Pride/fall
Turbo Mini Forums

Having finally got the midget on the road again,took it to Curborough for an informal sprint day with the TR lot and friends.
Over the day did 20 laps of the top circuit with good times.On lap 21 end of the day,sudden loss of power,smoke screen,death rattle from engine.I assume a piston let go but will see later.The moral of the story is,as you guys keep saying,get it set up on the RR BEFORE using it in anger.Ah well,back to the spanners.

The most scary part was being towed 50 miles home 6 feet behind a Renault GTA doing 60mph.

'Where does the engine go?'

Hi,
Being towed is always a bit scary!
Cheers,
Gavin :)

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Finally got the engine apart.No 2 piston in bits,broken across the oil ring groove.The top is still mostly ok,so I guess it siezed in the top land area,there is a big smear of aluminium at the top of the bore.Consequential damage is big scores in the bore from a naked gudgeon pin,a bent valve and bent pushrod.
The pistons were metro turbo,so cast not forged.Any thoughts on whether this is over heating,or could it be a mechanical piston failure?

'Where does the engine go?'

Could it be too rich mixture causing bore wash, so no lubrication, so then got hot and nipped up?

either way, bad news buddy

Team Racing

I,m running the same engine as you in an A35 and would be interested to know what boost you were using when it let go.Do you have an intercooler ?

mixture was around 12.5 on the AEM.
Yes I have a big cooler (in my picture file),boost is about 16psi.

'Where does the engine go?'

http://www.mlcmotorfactors.co.uk/Trouble%2...istonringTT.pdf

"Turbo's make torque, and torque makes fun"

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Hi,
Thanks for that,unfotunately the rings are in bits in the sump!However I hope to get more info when I take the other pistons out.This cylinder was down on compression before,suggesting stuck rings,but the lack of melting and the piston bosses being in bits made me wonder if it was simply overloaded.

'Where does the engine go?'

what compression are you running ??

Unlucky steve...hard way to learn a lesson m8. :(

Hi Steve,I'm running 8.6:1 according to the formula.Looking again at the (detatched) piston crown,it looks like the lands may have broken first.

'Where does the engine go?'

Some pics of the remains

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'Where does the engine go?'

Oh dear.

This should put anyone off the idea of driving their car in anger before getting it set up properly. If that was a mini engine, the box would be a goner!

Will you be building it up to the same spec, or using this as an excuse to build a powerhouse?

Edited by theoneeyedlizard on 24th Jun, 2008.

In the 13's at last!.. Just

Forged pistons seem like a good idea,and I have a Rover Tomcat turbo to replace the T3 at some stage.Otherwise the build is fairly trick anyway.

'Where does the engine go?'

Heya Steve.

What do the other pistons look like? Might be worth measuring the ring grooves, could be that the edges of the crown have bent down and trapped the rings, hence the blowby.

Once the blowby started, I guess the hot gas getting past heated the crown and lands up and expanded them enough to grab hold of the bore :o(

Do you have boost cut on your ECU? Possibility of spiking much higher than 17psi if not, especially using a bleed valve.

Catch you soon, would love to look at that piston crown in person.

--
Olly

Hi Olly,
Finally got the other pistons out:All look fine,no sign of detonation erosion on the crowns,no scuffing on the lands/skirts,no sign of excessive blowby.....BUT the second land of no.4 has 2 vertical cracks in it,either side of a boss.No sign of ring stick,but a second failure on the way.Is this caused by det in this area,or was the Pmax just too much for the cast pistons?

'Where does the engine go?'

Hi,
There seemed to be a consensus with the Mega pistons that land failures were caused by det. The crowns on these also looked fine to.
I think it's due to the shock wave caused by det, before you get to the higher temps that start melting crowns.
Cheers,
Gavin :)

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WB/EGT gauges. Click here for customers write-up

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My Mini build diary