compression and boost

The Reeves Mk2 uses 'machined' S2 pistons with late spec 16v connecting rods and ARP rod bolts, albeit it in a 1.8T engine but the S2/RS2/1.8T/KR's all share the same bore and stroke of 81.00mm x 86.40mm.

RS2 - 2226cc, 9.0:1
S2 - 2226cc, 9.3:1
1.8T - 1781cc, 9.5:1/9:1

Golf 16v (KR) - 1781cc, 10:1

If that is of any use?

 

Certainly very useful and interesting. So by obtaining either RS2 or S2 pistons, you can gain either 9.0 or 9.3:1, and they'll go straight into the KR.

Still wonder if there are any 'cons' of making a 'cheap' 16V unit suitable for mild boost by putting RS2 pistons into a KR. Is the resulting CR low enough? And, is it a sensible thing to simply place those pistons into a KR block that's probably done at least 100,000 miles, and then run it on boost?

 

From the Dubforce forum:

Possibly the same for the RS2/S2 CR's?

Mild boost, as per the Vortex thread you posted equates to 9.0:1 with the Hybrid KR on ABA (9A pistons/ABA Rods). I dont know what turbo's or boost they run with these setups though.

So from that, I cant see there being any problems using the RS2/S2 pistons in the KR - with whatever tweeks need doing of course. I dont know what parts will be put under more stress than usual with the N/A now running FI, anyone?

Only other main area to look into is the management, G60/Pug/Big name brands?

Other niggly bits like manifolds/downpipes, turbo cooling, sump modifications, fuel pressure, oil etc. etc.

I think if you convert an N/A engine to run FI compression and use forged items then it'll just be like an off-the-shelf bog standard turbo unit (bar the management, fueling, cooling and what not), electronics aside, as a physical unit I think it should be ok?

 

g60 engine it is then.
sounds like the fuelling, ignition timing and intercooling are quite critical. have sourced a vented bonnet, so this can only help air temps.
i,m assuming that an 8v exhaust manifold won't fit a kr head.?

 

Does that mean that the older V6 S4/RS4 engines have the same bore and stroke giving that:

445.25 x 4 = 1781 (1.8)
445.25 x 5 = 2226 (2.2)
445.25 x 6 = 2671 (2.6)

???

Are the S4/RS4 pistons the same spec by size as S2/RS2/1.8T/G60?

 

does a petrol turbo engine like or dislike back pressure through the exhaust?

 

You cant say if an engine likes something that doesn't exist.
Sorry..Had to be said.

Thing to remember with FI pistons mostly is the area beetween the crown and the first ring land. It need ot be beefyer than usual to cope with the heat and pressure.

Sharp edges aren't favourable either.

Some sort of strengthening is usually visable above the gudgeon pin on good pistons

Last of all good oil cooling through the piston.

Whatever istons you choose, just take a look at these things to see if the pistons is suitable for use.
Edited by: madmk4

 

you dont want any back pressure, the turbo will be pushing gas into the exhaust faster than the exhaust can extricate it by gas speed etc. so the free-er flowing exhaust the better!