Cylinder wall cracking thought...
10-06-2006, 06:49 PM
#1
Race Car
Thread Starter
Cylinder wall cracking thought...
I have been thinking of the cylinder cracking problem in the 996s. If this is a problem, how is the supercharged crowd doing?
After all, there cylinder pressure is substantially higher than our N/As which in theory should lead to more failure.
And if this is truly a problem, why would Ruf put his supercharger and name on a product that could potentially fail?
In the drag racing world, you would fill up the water passages (too an extent) throughout the block of an engine with block cement to increase the blocks' strength, and also increase cylinder strength.
I wondered if this is possible in our engines?
I want to run a turbo system (my homemade design) in the future but want to run higher than 6 lbs of boost, I want like 15-20 lbs depending on how I am running the car.
But to do this, you have to lower the compression ratio. I was wondering what kind of compression ratio change would there be by using thicker head gaskets?
I have faith in the 996 block to withstand high hp/tq, due to its 7 main bearings and I want to take advantage of the 4 valve design.
The older turbos had 2 valves and barely make the hp of the 996 so I know there is great potential to boost the 996 engine if I can just get the compression ratio down enough without changing the heads and costing
big dollars.
After all, there cylinder pressure is substantially higher than our N/As which in theory should lead to more failure.
And if this is truly a problem, why would Ruf put his supercharger and name on a product that could potentially fail?
In the drag racing world, you would fill up the water passages (too an extent) throughout the block of an engine with block cement to increase the blocks' strength, and also increase cylinder strength.
I wondered if this is possible in our engines?
I want to run a turbo system (my homemade design) in the future but want to run higher than 6 lbs of boost, I want like 15-20 lbs depending on how I am running the car.
But to do this, you have to lower the compression ratio. I was wondering what kind of compression ratio change would there be by using thicker head gaskets?
I have faith in the 996 block to withstand high hp/tq, due to its 7 main bearings and I want to take advantage of the 4 valve design.
The older turbos had 2 valves and barely make the hp of the 996 so I know there is great potential to boost the 996 engine if I can just get the compression ratio down enough without changing the heads and costing
big dollars.
10-06-2006, 07:17 PM
#2
Race Car
Who said that there was a problem with cylinder cracking? I run a higher effective compression ratio that the TT's in my little old stock 3.4 engine with a static compression ratio of 11.3:1.
10-06-2006, 09:44 PM
#3
Race Car
Thread Starter
1999Porsche911- there was a thread about cylinder wall failures I had read on this forum, I think it was called "engine blown" or something to that extent. The person said he was DE'ing and the motor popped, once torn down, he found that he had blown out the top of a cylinder wall. Many others chimed in with the same experience. Then someone had put a link to a British company that bores out the factory cylinder liner and puts like a 2 X's bigger sleeve in the block.
I dont understand what you mean by "higher effective ratio" over a TT. Cylinder pressure in a turbocharged engine (996 TT) I would asume is greater than our 11.3:1 engines.
I know that "compression ratio" and "cylinder pressure" dont go hand and hand (although there is to an extent a direct correlation) because of camshafts can bleed cylinder presssure (for supercharged applications so boost can be increased controlling detonation) or increase cylinder pressure (for N/A engines to increase power).
My point was, N/A motors have no doubt broken cylinder walls. I just dont know if it was from a weak cylinder wall or coolant leaking into the cylinder hydraulic locking the cylinder. Nothing can withstand hydraulic locking and I hope that this is the real problem because if it is the first (just a weak cylinder wall) , supercharging (turbocharging) the 996 could be a time bomb.
I dont understand what you mean by "higher effective ratio" over a TT. Cylinder pressure in a turbocharged engine (996 TT) I would asume is greater than our 11.3:1 engines.
I know that "compression ratio" and "cylinder pressure" dont go hand and hand (although there is to an extent a direct correlation) because of camshafts can bleed cylinder presssure (for supercharged applications so boost can be increased controlling detonation) or increase cylinder pressure (for N/A engines to increase power).
My point was, N/A motors have no doubt broken cylinder walls. I just dont know if it was from a weak cylinder wall or coolant leaking into the cylinder hydraulic locking the cylinder. Nothing can withstand hydraulic locking and I hope that this is the real problem because if it is the first (just a weak cylinder wall) , supercharging (turbocharging) the 996 could be a time bomb.
10-06-2006, 10:07 PM
#4
Rennlist Member
Mine was one that cracked cylinder #1. PM me for pics. It is simply a weak spot in the cylinder wall that could have been easily fixed with a small "bridge" between the weak part of the cylinder wall and the block edge, about 1/" away. It may have impeded coolant though. PM me if you have any questions. If I were going to supercharge a 996, it would be a 2002 or newer.
