Corvette + Track = Grenade?
11-29-2011, 10:52 PM
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Gary
11-30-2011, 12:44 AM
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mostly good info, here's some more detail.
cliff notes:
no car is perfect this side of $200k price range. Some people who go very fast in the corners have exceeded oiling capacity on the upper range C6 Corvettes, GM put in a "fix" in 09 that seems to have helped.
C5:
all C5 corvettes lack oil cooler. how would you like 300+ degree oil temps on a regular basis? Aftermarket coolers usually solve that, but I imagine that owners who ignore that eventually pay the price. The bottom line is that someone at GM decided to cut $100 off the manufacturing price. Thanks.
C5 engines come in 2 flavors - LS1 and LS6. Both have adequate oiling for track work, sans driver errors. LS6 is (or, until most recent shortages, has been) used extensively in SCCA T1 racecars and is known as one of the most reliable "off the shelf" race engines out there. Cheap too.
C6:
C6 motors come in many flavors. LS2, LS3, LS7 and LS9. Stock oiling systems in LS2, LS3, and pre- 2009 LS7s have been argued to be inadequate for cars developed to maintain 1.2+ sustained left-hander Gs. This usually just means R-comp tires and harness/seats, since stock "restraint" system is anything but. Well, and some skill, obviously. Those are the ones in "advanced" groups flying by most other cars out there, in case you wondered
There is likely some truth to the underlying engineering issue being in play.
pre-2009 LS7 motors seem to be affected the most (there is another issue specific to an "unfortunate" batch of LS7 engines produced in 06/early 07 but that's something completely different).
There have been recent reports of oiling failures in LS3s (non-Z06, non-ZR1 6.2L) in actual race cars as well, but we are talking about exponentially harder use there. Likely similar issue.
Multiple "fixes" are out there (even though the root cause is not universally understood/acknowleged), the simplest one being equivalent to GM's change in 2009 MY for the oil tank with ZR1 units fitted to all dry sump motors, increasing capacity. That applies to all dry sump system corvettes since 2009 (Z06, ZR1 and Grand Sport)
This is likely a band-aid from engineering perspective, but it seems to work for most. I imagine if you find a sweeper long enough to maintian 1.2+ Gs in a left hand turn for a long enough time, you would encounter the same issue, even in 09+ car. Other upgrade options include oil pan inserts, oil pans, oil pumps, secondary systems etc etc etc. There are enough scare stories out there to drive the market for years, I am sure. Think IMS failure
By the way, GM has been known to quietly replace Z06 motors lost due to oil starvation since people started tracking C6 Z06 cars, although owners with heavily modified card had trouble w this (duh). It is unknown if oil tank capacity increase in 09 was intended to address this, or is simply a cost cutting measure to avoid sourcing 2 differently sized oil tanks - since ZR1 needed a bigger one. Knowing GM, it is probably a half assed compromise in both directions. I am sorry - efficiency measure.
If I were to buy C6 Z06, something I seriously considered after selling my C5Z (which has never had oiling issues in 6 years of heavy track use with proper cooling upgrades), I'd probably invest in some upgrades for the oiling system before anything else - at least a bigger tank for pre -09 one, possibly better pan and pump.
I decided to not bother with buying a car that needs fixing before heavy track use, and since I am too poor to afford a really fast Porsche, I got an ACR. Would I have gone with Corvette if oiling issue was not a factor? Probably not, still a bunch of little annoyances to fix - which I have had enough of in my years of owning C5.
cliff notes:
no car is perfect this side of $200k price range. Some people who go very fast in the corners have exceeded oiling capacity on the upper range C6 Corvettes, GM put in a "fix" in 09 that seems to have helped.
C5:
all C5 corvettes lack oil cooler. how would you like 300+ degree oil temps on a regular basis? Aftermarket coolers usually solve that, but I imagine that owners who ignore that eventually pay the price. The bottom line is that someone at GM decided to cut $100 off the manufacturing price. Thanks.
C5 engines come in 2 flavors - LS1 and LS6. Both have adequate oiling for track work, sans driver errors. LS6 is (or, until most recent shortages, has been) used extensively in SCCA T1 racecars and is known as one of the most reliable "off the shelf" race engines out there. Cheap too.
