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Discussion Starter · #1 ·
This is my LSR busa piston and log from Febuary
Putting this up so you guys can see although an intercooler is important its not a magic fix all things. Its one of the tools used to manage your motor but ignor the others and it may as well not be there

The primary injector on cyl 2 failed so even though i had 26C inlet temps (Water/ice intercooler), minimal ign timing at 24 deg and A/F in low to mid 11's with 116 oct fuel at 25 psi boost it still toasted a piston and cylinder
The primary injector was not contributing a lot of the fuel supply so its failure barely changed the A/F which is an average of all cylinders , but that particular cylinder probably had 13.5-14 a/f at the time of the failure
And it happened about 10 seconds into the run it doesnt need long to melt Aluminium
 

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What could you have done to catch this before it was detrimental? I guess you could install a wideband in every exhaust outlet but that's not super practical.
 

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Discussion Starter · #3 ·
Yes the 4 O2 would have helped 4 Channel EGT would have logged it in more detail too but the Editor /Woolich flashing of the std ecu has no failsafe cutout like a standalone can do
I actually had 8 injectors for E85 tested then switched to the 116 leaded and used my old injectors without cleaning and testing then , my own fault ,

main point was any combination is only as good as the weakest link
 

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@OzBooster

Wow, thats a seriously melted hole. I'm always amazed at that.

Is it flame propagation that does that on one side only, and such a small hole ?

NOLA
 

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Discussion Starter · #5 ·
I have had a couple like that over the years , usually something simple causing an overboost , like a wastegate hose too close to an exhaust
most impressive pierced a hole in the top of the piston, through the side skirt,and through the cylinder wall, without smearing at 12000rpm on the 750 best i can figure it as some sort of plasma event , as the cut looks just like my plasma cutter does , but through much thicker material than the shop tool could ever do , just about always on the exhaust side, bit hotter over there

If you look close both sides at the top of the piston have lost material as it detonated and eroded the surface , what you cant see is the whole top of the piston is deformed , centre dished enough to contact the connecting rod
the head has similar erosion between the exhaust valves

This is a top of the range forged piston with ceramic coating on top ,
 

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For this scenario: Excessive cylinder pressure (for whatever reason) crushes a ring land (top/middle or both) and sticks the rings, which scores the bore/sticks/rocks the piston. This allows oil to enter the cylinder. Oil, under extreme pressure, will ignite without any flame (this is how diesel engines work). This diesel effect is out of time with with the normal spark cycle, which creates even more cylinder pressure, heat, flame, etc... The pressure/heat/flame must escape to somewhere - it's typically past the score in the cylinder wall (looks like that was the case here), through the piston dome, out of the exhaust valves/seats, past the head gasket, etc... - but it will always be thru the path of least resistance.

The damage to the piston typically receives all of the 'wow' attention. But damage to components under the pistons are likely also: rods, bearings, crank, and even cases. Detonation is incredibly destructive and happens almost instantly. Remember, a piston moves up/down 200 times per second in an engine spinning 12K rpms. This all happens in the time that it takes the rider to back off the gas because he just heard the bike 'flatten out'. The only way to stop it... is to not let it happen.

It's part of racing; it happens, and hopefully we learn from it and move on.

Brock
Brocks Performance
 

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Too much ignition timing can do that, too (causes cylinder pressure to go way up even without detonation, and if detonation happens along with it then ka-boom follows shortly afterward).
 

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Discussion Starter · #8 ·
Yep stripped the whole motor Brock ,also have to check the rod for ovality
Someone once asked me just how much damage detonation could do , and i told them to rest a 1 lb hammer on there finger , constant pressure , no big deal, now raise it an inch and let go
now they know what detonation feels like to a motor

I think this one overheated the piston and land more than breaking the land out from outright timimng induced detonation Funny but its only a narrow a/f range thats real bad, at a leaner range it would have run with no damage , i have done 4 miles at 17/1 with no problem when i lost a map sensor .
 

