3x Times The Same Problem Hole In The Piston Rb25det Why? Please Help

[JapanDyno.com]

hi Guys

i have a question / problem

we builed a few Rb25DET with diffrent setups

for example ruff list

R34 GTT HKS GT2835 @1,2bar 480cc power fc forged pistons 88mm

R34 GTT HKS GT2835 480cc @1,0bar power fc forged pistons 87mm

R33 GTST HKS GT2535 stock injectors @0,8bar Mines VX ecu

the cars are used in Drift , Drag and on the Nuerburgring race track ( not only daily drive)

here the problem

all 3 cars got the same damage on the 6th piston the piston got a whole on the side why? any idea

its not funny anymore please let me know any info will help

dino

[The Dan]

Pictures?

When you ask a question like that, you need pictures...very high detail close up pictures....that way I/we could identify the type of failure,

Any reason for going for 88mm pistons?

[JapanDyno.com]

Pictures?

dont have pics now here sorry

forgot to says that always when i get a hole in the 6th piston also another 3 pistons ring are killed too

Edited July 11, 2008 by JapanDyno.com

[R31Nismoid]

Sounds like good ole shit tuning to me.

Not enough fuel in the last, detonation, death.

[JapanDyno.com]

Sounds like good ole shit tuning to me.

Not enough fuel in the last, detonation, death.

yeah on the power fc i would understand also, but the R34s are dyno tuned air fuel ratio etc all perfect

but on the close to stock engine R33 with ready tuned ecu`???

dino

[R31Nismoid]

AFR's doesnt mean that much.

One cylinder might be getting a bit too hot.

Im assuming your putting the best flowing injectors in the 5th/6th spot etc?

Could be a number of things, even the assembly of the motor?

Get some pics

[GeeTR]

AFR's doesnt mean that much.

Zactly your (most likely) tuning from a single point (dump / tailpipe) which represents the accumulative AFR of each cyl. One's then assuming a cyl is under the same conditions as the one next to it (hence XYZ AFR applies to each)

The setups you listed don't mention plenum / e.manifold changes, so it could be simply they've been tuned too hard (lean)... From the tuning RB tuning experience I have (not much), RB's are quiet suceptable to rattleing once back on the road from a edgy dyno tune.

My cents

Edited July 11, 2008 by GeeTR

[craked]

read the spark plug they will tell you whats going on check if number 6 is white when the rest are darker

[The Dan]

but on the close to stock engine R33 with ready tuned ecu`???

There is no such thing as a ready tuned ECU. Every engine is different, stock or not.

The setups you listed don't mention plenum / e.manifold changes, so it could be simply they've been tuned too hard (lean)..

Exactly. It's more like NS.com here all the time....'Hey I have a hole, can anyone tell me what went wrong? I don't have pictures and I don't list the entire mod list'

Yeah sure, we'll all have a GUESS.

First, get pictures....Second, list ALL mods not matter how insignificant, Third...we give you some proper answers that actually mean something other than 'It could be this, or it could be that'

read the spark plug they will tell you whats going on check if number 6 is white when the rest are darker

That is true but also know that it will only usually tell you what happened in the five minutes leading up to the removal of it. If it went idle for a couple of minutes it will taint the results.

But yeah, still a good idea to check them.

[JapanDyno.com]

There is no such thing as a ready tuned ECU. Every engine is different, stock or not.

Exactly. It's more like NS.com here all the time....'Hey I have a hole, can anyone tell me what went wrong? I don't have pictures and I don't list the entire mod list'

Yeah sure, we'll all have a GUESS.

First, get pictures....Second, list ALL mods not matter how insignificant, Third...we give you some proper answers that actually mean something other than 'It could be this, or it could be that'

That is true but also know that it will only usually tell you what happened in the five minutes leading up to the removal of it. If it went idle for a couple of minutes it will taint the results.

But yeah, still a good idea to check them.

i realy want help

ok no problem i will make some pics tommorowof the 2 still damaged engines

the Neo engine is abit white over all pistons so probably to lean

the R33 engine was normal black like normal all sparks plugs look fine to me braun/black

just found strange that all cars have the same problem but

the one RB25DET NEo is already rebuilded now

here the details of the 2 still damaged engines one

R34 GTT Damage happen on higway at 260kmh

HKS Intercooler

HKS Power intake

HKS GT2835 Pro S @ 1,2bar

Tomei head gasket

DI splitfires

Forged Pistons 88mm

Forged Rods

Forged Stroke

NISMO 480cc

Oil Catch tank

Stock Plenum

Stock Exhaust manifold

Polished head intake and Tunnels

Kakimoto Exhaust (no cat)

Apexi Power FC

AVCR 3 Blue screen

NISMO Coppeer mix

probably run to lean on the high way for a long time

R33 damage happen on highway too 120km

Greddy Intercooler

HKS Power intake

HKS GT2535 @ 0,8bar

Oil Catch tank

DI splitfires

Stock Injectors

Stock Plenum

Stock Exhaust manifold

Kakimoto Z01 Exhaust (with cat)

Mines VX ecu

AVCR 3 Blue screen

Cusco twin platte

here i dont understand why ? maybe its just the age?

Edited July 11, 2008 by JapanDyno.com

[rb26s13]

i dont see any mention of fuel pumps there..

