26 replies to this topic

[the clarkster]

Has anyone seen how much damage there is on my powermax pistons on my 1380

the engine is just over 1 year old fully built by morspeed and done under 7000 miles.

is this normal.???

its amazing it hasn't caused any damage to the bore walls on the engine at all.

martin

Edited by the clarkster, 06 September 2009 - 05:55 PM.

[shorty]

i wouldnt of thought that is normal, atleast not on an engine that old

[m1tch]

Time to call morspeed?

[mars red mike]

Time to call morspeed?

LOL!!!!. Good one

[Cooperman]

That's not normal and there was clearly a problem with engine settings and/or detonation. The last time I saw pistons like that was on a Turbo mini where the comp ratio had not been properly calculated and had 10.4:1 static with 7 lbs boost.

Some thoughts:
What was the compression ratio?
What distributor were you using and was its advance curve set to match the engine spec?
Was it running too lean?

The engine builder should have supplied you with a detailed spec sheet which should have included the comp ratio calcs and the distributor type and static setting.

I've just been sorting out a 1380 engine which was built by someone else. It has a standard 12G940 head, but no allowance had been made for the fact that the swept volume was increased and the resultant C.R. was over 11:1. In addition, the bores were 0.004" oversize and the engine was not offset bored, which has resulted in a scrap block due to scoring of two of the cylinders and the inability to re-hone due to the oversize, which was part of the cause of the problems.
That's why I like to stick to a maximum of 1330 cc as it gives options in the event of a problem.

[bmcecosse]

Is that two different pistons ? Very similar damage - looks likely to be pinking/detonation damage - you may have been running too much ignition advance and/or poor fuel quality. Did you always use top grade petrol ?? Yet the crowns look to be undamaged - which makes me wonder.
Other possibility is that they have somehow gripped the pistons there while fitting the gudgeon pins - and have cracked them. Just amazed how similar the damage looks on both pistons - are the other two un-marked ?

Edited by bmcecosse, 06 September 2009 - 06:27 PM.

[Sprocket]

There is no such thing as poor fuel quality these days, its 95, 97 or 99 octane.

This engine has clearly detonated and I would be looking at the compresion ratio against the fuel octane used, as well as the ignition curve.

This is a running or set up fault, not a material or supplier fault.

Harsh, but thats how it is

There have been many sets of the Mega pistons on Turbo minis that looked like this, and it was not because of a high compression ratio and boost

[bmcecosse]

Aye - but the crowns aren't damaged -which is where the first signs of detonation usually show up! By 'poor' fuel quality - I was referring to the 95 stuff! Any performance engine needs the best fuel.

[the clarkster]

Hi no its just the 1 piston. the piston nearest the radiator, 2 be honest i dont know what the compression ratio is, the dizzy iam using is a aldon yellow suited for my engine with aldon ignitor, i didnt have a spec sheet for the engine, didnt even have a reciept for the engine for ages, then i had to phone him up and tell him the spec of the engine, All in all useless.

I brought the engine jan last year so do i still have a case?????. we've had sooooo many problems with morspeed and he never answers the bloody phone, or emails or voicemails.

Edited by the clarkster, 06 September 2009 - 06:34 PM.

[Sprocket]

Bought, not BROUGHT!!

[the clarkster]

Also the engine was fully rolling roaded by southham mini metro people so all the timing etc and carb was all set by them.

[Sprocket]

Aye - but the crowns aren't damaged -which is where the first signs of detonation usually show up! By 'poor' fuel quality - I was referring to the 95 stuff! Any performance engine needs the best fuel.

No, detonation will break the ring lands without any sign of damage on the crown.

Detonation brought on by pre ignition on the other hand will cause damage to the piston crown, as the combustion temperatures are much higher such that things start to melt, which then causes detonation wich is the high pressure shockwave.

Det breaks things pre ignition melts things and pre igntion leads to detonation, the evidence is very different.

Edit* 95 octane fuel is not poor quality, but yes you are correct that a performance engine needs a higher octane, but you can build a high performance engine using 95 octane fuel, the requirements of ignition and compression are very different however.

[Sprocket]

Also the engine was fully rolling roaded by southham mini metro people so all the timing etc and carb was all set by them.

maybe so, but the engine still detonated. It can be down to several factors which you cannot tell us. Namely the compression ratio, the fuel grade used and the total ignition advance

[welshdan]

this happened to several of my brothers pistons in his 1380 engine. once the damage pistons were replaced, they would break like this again. he runs high octane fuel, though the cr is high.

the pistons were powermax. it makes me wonder about the quality of the pistons/material used.

between each engine rebuild the car was properly set up on a rolling road.

he has since ditched the powermax (think he went through 3 pistons in total with numerous rebuilds)

now runs aus minisport pistons, they have been spot on. i will be using a set in my 1360 mpi.

[the clarkster]

So do people think ive got a case, for gettin in touch with morspeed or contracting powermax,

Im going to change all 4 piston to Cast Omega Pistons people think they are going to be ok.?