Cant Boost Past 7psi

[danielson]

guys i have a major prob...jst got my car bak from the kanic, ran sweer 4 bout 2 weeks. now she idles rough, accasionally puffs oil smoke,and wen gets boosted past 7psi, it throws u over the steering wheel...once u get revs up off boost its ok, if u rev 2 high or boost it, the catch can nearly explodes with overflowing oil.....i had sum work dun described below:

xtr high flowed turbo,zorst, hybrid cooler,850cc injectors,haltech ecu,550hp pump,twin plate clutch,etc.. u thnk possible lean out ending my rings? HELP!!!!!

[danielson]

o and its a rb25det...sorry...

[Wazz]

err i'd be taking it back to them.. catch can nearly exploding with overflowing oil? something aint right..

[Craved]

definately sounds like rings to me..

has it been tuned? AFR ok?

compression test will tell the story though .. would think that it would still boost past 7 psi though

[blind_elk]

Last time I saw an engine filling an oil catch can under boost, turned out one of the pistons had a big hole in it.

[danielson]

il do a comp test 2 day.. ive been meaning to but my lazy ass couldnt be fudged taking all that piping crap off...wat a bitch of a job just to do a plug ay.. its been tuned for 300rwkw so he says, it was leaving holden r8 s for dead, now im lucky if i can beat a vw beetle off the lights!

[R31Nismoid]

Sounds like rings to me

More than one... you might have the record of 5 by the sound of it

[danielson]

Sounds like rings to me 

More than one... you might have the record of 5 by the sound of it

<{POST_SNAPBACK}>

i just picked up a seal kit, ring set and 1.6mm head gasket. at a total price of $845...... gotta love aftermarket nissan gear...lol i hope ur rite r31nismoid, i cant really afford pistons on top of that

[rev210]

Ringlands of the piston will most likely be cactus I'm afraid.

Unless your motor has lots and lots of kms on it the factory nissan rings will last quite alot longer without losing compression.

You say the engine has been 'tuned' to 300rwkw. Do you have a dyno readout with the AFR's, RB25's need to run on the rich side of 12 to be save at higher boost due to having some decent compression ?

The other thing is that a 550hp fuel pump (I'm guessing walbro) is a tad small for 300rwkw given drivetrain losses. That sails very close to the wind. If you had a partially blocked fuel filter you could lean the motor out. At 412rwhp or 307rwkw figure that pump maxes out assuming it's going to even get 550hp worth of fuel in at the fuel pressure you are running.

Sorry mate. Sounds like rebuild time. At least you can put some forgies in there to handle the power better next time.

[rev210]

oh when I say ringlands I don't mean rings, I mean the actual part of the piston area the rings sit in (ie: your piston/s are dead).

[danielson]

Ringlands of the piston will most likely be cactus I'm afraid.

Unless your motor has lots and lots of kms on it the factory nissan rings will last quite alot longer without losing compression.

You say the engine has been 'tuned' to 300rwkw. Do you have a dyno readout with the AFR's, RB25's need to run on the rich side of 12 to be save at higher boost due to having some decent compression ?

The other thing is that a 550hp fuel pump (I'm guessing walbro) is a tad small for 300rwkw given drivetrain losses. That sails very close to the wind. If you had a partially blocked fuel filter you could lean the motor out. At 412rwhp or 307rwkw figure that pump maxes out assuming it's going to even get 550hp worth of fuel in at the fuel pressure you are running.

Sorry mate. Sounds like rebuild time. At least you can put some forgies in there to handle the power better next time.

<{POST_SNAPBACK}>

the motor has dun 175,000klms.... please say just the rings....

[rev210]

Thats alot of kms. However, the shear amount of oil going in to the catch can, the fact that the fuel pump is smallish, there wasn't a gradual increase in oil catch and it showers everyone in oil if you floor it means busted piston.

It's all over my friend. A compression test will show you the money very quickly. If you don't have a guage a cheap one can be bought for $30 from somewhere like supercheap auto.

[Bobjones]

have to agree totally with rev, its either rings gone (DEFINITELY more than 1), ringlands or the pistons themselves. If it were just a single ring it would take a little while to fill the catch can...

rebuild time, but definitely a comp test and possiblly a leak down will show the true colours of your problem!!!