So they are not really factory pistons?

excellent info there jmac.
how much honing is ok for a re-ring without needing the bigger pistons, enough too remove a slight lipping from seizing from sitting?

Lipping means there is wear. You can rering an engine like this but compression will not be great. The depth of the lip at the top of the bore is how far the bore is out of round.

Some very helpful information there but as much as i trust that standard pistons will hold boost i want to be safe than sorry and end up with another rebuild .
so the e15et pistons will fit but will stick out which in turn i can shave that amount of the top of them to work even if i do this will it still lower my compression ? or will this get rid of the dish on them altegethor

If there is a dish, machining the pistons will take some of the dish away, as the dish tapers.

What cylinder head are you using? you could try using a decompression plate or an open-chamber head such as a H72 to lower the compression.

thought so if that happens il just get them to machine a bit more dish , im just using standard a15 head which im gunna do a bit of work to , didnt really want to head down the path of plates and heads

The pistons in an a15, based on the listed compression height will stick out by about 3mm, which I can guarantee will cut right below the piston crown, possibly into the top ring groove.

I have to be honest, cast pistons - 2 things to look for is a thick crown and a solid skirt (I might have to do an mspaint pic to explain the second bit) - have those two in place and they'll tend to handle boost/rpm about as good as a cast piston can.

Some of the aftermarket factory replacement pistons are fantastic, some are really dodgy, as a general across the board comment. I'm not sure what is what for dattos, but I can only mention (again) I've put some serious boost on top of cast acl pistons in a couple of different engines, and it's amazing what they will handle

If you want to push more than 12-14psi in there, save yourself some money (more up front but _FAR_ less in the long run) and bite the bullet and get forged pistons. Thankfully it's not as expensive for us 4cyl guys as it is to get 6 or 8 made.

forged pistons will cost around $1400 for 5 (the fifth is a spare)
im sure if we had a group buy itd be less in price but then we would all need to be runing the same bore size if they where to get a group buy id nominate a size for a 1mm overbore on an a15

Here is a pic of the E15ET pistons. Bit hard to see but the dish is 'ice-cream scoop' like.. you could almost fit half a tennis ball in there. As I said A14 crank will reduce the lift and will probably rev a little nicer as well. I think i paid around $450-$500 direct from Nissan, it was a few years ago now though!

so can you run the e15 pistons with a a14 crank in a a15 and it will work? i.e. no boreing required.