Zivman

iTrader: (19)

and this car had some of those of those variables.

Julian@MRC

iTrader: (28)

17 psi is 17 psi to the motor no matter how you look at it....If a 4 banger can run a single GT40 at 30-40 psi of boost at whatever the airflow rating that would be on that motor, his piston should not have failed at 17 psi..I am leaning towards other heat related issues, or detonation issues...Not buying the simple "YOU NEED ARIAS EXTREME" or you will die, propaganda..Other manufacturers pistons have held up in the past to worse abuse..

Sharif@Forged

iTrader: (92)

This is 100% incorrect. 17psi psi through a tiny turbocharger is much less mass of air than 17psi through a GT35. This is turbochargering 101, Julian.

I dont care if he buys Arias ED's, Wiseco, CP or whatever. He posted a picture of an Arias standard duty piston, and I mentioned the reason we introduced the Arias ED piston.

I didnt tune this engine or build it so, I have no interest in it either way. Just pointing some things out for discussion.

Julian@MRC

iTrader: (28)

Im just pointing out the fact that there are other pistons out there that have seen much more boost pressure than any Arias Extreme or Standard has and have done just fine...In Fact Performance motorsports when they were around made 1300-1500whp on CP pistons....So has Carl Stevens from Extreme Motorwerks..
All I am pointing out is that I dont think his piston failed cause it was not an arias Extreme, otherwise you would have 100's of other people posting pictures of broken CP,Ross,Weisco Ect..Pistons..This is clearly not the case.
There are possibly other factors at play..Material defect,Nitrous,EGT's, Engine temps, detonation,timing,ect....

Oh and based on this comment , you contradict yourself from the previous post..Remember, he was running tiny little GT25's as supplied on the APS Standard kit...Therefore your point is mute..

Sharif@Forged

iTrader: (92)

^^I agree with that^^
Arias recommends a max of 20psi (single turbo) on their VQ35 shelf piston, which is a high silicon content piston. A lot of piston manufacturers use low or zero silicon content pistons, and even Arias uses zero/low silicon in some of their shelf pistons (Honda and 4G63 come to mind), and those designs will hold up to much more abuse.

We are still waiting for soemone to post a pic of a cracked Arias ED ring land.....havent seen it yet, which means that we must be doing something right.

Weqster

too much heat into that piston. for whatever reason..

blaukal

iTrader: (12)

mute: unable to make sound
moot: no longer applicable because already resolved / answered

I usually ignore most spelling/grammar stuff on here, but that one always drives me crazy for some reason. Sorry for the random post. But I feel better.

good luck with the re-build.

Cube

iTrader: (7)

I only took a few classes on heat transfer and fluid flow, dealing with various closed systems, open systems, and dozens of pressure and flow rate equations related to both...

So with that said, I'm not claiming to be an expert, but pressure is pressure. Where it comes from doesn't mean a thing. If 17psi is coming from huge quad turbos, the result at the intake where it matters will be 17 psi. If one large turbo was spinning much faster and producing 17psi by itself, it's still putting 17psi at that same point in the intake. The volume of your intake plenum hasn't changed, so there's the exact same mass of air at that intake plenum from 4 large turbos generating 17psi as the single turbo spinning faster producing 17psi at the same point in the intake.

17psi is 17psi. (unless one air charge is colder than the other )

Sharif@Forged

iTrader: (92)

An engine does not consume pressure, it consumes a mass (weight) of air. Try blowing 5psi though a straw with your mouth....pretty easy...right? Try doing this with a fire hose...not going to happen. It's the mass of air that determines power potential, not pressure. This is the reason that most turbocharger companies have moved away from CFM (Cubic feet per minute), and moved to lb/min. Its the mass or weight of the air that matters in these types of calculations.

Another simple example is from the STI and Evo world. Their stock turbochargers tend to loose efficiency past 20-23psi. If you run the turbochargers at 30psi, you do not achieve anymore peak power, and they are not flowing a larger mass of air...yes..more pressure...but no more mass air. If you run a GT35 at 20psi, you will get MUCH more power than running the stock turbocharger at 20psi.

I am sure Gurgen will chime and describe it better than I can...I am tired...and its Sunday...LOL.

Nealoc187

Cylinder pressure is what cracks ring lands. Not pressure in the intake manifold, not CFM, not pounds per minute of air. Cylinder pressure is a result of mass flow rate in conjunction with timing and compression.

As sharif said, with respect to turbocharging mass flow is what matters. The number of molecules of oxygen in any parcel of air is the only thing that is of any consequence. You can heat that air up and it will take up more volume (higher CFM) and exert more pressure (higher boost pressure) and still make no more power because the number oxygen molecules available to be reacted has not increased. This is what happens when we run a less efficient turbocharger than ideal. You heat the air up which causes higher boost pressures, higher volumetric flow rates, and yet no discerable power increase.

Julian@MRC

iTrader: (28)

I agree with the above that turbos do have their efficiency range, and when pushed beyond blow hot air..This also may be a factor if he were pushing 2 small turbos to 17 psi, they would indeed flow less CFM of intercooled dense air, over a larger turboflowing the same..The Air charge temperature may have played a role in the pistons demise, but not the CFM or PSI by any means..

Weqster

EGT's have raised due to whatever reason. be is blow by? oiling down? too agressive timing? extended periods of boost? I dont see much/amy scuffing on the skirts, so id have to assume they were clearenced properly. i know JE (hi-silicon content) would blame this fuel octane. But in the end, it all comes back to the tune. 17psi is very capable on street gas.

sentry65

iTrader: (11)

plus it's possible to have 17psi of hot air or 17 psi of cold air

Sharif@Forged

iTrader: (92)

I am not contradicting myself, becuase there are TWO of those tiny GT25's....roughly the same as one large GT40xx. Each APS turbocharger flows roughly 40lb/min worth of air at 2 bar pressure ratio (14.7psi relative pressure)...so times two is 80lb/min worth of air..thats a LOT of airflow, for just "just" 15psi.

OMG, I am sounding a lot like Peter from APS.

Sharif@Forged

iTrader: (92)

Absolutely....and the cold air will have much greater weight (more power potential) when compared to the hot air charge.

Julian@MRC

iTrader: (28)

Those 2 tiny GT35s are blowing Hot air at 17 psi, and you know this..
PS you need to follow with a CHEERS mate..

r0mey

iTrader: (35)

cheers

sentry65

iTrader: (11)

i was just thinking hot air is more prone to detonation even though it isn't as dense

denchan350gt

iTrader: (4)

I have the same problem with my engine.

I have standard 8:5 arias pistons with pauter rods running a GT35R at 10-12psi.

I had the piston go in cylinder 3 only, the others were fine with a little damage to the head.

I would sometimes get random cylinder misfires and sometime I would get cylinder 3 only. I would change the spark plug and it would go away thinking it was the plug.

I talked to arias and they said that maybe I have a faulty injector or bad coil pack for that cylinder and that I should check it out. What do you guys think?

Well here are pics of my piston with obvious detonation.

rcdash

iTrader: (18)

denchan350gt, what EMS were you running and was it reading knock?