I've been on the board enough to know why the reason we go with 8:1. They include, more margin for error, all stock turbo cars come with low compression pistons, etc...


Ya know, I was thinking about this though. I am planning to boost 10-12 psi with forged internals and I was wondering if I could go with 9:1 instead of the regular 8. Aren't 9:1 forged pistons stronger than the stock cast pistons, and, will therefore, hold up much better than the stockers?

-------jezreel
hrc stage 1, sfmu, ml, prokits, egt, boost gauge, apexi tt, costum dp, dynotune fp gauge. gst muff, turbo spoiler

nothing like driving with the windows down and the music low: i love hearing the turbo spool, swwwhhhttt!!!!
thanks for www.kaptainmyke.com for the sig hosting :thumbsup

yes, forged will definitely hold up longer than stock pistons, but you may need to pay extra to have the 9:1 pistons custom made. I'm not sure if they do a 9:1 normally.

I could be talking out of my ass, but I'm not sure.

Most people run a 8.5, 8.6, or 8.8. You can get custom compression ratios made for about an extra $150. I'm still looking at running forged pistons at a stock 9.6:1. I'm still a couple months off though.

Corbin

'95 ESI-T
HRC+FMIC+ETC...



Gimme fuel...Gimme fire...Gimme that which I desire

I got my CP's made custom 9.0:1 for no extra charge. look up raceeng.com and give them a call.

Race engineering is a GREAT company to deal with.

You can run higher compression, and your going to gain some horsepower from it. BUT, your going to get to the point where you must run race gas to run lower boost level. For example w/ my 8.8:1 pistons I an tuned for 22 psi on 93 octane petrol. 14.7+22*8.8 ~ 322 psi. With 9.6 (stock compression rate) its 352. Only 30 more psi, but it does matter! That's like me running 26 psi on 93 octane, which may be bad.

I actually wish my comp was a bit higher. Next winter ill be rebuilding the motor in my Z for high boost and some 9-10:1 comp pistons. Mabye even higher.

Same here, you can run 9.0 in compression, but the marging for detonation will be higher than with low comp. pistons. You will end up needing to retard the ignition, use the highest octane fuel or race fuel or fuel additives. You will have to monitor the engine more for proper tunning and maintenance.



Stock Rebuild Block, Custom Turbo Kit: Custom 3" Downpipe, TEO4H Turbocharger : 10-12 psi, Starion Intercooler, Custom IC Piping, HKS By-pass, HKS AIC, (4) 330 cc extra injectors, Autometer Gauges

Ok so how about this theoretical question. Let say there are two blocks, both built by FTY, same bearings same oil pump. Their only difference is one is running low comp pistons, the other one is stock compression. BOTH ARE FORGED!!! They experience detonation with the exact same intensity. Which one will "survive." I vote both have an equal chance. What do you all think?



-------jezreel
hrc stage 1, sfmu, ml, prokits, egt, boost gauge, apexi tt, costum dp, dynotune fp gauge. gst muff, turbo spoiler

nothing like driving with the windows down and the music low: i love hearing the turbo spool, swwwhhhttt!!!!
thanks for www.kaptainmyke.com for the sig hosting :thumbsup

Detonation is cause by extreme high pressure and high temperature that ignite the mixture in the chamber multiple times. It can be cause by a lean condition (little fuel on the mixture), or to much timing that creates the spark before time of TDC (Top Dead Center or highest position of the piston in the compression stroke). Even forged pistons can melt under very extreme conditions. It doesn't matter wich engine will get detonation, the episode will occour on each engine in different tune settings. A fuel curve and timing setting for one is not a proper setting for the other.
To me is better to be safe than to be sorry, that's why I run my car a little richer.



Stock Rebuild Block, Custom Turbo Kit: Custom 3" Downpipe, TEO4H Turbocharger : 10-12 psi, Starion Intercooler, Custom IC Piping, HKS By-pass, HKS AIC, (4) 330 cc extra injectors, Autometer Gauges