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Yep stripped the whole motor Brock ,also have to check the rod for ovality
Someone once asked me just how much damage detonation could do , and i told them to rest a 1 lb hammer on there finger , constant pressure , no big deal, now raise it an inch and let go
now they know what detonation feels like to a motor

I think this one overheated the piston and land more than breaking the land out from outright timing induced detonation Funny but its only a narrow a/f range thats real bad, at a leaner range it would have run with no damage , i have done 4 miles at 17/1 with no problem when i lost a map sensor .
I drag raced nitrous bikes for 20 years - I had a couple of bikes (low 8 second fuel injected/nitrous 750 in 2000, for example...) that I really didn't need to tighten the motor mount bolts, the pistons melted so often, lol. What causes the excessive cylinder pressure in one cylinder can usually be determined best by viewing the plugs and pistons in the ones that didn't die (yet). Of course, if you had a definite failure, like an non-functional injector, it's easy to determine the cause of the problem. If not, it can be quite a bit tougher, as things can appear 'random' in the world of engine failures. Of course, they aren't, but you might get to spilling hairs to figure out the culprit. I had a pro mod bike once that kept melting pistons, same bike did it half a dozen times in multiple cylinders, but only with my #1 engine. My 'identical' back up engine' would absolutely haul a** with the same tune up and not miss a beat. I would take it out to save it for race day and try to get #2 to work... which would melt in a pass or two. It had 2 rods that had 'stretched' over time. They weren't bent, they were about .007/.008 longer than they should have been (rockwell test showed they were too soft). In a big cc engine, the added static compression/squish created too much compression in those cylinders... so they would die. Replaced the rods, and the problem went away.

All that work/expense taught me to check the measured assembled clearance (piston to head), on all 4 cylinders, from that point forward. That was in the mid 90's. It happens, we learn, we move on ;)

Brock
Brocks Performance
 

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Ozbooster is very knowledgeable and helpful, I love reading your posts and will enjoy your intercooler when my time comes around;)
 

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Discussion Starter · #12 ·
I drag raced nitrous bikes for 20 years - I had a couple of bikes (low 8 second fuel injected/nitrous 750 in 2000, for example...) that I really didn't need to tighten the motor mount bolts, the pistons melted so often, lol. What causes the excessive cylinder pressure in one cylinder can usually be determined best by viewing the plugs and pistons in the ones that didn't die (yet). Of course, if you had a definite failure, like an non-functional injector, it's easy to determine the cause of the problem. If not, it can be quite a bit tougher, as things can appear 'random' in the world of engine failures. Of course, they aren't, but you might get to spilling hairs to figure out the culprit. I had a pro mod bike once that kept melting pistons, same bike did it half a dozen times in multiple cylinders, but only with my #1 engine. My 'identical' back up engine' would absolutely haul a** with the same tune up and not miss a beat. I would take it out to save it for race day and try to get #2 to work... which would melt in a pass or two. It had 2 rods that had 'stretched' over time. They weren't bent, they were about .007/.008 longer than they should have been (rockwell test showed they were too soft). In a big cc engine, the added static compression/squish created too much compression in those cylinders... so they would die. Replaced the rods, and the problem went away.

All that work/expense taught me to check the measured assembled clearance (piston to head), on all 4 cylinders, from that point forward. That was in the mid 90's. It happens, we learn, we move on ;)

Brock
Brocks Performance
Never way game enough to play with much NOS , it seemed too prone to outside influence , bottle temp goes up and you run lean, down and its rich

I bet it took some time to find that , For the guys that cant quite picture what .007-8 is , an experianced person can just feel a .002 ledge scratching a surface with a fingernail , and many people would not be able to measure accurately enough to even find this problem

It happens so we can learn and go faster ;)
 

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Discussion Starter · #13 ·
Thanks VMax+H2 Ben will have sales in his online store soon, there will be about a 4 week wait for each batch of 10
 

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Never way game enough to play with much NOS , it seemed too prone to outside influence , bottle temp goes up and you run lean, down and its rich

I bet it took some time to find that , For the guys that cant quite picture what .007-8 is , an experianced person can just feel a .002 ledge scratching a surface with a fingernail , and many people would not be able to measure accurately enough to even find this problem

It happens so we can learn and go faster ;)
According to google: Europeans consider hair with a diameter of 0.04 to 0.06 mm (.0015-.0020 inch) as thin, hair with a diameter between 0.06 and 0.08 mm as normal, and hair with a diameter between 0.08 and 0.1 mm (.0030-.0039 inch) as thick. By comparison with European hair, Asian hair is significantly thicker. The average diameter of Asian hair is 0.08 to 0.12 mm (.0039-.0047 inch).

We won't get into the American 'RCH'. But it is the standard unit of measure in the R&D room at Brock's, and I understand it is an accepted standard down under also. @QzBooster would have to confim ;)

Brock
Brocks Performance
 
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