mini spares +0.040 mega piston failure!!!!
Turbo Mini Forums

this thread was started by a chap who had just had his car set up on a rr, and iirc terry had his set up on a rr too?

so the fuelling/ignition should have been ok or in the right ball park at least?

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

"did you know you can toast potato waffles?"

I know lots of other cars (minis) that use the same rolling road as hoggy including me, and no problems with the pistons, but there are all different makes to the above spoken about ones. So like you say Joey, fueling ect shouldn't be an issue.

Best 1/4 mile 13.2 seconds @116 mph
First 5 port miniturbo to make over 200 bhp on a carb?
First 5 port miniturbo to make over 200 bhp on Injection?

http://www.mattwoodsphotography.com

Hi,
Well you can look at this from allsorts of viewpoints, but until there's an official response you'll never know...
Cheers,
Gavin :)

VEMs Authorised Installer / Re-seller. K head kits now available!

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My Mini build diary

well for my bit i sent a set back and they said the same, as the piston had gone after only a few short miles eg about 400 and had nt even been thrashed or even loaded i was still scepical about my reply.

putting it into perspective i used 1380 power max for 3 years running very high cr eg 9.8 at one stage on 10 psi the engine was running near det all the time some times the fueling was way to rich.

did any fail nope,

and the reply i got back when asked if 40 to 50 thou was an exspetical gap for and oil control ring, AE said it was injh tollerance.

so if minspares would like to pay to have the rods removed and the postage i will send them all back.

in the end all other peeps i have spoken to have all said the same, they are CRAP. ok if you are running low boost, i have a feeling that the earlier ones were better made witrh better heat treatment.

i wont be touching them again thats for sure.

allthough i will say GAV, Gary and neil at north have all been great in the past, but my advise is ditch those pistons or at least say for low boost only, as most peeps now adays will want to run 115 to 20 psi.

and stock some decent forged ones.


and keith you also did say in one email that you told AE how to make the piston better and they ignored you.

always looking for them bigger bunches of bannanas

Are so a Set HAVE been sent back! I wonder how many more have been sent back!

Best 1/4 mile 13.2 seconds @116 mph
First 5 port miniturbo to make over 200 bhp on a carb?
First 5 port miniturbo to make over 200 bhp on Injection?

http://www.mattwoodsphotography.com

Powermax were by Hepolite, Hepolite are AE.

Its clear that there is a demand for pistons for a turbo motor, so why dont Minispares produce a piston specific for forced induction, after all if you look at the BL turbo pistons, the first ring land is thicker than the second (apear to be thicker than the Megas at least), with a 12cc dish and a very thick crown.

Maybe the key is the thicker ring land?

Edited by Sprocket on 5th Aug, 2008.

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

"did you know you can toast potato waffles?"

Edited by Turbo Tel on 5th Aug, 2008.

website:- http://www.terryhunt.co.uk

Could someone post or PM me Neil at Minispares e-mail address??

Terry

website:- http://www.terryhunt.co.uk

Hi,
Is there anyway of getting a failed piston independantly examined?
Can someone find the link where "improvements rejected" was said?
Edit: looking at the OP this reminds me of a post I read, think it was efi101? The post was from a RR operator who'd had a failure of a high powered jap motor after he'd set it up. Other operators asked if he'd ran it up under a high load to give slow acceleration of the engine. This should be done as you can get a compounding effect which you wouldn't detect on a normal Dyno pull...
Cheers,
Gavin :)

Edited by Bat on 6th Aug, 2008.

VEMs Authorised Installer / Re-seller. K head kits now available!

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

Visit www.doyouneedabrain.co.uk

My Mini build diary

well after seeing loads of detted pistons in my time from various engines, one thing sprung to mind.

normally when you see a detted piston there is bad melt marks on the side piston crown before the top ring as well as round the top edge.

and most realy dab ones were pretty emlted in this area, and gues what i never in my time have seen a broken land.

well i have but only in the mega bad cases.

which brings me on to my next bit.

