Ruf 3.4 P&C piston slap

IMR-Merlin · 11-14-2015, 08:25 AM

Hi all,

I have a built engine with Ruf 3.4 P&C installed. I have a rap that is throttle (engine load) based. It comes on at light throttle and can be held through out the rev range until I add power or reduce power. I am leaning toward piston slap and have heard that some or the Ruf 3.4 pistons were short skirt and prone to this. Anyone on this forum have any input?

Thanks in advance

Brendon

Steve@Rennsport · 11-14-2015, 09:34 AM

Indeed, the Ruf 98mm pistons had a shorter skirt than the regular Mahle ones and they do make noise; Due to piston rocking and higher ring wear, we don't due these in any engines.

Short skirt pistons can be used in street engines, however VERY careful design is required to prevent these kinds of problems.

IMR-Merlin · 11-14-2015, 09:57 AM

I guess the next question is....

Rebuild or run it?

I have about 4k on it since tuning and the noise has not gotten worse.

IMR-Merlin · 11-14-2015, 03:31 PM

That was a serious question. We first heard this on initial start up and pre-tuning. It is only there under light (maintenance) throttle and goes away toward WOT and decel.

So is the noise something that is lived with or is it safe to do a rebuild and change out P&C?

cgarr · cgarr's Garage

Is it only when cold? does it go away as it warms up?

IMR-Merlin · 11-14-2015, 04:25 PM

Quote:

Originally Posted by cgarr

Is it only when cold? does it go away as it warms up?

all the way through temp range, but I never get engine temps above 140-160 unless in traffic.

If these are the 3.4 short skirts, they're known for this. Just not sure if its a livable sound or I should pull the engine and mic the bore then look for pistons.

the car pulls like a monster and I have a GT35R with billet wheel for next year so i should be 500+ RWHP.