10-06-2006, 10:25 PM
#5
the problem was more with dropped sleves then randomly cracking cylinder walls. If you blow out a cyl wall chance are its from a hydrolock condition where the cyl was filled with water and it tried to compress it, or you overheated the engine at some point and oit lead to a stress fracture.
I would not use block filler on a any porsche engine, coolant passages are designe to prevent hotspoting in the cylinders which is a big deal especialy if your gonan be forcing extra air into the engine.
YOu can lower the compression how much depends on how thick of head gaskets, but to run 15+ psi your gonna need to get some forged pistons
You will also need to tune it somehow along with lots of other things i just did a whole run down about why not to turbo a na 996 search for boost
Do a lot of home work and alot of research before you start your project, unless youve fabbed turbo setups before i wouldnt recomned your first one being a porche.
I would not use block filler on a any porsche engine, coolant passages are designe to prevent hotspoting in the cylinders which is a big deal especialy if your gonan be forcing extra air into the engine.
YOu can lower the compression how much depends on how thick of head gaskets, but to run 15+ psi your gonna need to get some forged pistons
You will also need to tune it somehow along with lots of other things i just did a whole run down about why not to turbo a na 996 search for boost
Do a lot of home work and alot of research before you start your project, unless youve fabbed turbo setups before i wouldnt recomned your first one being a porche.
10-06-2006, 10:27 PM
#6
The actuall problem was not that the sleeve cracked per say. The sleeves were slipping. Due to casting problems (not known to Porsche, Block casting was outsourced) the sleeves were slipping. This means that the sleeve would come loose from the block. Then a piston headed twards bdc would grab the sleeve, take it to bdc, and then back up to tdc. Then whamo! Pull it apart and youve got lots of broken parts/cracked head/sleeve/piston/block it all usually depends on where in the rod ratio scope that the sleeve slipped on that cylinder.
10-07-2006, 12:15 AM
#7
Race Car
Thread Starter
Joe - I hate to hear that happened, I pray it doesnt happen to me. Sometimes I think Porsche should owe up to something this unbelievable and uncalled for.
Any engine regardless of miles should not have a sleeve slip and Porsche should pay.
99 & pwr2lbs - I was completely wrong on what caused the cylinder breaking, but the British company said, I believe, that it was just a weak casting.
Yes, I forgot that the $80,000 car I own doesnt have forged pistons!
This is forcing me that much closer to a 964 T.
Any engine regardless of miles should not have a sleeve slip and Porsche should pay.
99 & pwr2lbs - I was completely wrong on what caused the cylinder breaking, but the British company said, I believe, that it was just a weak casting.
Yes, I forgot that the $80,000 car I own doesnt have forged pistons!
This is forcing me that much closer to a 964 T.
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10-07-2006, 12:17 AM
#8
Drifting
The Porsche TTs use a totally different motor design and I doubt they share very few if any parts. I believe they are based on the air cooled design of years past although they are water cooled, and have a dry sump oiling system. They are much more robust and lend themselves to being heavily modified for racing. This is my understanding, please correct me if I'm wrong.
10-07-2006, 01:38 AM
#9
Race Car
Originally Posted by Tippy
1999Porsche911- there was a thread about cylinder wall failures I had read on this forum, I think it was called "engine blown" or something to that extent. The person said he was DE'ing and the motor popped, once torn down, he found that he had blown out the top of a cylinder wall. Many others chimed in with the same experience. Then someone had put a link to a British company that bores out the factory cylinder liner and puts like a 2 X's bigger sleeve in the block.
I dont understand what you mean by "higher effective ratio" over a TT. Cylinder pressure in a turbocharged engine (996 TT) I would asume is greater than our 11.3:1 engines.
I know that "compression ratio" and "cylinder pressure" dont go hand and hand (although there is to an extent a direct correlation) because of camshafts can bleed cylinder presssure (for supercharged applications so boost can be increased controlling detonation) or increase cylinder pressure (for N/A engines to increase power).
My point was, N/A motors have no doubt broken cylinder walls. I just dont know if it was from a weak cylinder wall or coolant leaking into the cylinder hydraulic locking the cylinder. Nothing can withstand hydraulic locking and I hope that this is the real problem because if it is the first (just a weak cylinder wall) , supercharging (turbocharging) the 996 could be a time bomb.
I dont understand what you mean by "higher effective ratio" over a TT. Cylinder pressure in a turbocharged engine (996 TT) I would asume is greater than our 11.3:1 engines.
