turbo.jon

Ive got a std set of mahle pistons dont no if its a good idea but i no u can get them skimmed to lower comp has anyone done this before and how much was taken off and what comp ratio does this make them???

I no this aint best way to do it

cheers
jon

MadMac

I heard you shouldn't do it as it weakens them.... I think

james_birch

loads of people have done it! you can either go for .5mil or a complete 1mm off them! havent heard any bad stories yet!

turbo.jon

Thats what i thought too prob wont do it just want to no if anyone has done it really an if had any probs...

Rallyesport

You can skim new pistons, but old pistons are not up for skimming. Why do you need to lower the compression? What kind of boost are you planning?

sf

ye u can skim them, mine are mahle low comp ones, but the compression wasnt low enough so we took of a wee wee bit more

GrimmeRS2K

Cant u buy those thicker headgaskets now?. thought i saw them in fast ford

fernando_khan

i was looking at pistons for a 2.1 zvh conversion...i heard with normal mahle mistons its 8.2.1 i fink however machined a little its 7.5.1 ....i may be wrong..

i would like to run around 20 psi so what would be the best compression ratio and what pistons??? i heard accrallite are the top ones to buy..but is there a use lashing out that much money??

at the end of the day 20 psi would be quite alot and reliabilty will be dependant on the mapping more than anything but what other mods would you carry out on the engine for further reliablity?

many thanks

james_birch

you can run 20psi on std comp with a good intercooler! and maybe just to be really safe water injection! im hopeing to be runnning 18-20psi on std pistons and rods come friday!

220TC

I ran 26psi on standard comp, standard rods & pistons and never had any problems......although I do have a very efficient intercooler & loads of fuel !

I now run 15psi as I want the engine to last as long as possible

cheers, Duncan

james_birch

11psi drop! how much power ya loose for that?!

220TC

not sure yet mate, it still feels quick though ! I used to crave for more power all the time and I think I got a bit carried away All I want now is a reliable car that I can enjoy rather than fix every 5 miutes !!

JesseT

I also tried my Orion with 30psi and standard S1 bottom end. Seemed to be just fine with LOADS of power. I now have it at 22psi for daily use to get to work and back.

sf

try calibra turbo pistons

james_birch

i notice your from finland! what is the ambiant temp there?!

Moonie

Just rebuilt my engine, got a new set of mahle pistons and had 1mm machined off the top. Will soon be runnin 20+ psi

JamboRS

you runnin it on jet fuel m8

turbo.jon

[quote="james_birch"]you can run 20psi on std comp with a good intercooler! and maybe just to be really safe water injection! im hopeing to be runnning 18-20psi on std pistons and rods come friday!

Sod it keep them std then i think was only going to run about 15psi to start with but i no i will get bored an turn it up
got a big intercooler GRS so should be up to it

JesseT

Ambient has been around +5C for the whole January.
The car handles high boost well as it's live mapped properly by me

turbo.jon

Lot a good my post about this was as just been down to see about my engine an have been told need a rebore so std pistons no good now need to be about 1mm overbore better get me wallet out

GrimmeRS2K

alan told u that u need a 1mm overbore aswell!, same as daves and mine then, 1mm pistons are hard to get hold of if u want low comp, mahle said they dont do 1mm anymore, got mine from P.T.S mate, 01582 731733

Get ya money out!!.

JesseT

I've never rebored anything as good standard size blocks (doesn't need to be turbo, any NA 1.6 CVH) are widely available for very little money.

Rallyesport

High boost on standard compression is no problem as long as the ignition is spot on and the fueling is good. Lowering the compression will make the engine even more dead at low revs.