Why My Rings Failed?

[rad100]

well i have (had) a rb25det s2..

gt3076r .82 @16psi

38mm gate

stock 25

splitfires

740cc

gtr pump

nistune

fmic etc etc..

now i had a grip day at mallala and the car was strong and did 15-20 laps, slight traction loss to limiter..

then i was exiting a corner (on the 15th-20th lap) and oil shot out my rocker covers..

then contnued for the rest of the day, when i exceeded 5-6000rpm..

i thought this was the usual rb issue so thought nothing of it..

bought baffles and rb26 rocker covers..

now i got the car to my workshop, to install plazmaman plenum, rocker covers and baffles..

got it on the dyno and excessive blowby, oil into catch can.. RINGS GONE!

any reason y the rings went all of a sudden?

tune related?

now im up for a rebuild!?

cheers

[San-Ni]

Stock bottom end? stock rings?

[rad100]

yes says stock rb25

[San-Ni]

well is the rule of thumb with RB25 rings that they are prone to fail?

[rad100]

you would think that 280kw wouldnt want to kill them...

does the tune have a big factor in this?

[San-Ni]

I think its just Nissan thing for the 25's...

I hear countless stories about the ring lands failing them...

[snozzle]

15-20 laps with that power level is alot of hardwork on the motor, did you think your stock bottom end was invincible? lol

pull the motor apart and you will be one step closer to the reason for failure

[MBS206]

Do a comp and leak down test, the issue may not be the rings.

[rad100]

no i didnt think it was.. but it was 5 -7laps 40min rest, so on and so on..

i was planning a build but just wanna enlighten myself as to why so i can help prevent it with a new engine!

[rad100]

Do a comp and leak down test, the issue may not be the rings.

compression is down on cyl 5, read approx 100psi..

and u can hear its uneven..

[dazmo]

First thing to do would be comp and leakdown as stated above and agree with the post above that 15 - 20 laps flat out would have your standard bottom end working pretty hard as cylinder temps would be right up there. What sort of A/F are you running and Does the nistune have air temp compensation ?. I would hazzard a guess that more than likely due to cylinder temp and probably some detonation that you will have a piston that has started to go soft allowing the crown to start to collapse pinching a ring allowing excessive blow bye But untill you do a comp and leakdown test you really wont know.

[GTScotT]

100% tune related.

the ring lands die from excessive heat and detonation. a 3076r @ 280rwkw on a 25 warrants neither.

its not to say it couldnt be user error, yet generally my cars see 30 minute floggings at a time and are yet to see this issue.

what are your AFs like? in the 12s i bet

[R31Nismoid]

you would think that 280kw wouldnt want to kill them...

does the tune have a big factor in this?

100% tune related.

the ring lands die from excessive heat and detonation. a 3076r @ 280rwkw on a 25 warrants neither.

its not to say it couldnt be user error, yet generally my cars see 30 minute floggings at a time and are yet to see this issue.

what are your AFs like? in the 12s i bet

See i'd argue that it was 100% tune related. You don't know that for certain.

5-7 laps will get a large amount of heat into everything that's for sure, especially upper RPM's.

You don't know the perevious history of the motor either. It might have had a rough life before the current owner as an example.

Could even have been running slightly lean for a number of reasons.

All of which are totally unrelated to the tune.

Either way I'm far from surprised. Tracking a motor @ around 2.5x the factory output - something will give eventually.

A few stock, good condition/low KM RB26's have been tracked for 2-3 years @ 300-330rwkw, they eventually have died also. Just how it goes.

There are also plenty of cars getting around with AFR's in the 12's on the circuit without a drama after years (these are built mind you).

Honestly what caused the motor to fail IMO could have been any long number of things, and perhaps not a singular one thing but a culmination of several.

[GTScotT]

You don't know the perevious history of the motor either. It might have had a rough life before the current owner as an example.

Very true, that could be the missing link.

I guess we dont really know enough of its history to give an accurate opinion, with this owner or the last.

[rad100]

yeh al good guys.. the engine will be getting removed today..

i have a new bottom end arriving soon, just dont want this happening to the built one!

ill take some snaps of the bottom end wen it comes out.

also would i need to do any work to the head to bolt it to my new block?

[zebra]

It may have been tune related, BUT, parts can fail, as ash said you are pushing 2.5x the factory power output, parts in F1 engines fail and they have the absolute best of everything inside them, so I wouldnt just be blaming the tune.

[rad100]

yeh totally understand..

i wasnt expecting it to hang in there forever..

just wanted some enlightment...

ill strip it down and take a look and hopefully learn..

but ill start a build thread soon

[MrStabby]

yeh al good guys.. the engine will be getting removed today..

i have a new bottom end arriving soon, just dont want this happening to the built one!

For insurance, you could install a wideband AFR, and an oil pressure gauge. That way you can keep an eye things - eg if a FPR or fuel pump are flaky you will see the full load AFRs change and can take action before the motor pops.

Also - what oil were you using?

[rad100]

i have defi oil temp, oil pressure and water temp gauges.

i also run motul 4100..

was brand new oil put in.

[GTScotT]

Have you got a fuel pressure guage? Perhaps test that GTR pump.

Im assuming its not a brand new pump, maybe it leaned out momentarily. AFAIK 280rwkw is borderline for a stock GTR pump.