Head lift on a SC @ 13.5psi ?
04-20-2006, 04:42 AM
#81
Originally Posted by 350zDCalb
it is moreso an issue of detonation creating extreme pressures within the cylinder, forcing the head to seperate from the block (in thousandths of an inch)
detonation is not the only answer here, there becomes a limitation of matter...the standard arp studs do provide a tremendous amount of clamping force between the heads and the block. Greater amounts of torque to the studs will decrease the instances of cylinder head lift, the choices are; stronger studs, steel inserts in the aluminum block, larger diameter studs...or all of the above.
GT motorsports claims that there are a few vq35's that are in a drag race platform making 1500+hp and do not have a hint of cylinder head lift issues (these motors are built with 14mm studs)
detonation is not the only answer here, there becomes a limitation of matter...the standard arp studs do provide a tremendous amount of clamping force between the heads and the block. Greater amounts of torque to the studs will decrease the instances of cylinder head lift, the choices are; stronger studs, steel inserts in the aluminum block, larger diameter studs...or all of the above.
GT motorsports claims that there are a few vq35's that are in a drag race platform making 1500+hp and do not have a hint of cylinder head lift issues (these motors are built with 14mm studs)
Did they ever say what the 1/2 inch or 14mm studs are trq. to ?
04-20-2006, 05:02 AM
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"it is moreso an issue of detonation creating extreme pressures within the cylinder, forcing the head to seperate from the block (in thousandths of an inch)"
Does detonation cause a greater combustion chamber pressure than the ignition chamber pressure ??? Detonation occurs after the ignition phase and the internal pressure in the cylinder at this time is way low.
Can't imagine it does but perhaps the total force acting at the heads is greater when a neighbor cylinder is firing and detonation is occuring within another cylinder(s)...
Does detonation cause a greater combustion chamber pressure than the ignition chamber pressure ??? Detonation occurs after the ignition phase and the internal pressure in the cylinder at this time is way low.
Can't imagine it does but perhaps the total force acting at the heads is greater when a neighbor cylinder is firing and detonation is occuring within another cylinder(s)...
04-20-2006, 05:19 AM
#83
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Originally Posted by jpc350z
Does detonation cause a greater combustion chamber pressure than the ignition chamber pressure ??? Detonation occurs after the ignition phase and the internal pressure in the cylinder at this time is way low.
Can't imagine it does but perhaps the total force acting at the heads is greater when a neighbor cylinder is firing and detonation is occuring within another cylinder(s)...
04-20-2006, 06:49 AM
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Originally Posted by 350zDCalb
Detonation can cause the cylinder pressure to increase several times over that of normal combustion!
04-20-2006, 07:37 AM
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Originally Posted by jpc350z
Yes , but the pressure pulse is very sharp and of little duration...Suggesting in Booger's case that it might be headlift due to detonation without the classical signs of pinging/ringing of detonation that certainly Booger would have noticed at least to me makes detonation/headlift not very probable..Plus I believe he say's the engine temp was ok another sign of non- detonation...
Godd luck Booger
04-20-2006, 08:21 AM
#87
We've seen headlift on the dyno with C16 race fuel, at 15psi boost pressure...so I feel comfortable sayings it wasnt detonation in our case. And because the cooling blows out suddenly, after 3 seconds of WOT, and 200F coolant temps, its also unlikely to be a cooling system issue.
04-20-2006, 09:29 AM
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So, we eleminate headlift/detonation, the cooling system (temp's are normal) but something is causing the coolant out the engine at a rapid rate and into the overfill...Takes pressure to do that...What is the likely cause? How/what will cause the coolant pressure to rise suddenly when under boost?
04-20-2006, 09:34 AM
#89
Originally Posted by jpc350z
So, we eleminate headlift/detonation, the cooling system (temp's are normal) but something is causing the coolant out the engine at a rapid rate and into the overfill...Takes pressure to do that...What is the likely cause? How/what will cause the coolant pressure to rise suddenly when under boost?
04-20-2006, 10:20 AM
#91
Originally Posted by jpc350z
Some indications of combustion gas byproducts should then be evident in the coolant reservoir...
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