Turbo'ing a willy engine!

[tutuur]

Hi guys,
I already have a full forged engine to go in my 5 but i want to do a bit of a budget build so i can enjoy turbo power in the 9 for the time being.

I already sourced myself an meggie engine and torn it apart.
Turbo, manifold, DV, injectors, chargecooler, fuelpump etc. Has already been bought.

I'm picking up new bearings and piston rings next week.
As for lowering the compression i used some formula's to know how much material should be machined of the pistons to give a CR9:1

As a willy piston is dished i want to keep it that way, my plan was to machine 1.25mm of the edge and then deepen the dish by 1.4mm.
As for my calculations that would be 7.2cc which provides the CR to drop to 9:1.

Now for the guru's: the thickness of the piston bottom is 7mm, what's the least i want the thickness to be?
I also considered machining the dish 1mm which would see a CR9,4:1.
I think this would be fair low enough for 8-10psi max considering VAG 20v's have 9,5:1 and can produce 280hp max on standard internals...

Thanks in advance for the advice!

[Coops]

can run 9psi on stock internals, i did, returned 217bhp@9psi on stock compression. just a spesso 1.6mm gasket, that was it

for reliability i would maybe skim 1mm off the lot, gives a bit of comp drop so wiggle room on the boost and also shouldn't weaken piston too much

[tutuur]

Maybe sideways Danny could shine a light?

[Coops]

if you want to go that route, my point is its not needed for such low boost ;-)

[tutuur]

I get the point but since the engine is already apart it would be very low effort to machine them maybe allowing me to run a bit more boost when i get bored and have a shitload of gearboxes in the shed :P

[tutuur]

i decided to skim 1,25 off the edge and 1mm off the dish.
would see 9,4:1 but maybe with skimming the bottom end and skimming the head would see around 9,5:1. (considering 0,1mm skimmed from both.)

going to run 7psi so won't be a problem and stay reliable :)

[-jo-]

smartass...

[tutuur]

Just noticed a mistake, would be 9,3:1 including skimming.
Going to machine them next week :)