blackeg

lost my #3 piston on the dyno yesterday. i cant really figure out how it happened, everything seemed to be within spec. air fuel was actually a tad rich (10.9) and i was in the process of leaning it out a bit. oil pressure was good, temps were nice and cool, 180 oil and 190 coolant, 118 iat all from the neptune datalog. i have an egt gauge in the #3 runner about 1 inch from the head and it was reading in the 800c range. plugs did not show any detonation, bkr7e's gapped to .020. the motor is an 84x89 benson sleeved gsr, cp pistons and eagle rods. ptw was set at .0035. the last motor i had made 425hp and never had an issue at the same ptw tolerence...

the run it gave out on was 412hp/288tq, 93 octane pump gas. boost pressure was 17 psi and my total timing was 11 degrees. i have a tiny little dip on the graph at like 6800 rpm. i didnt even feel it through the throttle. when it came back down to idle i heard it slapping a tiny bit and had some puffs of smoke out of the catchcan so i shut it down. i pulled the plug and it had a very light coat of oil on it so i packed it up and went home.



thats the intake side. it did a pretty good number on it.


all the other pistons are fine


there's the cyl. definately got some grooves that catch your fingernail. im hoping i can get it clean with only .020 over


#3 cyl exhaust valves. they definately have carbon on them leading me to think it didnt lean out.


#3 cyl. looks even a lil rich on the valves. please disregard the bottom half of the plug fire ring, that was the glare from the camera, as was the head below the exhaust valves.





the adjacent cylinders.


crappy picture of the run it happened on, if it helps. i understand it is rich, mostly in the high 10's. it was my first pull at that boost and i wanted to work my way leaner. my afr goal was 11.5 on pump gas 93 octane

also on closer look, one of my other pistons was starting to score, it has one tiny spot about 3/4 of the way up the bottom of the skirt to the oil ring


yeah, im just not sure..

B20luda

ive always ran more P2W im at .0425

have the injectors flow tested

pistons installed correctly?

tofast4uh22

that looks like the piston was hot. either front too lean (doesnt have to be during wot could even be under partial throttle) and looks like too little p2w clearance when the piston expanded. check that cylinders fuel injector, you might find that it has a issue!!!

Turbo-LS

iTrader: (4)

Agree with above post and looks like Hg failure might be possible as well. .035 PTW at 400hp shouldnt be a problem IMO Timings a bit low. to little timing isnt good

blackeg

yeah i can agree that i might not have had enough ptw especially if it wasnt detonating or running lean. i do have to think that much heat have shown on my egt gauge though.. it is in that cyls runner. the sparkplug was black on the fire ring consistant with the other cylinders. i do have that cyl fuel trim up a bit from the others to account for increased temp potential.


in hindsight, the gas i had in the car has 15%mtbe and i know some people who have had issues with the 15% instead of the 10%...

blackeg

block is getting machined, pretty sure a .5mm over will clear it up. damn i dont remember pistons being this expensive..

blackeg

nevermind its 10%mtbe i checked.

that was my first pull on that boost level and i wanted to start low and work my way up with timing. i was anticipating winding up running around 13-14 degrees but i wanted to not go over the top on it right away..


contemplating going to .004 or so on the rebuild to ensure this does not happen again, but i still am not sure how it got hot enough to do that but not detonate or melt up the piston a bit or even put my egt levels up toward 1600f

blackeg

other bit of info,

im not using the oem oil squirters, they are plugged with the ge kit. ive always heard that you can not use them with the longer stroke of the ls crank in the gsr block. actually i never have run them, even in the last build with the same block, pistons, rods power level and same tune within .5 afr and 2 degrees timing. would this have had something to do with it?

also the cp's have 4 oil holes on each side, lets say as compared to my old wiseco's that only had 3. wouldnt this help compensate??

2k.civic.si

check the injector for that cylinder...looks like the piston got hot and expanded

Thomascivicsi

X2 ^^^^

blackeg

oh i know that piston got hot, i also know it didnt lean out. wideband, spark plug, egt in that cylinders runner and even the valves and quench area on the head indicate adequate fuel. in fact, they have a little more carbon than the other cylinders.

injectors are precision 880s that were new when i assembled the engine, so 2500 miles



im entertaining the idea of hg failure, as it did have a little bit of oil get in the cylinder during the pull. however, it still compression checked 195 psi consistant with the other cyls and leakdown was 25% through the rings. there was no coolant consumption

blackeg

whats the best way to go about checking that injector in case i cant figure out any other viable reason for this to happen?

Sr420Det

man sorry to c that, Id have em all flow tested at a local joint or if u got to send em off to rc or someone.

blackeg

new pics added.

i was using the cylinder trims in my neptune, running #3 at 3 and my other cylinders at 0.


also, even though my iat, coolant and oil temps were low, i did my last 3 pulls in about a 10 minute span. that too close in time??