2 seperate peeps one of which builds high performance race engines said the same thing about these pistons.

which was the cast material was to hard making it brittle andthe land thickness between sets of rings was to small making the land a big weak area.

well all now that severe over fueling and to advance ign will kill pistons, how ever on my first set they was a very slight sign of det, i do say very slight, which brings me to say that the 2 guys i spoke to were right.

the land area being to weak so on the first signs of det the lands just fail before the piston crown even gets to any were near melting.

and to the above post about powermax pistons yes i know they were made buy AE how ever materials used and design is different from the usual pistons and also heat treatment.

that also shows in the price difference from a 9.5 cr piston at say £50 and a 8.8cr piston at £20

as the 8.8 would be made from inferior material and a lesser time heat treating it, hance the cost difference.

always looking for them bigger bunches of bannanas

good points hoggy but where is the line drawn between poor quality pistons that shit themselves at slight overfuelling and quality pistons that will take some detonation and the associated costs

i certainly will be thinking of using something other than mega on my next build if they are proving to be this fragile

my engine was built by one of the most respected mini engine builders (his engines have won the mini7 championship several years along with the miglia championship and mighty mini champion ship) and the ring land fell out just like the ones in the photos, i've blown pistons before, but never like these. when he saw them he sugested a change of piston.

Ok

I have packed up my pistons 2 from the first time (dunno what happened to the 2 good ones from that set) and all 4 from the second time, interestingly 2 of these have dropped the lands but the other 2 also have cracked lands, though the lands are still attached. Of the second set I only cleaned up one of them looking for signs of detonation so 3 are in the condition they were in when removed.

I'm going to send these off to Neil this week, lets see what they find.

Terry

website:- http://www.terryhunt.co.uk

Detonation breaks things Pre Ignition melts things. Detonation can lead to pre ignition, and pre ignition can lead to detonation. Where you have signs of both, diagnosing which happened first is extremely difficult.

Pistons that failed by detonation do not nescisaraly suffer symptoms of pre ignition.

Pistons can melt due to pre ignition and not break with detonation, pistons can also break due to detonation and not melt with pre ignition, and pistons can both melt and break at the same time because of either pre igntion or detonation

Can I make that any more confusing

I may not know the full ins and outs of the whole process, but I' ve had lengthy discussions with people who run dyno engine testing all day, about this very subject, and they have seen it all. Their trophy cabinet is quite something else :)


Oh, and detonation usualy happens at 14 degrees ATDC

Not a mega piston, but found this last night in a vmax'd spi.
It was an AE21253 +60thou

Edited by eaton_mini on 7th Aug, 2008.

I've still got my omegas that failed in the same way as those pictured in this message thread.... That was the one and only time I didn't drive back from Avon on my own.

Cast omegas, not forged.

Caused by too much boost than I'd ever run before - and didn't have ignition timing optimised for.

The pistons I failed so spectacularly in June were .040 size turbo pistons bought 2 years ago from Min-its.Could these also be from the same suspect source?

'Where does the engine go?'

This is the piston that hadn't failed (yet!)

Attachments:

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'Where does the engine go?'

Steve, Looking at the (outer face of the)top ring itself, it's no wonder that piston failed. was it ever set up?

No Dave,it was timed and fuelled according to data from this site,but not on a RR. what do you see on the top ring outer face?

'Where does the engine go?'

its half melted.

My Pistons were received and have gone to AE for inspection..

website:- http://www.terryhunt.co.uk

bit of a post dig out bey MS have put a disclamer on the website now

Description

Sold as a single piston and although for Turbos is from original Rover casting and tooling to run on 5psi turbo boost. They use our mega ringset C-AJJ3379-40 If using more boost you need to be working on a lower CR with a total cylinder volume of 55cc in piston/block/head gasket and cylinder head. Also when inreasing Boost pressures it is essential to have a modified ignition advance/retard curve to prevent detonation and ensure the Inlet charge temperature does not exceed 40 degrees C by the fittment of a suitable Intercooler. If our advise is not followed it is very likley you will break the ring lands on your new pistons.