lewisdj

Hi there i have recently purchased a 2004 sti with a TSL remap to 333 bhp. It has covered 52k with FSSH.

When i cold start the car, i can hear a slight knock when i very gently rev the engine, at around 1500rpm to 1800 rpm

It doesnt knock at any other rpm and as soon as it warm its sweet as a nutt..

I have read through these forums and aparantly a tiny bit of piston slap is perfectly normal on these engines.

It has Silkoline ProS 10w/50 high performance Ester Synthetic oil and was last serviced at 47500 miles last november.

Im due to give it a service, would you recommend using this grade of oil again? Or stick to a quality 10w-40 oil?

I have read that higher performance engines are best suited to 10w-50 oil?

Hopefully a service will get rid of this slight knock at cold start... im very paranoid

Any help appreciated

Billet

iTrader: (60)

i'm using silkolene pro s 5w-40. Better cold protection than 10w-50 and you don't need a 10w-50 until your car is modified quite a bit and you see higher temps, imho of course.

lewisdj

Can you enlighten me as to why there is a slight knock at 1500 rpm to 1800rpm?

Power is estimated at around 350 bhp as it has has TSL unequal length Tubular Exhaust Headers fitted, with an aditional remap to suit.

Which oil would i be recommended to use? I dont drive the car hard

JohnD

iTrader: (5)

That's the classic symptom of piston slap.
As the weather gets colder it may become more noticable on cold starts. As long as it's pretty mild and goes away as the engine reaches working temp. then don't worry. My 03 STi with 41k is similar so I let the engine run for a couple of minutes with no load before driving.
The grade of oil has little effect on piston slap so don't expect a magical cure. Just drive it gently until the temp. gauge is at normal but don't give it a bootful until the oil has reached a decent temp. (70-80degC if you've a gauge)
As winters coming I'd recommend the 10/40 over 10/50. Save the 10/50 for the summer months.

JohnD

PS Lots of cars have some piston slap when cold. It's been a feature of the internal combustion engine since it was invented!

lewisdj

Thanks for info johnD, can piston slap be prevented and cured any way? And why does it happen in the first place if the car has been well looked after?

Yes i have a guage and always let the oil temp reach operating temperature.

Pramas

metal expands and when cold the pistons can rattle slighty, once up to heat they fit proper, thats kinda the laymans term but as far as iam aware is correct

lewisdj

So it's nothing to worry about and is perfectly normal for it to happen a tiny bit when the engine is clap cold?

JohnD

iTrader: (5)

It takes only the slightest increase in clearance between componants to produce a noticable increase in mechanical noise.
Because of the differing rates of expansion of different materials, certain amounts of clearance must be allowed for. It's not unusual for an engine to become a bit noisier a minute or so after a cold start before quietening down again.
Obviously, a small amount of wear is enevitable and engines become a bit noisier at the stage where everything is at maximum clearance - usually following a cold start or just after.
It would do you good to listen to a re-built, race spec. engine with forged pistons and wider valve clearances at cold start!

JohnD

alcazar

iTrader: (2)

As above, mine rattles cold, fully forged, 400/400 on a 2.5.

lewisdj

Thanks for the reassuring information guys

poolio74

mine slaps mate.low mileage,great service history.just let it warm up and dont worry bout it.if it drives well and doesnt use much oil forget about it