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mynameisowen wrote:Man thats very cool news, I wonder how different it is. I would like to use a Y8 head and these Z2 pistons on my mini-me to bump up compression even further.

I will recommend you to use D13 pistons because their deck height is positive. It will give you more compression than Z2 pistons.

Law_ wrote:

marty40 wrote:1.3mm skimmed of my head

How much should that raise compression? Compared to removing a layer from head gasket, is it different? How much space left between the valves and piston?Cheers

1.3 mm skimmed give more compression that removing just a layer from gasket. Use some of CR calculators to suit your setups.

Here it is one for example:
http://www.csgnetwork.com/compcalc.html

I would not use D13 pistons in a D14
The compression height of the D13 piston is 30.70mm , D14a4 is 29.50mm .Piston will stick out the engine deck .

I'd love to see pictures or more info on those D14Z pistons if they really are flat top pistons a lot of D16 /D15 N/A builders have another piston they can use in their builds.I just might get me a D14z donor engine to get the specs of the pistons

Btw D14a4 engine deck height is the same as the D15 engine.
You can actually calculate it :

Half of the engine's stroke + rod length (center -center) + piston's compression height = Engine's deck height

Example D14a4=
Stroke : 79mm / 2 = 39,5mm
Rod length: 138mm
Piston's Compression height: 29,5mm
Totall= 207mm

NIO wrote:

mynameisowen wrote:Man thats very cool news, I wonder how different it is. I would like to use a Y8 head and these Z2 pistons on my mini-me to bump up compression even further.

I will recommend you to use D13 pistons because their deck height is positive. It will give you more compression than Z2 pistons.

Law_ wrote:

marty40 wrote:1.3mm skimmed of my head

How much should that raise compression? Compared to removing a layer from head gasket, is it different? How much space left between the valves and piston?Cheers

1.3 mm skimmed give more compression that removing just a layer from gasket. Use some of CR calculators to suit your setups.

Here it is one for example:
http://www.csgnetwork.com/compcalc.html

I worked it out roughly and it gave me around 10.3:1. i think. cant remembr exactly... piston to valve clearance is fine. id say max that can be skimmed would be around 1.5mm. and a camgear would be essential. car ran ok with this compression even on standard ecu. wouldnt recomend it for too long tho.

Guys I just read on an excel sheet i found on the web that had specs of various d series engines, that the d14z2 has 9.8 compared to 9.1~9.3 for other d14s. According to this sheet the z2 has 138nm of torque while hp is 90 as other d14s. Also this is not the first time I'm seeing someone stating that d14z2 has 9.8:1 compression but i have always assumed that stock compression ratio was ~9.3 upto now. What do you guys think about the credibility of this data?

We know that the z2 piston (the PHX) has lower dish cc in comparison to a d14a4 one. The stock head code for my d14 is P2A-1 and d16y4(120hp) engine which can be found in my country has P2A-2 code. I've heard from honda mechanics that they are identical except differences in the cam. I also had read on an australian forum (they get d16y4 in australia) that the P2A-2 was identical to d16y8 minus the vtec. They had also measured the combustion chamber cc to verify this.

Using this data with an estimation of -2.7 cc dish, 29.5mm compression height for the piston, 138mm rod length, 207mm deck height, 79mm stroke, 75mm bore, and 32.8cc combustion chamber cc of d16y8 i get 9.8:1 compression ratio exactly with 0 piston to deck height. What u guys think?

i was double checking on autodata and D14Z2 appears with 9.2:1 compression. Cheers

I recently bought a Used D14Z2 pistons ,ideal for some research

The 96-98 civic EJ9 (D14A4/D14A3) uses the P3Y pistons and they have a stock compression ratio of 9.1 :1.
The 99-00 civic Ej9 (D14Z2/D14Z3/...) uses the PHXG pistons and they are presumed in having 9.2 :1 compression ratio.

When i did my earlier measurements on the P3Y pistons i found this:

Piston pin diameter: 19mm
Compressie height 29.5mm
Piston dish volume: -5.4cc
Totall height: 49.55mm

On the PHXG pistons i found this:

Pistons pin diameter: 19mm
Compressie height: 29.5mm
Piston dish volume: -2.4cc
Totall height : 49.10mm

The PHXG pistons are almost flat top pistons.
This means the 99-00 D14Z engines have a compression ratio of 9.7 :1.All the rest of the parts cylinderhead ,head gasket ,rods are all the same as the earlier D14 engines.One thing i also noticed is that the PHXG pistons are obviously stronger and thicker shaped.This could also mean they can handle much more power then the older P3Y pistons.
I Learned a lot from this ,i hope other people can use this info too

Picture time

Great work
But why the D14a3/4 have the same hosrepower with D14z2/3?
Maybe milder ecu bacemap on 99-00 ej9s?
Once I was speaking 3-4 years ago with a guy that had facelift ej9 99-00 (stock) he said that his final speed was around 200km/h.
But on my car '98 ej9 the final speed was 180km/h
Maybe the answer is the torque
So the D14z2/3 must have more torque from D14a3/4, am I right?

BETEK wrote:Great work
But why the D14a3/4 have the same hosrepower with D14z2/3?
Maybe milder ecu bacemap on 99-00 ej9s?
Once I was speaking 3-4 years ago with a guy that had facelift ej9 99-00 (stock) he said that his final speed was around 200km/h.
But on my car '98 ej9 the final speed was 180km/h
Maybe the answer is the torque
So the D14z2/3 must have more torque from D14a3/4, am I right?

Yes More compression usually translates in more torque and not so much more hp.
Like Lumpenst allready said before it has 138NM of torque vs 125Nm from the D14A4.
I think the data that Lumpenst got was about right
Now i also know why Sebastix had so much more torque then mine when the Hp difference wasn't that much.

Also people with D14z2 engines that put on a D16y8 head will have 10.1 :1 Compression.

So people with 96-98 ej9s don't be despaired
One advantage for P3Y pistons is that they have smaller skirts and mass than PHXG, so I think that is equal to less friction and better reving
And if 96-98 have less compression is because you can go light turbo (stock internals) without of fear of detonation like D14z


There are any D series pistons with dome that will give compression around 10.5:1 or 11:1 and what happens between valve to piston clearance then?

great news! c/r is key factor in our d14s. Are we sure that the heads are identical and the gaskets too? Because 9.7 c/r is way too much not to have been released in performance charts for d14z.