Compression ratio of hybrid JZ engines.

[wilbo666]

The material properties and construction method are going to affect this somewhat.

I'm sure we could always send some samples to our materials friend in Japan (Oldrola)

But we know that JZGTE pistons aren't forged...as such I think it would be a fair assumption to assume that JZGE pistons would be manufactured in a similar process...however this would be an assumption of course!

Cheers
Wilbo

[big_zop]

Didnt know the GTE ones werent forged, still tough though.

In all honesty Wildsupra - if you can control detonation (through fuel or conservative tuning) then you can run whatever you want. I know that you wan to know if it could be done but the problem is that most people wouldnt try - i just hope you dont blow it up finding out.

[Wildsupra]

Biz zop, yeah i dont think i will try it, im not a fan of conservative tuning so i dont think high high compression plus 20psi is the right road for me. Looks like i'l stick with the 2jz pistons and maybe a thinner head gasket combined with some facing of the head

wilbo i have both 1jz and 2jz pistons here, i can measure the dome thicknesses if you like.

[Gavatron]

Gotta get me some 1JZGE pistons + 0.3mm head gasket for the 2JZGE

[Wildsupra]

ok did some measurements.

These are NOT EXACT measurements but are close. i dont have any micrometres at home so best i can do is verniers and straight edges etc.
These are meanurements for 1jz-gte and 2jz-gte

1JZ dome thickness ~7.9mm
2JZ dome thickness ~9.2mm

1JZ Piston
Above top ring thickness ~7.35mm
Between top ring and #2 ~4.45mm
Between 2nd and oil ring ~2.5mm

2JZ Piston
Above top ring thickness ~7.5mm
Between top ring and #2 ~4.5mm
Between 2nd and oil ring ~2.6mm

So it would seem the 2jz piston is going to be stronger on all fronts.
It also appears the 2jz piston has an actual machined finish on the top of the piston as opposed to the 1jz which appears to have casting marks on the top and not machine finished.

Cheers
Matty

[wilbo666]

Awesome post matty! Any chance of some comparison pics!?


Also anyone (e.g. gianttomato ) have a 2jzge piston they can do the same rough measurements on!?


Oh and Gavatron, 1jzge pistons with 0.3mm HG -> ~11.11!


Also can anyone confirm that 2jzge runs a 0.3mm Headgasket? Seems quite thin...

Cheers
Wilbo

[Wildsupra]

Oh yeah i reckon i could do that

In all pictures the 1jz piston is on the left and 2jz on the right

[big_zop]

Do the cutouts differ in depth because the 2JZ look shallower but tha may be because of the dish.

The other thing i can see is a cast arrow in the 1JZ (assume for front of engine) and none in the 2JZ but there is a small dimple in the top of the picture - does that align with anything on the 2JZ (im thinking spark plug but im pretty sure they are in the centre of the head - but havent seen to many open 2JZs - for obvious reasons...)

[Wildsupra]

hmm didnt check the cutouts...
the dot is the marking for front of engine instead of the arrow

[big_zop]

ok, cheers.

one more thing that could affect clearances is how far the spark plug sits in the head, etc.

[Wildsupra]

yeah thats true, unfortunaly i no longer have the 2jz head, i would assume the positions would be the same, e.g. fairly flush with the combustion chamber face. either way it would be easy to select a plug to eliminate any possible problem.

[Gavatron]

Oh and Gavatron, 1jzge pistons with 0.3mm HG -> ~11.11!

Yeah, that was what I worked out too

[gianttomato]

Also anyone (e.g. gianttomato ) have a 2jzge piston they can do the same rough measurements on!?

Pretty sure compressed 2JZGE head gasket is 0.4mm.

I have VVTi and non VVTi 2JZGE pistons here. What measurements do you want?

[wilbo666]

Pretty sure compressed 2JZGE head gasket is 0.4mm.

I have VVTi and non VVTi 2JZGE pistons here. What measurements do you want?

Awesome

>Dome thickness
>Ring land thicknesses
#Above top ring thickness
#Between top ring and #2
#Between 2nd and oil ring


Big_zop:
In regards to clearance, all JZs sit the pistons with negligible setback in the bores is my understanding.

Pretty sure the plugs don't extend into the bore on any JZ head so that should rule out that interference issue...

In regards to valve cutouts, the 1JZ-GTE valve sizes vs 2JZ-GTE valve sizes are ver similar, and I'm assuming that the valve angle is very similar... The distance between the cams must be the same as 1JZ as they use the same cam gears and timing belt tooth dimensions


Cheers
Wilbo

[cambelt]

The VVTi GE pistons have a taller dome and are graphite coated apart from that i think there the same as non VVTi GE pistons .
Dave