Z350Lover

iTrader: (2)

Hi guys,

Many of you already know that I am going for N/A high compression engine already and I have a set of pistons made here in a very reputable pistons makers downunder...

When I got the piston an hour ago, I was so surprised to see that the crown of the piston isn't that high compare to Esprit 11.5:1 pistons though... but on the box, it says... Bore: 95.78mm, CR: 11.5:1 for Nissan 350Z... then when I came home to compare those pistons with the picture of Esprit pistons, mine ones "look" lower than 11.5:1 though... Here are a few pictures with the stock standard piston... any opinion is welcome before I talk to the guy monday morning again!

I will not want to put in anything lower than 11.5:1 since I ordered 11.5:1 though!

Thanks heaps!

cheers,

richie

Z350Lover

iTrader: (2)

a few more photos... and a pic of Esprit piston set!

The only thing that I can convince myself is that the valve relives on my pistons are not as deep as those on the Esprit ones... just to trade for lower crowns?????

johnlotusboy

iTrader: (1)

Those are plenty for 11.5 to 1 VQ35 motors don't have that big of combustion chambers so 10cc-15cc change is a lot of compression. Also check the deck height installed in the block for these pistons. New motors have small cc heads with dish pistons for better combustion/less emissions. Old school "POP-UP" not the best anymore.

Z350Lover

iTrader: (2)

John,

Thanks for your input mate! So there are many ways of shapping a piston to reach the same compression ratio, is it? I just double checked the wrist pin (at the top of it) to crown distances for both new piston and the standard piston... they are roughly like these figures:

New piston: 10.5mm (roughly)
Old piston: 9.8mm (roughly)

cheers,

richie

Z350Lover

iTrader: (2)

Anyone?? want to find out if there is any way to shape the pistons differently to achieve the same compression ratio?!

thanks in advance!

richie

g356gear

iTrader: (12)

Typically manufacturers will build up the center section between the valves the increase compression. The only problem with this is that is tends to block the flame propogation when the mixture ignites. In other words the fuel mixture can't burn properly. If they did not raise the center section then they would raise the entire top surface like your measurements would suggest when you measured the pin placement. To do this the valve reliefs would have to be deeper to keep the valves from hitting the piston top. Do the reliefs look bigger and deeper on your new pistons??

Z350Lover

iTrader: (2)

g356gear:

Yes... the valve reliefs are larger and they look deeper than the standard ones... so I guess that is correct than?!

Thanks a lot!

richie