectors. Since the problem shows up in the #7 cyl it's injector could be failing or the harness's #7 pigtail or connector. Assuming there are no cylinder bore anomlies, when you go back up, check compression values for mechanical top end issues and do a plug check. If the #7 plug wasn't damaged and the piston failure didn't throw oil on it, have a look at it to see if there could be signs of lean induced detonation. Wasn't aware of oilling system issues that contribute to #7 cyl problems
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Safety Car
Joined: May 2008
Posts: 4,237
Likes: 11
From: Lacombe Louisiana
Bill for use road races, it is the high G Left hand corners that pulls the oil away from the Oil pick up in the pan. and guess what that oil pick up is near the #7 and #8 bearings.
or the 2 plus G Braking that keeps the oil in the heads, again starves the oil pick up ( huge problem in the LS3 and LS3 / L92 heads)
only takes a second or so without oil on that bearing
Other issue with #7 is the coolant galleys are so thin around the cylinder that part of the block OVER heats soo quickly. This was fixed in the LS2 blocks.
ie weakest part of the LS6 block is around #7
LS1 blocks were very poor here. LS6s are better, LS2 blocks better still.
SO it not just the oil flowing but oil volume to prevent problems. an Accu-sump is good or dry sump better.
and 40 psi is NOT enough. Need 10 psi / 1000 rpms. if your running a 6500 red line you need 65+ PSI at red line for race engines.
or the 2 plus G Braking that keeps the oil in the heads, again starves the oil pick up ( huge problem in the LS3 and LS3 / L92 heads)
only takes a second or so without oil on that bearing
Other issue with #7 is the coolant galleys are so thin around the cylinder that part of the block OVER heats soo quickly. This was fixed in the LS2 blocks.
ie weakest part of the LS6 block is around #7
LS1 blocks were very poor here. LS6s are better, LS2 blocks better still.
SO it not just the oil flowing but oil volume to prevent problems. an Accu-sump is good or dry sump better.
and 40 psi is NOT enough. Need 10 psi / 1000 rpms. if your running a 6500 red line you need 65+ PSI at red line for race engines.
Thread Starter
Drifting
Joined: Aug 2007
Posts: 1,495
Likes: 0
From: Homer Glen IL
If the duty cycle for your injectors are maxed or always close to it you could have a bit more of a safety margin with higher delivery injectors. Since the problem shows up in the #7 cyl it's injector could be failing or the harness's #7 pigtail or connector. Assuming there are no cylinder bore anomlies, when you go back up, check compression values for mechanical top end issues and do a plug check. If the #7 plug wasn't damaged and the piston failure didn't throw oil on it, have a look at it to see if there could be signs of lean induced detonation. Wasn't aware of oilling system issues that contribute to #7 cyl problems
Le Mans Master
Joined: Jun 2006
Posts: 6,979
Likes: 31
From: Wichita KS
1) As stated have your injectors checked then have them ALL flow matched, when you get the chart back put the one that flows the most on #7 and the other most flowing one on #8 to help those 2 rear cyl's out, they wont flow a lot more than the others once flow matched but will be within 3%.
2) If your tuner is tuning with a wideband in the rear of the tail pipe like some low end shops do then I can almost put money on it that your tune was way too lean, ESPECIALLY if your running cats. Always make sure your tuner uses a bung in FRONT of the cat when tuning, if he cant weld a bung in take it to a exhaust shop and pay the $20 to have it done, if it was not a reputable tuner then most likely he tuned it with the wideband in the back of the pipe. This is a huge NO NO and is no where near as accurate as having it 12-15" behind the headers/manifolds.
2) If your tuner is tuning with a wideband in the rear of the tail pipe like some low end shops do then I can almost put money on it that your tune was way too lean, ESPECIALLY if your running cats. Always make sure your tuner uses a bung in FRONT of the cat when tuning, if he cant weld a bung in take it to a exhaust shop and pay the $20 to have it done, if it was not a reputable tuner then most likely he tuned it with the wideband in the back of the pipe. This is a huge NO NO and is no where near as accurate as having it 12-15" behind the headers/manifolds.
