Hello All,
What are the advantages and/or disadvantages of using forged Gti-r (stock DET size) pistons as opposed to using forged 87mm (300zxTT size) pistons? Which would be best to use for 350-400 reliable hp? How about turbo lag?

I tried looking for an answer in the archives, but got more confused.

Anyone know the compression ratio of either size pistons in a DE block?

I would greatly appreciate any feedback. Thanks

The 86mm forged gti-r pistons are "stock bore" good if the cylinder bore are with in spec. If there not then going with the 87mm would be the way to go by boring/honing properly with tirque plate 1mm over. Correct me if im wrong but a bigger piston/bore would give a larger area for combustion to take place?

Lawrence
92 se-r turbo
jwt 87mm block w/squirters
sitting in the garage

Keep in mind the compression ratio of VG30DETT pistons that are not dished will be 9:1, GTi-R pistons will be.. 8.3:1 ? I went with VG30's due to the low cost.

Thanks for info:D

Originally posted by PDX S2000
Keep in mind the compression ratio of VG30DETT pistons that are not dished will be 9:1, GTi-R pistons will be.. 8.3:1 ? I went with VG30's due to the low cost.

Actually, GTi-R pistons in a DE will give 8.5:1 CR. The GTi-R and the BB DET use the same pistons.... the GTi-R has a lower CR because it has a bigger combustion chamber (different head)

Please forgive my ignorance, but what exactly does boring the cyliners 1mm over accomplish? If both 87mm pistons and Gti-r (or BB) pistons net 8.5:1 CR in a DE, which has the advantage? How does that 1mm over-bore benefit a turbo engine if it has the same CR as a stock (86mm) piston? Thanks

GTiR Pistons are Cast.....NOT Forged!
GTiR Pistons and Bluebird Pistons are exactly the same!
GTiR Pistons net 8.3:1 CR in a GTiR
GTiR Pistons net 8.5:1 CR in a BB DET or DE.

Factory Cast DE and DET pistons are 86mm

JWT/ARIAS pistons are 87mm which requires a .040" (1mm) over bore of the cylinder wall.

A 1mm over bore *REQUIRES* the use of a torque plate. A torque plate simulates a torqued head onto the block. The shape of the cylinder walls change when the ead is torqued onto the block, thus creating the need to use a torque plate to plateau hone the cylinders evenly.

Over boring the motor gives you more displacement as well.

More displacement =More power!!!!!

Your motor is just a air pump bigger pistons move more air which inturn when added with fuel makes more HP.

If i do go 87mm pistion were do i get the torque plate ?

Richie

Originally posted by TurboJesus
If i do go 87mm pistion were do i get the torque plate ?

Richie

Have JWT do it. They have a torque plate, and have probably bored more SR20's than anyone else in the country.

what are the stock pistons 86 mm right???

Richie

yes stock pistons are indeed 86mm



92 se-r turbo
90 talon tsi awd
Lawrence