Piston failure
Turbo Mini Forums

I had a piston fail today it has broken the top two rings and the ring lands only 1800 miles since a rebore.
Was it my fault damaging a ring on assembly or runing to much boost 9psi with 9.4-1 comp?.
Or was it a poor piston?it was a +40 from minispares.
Allan

http://www.rabdunn.co.uk/

who knows!!
too much boost melts things , not snap rings, poor pistons could snap rings , don`t know how you would prove it .......
leaving you with

Everyone knows that instructions only have to be read if the thing doesn't work....

Thats what I thought about boost,I am not fussy about blaming anyone just dont want the same to happen again.

Edited by AllanMcD on 29th Jan, 2005.

http://www.rabdunn.co.uk/

which +040 piston?
If one of the 'mega' pistons, it isn't a poor piston at all...

Yes they are mega pistons.

http://www.rabdunn.co.uk/

Allan you running an intercooler ?? because it sounds like a classic case of detonation to me...
and 9.4:1 on 9 psi will cause things to rattle under load.
Knock Knock.

:)
Karl.

Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe.

No intercooler but there isn't any sighns of detination on the crown of the pistons.
I am up early 6am (shit I must be mad) going to bingley hall to see if I can get some parts

http://www.rabdunn.co.uk/

Detonation kills pistons easily. First the top ring gets tight in the groove, then the hammering is concentrated to the ring land and voila. Old powermax pistons were famous for looking great but came out in pieces, usually the ringland was loose between the rings.

Sounds like Det to me too...

light det always kills the ring lands.

aLex

AlexF

I didnt know that.
I expected to find signs of detination on the piston crown if that was the problem and I have never heard it pink.
I am learning all the time it sometimes costs lots of money somtimes just time.
I do have an intercooler but need pipe work , and a bit of space in a mini van is hard to find but I will do it.
Thanks

Edited by AllanMcD on 30th Jan, 2005.

http://www.rabdunn.co.uk/

what boost, ign advance and fueling where u running?

You also can't here damaging det... pinking is just a very very mild from and the shock waves from it are very different, hence you can hear them. Det is far worse and all but silent.

Alex

AlexF

9 psi
Standard metro turbo ignition timing and advance cant remember of the top of my head but I checked it with strobe lamp using the haynes manual.
Fueling may have been a bit lean mid range when the motor had only around 400 miles on it, it started smoking fairly sudenly at tickover around then.(was only checking plugs for fueling)
Got a needle from Avonbar which is a bit rich since then (now have a fuell meter and lambda)

Edited by AllanMcD on 31st Jan, 2005.

http://www.rabdunn.co.uk/

Got a new piston today also new valve guides the inlet valves were all wet with oil I thought I had turbo problems before so I got a good used turbo which I put new seals and bearings in just to be sure it was ok, but it still smoked at tickover.
With a bit of luck I will have a clean burrning turbo motor running by Thusday pm.

http://www.rabdunn.co.uk/

You need to get it setup...

an off the shelf needle and lean in the mid range is no good at all!

Your lucky it only broke a ring land and not melted the whole piston and wrecked the entire engine!!

Good news you got a lambda meter now

alex

AlexF