forged pistons

[R32-GTS]

I would have to say that the Arias are a better designed piston than the wiseco's.

The Arias are made specifically for each car and are not made from moulded blanks like the wiseco's. The Arias also seem to be dead quiet , even when cold. The Arias are also nicely rounded on all surfaces to avoid detonation hot spots.

[GTRgeoff]

Good advice Chris. I'm still looking for a keenly priced boreguage myself to check the dims right through the bore. Should never have trusted that guy in canberra. Explains a lot though. Surprised I made the power I did.

These spec sheets from Arias should help.

[ylwgtr2]

i am using hks pistons in my engine...i went for this coz its tried and true...i couldnt think of anything worse than something let go coz i wanted to save a little bit of money and damaging the more expensive stuff...also it was good coz i just got all the matching rods cams ect

[wrxhoon]

chris i'm still waiting for ur contact details for the turbos , if ur not interested let me know cause i have some other offers . i know the size of my bore i already measured it its 86.53 mm and it has 86.49 nissan pistons .

skylinegoff thx for puting up the arias specs .i'll go with them if my bore will clean up for the 87 mm pistons as they dont list 87.5mm.

are they the pistons ur using ? surely the machine shop would have machined ur bore piston diameter +4-5 thou clearence u did give him the pistons at the time he bored it put didnt u ? i have a good machine shop but i always check the clearence piston to wall and always check the rings as well put them in the bore and check the gap to make sure its right , if someone makes a mistake and u get the wrong rings ur stuffed big time .

also if the top ring is chrome i give it a coarser hone otherwise the rings never bed in and it will blow smoke .

[wrxhoon]

ylwgtr2 i dont think hks make pistons ( someone may correct me if i'm wrong ), they buy them from someone else dont know who though .

[ylwgtr2]

dunno who makes them...they have got HKS cast into the bottom of them tho.....but my point is its all kit form so it works...

[JNR24]

If your intrested, i can get you brand new wiseco pistons for $1000 deliverd to your door.

Just pm me the kit number and oversize you want.

http://www.wiseco.com/PDFcatalogs/sc-niss.pdf

Cheers,

Trev

[Field]

What has boost got to do with destroying pistons????  detonation destroys pistons.  

Just wondering how many forget pistons you have belted with a hammer?  Strange, every mechanic and engine builder I have spoken to tell me forget pistons are more brittle than cast.

wrxhoon, a guy on the rb30 conversion thread, very recently, posted up that he can get weisco pistons for 1K with rings, pins, clips.

I am afraid I will have to agree to disagree on that.

Boost is a major player in damaged pistons. The more boost you run in a car, the more heat it generates. The more heat that is made, the hotter a piston gets and the closer it gets to melting point. This goes for exhaust valves and turbine blades too. If turbine wheels get too hot, they can get to the point of disintergrating. Hence the reason why people are using inconel shafts. They are much lighter and tolerate more heat. Even when you dump fuel into a cast piston motor, you are just delaying the inevitable.

How does WRXHOON have melted pistons from detonation???

Ok, if latent heat was not a problem, why would people change to forged pistons?

Detonation is something you can easliy aviod with reduced ignition timming or water injection to name a few. They run the forged pistons so they can run MORE boost on pistons that are designed to take MORE heat as the melting point is much higher.

You don't hear of people saying "ohh, yeah I have decided on putting forgies in my car because it detonates" as he would kindly get flamed on any forum/pub/track/auto salon? well maybe not the last one...they would be a "ohh and ahh" coming from teh audiance

I have been playing around with forged pistons with a mate of mine for about 2 weeks. We had a set of pistons that his customer distroyed and decided to play experiment with them. These were not the factory forged pistons in an RB26 (already done that one) , these were ROSS forged pistons.

We (well, I did anyway) put one in the press, smashed one around with a hammer and put one in the lath to see how it machined up. I cant think of anything to do with the last one... On that note, you would be surprised how much load a gudgeon pin will take before it is deemed useless.

Brittle can be taken in a few ways on a forged piston. Run lean mixtures and death spiral the engine and they will be "brittle" in a sence and almost flake away instead of melt. Death spiral only happens on race engines running race gas. VP, ELF, METHANOL, AVGAS etc. What happens is the mixture is too lean and too much timming, however you can not tell that it is pinging due to the race fuel. After a hard dyno run then engine idles funny. Then a comp test shows that they are all different. A leak down test shows that the rings are still sealing.

This must be what they mean...Why would anyone run a piston that is more suseptable to shattering, breaking ring land and generally being "brittle" etc as a performance upgrade? The engine would shlt itself!

So, what WRHOON might want to do is bore the damaged cylinder until it cleans up then see if you can get pistons in the required oversize then bore the rest. Obvoiusly if it is excessive he will need a new block.

