How to get higher compression

nissancherryn12 · Post by **nissancherryn12** » Tue Nov 27, 2012 10:21 pm

Hi all!

So i have some questions. My E15ET needs new rod-bearings and therefore i want to take the possebility to give it a higher compression. Now the engine gas 140psi compression but i would like to get more. A friend of mine has an old style leaded engine witch is way more fun to drive because of the enthousiasm in low RPM where my ET is way slower under 3000rpm.

I found these things out:

-leaded pistons are 1mm higher => more compression
-E15s rods make the pistons come 3mm higher => higher compression together with the unleaded pistons, otherwise they come to high.

What other options do i have to make the compression ratio higher? I want to have a comp. ratio of 8-8.5:1 with about 0.6 bar turbo-pressure.

Thanks all for your help peeps!

Damo · Post by **Damo** » Tue Nov 27, 2012 11:50 pm

O.k, just to clear up a small issue, the turbo leaded pistons do sit 1mm higher in the bore than the unleaded ones, BUT have a bigger dish which ultimately gives a lower compression.
I would consider changing pistons to gain 1 ratio or so quite a large investment of time and money, so I would think you would be better off rebuilding a completely new engine to do a straight swap rather than spend far more than worthwhile to gain very little.

As for upping the compression ratio, you could always get hold of a NA E15 and bolt the turbo bits to it, that would be cheaper and easier. If you are dead set on going for a piston swap, have a look here and download the nissan piston selection. Have a look at the 76mm pistons and pick one.

http://www.totopiston.co.jp/cat/catmenu.html

You could use GA16 pistons with NA rods for close to 9:1 and have lots of valve clearance.
Or go the E16 crank with your turbo rods and the GA16's pistons for the same ratio.

Damo

nissancherryn12 · Post by **nissancherryn12** » Wed Nov 28, 2012 12:45 am

Tnx for your write-up!

But the GA16 and E15s pistons, how much compression will these built-up together with the E15ET/E16s rods? Would this be more then the standard 7.4? And how will these handle with the turbo-pressure?

Thanks for your help!

Damo · Post by **Damo** » Wed Nov 28, 2012 9:48 am

Both would give around the 9:1 ratio mark. As for strength, there are a few turbo'd GA's on the Pulsar forum which run the stock pistons, but you need to remember that the stock GA16 runs around 9.5:1 or so, which will limit the amount of boost and (therefore) stress the pistons would be under if tuned correctly.
For detonation resistance, the turbo leaded pistons would be my choice for the strongest. I haven't seen a GA piston up close yet, so its a little hard to tell where it would rate. Either way, if the engine doesn't detonate, any piston will be fine.

Damo