Static engine CR..

[VEEDUBBED 0]

Right then,

Lets take a normal Vw 2.0 9A 16v engine that has a factory CR of 10/1.

If you take off 2mm from the piston crowns and lower the con-rod gungeon pin by another 2mm,making 4mm total what's the CR your left with??

[Chris VR6nos 0]

Pi*r2*h-clearence volume/swept volume is what you need, i'll tell you if you get the dimentions needed to work it out.

 

 

 

Chris

[Crasher 3]

2-mm off the piston crown would significantly weaken the piston leading to a risk of the crown cracking under the slightest detonation and the overall 4-mm drop in compression height would destroy the close collision squish (optimum being around 1-mm) so making a theoretical 8.0:1 compression even more prone to detonation than the original 10.5:1.

[VEEDUBBED 0]

I never had any problems with my old golf 2 16v 1800cc turbo with those mods and i had the boost pressure running at 1.7Bar using 8 injectors,big intercooler,Weber/IAW injection.

The car was a bullit,slautering modified cosworths etc.

The only problem i had after two years of high speed motorway work was that the ring lands started to look worn so i just changed the pistons for another set(same mods as before),original con-rods,crank oh and i fuced two gearboxs and a few wheel bearings...

[Crasher 3]

You kept det under control by dumping fuel in then? Whenever I built KR turbo’s in the past I used the Audi 5 cylinder 20v Turbo pistons as used in the RS2. These have the VW number 034 107 065 M but are cheaper from Mahle (034 92 00) or KS (90 037 600) and give a 9:1 compression with the correct squish. Unfortunately there isn’t a 9A suitable piston that I know of, off the shelf that is.

[VEEDUBBED 0]

Yeah,that was the only feasable way and being conservative with the ignition advance under boost.

Back in the day i could never seem to locate a decent set set of Audi 20v turbo pistons,there was no eBay and very little internet pages(~'96 onwards).

I think i'll just buy a set of forged slugs and have done,only problem is that my corrados only got 34000miles on the clock from new and the pistons are perfect as are the bores.

[Crasher 3]

I would use the S2 pistons, forged ones rattle and burn oil or at least my JE's do.

[VEEDUBBED 0]

I can't use the Audi pistons in the 9A's engine block because the audi pistons are 81mm in diam. were as the 9A's are 82.5mm so i'm bloodywell stuck.

Interesting you mention the noise and oil burning issue regarding the JE forged pistons,you're not the only person i've heard saying the same thing.

How about Mahle??,don't they make forged custom jobbies??.