Last edited by Corvette Don; Jun 14, 2011 at 06:48 PM.
Thread Starter
Drifting
Joined: Aug 2007
Posts: 1,495
Likes: 0
From: Homer Glen IL
1) As stated have your injectors checked then have them ALL flow matched, when you get the chart back put the one that flows the most on #7 and the other most flowing one on #8 to help those 2 rear cyl's out, they wont flow a lot more than the others once flow matched but will be within 3%.
2) If your tuner is tuning with a wideband in the rear of the tail pipe like some low end shops do then I can almost put money on it that your tune was way too lean, ESPECIALLY if your running cats. Always make sure your tuner uses a bung in FRONT of the cat when tuning, if he cant weld a bung in take it to a exhaust shop and pay the $20 to have it done, if it was not a reputable tuner then most likely he tuned it with the wideband in the back of the pipe. This is a huge NO NO and is no where near as accurate as having it 12-15" behind the headers/manifolds.
2) If your tuner is tuning with a wideband in the rear of the tail pipe like some low end shops do then I can almost put money on it that your tune was way too lean, ESPECIALLY if your running cats. Always make sure your tuner uses a bung in FRONT of the cat when tuning, if he cant weld a bung in take it to a exhaust shop and pay the $20 to have it done, if it was not a reputable tuner then most likely he tuned it with the wideband in the back of the pipe. This is a huge NO NO and is no where near as accurate as having it 12-15" behind the headers/manifolds.
Former Vendor
Joined: Apr 2006
Posts: 2,470
Likes: 2
From: Portland OR
St. Jude Donor '10-'11-'12
No forged components will not prevent that from happening again. It might take longer but it will happen again if you don't correct the issue. detonation takes chunks out of pistons ... fix the tune... if its not getting enough fuel it should have been known in the tuning session...
Thread Starter
Drifting
Joined: Aug 2007
Posts: 1,495
Likes: 0
From: Homer Glen IL
No forged components will not prevent that from happening again. It might take longer but it will happen again if you don't correct the issue. detonation takes chunks out of pistons ... fix the tune... if its not getting enough fuel it should have been known in the tuning session...
Last edited by futuretech; Jun 16, 2011 at 03:44 PM.
Tech Contributor
Joined: Jan 2007
Posts: 19,293
Likes: 1,109
From: Dyer, IN
Are we talking using the tune to make it a richer mixture or larger injectors? Does a richer mixture reduce power (not that I care)? Are there any disadvantages to a richer mixture? I have the HP tuner software and logger. Can I see the mixture that is currently being used?
Thread Starter
Drifting
Joined: Aug 2007
Posts: 1,495
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From: Homer Glen IL
Tech Contributor
Joined: Jan 2007
Posts: 19,293
Likes: 1,109
From: Dyer, IN
Le Mans Master
Joined: Jun 2006
Posts: 6,979
Likes: 31
From: Wichita KS
I know some of you guys know this but some dont, even if he posts his AFR its not going to be 100% correct cause 1) he has cats and 2) the wideband O2 was put in the REAR tailpipe. It could be off by a LOT.
To the OP, if you have HP Tuners, take some time and read up on some basic tuning skills over on HPTuners.com, buy a wideband, install a bung in from of the cats and do the tuning yourself, since you had it tuned already you could just tweak it a tad to get you where you need to be on the safe side. I learned a lot reading different posts over on that forum but I have about 10 hours of FINE adjustments in my tune to get it to where I wanted along with countless hours of reading and asking questions over on those forums.
To the OP, if you have HP Tuners, take some time and read up on some basic tuning skills over on HPTuners.com, buy a wideband, install a bung in from of the cats and do the tuning yourself, since you had it tuned already you could just tweak it a tad to get you where you need to be on the safe side. I learned a lot reading different posts over on that forum but I have about 10 hours of FINE adjustments in my tune to get it to where I wanted along with countless hours of reading and asking questions over on those forums.
Last edited by Corvette Don; Jun 17, 2011 at 12:24 PM.