Stock RB25DET pistons

[whatsisname]

Now I know plenty of people have made big power on stock RB25DET internals but having had a good look at the cast RB25DET pistons (in fact many examples of them) I'm amazed that there aren't more failures! Ringlands are the number 1 point of failure on all the pistons I recently looked at ( lots & all RB25DET!).

As an aside the state of my engine internals were bloody excellent when it was pulled down! The pistons are good (apart from 1 with a 2-3" section of RL missing) nil detonation damage, all rods perfect, bores perfect, crank etc... Basically there is ZERO traces of any detonation at all.

Attached is a pic of the failed piston-

[whatsisname]

Another old piston pic -

*The marking on the top of the piston is just from sratching against something on the bench. Which has removed some of the carbon build up.*

[whatsisname]

Here's what is replacing the old pistons -

Along with a Trust H/G (not O'ring now)

New fuel rail/injectors (top feed & still using the stock plenum - yes is can be done)

[whatsisname]

Another -

[japtaxi]

New pistons looks good (shiny! ) .. any reason you goto 8:1 instead of keeping 9:1 compression if it is street application?

Let us know what else you are doing with it (engine/turbo/etc..etc..)

[whatsisname]

I actually have a few better pic's of the CP pistons but they don't want to load up?

The idea behind the 8.0:1 CR is to allow 20+psi boost & more timing on pump fuel all day every day. Well that's the idea anyway

Other engine/turbo mods limited to the follow basics;

I already have a T3/T4 combo (exact housings wheel trims I'm not sure?)

The cams will remain stock (have adj' c/gear already)

The head is just getting a basic clean up (will stick to 7500rpm limit)

Stock manifolds - with a basic port match

TRUST head gasket - stock thickness

The rest is just your usual basic rebuild freshen up

Then the new fuel rail & 550 to 600cc injectors (Bosch most likely)

Everthing else was already in place in the pre rebuild stage (ie. ECU, EBC, intake, exhaust etc...)

[Clint32]

Hi Matt good to see your keeping your car, so you can have some more fun at the drags.

I recently got a rb25 with the same thing, 3 pistons with cracked ring lands, apart from that everthing is perfect. I was going to just buy a std one but after seeing all the others fail i though i would build it anyway so i just bought a stuffed one, cost $800 after i sold the turbo and is basically compete and ready to be done properly for 300rwkw. Let us know what you think of nisspeed for future refrence.

[hippy]

i thought your car was crazy the last time you gave me a ride in it matt ... and that was on 14psi ?? 20+ psi?? do u have a death wish ??

[T0nyGTSt]

I have GT-R n1 slugs in my car and it's doughy off the line with standard boost. I don't know how big a turbo you have to run or how much boost you need to run to restore response.

T.

[whatsisname]

G'day Clint,

Yeah mate I'm so glad I didn't let it go! I'm hangin' to get it back on the road, & even more so to hit the track again!

$800 is bloody excellent! Even after a full rebuild using quality components it'll still be a low cost motor. 300+rwkw of 2.5L in a 32 GTS-t is a great combo

I'll let you know how things go re Nisspeed. So far I've got nothing but huge praise for James (Nisspeed). He's got a lot of knowledge & experience with performance engine builds, epsecially Nissan stuff (surprise surprise ). He spent ~5hrs going over everything about my rebuild with me last Friday in the workshop. He's kept me informed about the progress of parts. He's taken on every little extra I've requested. He charges sensible prices for top quality work. His motto is built it right the first time & it'll make good reliable power. And he is keen to make up custom parts to suit my requirements for just the cost of the materials!

Hip,

Haha, no death wish dude, just the aim of a 12sec daily driver. Ok I'll tell the truth. You see I bought a 30psi boost gauge ages back & I always felt I was missing out by only using 15psi of it, so soon I'll be getting my moneys worth

Tony,

Yeah I'm expecting a slightly doughy bottom end, I can live with that. As long as it's on full song by 4000-4500 & has a healthy spread of power/torque to ~7500 I'll be happy enough.

[hippy]

yeah you're just as crazy as steve ... who wants to have bigger traction problems??

maybe u should think about getting some slicks to see what it can really do ...

[Steve]

Hi Matt, no signs of detonation???? FARK, now I am paranoid again.

I have just seen my pistons and they are all in perfect condition with 'no signs of detonation'.

I thought it was the knock sensor keeping me in line. Mind you it can still detect knock way before my ears can - which probably has something to do with the screamer and me being part deaf (getting old you know).

Those pistons do look nice and shiney Matt, seems a shame to put them inside an engine. I suppose you will always have your souvenir smashed ring land piston that you could polish up and use as a centre piece, if you have any spares, I need an new ashtray:)

With an 8:1, you should be giving 30psi a nudge, just for shits and giggles;)

Go on, you know you want to, dont be weak:D

[MattR]

Hey matt how much you after for them, my number six was due to injector failure we think. It just melted the side of number six, even the rings were still intact

[whatsisname]

Naa Hip slicks is cheating.

Steve,

Yeah it doesn't surprise me your pistons are in good nick mate, just about all the ones James showed me were quite healthy looking except for the ring lands (some had 2 or 3 sections cracked). The way I see it there's no need to worry about your pistons, if they let go then it's time to go to the next stage. If they hold on for a yr or so then it's a bonus

I plan to make the dud one into a nice little display, gotta' have a few bloke things in the display unit beside all the girl trinkets I'm sure James can spare a few for ash tray purposes.

The plan is to see what it'll put out in everyday trim & then go for an all out big boost & exotic fuel combo. So yeah well over 20psi should be on the cards. I doubt it'll make much more than mid to high 200's as the turbo isn't up to the task I don't think. Should be fun anyway

Matt,

I dunno' mate? Not much. Once I pick them up I'll let you know & you can pick out which ones you want

[MattR]

Matt ive still got about 7 litres of toluene when the time comes and I am able to get you cheap avgas too. uve got to go for the big 300.

[Steve]

I am sure someone around here has a nice T04R HKS turbs sitting around looking for a new home add 25lbs of boost = mayhem.

[T0nyGTSt]

Thing is 8.0 is getting down there...

GT-R pistons get it to ~8.5 or so.

I'd imagine 20psi is need for 8.0, perhaps 14psi needed for 8.5:1 - it's all guessing until you got the right turbo, ECU and dyno tune it.

T.

[Clint32]

TonyGTSt, what did the N1 pistons cost you? you dont hear of GTR pistons cracking the ring lands do you

[T0nyGTSt]

Originally posted by Clint32

TonyGTSt, what did the N1 pistons cost you? you dont hear of GTR pistons cracking the ring lands do you

N1 pistons are not worth it IMO.

$250 each + $200 for rings.

However I got mine for a very good price.

Say close to $800 or so inc. rings. Use Nissan rings. They're good.

GT-R's do break pistons and rods but they are tougher than GTS pistons. It's just that I didn't have the money to stretch to $1,400 forged and my HP requirements are meagre.

If I do 250rwkW I'd be happy.

T.

[MattR]

300rwkw is possible with standard engine if tuned properly, and yeah steve ive got the turbo kit if anyone wants it(at the right price) or I may keep it and put it on a R when I get one