Piston Longevity of a Busa

[Enemy]

"Everything must come to an end" right? ..At least that what the voices tell me from time to time. 

Well I think I just found the limits of my cylinder head anyway, but she was still running just fine and the compression on the #3 is still within specs before digging into it to find the problem!!

First I must point out that this motor had 68000 on it when I pulled it from the bike and it had a very-very hard life before going in this build. Countless dragstrip blasts, and its been to 2 countries and both coasts a few times. RedLine 15/50 before boosting, then Mobil1 15/50 Synthetic to present day. I freshened up the rings and bearings last winter (all still within service manual specs!) Unfortunately at the time I decided against rebuilding the head with some good titanium and stainless components ($$Ouch.. ) We added boost after the first year (07), and has been @ 10psi ever since, mostly 50/50 pump gas/tt111 slightly rich tune (11.8-12.2afr)

I was going through the woops section coming in the entrance on the waste gate at around 9000rpm in 3rd gear when it started having some interesting valve-train noises.. I believe I floated the intake valve and it took a nice little chunk out of the piston ring landing. I have a good friend that does awesome cylinder head work investigating more for me right now. The chunk of piston must of left the cylinder quick for the combustion chamber shows no signs of a grenade going off in it, and no visible signs of damage to the valves (probably a bit bent im sure ).. WOW.... Starting to feel I really lucked out on this episode!





On a happy note though, I am glad I was in boost when it happened, because the chunk went through the wategate and bypassed the turbo impeller!

I am just soo friggin' tickled you well Suzuki designed this motor.
Got a few ideas brewing for the new build...Could be interesting! For now I'm going to swap my tranny, clutch and basket, and case/head studs into a used motor and get it back in the sand. So with that said, if anyone has a good source for a used Busa motor (preferably 04-07) please chime in here or throw me a PM! Have a few looking already, got some good prospects..

[fabr]

Why do you feel it was a head issue?

[Enemy]

Tired and weak valve springs I would say. Cant think of any other reason the valve touched the piston? Cam timing is still spot on.

Or the piston let go, wedged between the valve and cylinder, then the valve touched? Problem is the head shows no sign of that.   

I could have a broken valve spring.. Gotta keep digging into this

Thoughts?

[fabr]

High speed run and detonation. Piece of piston ring land broke off, caught under valve for a rev or 2 causing valve/piston contact.Pretty classic example most likely.

[trans man]

  I'm glad to hear it didn't take out the turbo.

[BDKW1]

High speed run and detonation. Piece of piston ring land broke off, caught under valve for a rev or 2 causing valve/piston contact.Pretty classic example most likely.

This would be My guess also, if the one valve hit's you should see marks on the other pocket and other pistons. If only that one has a mark, most likely it was from the chunk holding it open. Real easy to check the springs...........

[Enemy]

I completely understand that theory as well, I just don't see the signs of it. No pitting on the piston, no aluminum on the plug ceramic. All cylinders, pistons, and plugs look wonderful...except for that chunk missing    Hell, I dunno!

I was leaning towards weak or broken spring cause it is the intake side that hit, and I never installed the heavier spring like has been highly suggested from other builders.

High speed detonation..

[fabr]

That's preignition damage.  IMO. What I see in your engine is detonation. Detonation does not make the piston melting heat that preignition does.

[fabr]

Pre-ignition

Pre-ignition (or preignition) in a spark-ignition engine is a technically different phenomenon from engine knocking, and describes the event wherein the air/fuel mixture in the cylinder ignites before the spark plug fires. Pre-ignition is initiated by an ignition source other than the spark, such as hot spots in the combustion chamber, a spark plug that runs too hot for the application, or carbonaceous deposits in the combustion chamber heated to incandescence by previous engine combustion events.

The phenomenon is also referred to as 'after-run', or 'run-on' or sometimes dieseling, when it causes the engine to carry on running after the ignition is shut off. This effect is more readily achieved on carbureted gasoline engines, because the fuel supply to the carburetor is typically regulated by a passive mechanical float valve and fuel delivery can feasibly continue until fuel line pressure has been relieved, provided the fuel can be somehow drawn past the throttle plate. The occurrence is rare in modern engines with throttle-body or electronic fuel injection, because the injectors will not be permitted to continue delivering fuel after the engine is shut off, and any occurrence may indicate the presence of a leaking (failed) injector.[3]

In the case of highly supercharged or high compression multi-cylinder engines particularly ones that use methanol (or other fuels prone to pre-ignition) pre-ignition can quickly melt or burn pistons since the power generated by other still functioning pistons will force the overheated ones along no matter how early the mix pre-ignites. Many engines have suffered such failure where improper fuel delivery is present. Often one injector may clog while the others carry on normally allowing mild detonation in one cylinder that leads to serious detonation, then pre-ignition.[4]

The challenges associated with pre-ignition have increased in recent years with the development of highly supercharged and "downspeeded" spark ignition engines. The reduced engine speeds allow more time for autoignition chemistry to complete thus promoting the possibility of pre-ignition and so called "mega-knock". Under these circumstances, there is still significant debate as to the sources of the pre-ignition event.[5]

"Pre-ignition and engine knock both sharply increase combustion chamber temperatures. Consequently, either effect increases the likelihood of the other effect occurring, and both can produce similar effects from the operator's perspective, such as rough engine operation or loss of performance due to operational intervention by a powertrain-management computer. For reasons like these, a person not familiarized with the distinction might describe one by the name of the other. Given proper combustion chamber design, pre-ignition can generally be eliminated by proper spark plug selection, proper fuel/air mixture adjustment, and periodic cleaning of the combustion chambers."


"Detonation induced pre-ignition

Because of the way detonation breaks down the boundary layer of protective gas surrounding components in the cylinder, such as the spark plug electrode, these components can start to get very hot over sustained periods of detonation and glow. Eventually this can lead to the far more catastrophic Pre-Ignition as described above.

While it is not uncommon for an automobile engine to continue on for thousands of miles with mild detonation, preignition can destroy an engine in just a few strokes of the piston."


You never got to preignition IMO. Ring land broke first. Lucky guy!

[Enemy]

Good read!

Hmmm, time to up the octane as well.

[fabr]

Reading your piston crown ,I'd also say you are a bit lean. Note the aligator skin appearance of the carbon deposits. The carbon should be an even covering and not broken up like that normally. Do all pistons appear similar? If so you may have gone lean in the tune. If not ,might be a partially obstructed injector or other issue. The area around the piston damage also is too clean. My thinking it is detonation damage that was soon to be followed by preignition due to the way the crown looks/reads.

[fabr]

Good read!

Hmmm, time to up the octane as well.

That was my first thought..........................

[fabr]

That pump gas,is it straight gas or blended with alky?

[fabr]

"carbonaceous deposits in the combustion chamber heated to incandescence by previous engine combustion events."


^^^ That is why the carbon on the piston crown looks like it does.

[Enemy]

"carbonaceous deposits in the combustion chamber heated to incandescence by previous engine combustion events."


^^^ That is why the carbon on the piston crown looks like it does.

I scrubbed (and scrubbed, and scrubbed) the carbon from tops of the piston the best I could when I freshened up the motor last winter. All those miles, it was pretty thick. That's why the clean areas are there.

At 8psi, I run 92 octane, no WOT pulls after 4th gear. When running to 10psi I use 92/111 mix. If I plan to do full pulls through 6th, straight 111 and a few degrees of timing pulled on the top side of the map for a bit of added safety.