C6:
C6 motors come in many flavors. LS2, LS3, LS7 and LS9. Stock oiling systems in LS2, LS3, and pre- 2009 LS7s have been argued to be inadequate for cars developed to maintain 1.2+ sustained left-hander Gs. This usually just means R-comp tires and harness/seats, since stock "restraint" system is anything but. Well, and some skill, obviously. Those are the ones in "advanced" groups flying by most other cars out there, in case you wondered
There is likely some truth to the underlying engineering issue being in play.
pre-2009 LS7 motors seem to be affected the most (there is another issue specific to an "unfortunate" batch of LS7 engines produced in 06/early 07 but that's something completely different).
There have been recent reports of oiling failures in LS3s (non-Z06, non-ZR1 6.2L) in actual race cars as well, but we are talking about exponentially harder use there. Likely similar issue.
Multiple "fixes" are out there (even though the root cause is not universally understood/acknowleged), the simplest one being equivalent to GM's change in 2009 MY for the oil tank with ZR1 units fitted to all dry sump motors, increasing capacity. That applies to all dry sump system corvettes since 2009 (Z06, ZR1 and Grand Sport)
This is likely a band-aid from engineering perspective, but it seems to work for most. I imagine if you find a sweeper long enough to maintian 1.2+ Gs in a left hand turn for a long enough time, you would encounter the same issue, even in 09+ car. Other upgrade options include oil pan inserts, oil pans, oil pumps, secondary systems etc etc etc. There are enough scare stories out there to drive the market for years, I am sure. Think IMS failure
By the way, GM has been known to quietly replace Z06 motors lost due to oil starvation since people started tracking C6 Z06 cars, although owners with heavily modified card had trouble w this (duh). It is unknown if oil tank capacity increase in 09 was intended to address this, or is simply a cost cutting measure to avoid sourcing 2 differently sized oil tanks - since ZR1 needed a bigger one. Knowing GM, it is probably a half assed compromise in both directions. I am sorry - efficiency measure.
If I were to buy C6 Z06, something I seriously considered after selling my C5Z (which has never had oiling issues in 6 years of heavy track use with proper cooling upgrades), I'd probably invest in some upgrades for the oiling system before anything else - at least a bigger tank for pre -09 one, possibly better pan and pump.
I decided to not bother with buying a car that needs fixing before heavy track use, and since I am too poor to afford a really fast Porsche, I got an ACR. Would I have gone with Corvette if oiling issue was not a factor? Probably not, still a bunch of little annoyances to fix - which I have had enough of in my years of owning C5.
11-30-2011, 02:22 PM
#37
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Mods?
11-30-2011, 03:47 PM
#39
Full cage, seats, Hoosiers, no mods to engine
High Gs with hohos and no accusump will sometimes blow those suckers up.... hence why I run the tried and true boat anchor iron block instead
video was pretty cool too...
11-30-2011, 04:12 PM
#40
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….in 2009 MY for the oil tank with ZR1 units fitted to all dry sump motors, increasing capacity. That applies to all dry sump system corvettes since 2009 (Z06, ZR1 and Grand Sport)… I imagine if you find a sweeper long enough to maintian 1.2+ Gs in a left hand turn for a long enough time, you would encounter the same issue, even in 09+ car. …..
11-30-2011, 06:52 PM
#41
Three Wheelin'
There are many different ways to design a dry sump. 1, 2...up to something like 6 scavenge points, baffling, sump design, capacity, etc. With increased capacity in the later cars there is more time that could be spent at max lat before draining the tank (assuming no feed from the scavenge side). Another possibility is the number and location of scavenge pickups. The C6Z's have two I think. The C6Rs have 5 I believe. More complexity, but more consistency in pulling oil out of the sump.
The C5Z and C6Z are suffering from different issues though. Its not a common cause. From what I've heard is that there are solutions in the aftermarket for each that will make them nearly bulletproof, but it takes a bit of research.
The C5Z and C6Z are suffering from different issues though. Its not a common cause. From what I've heard is that there are solutions in the aftermarket for each that will make them nearly bulletproof, but it takes a bit of research.
