Compression ratio for Pistons

[pegliobaglio]

Just nailing down the final few parts for my engine build need some advice .
i am getting 86.5mm Pistons and am swaying towards a slightly higher compression ratio 9:0:1 is there any solid reason not to go for this? Would I be better sticking to the 8:5:1 ?
car will be running around 450 Hp I should think and just want the car to be as responsive and reliable as possible.
any advice would be greatly received
thanks

 

[Ajbulger]

im going through a build right now ive found that it all matters on what if any work your having done to the head how thick your having the gasket etc. if its a det engine be sure to get the right pistons as the n/a pistons are flat and dets are shaped to give a better volume. mine were high comp pistons but were machined anyway to suite my needs all depends on the rest of the build buddy id make sure your not running to high a comp though 9:0:1 is top id go for a sturdy reliable build but hey just one mans opinion hope the build goes well

 

[sammos13]

depends on the rest of the build bud and engine management and mapping, higher static compression ratio is just the beginning as all sorts of engine parameters, cam timing, cam lift, cam duration, head work etc will have an effect on the dynamic compression and expansion ratio.

over all and generally higher compression ratio should help off boost driveability a little due to increased NA torque improving spool time / part throttle response etc.

limitation will be the mapping / management though as it will push you closer to you knock limit due to high peak cylinder pressure / temperatures etc but all in all 9.0:1 compression ratio isn't that high in modern terms with decent management and being well mapped.

just remember to take the rest of the engine into account as per above as any changes in HG, combustion bowl change in the head, head skimming / block shimming will change you static compression ratio

i've gone for 9.0:1 static compression ratio on mine

 

[pegliobaglio]

Thanks for the advice guys tbh I think I will stick with the standard 8:5:1 just to be on the safe side. Will be running a 1.1 mm gasket,supertech valves, springs, retainers and tomei poncams. As for management I have a syvecs s6gp with advanced knock function so that side of it wont be an issue . Think I will just play it safe and stick with stock , I'm going to be running a pretty responsive set up anyway so hopefully won't miss the extra down low
Thanks again

 

[sammos13]

with the syvecs and the rest i would be tempted to push it up a little... but may mean you might not get exactly to your power figure depending on what turbo you are using similar set up to mine but am running 260deg procams and a PFC but my power aim is somewhere in the 370-400ish (expecting to have to limit power due to the lack of know control on the PFC )

hopefully will have mine done and you can see what that is like soon !

i want a syvec !

 

[pegliobaglio]

I'm looking to run around the 4-450 mark so think the lower ratio would probably be better suited. I'm not chasing figures just want the most responsive set up I can safely run around that power as the tubby will be good for THATS. I have read a few people say that the 9:0:1 is perfect up to 500hp but I think that's pushing it a bit too close .
Was tempted to swap for pro cams myself will have to see how I get on with everything .
Yeah that would be cool man get out in that see what it's like . Syvecs are the nuts but not cheap !!