Piston Issue
Turbo Mini Forums

A quick bit of background, towards the end of last year I had an issue with my drivers wheel almost falling off, after sorting the problem I took the car out for a test drive to check the tracking etc.

Fuel was low so nipped into Tesco, no 99 available so put some 95 in (could this be the start of my issues)

Car drove fine so went for a bit of boost, quick squirt all was well, big squirt and it all went horribly wrong, car full of smoke, smoke pouring from the bonnet and exhaust, smoke is of course oil.

Crawled home sounding like it was on 3 cylinders with a smoke trail the red arrows would be proud of. A quick pull of the HT leads one at a time and cylinder no 2 didnt appear to be doing very much.

A usual life got in the way a bit and only today have I managed to pop the head of and have a peak inside. At this point its dark and chucking it down but at first glance it looks like piston no.2 as 'shrunk' in the 2 o'clock region. Maybe I'm talking out of my arse but thats what is looks like, I'll try and get some better photos in the morning with daylight and a decent camera.

http://turbominis.co.uk/forums/index.php?p=vt&tid=170151

That's detonation, it's melted the edge of the piston.

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As above ^^^^ engine out time.

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1/4mile in 13.2sec @ 111 terminal on 15psi

oh, and it is funny how it's #2 and on the exhaust side nearest the front of the engine, same as that one I made^^

Edited by Sprocket on 6th Apr, 2012.

Could it be a bad batch of fuel that started?

Audi s4 b5 - 470bhp & 486ft lbs

On 30th Apr, 2012 Brett said:
yeah stick the bit in and give it a wobble

i blame myself for putting 95 in

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Yes, or overly advanced ignition, lean mixture, high charge temps, to high a compression ratio, to much boost or a mixture.

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95 ron would have just took it to the limit and over on detonation. As the advice above. .

What boost was you running and do you run a intercooler.

What pistons were these? Dan

ummmmmm simon as they say i think they are fooooooooooooooooked acrilites coming up i feel lol

always looking for them bigger bunches of bannanas

Would have been around 16psi, big ass intercooler and a 7.9 cr as calculated by Benross.

Pistons were 'ahem' Morspeed supplied, 11cc resized to 13cc.

Not sure I can stretch to acrilites :(

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The type of piston isn't the issue here. Detonation will destroy any piston. What's your max ignition advance ? Do you have a wideband ?
At 7.9-1 you should be more than safe on 16psi. Though the 95 ron fuel could be the issue here.

Edited by Turbo Phil on 6th Apr, 2012.

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Just out of interest. How far down the bores do the pistons sit?

Sorry to hear you bad luck :(

I've used more boost on a higher CR with the same fuel. I'm using pretty conservative ingnition timing though.

As above. What's your ign advance?

In the 13's at last!.. Just

You say towards the end of last year so charge temps should be pretty low, were the afr's ok, I would say the fuel played a big part in it.

Audi s4 b5 - 470bhp & 486ft lbs

On 30th Apr, 2012 Brett said:
yeah stick the bit in and give it a wobble

Yes I have a UEGO but couldn't tell you what it was reading when it went bang. It had been running a little leaner than I would like prior to that though and was top of my list to richen it up a bit on the next visit to the rollers (which was the day the wheel fell off on the way to the rollers!)

I'll have to double check my MJ map in the morning for timing figures.

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Combination of fueling and poor quality fuel imo, I religiously ran v-power in mine for this exact reason.

Audi s4 b5 - 470bhp & 486ft lbs

On 30th Apr, 2012 Brett said:
yeah stick the bit in and give it a wobble

just found a copy of my map on the latop actually. 95% sure this is whats currently saved on the MJ but will double check tomorrow.

Edited by Simon on 6th Apr, 2012.

http://turbominis.co.uk/forums/index.php?p=vt&tid=170151

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get a set of cast omegas slapped in there, the amount of abuse and miss use mine have taken, im honestly gob smacked it still ok




....touch wood..

Yes i moved to the darkside

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that map on that cr should just about survive , have you put a timing light on it to see if its really the right numbers ? what turbo ?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Pull the piston out to try to identify what they are, someone might have one lying round on the shelf. Though the others might have sustained damage too.

Isn't 180kpa around 11-12psi?

I'd change the buckets in your map to cater for more boost.

At the moment, if you stick any more than 11-12psi through it, you'd still be running 25deg adv. Even at 20+ psi.

In the 13's at last!.. Just

think i found the problem with piston no.2

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I'd happily re-use that!