Strange piston development...
Turbo Mini Forums

Hi all, first post and all. Someone gave me a link to here from www.miniresource.com forums.

Bought a turbo short engine the other day, got it on tuesday, but only just got the chance to look it over this evening. Came from a turbo engine that apparently blew its turbo and was susequently split.

After inspection i discovered that 2 of the pistons have a strage mottle effect on the top, where the other 2 are smooth with a machined like finish? any ideas what would have caused it? never seen or heard anything like it before and i cant find anything on the web about it.

i have posted pics here: http://www.miniresource.com/forums/index.php?showtopic=1815 on this topic. they are on the 3rd,4th and 5th post.

Any thoughts or comments would be much appricated.

thanks,
Andy

I've seen the future and tbh its Pie

I think that looks as though it might be a bit of 'pinking' there, I have seen this sort of thing before when I used to be into 5 turbos. I know it can actually cause the pitting your seeing on them 2 pistons, bit strange how it is only on 2 of the pistons.

Not sure about minis but 5's used to run a bit lean on the outside chambers due to the manifold design, making them a bit hotter in these chambers, making it even more prone to 'pinking'

I should imagine some of the other people on here may have a better idea, quite interesting though!!

Edited by dan on 2nd Dec, 2003.

That "det" or detonation....

too much boost, or too much advance, or too lean.


alex

AlexF

Plus high compression can add to the problem...

your compression ratio is set so its just somthing you have deal with...

you need to run the engine in a condition where the CR is taken into account... a high CR means low boost.

The A-series also runs lean on the outer cylinders due to design not only of the inlet maniflow, but also the head, the firing order and cam design!!

Its usually these cylinders that suffer 1st. There are of course lots of reasons it might not be these two cylinders, but I can't tell from the pics which cylinders are effected...

alex

AlexF

counting from the water pump end, its the pistons in cylinder 1 and 2 that seem to be the problem. After responses on here and elsewhere, i think i've made my mind up in saying that its probably going to be a problem with mixture being to lean feeding the two cylinders. Maybe they didnt tighten up the manifold properly on that side which caused a leak.

Cheers for the responses lads.

I've seen the future and tbh its Pie

Well, truth is, that looks pretty knacked, and will likely smoke, and/or not last very long. If you have a genuine 'turbo' crank in there, it might not be a total loss, but that does not look good - at all...

D

i think its +20 new pistons and some crank work for this baby...

cant decide wether to go turbo or not tho....hummm

I've seen the future and tbh its Pie

turob turbo turbo!


alex

AlexF

humm im torn.... i like the idea of a crossflow head... but can decide wether to turbo or not.... have have heard that some1 tried it and had problems with the 8port? maybe i should go standard... cant decide

Edited by andeh on 8th Dec, 2003.

I've seen the future and tbh its Pie