BLU CIVIC

I searched and got a lot of conflicting answers (injectors, detonation, pre-ignition) and unsure what caused the problem so I can try to avoid this happening.

Background:

Engine set-up
B18c1 w/ ARP headstuds
Skunk2 intake manifold
Omni Power 70mm throttle body
Garrett T3 turbo (60 hot, 48 or 52 cold)
550cc Chrysler injectors
Walbro 255 fuel pump

car was tuned 3/12 and made 249/184 @ 9psi and then retuned on 10/12 and made 296/229 @ 13psi

Scenario that led to cracked ringland
leaving my neighborhood and floored it. tunerview read 11psi @ 7900rpm. nothing that i haven't done 100's of times before. and no, i do not have an a/f guage. car started smoking heavily from catch can and took the car home and parked it.

Compression test readings:
200
180
200
60

this was cylinder #4


so bought everything to rebuild the block and had my friend disassemble it for me. upon being removing the pistons/rods, found out the reason for low compression in #2 cylinder


yeah, I wasn't expecting that. so now I'm trying to be proactive in trying to figure out the how and why this happened. all help is much appreciated.

Computer_Nerd

problem? you tried to make a honda go fast.

Computer_Nerd

your oil pump may not be able to keep up.

brandini

"leaving my neighborhood and I floored it"

You floored it on a cold engine?

sixcyl?

I was thinking that.

I'm also on the oil pump bandwagon.

BLU CIVIC

nope, never. don't drive until my car is warmed up

if it's an oem oil pump, wouldn't this signs show while on dyno and not 7 months later?

sixcyl?

That's still crazy. Even stock rings should be good at what you were running(on a good tune).

Fabrik8

Now you know why forced induction pistons have heavier ring lands than N/A applications.

Pre-ignition doesn't generally crack ring lands, because the pressure rise is slow. It usually melts stuff because the heat buildup is fairly localized. The broken ring lands and skirt scuffing are usually an indication of detonation, which makes a really fast pressure wave that will find the weak spots in the piston. The skirt scuffing is usually from excessive side loading of the piston or because the piston skirt expanded too much due to heat buildup (both signs of detonation). There are other causes of piston scuffing though, so you can't necessarily say that's from detonation by itself. The fact that the second ring land is broken (on two different pistons) really points to detonation though.

Why did it happen? That's harder to track down without seeing what happened real-time, with a datalogger or whatever. You'd need to see the A/F ratio and ignition timing and ideally something like EGT also. It could be the tune, or it could be a problem with the fuel system or ignition system, etc. I'm not going to throw the tuner under the bus without knowing how complete the tune was and how conservatively it was tuned, etc., but the tune has the most ability to impact engine operation if everything else is working properly (ignition, fuel system, etc). Don't automatically assume the tune was the issue though, unless you have some reason to suspect that.

What do the tops of the pistons and the combustion chambers look like? Are they pitted at all? I don't mean melted, I mean pitted like they've been sandblasted...

sleeperteg

Amateurs don't use nitrous oxide. I've seen the way you drive, you've got a heavy foot.






In all seriousness though, how long were you running this setup? Maybe it was running way too lean for some reason and you got bad pre-ignition or maybe ignition timing is off

power2weight

Are the injectors new? Did you send them off to be flow tested if they're used? Stock fuel pump? How many miles were on the spark plugs?