Getting back to the Stock = forged piston debate, how many RB26DETT engines have you seen running 1.5 -1.7 Bar with stock internals? I have seen many and when done properly they are fine. Keep it away from detonation and lean mixtures and you won't bend rods, you won't break rings and ring lands, and you won't melt the pistons or pop the head gasket.

Heck, my car was running 1.6 bar with Nismo N1 turbos (now for sale) 700 cc injectors, nismo fuel pump and Motec M8 and it has done so for the past 3 years without a problem.

What cast piston can do this? none, they will melt even with a good tunner keeping it away from det!!!

[Field]

sorry for the long ass post

[wrxhoon]

field , as posted earlier i didnt bust a piston .the rear turbo shit itself and pieces went though the engine so it marked the bore in the rear 3 cil. it had been rebuild before with o/s pistons ( .5 mm ) . it may clean up boring it out another .5 mm if it doesnt i can get 87.5 mm pistons ( wiseco make them ) but then i need aftermarket h/gasket ( nissan is 87 mm ).

i will find out tomorrow . by the way stock nissan gtr pistons are cast not forged .

[Steve]

I agree that forged pistons have better thermal qualities, but I dont see how if you are cooling the charge air properly, and use conservative timing around peak torque, detonation will be an issue.

I have been running 1.7bar in my R33 for weeks now, and using it every day with stock pistons. Detonation will tell me if the things are starting to go south. I have never heard of anybody melting Rb25 pistons (not saying it doesnt happen), usually its the ringlands that get smashed - detonation.

On the weekend decided it was time to give it a good caining. I spent about 2 hours pushing the car as hard as I could through the adelaide hills, regularly using the 1.7bar, detonation only hit a peak of 28 (power fc), the engine didnt skip a beat.

[51jay]

I believe they were for the RB 25/30 conversion.He later pm'd me to say that they provided a cr of 7.0:1....much too low unless you'r going for huge boost levels. If anyone wants to talk to him it was JNR24

[KamikazeR33]

im putting in a set of arias pistons this week and bringing the c/r down to 7.0:1

been told its pretty safe like this?

also i will be running boost levels of upto 28psi

[GTS-t VSPEC]

Kamikaze, Why such low compression? You'll have hell sluggish performance down low and 28psi isn't exactly high boost. My mates GTR made 616hp at all 4 with 28psi and 8.5:1 CR ARIAS pistons, he's planning on running up to 32psi for AUTOSALON, so I don't see the need for such low CR. It will be very safe cause you'll never make any damn power.

[JNR24]

I believe they were for the RB 25/30 conversion.He later pm'd me to say that they provided a cr of 7.0:1....much too low unless you'r going for huge boost levels. If anyone wants to talk to him it was JNR24

Hi Jay,

First of all, i wrong to post with out first validating the information that i was givin, by a fairly reputable performance workshop here in vic. but anyhow...

I was told that these pistons would raise the compression ratio to around 8.5:1 with the RB25/30 build, but its says on Wisecos catalog "SKYLINE RB30 GTR (w/DOHC RB25DET CYLINDER HEAD)"

CR = 7.0:1

To me these sound like stock RB30DET Pistons?

Standard RB30DET (single over head cam, 12 valve head) run a CR of 7.9:1

and with the 63CC RB25 cumbustion chamber, that would push compression ratio even lower.

If anyone could make heads or tails of this that would be greate.

heres the catalog: http://www.wiseco.com/PDFcatalogs/sc-niss.pdf

Cheers

Trev

P.S by the way, i can get all pistons on this list.

[KamikazeR33]

Kamikaze, Why such low compression? You'll have hell sluggish performance down low and 28psi isn't exactly high boost. My mates GTR made 616hp at all 4 with 28psi and 8.5:1 CR ARIAS pistons, he's planning on running up to 32psi for AUTOSALON, so I don't see the need for such low CR. It will be very safe cause you'll never make any damn power.

what would u suggest would be a better suggestion? 8.5:1?

i suggested that but was told to go lower

ill ask him y tho

[JNR24]

8.5:1 is a good round fiure.

Low enough to run big boost, and high enough for good off boost performance.

[JNR24]

VL Turbos run 7.9:1

And they are responsive enough off boost.

[Sydneykid]

Hi KamikazeR33, my suggestion would be 9 to 1, that's what we run in RB31DET's up to 400 rwkw, over that we use 8.6 to 1. I have seeen an 1100 ps RB with 9.3 to 1.

[T0nyGTSt]

The reason why VL Turbos use 7.9:1 or whatever is that there was only 91 octane unleaded back then and hi comp motors were just not common back then.

T.