[The Dan]

i realy want help

ok no problem i will make some pics tommorowof the 2 still damaged engines

the Neo engine is abit white over all pistons so probably to lean

the R33 engine was normal black like normal all sparks plugs look fine to me braun/black

just found strange that all cars have the same problem but

the one RB25DET NEo is already rebuilded now

here the details of the 2 still damaged engines one

R34 GTT Damage happen on higway at 260kmh

HKS Intercooler

HKS Power intake

HKS GT2835 Pro S @ 1,2bar

Tomei head gasket

DI splitfires

Forged Pistons 88mm

Forged Rods

Forged Stroke

NISMO 480cc

Oil Catch tank

Stock Plenum

Stock Exhaust manifold

Polished head intake and Tunnels

Kakimoto Exhaust (no cat)

Apexi Power FC

AVCR 3 Blue screen

NISMO Coppeer mix

probably run to lean on the high way for a long time

R33 damage happen on highway too 120km

Greddy Intercooler

HKS Power intake

HKS GT2535 @ 0,8bar

Oil Catch tank

DI splitfires

Stock Injectors

Stock Plenum

Stock Exhaust manifold

Kakimoto Z01 Exhaust (with cat)

Mines VX ecu

AVCR 3 Blue screen

Cusco twin platte

here i dont understand why ? maybe its just the age?

Good stuff.

And yeah, what Wazz said...what fuel pump/s are you using?

If the pump is good and the tune is good then there will be only a few possibilities.

Be sure to take high res photos of the rings if you can too. Also, of the pistons skirts and crown...top as well. Pretty much every angle.

With the Neo, what piston to bore clearance did you use and who does your engineering work?

What ring end gap was used? Have you used the same engineer to do all the machining work for all of these engines?

[RPMGTR]

Forget about fuel, machining, fuel pumps, wah, wah, wah.....

Lets clear up a fallicy here...THE ONE thing that breaks and melts engines is ignition/detonation!!!

If the engine doesnt have enough fuel it wont make power or will stop.

It only melts or breaks if you are using an overly rich mixture to dampen detonation and you then remove some of the fuel.

If the timing is in the correct zone then you can remove some or all of the fuel without hurting anything except the performance.

However, the real reason the cylinder that fails most is nearly always number 6 is quite simple really.

The load is on the flywheel end of the crank. the CAS is on the opposite end.

When under load, the crank winds up, effectively advancing the timing on the engine as you head towards the rear.

So the rear cylinder gets the most timing as it is closest to the load.

That IS why it most often fails.

Throw more fuel at it if you wish, but it is not the answer.

Retard it 10 degrees and you wont be able to hurt it no matter what you do to the a/f, but nor will it make much power.

Finding that balance is the art of tuning.

cheers

[crack]

well bugger me. i would never have thought of that. makes complete sense too.

thanks for the insight ben.

[GeeTR]

...The load is on the flywheel end of the crank. the CAS is on the opposite end.

When under load, the crank winds up...

Could the crank distortion seriously be that great? I know of 2000 HP drag racing 2J's in the US run a hall effect and disc on the crank to limit timing errors from cam belt stretch, but crank twist? Crazy stuff

[GTR1993]

Forget about fuel, machining, fuel pumps, wah, wah, wah.....

Lets clear up a fallicy here...THE ONE thing that breaks and melts engines is ignition/detonation!!!

If the engine doesnt have enough fuel it wont make power or will stop.

It only melts or breaks if you are using an overly rich mixture to dampen detonation and you then remove some of the fuel.

If the timing is in the correct zone then you can remove some or all of the fuel without hurting anything except the performance.

However, the real reason the cylinder that fails most is nearly always number 6 is quite simple really.

The load is on the flywheel end of the crank. the CAS is on the opposite end.

When under load, the crank winds up, effectively advancing the timing on the engine as you head towards the rear.

So the rear cylinder gets the most timing as it is closest to the load.

That IS why it most often fails.

Throw more fuel at it if you wish, but it is not the answer.

Retard it 10 degrees and you wont be able to hurt it no matter what you do to the a/f, but nor will it make much power.

Finding that balance is the art of tuning.

cheers

Do you have any info to back this up? I done a quick google and it seems that its under a degree of twist in most cranks, and a good balancer is designed to reduce this twisting motion. Either way if it was more then a few degrees the crank would fatigue and fail.

Edited July 12, 2008 by GTR1993

[robots]

I think what he meant is that the tune sucked. And you have to look into that.

Cheers !

[tridentt150v]

I'd question the 480/the stock injectors>>>They'd be fine until you get sustained high demand, can't see how they can maintain the fuel delivery at 260kmh. I would have thought that you'd need bigger?

[AutoTrust]

In my limited experience running aggressively advanced cam timing with the correct or rich fuel mix will cause severe piston damage, alot of good points have been made in regard to general tune but in this circumstance it seems the same tuning error has been made three times. if this was a customer of mine or my own car i would be monitoring the exhaust temp or cylinder temperature on each cylinder for more information.

I would also think that with these mods an aftermarket fuel pump and regulator would be part of the equation.

The most likely problem is however that the drivers of these cars are most likely thrashing the living sh1t out of the engines regularly.

When I was young I could kill a freshly rebuilt engine in a matter of months, or weeks if i was in the mood.

When these cars were tuned what were the fuel ratios at max power? and WTF is with the 34 doing 260kph on a highway? that's 8000 rpm or there abouts.....

PICS

[Shaun]

I was told (and it makes sense to me) that cylinder 6 fails commonly due to the simple fact that its the furtherest away from the water pump and radiator, thus running hotter. Also, on a stock setup, number 6 injector is the last to be fed with fuel from the front of the rail. Doesnt help your problem, but just added input.

Mine went bang on 6 too. Its a bitch of a thing.

Shaun.