Piston slap, not impresed but all goes away when warm. should i worry as heard its common and its the way it is

 

If you have forged pistons inside, then totally normal... So long as the noise totally goes away when up to temp!

The metal properties of forged pistons mean that they're in tolerence when up to normal operating temp i.e. expanded, therefore physically larger diameter. So when cold/below normal op. temp., the metal contracts a minute amount making them slightly undersize, hence the 'slapping noise' as the piston rings hit-come away-hit-etc... the cylinders' walls.

 

i can sleep again cheerz

 

If it makes you feel any better, I have a ZEN-built refreshed WRX v.1 ODB block with forged STi v.3/4 pistons in, and have exactly the same symptoms. When it had the original OEM non-forged WRX v.1 pistons in, no noise from cold whatsoever.

 

FEEL ALOT BETER I HAV EXACTLY THE SAME IT WAS A WRX BLOCK NOW STI SPEC YOU DONT KNOW HOW MUCH YOU HAVE MADE ME CHILL. SORRY BOUT THE CAPS GOT 1/2 WAY AND CBB TO GO BACK. WT BHP R YOU RUNNIN

 

This might explain why your start up from colds not so good! (if you aint found anything else that is)

 

It's running 1.15bar (as mapped by JGM) on a Power FC, Walbro, Green panel, PFR7s, decat, etc. for about 280bhp.

This new engine has just finished running in, and am at ZEN's tomoz for oil/filter, and its remap. Still got the 380s and TMIC (silver STi v.2) on, but have the A'PEXi 3bar MAP sensor, so will bring that along to see if Paul agrees on fitting it, so as to map at 1.2bar (or more?). If so, hopefully will see 300!

 

piston slap here. sounds like a bag of spanners in the morning but perrs like a kitten when warm. doesnt bother me anymore. no ill effects. forget about it mate and enjoy the car.

 

mines the same but as soon as up to temp shes quiet dont worry

 

im having mine mapped by jgm wednesday its wrx spec with an sti block want to go 1bar of boost ive been told i can expect betweet 280 and 313 bhp. im thinking of getting a front mount and injectors next

 

Same boat as me! See here for my dyno plot (post # 19):-

https://www.scoobynet.com/general-te...ml#post8748684

 

i hope i get the 300 or im going to have to get a front mount

 

My WRX has slap in when cold,lasts about 5 mins

 

happy slapping is nothing to worry your head about my 97 wrx had it for years