I know that "compression ratio" and "cylinder pressure" dont go hand and hand (although there is to an extent a direct correlation) because of camshafts can bleed cylinder presssure (for supercharged applications so boost can be increased controlling detonation) or increase cylinder pressure (for N/A engines to increase power).
My point was, N/A motors have no doubt broken cylinder walls. I just dont know if it was from a weak cylinder wall or coolant leaking into the cylinder hydraulic locking the cylinder. Nothing can withstand hydraulic locking and I hope that this is the real problem because if it is the first (just a weak cylinder wall) , supercharging (turbocharging) the 996 could be a time bomb.
Well, I don't lose any sleep over my 996 "timebomb" that has been boosted with an SC for more than 35,000 miles. No seal leaks or burning oil. But, I also do not run the Mobil Water (0W40).
When she blows...she blows.
10-07-2006, 11:54 AM
#10
Race Car
Thread Starter
Originally Posted by 1999Porsche911
Well, I don't lose any sleep over my 996 "timebomb" that has been boosted with an SC for more than 35,000 miles. No seal leaks or burning oil. But, I also do not run the Mobil Water (0W40). When she blows...she blows.
When she blows...she blows.
10-07-2006, 03:02 PM
#11
Originally Posted by nick49
The Porsche TTs use a totally different motor design and I doubt they share very few if any parts. I believe they are based on the air cooled design of years past although they are water cooled, and have a dry sump oiling system. They are much more robust and lend themselves to being heavily modified for racing. This is my understanding, please correct me if I'm wrong.
10-09-2006, 01:00 PM
#12
Rennlist Member
My 2000 996 has 54k miles on it, and last week the lube oil and coolant fluids had comingled. According to Houston based Pro-Technik (281-879-8861) and Porsche dealership Momentum, this is a pretty common problem on early water cooled engines, both 996 and Boxster. According to Pro-Technik, the probelm is combination of magnesium and aluminum in the cylinders, heads and block, where galvanic corrosion between the different metals causes the magnesium to corrode. According to Momentum, there is no way of preventing this, and no way to know before it already has happened. Basically every 996/Boxster before 2002 is a sitting duck, knowing that sooner or later this will happen. The only solution is a complete engine change! As a Porsche enthusiast for more than 30 years, I would believe that the Weissach metalurgists would have known this basic chemistry/physics. But now, when warranties are gone, the costs are thrown in the face of unfortunate Porsche owners. Momentum has suggested $18k to $20k for the job. Where is Porsche's liability in this case, where the cause is an obvious design fault? Anyone out there with some good answers?
10-09-2006, 01:54 PM
#13
Addict
Rennlist Member
Rennlist Member
Originally Posted by Fly911
.......now, when warranties are gone, the costs are thrown in the face of unfortunate Porsche owners. Momentum has suggested $18k to $20k for the job.
Hey really, most any significant issue on the M96 driveline from engine, bearings, gears, shafts, whole gear boxes, etc, can be remedied........with replacement.
On the upside, the $18-20K sounds steep......I don't think a reman. plus core plus labor really should be much more than $12K.
Fly....hopefully PCNA will step up and help ya out........good luck to ya.
10-09-2006, 03:38 PM
#14
Originally Posted by Fly911
My 2000 996 has 54k miles on it, and last week the lube oil and coolant fluids had comingled. According to Houston based Pro-Technik (281-879-8861) and Porsche dealership Momentum, this is a pretty common problem on early water cooled engines, both 996 and Boxster. According to Pro-Technik, the probelm is combination of magnesium and aluminum in the cylinders, heads and block, where galvanic corrosion between the different metals causes the magnesium to corrode. According to Momentum, there is no way of preventing this, and no way to know before it already has happened. Basically every 996/Boxster before 2002 is a sitting duck, knowing that sooner or later this will happen. The only solution is a complete engine change! As a Porsche enthusiast for more than 30 years, I would believe that the Weissach metalurgists would have known this basic chemistry/physics. But now, when warranties are gone, the costs are thrown in the face of unfortunate Porsche owners. Momentum has suggested $18k to $20k for the job. Where is Porsche's liability in this case, where the cause is an obvious design fault? Anyone out there with some good answers?
EVERY 996 IS NOT A TIME BOMB
10-09-2006, 07:36 PM
#15
Race Car
Thread Starter
Magnesium nor aluminum would hold up to the heat and stress of a cylinder. It has to be steel, cast iron, or chromium lined (like aircraft cylinders) which I do not know what Porsche uses. Every aluminum engine I know of uses a disimilar metal sleeve and I have never heard of a reaction of the two causing issues, I believe there is more to it like, fits and clearances. Although I dont claim to be an expert, just my knowledge of engines over the years.