Halon

iTrader: (6)

There's lots of information floating around regarding the difference in rods in these motors. There's also lots of information out there regarding 2JZGE Non-VVTi rods/pistons compared to 2JZGTE rods/pistons. But I don't seem to find a ton of data regarding the Piston Differences between the two 2JZGE motors (VVTi / Non-VVTi). I had some photos / measurements I took today comparing GE VVTi and GE Non-VVTi pistons that I wanted to share. I'm not a machinest, so don't take my measurements as gospel. Most of my measurements are simply to show there is a difference. I was curious to see the difference just due to my natural curiousity. But also I was trying to figure out how the GE VVTi is rated at 10.5:1 where as the GE Non-VVTi is only rated at 10:1, where is that extra compression coming from? Lastly, you always hear about the VVTi motors skinny rods being the weak point, but you also hear about the pistons ring lands failing at power levels the GE Non-VVTi hardly ever have issues, so I wanted to see if there was a difference there as well. So here's what I found.

I have a IS300 motor that I'm having built. So the VVTi piston/rod set came from my donor motor. The Non-VVTi piston/rod set was donated by Gerrb (thanks again).


Here they are side by side. GE VVTi on left. GE Non-VVTi on right.




Ring Lands. The size of the ring land openings are all the same, and the distance between ring lands are all the same. However you can see that the Non-VVTi Piston has more material from the top ring land to the crown of the piston. So perhaps that is why the GE VVTi guys notice ring land failure at say 500-600hp, yet the GE Non-VVTi guys you rarely hear of it?








I also noticed the piston skirt design is different. The GE Non-VVTi is I guess what you'd call more of a full round skirt piston, and the overal length of the skirt is longer. The GE VVTi is more of what I guess you'd call say a strutted design where the skirt isn't full round, and the skirt is a bit shorter.

Halon

iTrader: (6)

The face/dish of the pistons have some differences. First you will notice the GE Non-VVTi has much deeper valve reliefs. Also, the Non-VVTi has a shallower dish. I had my machinest CC them, and he actually found the Non-VVTi has 1.5cc less volume that the VVTi piston. That really confused me as I was expecting the VVTi to have less volume, thus explaining where some of that added compression came from. But nope, and you can see it in the photos that the VVTi piston has a deeper dish, so I suppose yeah it does have more volume.












To try and show the difference in dish depth, I just took a crude measurement with a caliper showing how much deeper it is. Don't use these measurements for any sort of calculations, they are crude. But the point was just to show there is a noticable difference in dish depth.






And this was just to show that basically the piston height is the same. I just measured from the top of the pin hole to the crown, and they were basically the same.

Halon

iTrader: (6)

And couple other things I had the machinest check on my Virgin GE VVTi Head, here's the values he sent me:

Recess: 0.028"
Volume: 41cc


So in the end, I guess I'm not completely sure where all the extra compression comes from. The 2JZGE VVTi piston has a hair more volume, and the 2JZGE VVTi head has a hair less volume. So not really sure how they get the extra 0.5 compression, but at this point I don't have the time or money to do anymore experimenting with this, so take it for what it's worth. This experiment is over and the donor engine that was used for this is now officially under the knife getting some Manley guts

STRETCHAU

The vvti ge piston holds 7cc where the non vvti ge piston 9.5cc the -1.5cc in the vvti ge piston creates the extra .5 compression ratio