Opinions needed on this piston damage
Turbo Mini Forums

I'm stripping down my engine for a rebuild and I have found what I believe to be detonation damage to number 4 piston. The strange thing is (or maybe it isn't strange?) that it is only this piston with any damage other than a few scuff marks. The damage is on the side that faces towards number 3 cylinder. Is there any reason for this to happen in this way? It is a standard turbo engine, apart from megajolt.

I'm guessing this piston is now only of use as a paper weight?

Paperweight indeed.

very scrap mate.

Yes i moved to the darkside

Instagram @jdm_brett

do you have a cooling pipe connected to that end of the head?

if not i think thats definatly worth adding.

So that is the intake side of the piston. Is that the norm? i would have thought the exaust side is more prone, no?

Thanks for the replies.

No cooling connected at that side of the head but the heater take off is open on the replacement head I'm fitting. I did wonder if it was down to the higher temperature at that side of the engine but I couldn't understand why it didn't make a mark on number 3 as well?

Well your both thinking in a logical manner :)

I would assume that the exhaust side would go first too, but the intake side has less cooling as there is no water jacket, but then as said you would expect no 3 to me marked too... can no 3 really be running that much cooler?

fucked if I know! lol

assuming this is on a metty i'd ditch the sandwich plate under the thermostat and re rout the pipe to no 4 end of the head.

what boost, compression and intercooler are you running?

HHMMM, so water flow is staying to the outside of the casting with an eddy hotspot! and no, or perhaps, not jst yet , signs on 3?

Boost is standard 4psi modulated to 7psi, standard compression and no intercooler.

I was planning to plumb in the heater take off on the new head regardless, but this has made it a priority.

Not a mark on no 3, which is surprising considering the damage to no 4.

Edited by metroturbo on 1st Jun, 2010.

Could it be a combination of high temp and outer cylinders running more lean than inner cylinders?

Dazed and Confused....

Mate.

Mine's gone in exactly the same place, No 4 piston inlet valve side, facing No 3 cylinder.

More cooling flow required at No 4.

Strippin mine down starting next week.

Richard.

Minivanless, but reluctantly happy living with the decision. There'll be another one day.
http://www.youtube.com/profile?user=minimadmotorman#p/u

Yes I've had exactly the same problem in the past. Pots one two & three were unmarked, no4 was like yours. My answer was to block the waterways in the head & run a dry deck type system. The water temp is far more consistent now as well.

Edited by Turbo Phil on 1st Jun, 2010.

WWW.TURBO-MINI.COM

Aside from obvious melting...thats some very weird colouration ??

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

phil, do you run true dry deck or do you only block the water ways in the block, and where on earth did you get that big grub screw?, M14 i think mine ended up in the block i had to make my own

Yes i moved to the darkside

Instagram @jdm_brett

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I would say its lean. The colour and texture look similar to my nitrous lean burn piston

I use 1/4" bsp or NPT plugs like the one Phil shows. no real need to drill the hole bigger, just run the tap down the hole

Edited by Brett on 2nd Jun, 2010.

Yes i moved to the darkside

Instagram @jdm_brett

yes.

http://www.airlink-compressors.co.uk/Fitti...UG%20M%20METRIC

Edited by apbellamy on 2nd Jun, 2010.

Thanks for all the comments. At least I know it isn't something out of the ordinary.

Yes i moved to the darkside

Instagram @jdm_brett

Don't order from the site, default postage is courier at about £8. Ring them up. They where very helpful when I messed my order up

in my opionion its CLEARLY detonation caused by fueling too! LEAN and ignition advance been too great with the megajolt i suspect well above 28 deg on max advance

this needs to be looked at pronto! after your next build, or you will suffer the same fate.

no amount of cooling in areas you think may be giving you the trouble will rectifie this

an intercooler will help big time,
i also would look at you static compression as well for the future if you want to run more boost

hope this helps

Granted the mixture, ignition or both are incorrect, but the fact that there's no damage to the other pistons seems to say that no.4 running hotter has lead to detonation on that cylinder.
IMO it's still worth doing some mods to the cooling around that end of the block.

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