Oversized pistons Mitsi made!?

[MarkSanne]

My buddy Mark (dutchdriver) has got himself a spare VR4 engine too, and like the spare engine that I bought earlier this year from Stefan (crazydriver) it has some cylinderwall scratch-damage. First I was en-route of special, aftermarket pistons, but... Mark found out that Mitsubishi offers 2 pistons off-the shelf that are "oversized":

MD344090
and
MD344091

Now in the description it states
PISTON & PIN ASSY O/SIZE 0.50
PISTON & PIN ASSY O/SIZE 1.00

What is exactly meant by 0.50 / 1.00? Is it half a mm / 1 mm larger? And what would that mean/result in total volume/cc?
Because from what I see online these pistons cost next-to-nothing!

[Louis]

Yes, the diameter will be 0.5mm bigger (so 0.5mm wider), so you can have them rebored out by .5mm.
If damage is badly scored then 1mm, but you can't do anything to save a scored bore that has already beed bored out to full 1mm oversize.

[Adam.Findlay]

yep incase your engine has failed a ring land or cracked a piston due to detonation or something similar which has left the bore washed out out scored in some way you can get the block +0.5mm or +1mm overbored and used oversize pistions in the rebuild.

say std bore is 81mm (from memory i think) and 80.8 stroke so some maths
std cylinder volume (ignoring clearance volume in the combustion chamber)
((Pi*81^2)/4)*80.8 = 416362.2mm^3

416362.2*6 = 2498173mm^3 or 2498cc

1mm overbore
((Pi*82^2)/4)*80.8 = 426706.2mm^3
426706.2*6 = 2560237mm^3 or 2560cc

big job just to gain 62cc and no extra strength in the piston at all

[MarkSanne]

Thanks! Oh and... does anyone know if the headgasket will still fit? I didn't find other partnrs in ASA besides the regular headgasket number.

[Adam.Findlay]

yes stock headgaskets will be fine

[dutch driver]

a cool to read this.
i'm also looking for aftermarket pistons.
so it will come to 2,7L

if i understand it correctly the size will be 84mm then?
but the problem is that i cant find them.

does anybody knows where i can find them.

and i contact a mitsu dealer in the UK for the oversize pistons(genuine) because here in holland they are not for sale at mitsubishi.
But f*ck why is it also so hard to give just a price, its everywhere the same with the mitsu dealers.
i just whant to know the price and shipping to holland.

[Louis]

No, it will come to 2560cc with the 1mm oversize pistons, so you only gain 62cc (as stated above), not worth it for 62cc.

[dutch driver]

i just recieved the final email from the UK for the pistons.
the problem is/was that we use a asa from 2008.
in the asa (updated) they use the pistons are out of the list.

this is the quote from him:
Mark,

Have checked with Mitsubishi and we definately only have the option of ordering the three standard pistons.

Your version of ASA is dated 2008 so it is likely that the oversized pistons are no longer available and the reason why they don't appear on our version.

Regards

Paul

so it needs to be aftermarket pistons for me/us.

[dutch driver]

does any know how much the compression is in de vr4?
maybe these will work?
http://www.ebay.com.au/itm/CP-Piston...item2ebb250d66

[Gly]

8.5 comp

[NLduffyNL]

Edit

[Adam.Findlay]

if you want 2.7l there is a hyuandi variant of the 6a13tt. which is 2.7l i think. will require a big overbore and pistons from that engine

[dutch driver]

does somebody knows what the size is of the pin that goes in the piston and the rod?

[dutch driver]

I would like to know the stroke and rod length in the vr4's

can somebody tell me that?

[Adam.Findlay]

rod length is 138.5mm centre to centre. 19mm pin and ig memory serves 54mm big end

[Adam.Findlay]

does any know how much the compression is in de vr4?
maybe these will work?
http://www.ebay.com.au/itm/CP-Piston...item2ebb250d66

NO if you read the posts above. 6A13TT's have a 81x80.8 bore and stroke respectivly so unless you want to bore your cylinders out 6mm. which will be a bloody big job and just because a piston's bore may fit doesnt mean the piston will, there is pin offset, pin size, deck height, valve relif size blah blah. all well and good putting a larger diameter piston in but if its just going to hit your valves the first time you turn it over theres not much point.

if you did manage to fit 87mm pistons in a 6a13tt with a 80.8mm stroke it would have displacement of 2882cc
so almost 2.9 litres
however i dont think the stock cylinders would have enough meat in them to safely bore out that much.
would need to resleve the block. there is a video on youtube somewhere of one of the russian members who did it bored and resleeved out to 3l but i cant for the life of me find the video

[Adam.Findlay]

found it
watch this and related videos
http://www.youtube.com/watch?v=xNdb3gsczVk&feature=plcp