Power And Reliability Using Stock Rb30e Pistons

[works 510]

Guys,

Looking to start a rb30det project since the bottom end has died in my rb25.

Motor is a series 1 r33 rb25det.

Have done abit or research and am armed with the twin cam rb30 guide.

Chose to go the rb30 route due to overall cost involved, and cubes are good

I have a decent budget but am not overly rich so seeing if I can save some moneys.

Current things I have bolted to the rb25 are:

kkk k26 2670 (330ps rated) with external wastegate, 480ccc injectors,z32 afm, exh, intercooler,

Will be using stock cam's, but going to using greedy/jun or copy inlet manifold to make sure I dont get into trouble with the extra deck height in the cefiro.

Now,

I need some opinions, especially from the guys who are running standard bottom ends.

How long have they been running for, with what modifications and what boost?

I plan on upgrading to a larger k26, looking for 250~ rwkw's

Possible to get away with using some new cast ACL or similar brand pistons for the power Im chasing?

Its a drift car, but not daily driven, reliability is a must.

Or just buy (insert brand name) forged pistons for peice of mind?

Dont mind spending the extra on forgies, but any money saved is a bonus.

Thanks for your time

Dan.

[works 510]

Just did some more reading, looks like Im going the stock piston route, either with new pistons or just a hone and re-ring.

Now to find some time to get a series 2 bottom end

[Sydneykid]

9 years, 10 in couple of months

1 bar of boost

6500 rpm limit

300 rwkw

Cheers

Gary

[R.I.P.S NZ]

7 years, 1.5 bar + 100hp NOS, 450wkw with nos, low 10s, 7200rpm limit, stock bottom end with new rings and bearings only.

the power your after is effortless on stock pistons, its all in the tune.

[GT-RZ]

7 years, 1.5 bar + 100hp NOS, 450wkw with nos, low 10s, 7200rpm limit, stock bottom end with new rings and bearings only.

the power your after is effortless on stock pistons, its all in the tune.

When you post info like that it makes me wonder why i'm bothering to build my setup with forgies... i'm going for <400kw...

o well. better safe than sorry... i don't have a book of secret tricks that you guys do...

[bubba]

i don't have a book of secret tricks that you guys do...

I think that's the money winner right there.

[R32Abuser]

i think the thing to keep in mind is that irrelevent of pistons, the reliability comes from the tune. Forgies will give you a little more tolerance to a bad tune, but at the end of the day, if the tune is terrible, it wont matter whether you have forgies or stockies, they both will fail. However your engine is only as good as its weakest link in reality.

I have decided to go with forgies, not for the strength (thats a bonus), but for the higher compression ratio (9:1). They will give me better off boost response. I think there are numerous stock bottom ends going round with 300RWKW.

As Sydneykid said,

1 bar of boost

6500 rpm limit

that paired with a good tune, and regular maintenance will yield a reliable motor.

Edited July 8, 2009 by R32Abuser

[GT-RZ]

i think the thing to keep in mind is that irrelevent of pistons, the reliability comes from the tune. Forgies will give you a little more tolerance to a bad tune, but at the end of the day, if the tune is terrible, it wont matter whether you have forgies or stockies, they both will fail. However your engine is only as good as its weakest link in reality.

I have decided to go with forgies, not for the strength (thats a bonus), but for the higher compression ratio (9:1). They will give me better off boost response. I think there are numerous stock bottom ends going round with 300RWKW.

As Sydneykid said,

1 bar of boost

6500 rpm limit

that paired with a good tune, and regular maintenance will yield a reliable motor.

That's all true but really i like a bit of tolerance with my engines...

The winning combo for them both is the relatively low RPM limits. With the 3litre being quite a bit longer in the stroke it suffers far greater piston speeds than the likes off the rb26 at the same RPM.

Apparently even 450kw is fine for the stock rods in regards to combustion pressures. With that said the true benefit of the RB30 is getting higher torque @ lower RPM often proving a more reliable engine due to everything else operating in a more 'comfortable' zone for the target HP in comparison to a 26. Given them figures unless you're chasing after a massive HP engine i can't see the need to go over 7200rpm...

I was thinking about just new pistons to get the higher cr but for the price of rods and the piece of mind and potential progression of the engine in the future it's hard to resist!

Edited July 8, 2009 by GT-RZ

[Adriano]

I have bent an rb30 rod at less than 450rwkw. IMO the safe limit of the stock rods is more like 370rwkw depending on revs

Edited July 9, 2009 by Adriano

[works 510]

Thanks for the info guys.

Even with the low CR of 8.2, I would of thought being a 3litre, it would be still tractable?

Looks like If I dont stuff up the initial build of the motor (clearances etc) my motor should like a long happy life.

Tune pending haha

Cheers,

[R32Abuser]

if your comparing it to the RB25, then yes it will have more "balls" down low, but a stock RB25 has a 9:1 CR, so dont expect it to be anything gobsmackingly huge like it is going from an RB20 to a 30. Keeping VVT will help a little but its up to you whether you want teh added effort.

[N1GTR]

Why not go higher CR?

I had a motor with that compression, would never do it again

[works 510]

Its starting to come down to a budget VS need thing.

Build it properly the first time etc, but the budget is already getting killed as I think of other things that need to be changed/modified to suit the extra deck height.

From what ive red so far, the rb30e pistons will be good for the output im chasing.

Big boost wont be used either, and ive got a baby turbo so should be responsive as.

[R.I.P.S NZ]

I have bent an rb30 rod at less than 450rwkw. IMO the safe limit of the stock rods is more like 370rwkw depending on revs

There will be a reason you bent a rod and I'd be pretty sure you had a dud rod or another issue all together.

A friend has a RB30 with stock rods in a track gtst, he runs well over 500wkw/8000rpm and its been going for a very long time.

I still maintain that stock parts are incredibly durable if everything is setup and tuned properly and its highly unlikely you'd be hurting parts from power alone, there will surely be other factors.

My 240z engine with a totally stock, unfilled, non braced 2wd RB30 block with a stock crank running around 1400hp, 9500-10,000 rpm is WAY beyond what I was told by everyone was possible yet with extreemly carefull setup and tune it has been reliable and we intend to push them alot further yet with the ultimate goal being a 6 and 200mph on the same old stock block and crank and I genuinley think we'll do it.

Rob

[GT-RZ]

That will be something special. I have been thinking for a while about getting a stock rod tested just to see what the maximum stresses are! Unless someone knows the metal properties of one then i could work it out... R.I.P.S??? any info

It would be very nice to be able to work out the theoretical max of HP vs RPM combination's.

The problem with having higher RPM with stock rods is where i'd be worried tbh. theoretically before we take in to account other 'weaknesses' if we were to double the combustion pressures (more fuel,boost) we only double the force on the rods, but if we were to double the RPM we quadruple the force on the rods.

Rob, you say your freind was running 8000rpm with stock rods, but what pistons did he have? If he had forged pistons which are generally allot lighter than the standard cast pistons then adrianno was certainly at a disadvantage.

Adrianno what max RPM were you using?

Edited July 11, 2009 by GT-RZ

[MBS206]

If you're using it for circuit work, the best way to keep it reliable, is to look at your oil supply.

Engines are not a fan of oil surge, and these motors are known to surge on the track... Mine did...

[SLAPS]

There was a thread on calaisturbo some time ago as to what rpm the stock rods can handle.

A lot had pushed in to the 8000rpm territory.

I presume those that hung together run an ATI balancer of sorts.

I've been running mine to 7300rpm since I can remember with out issues on stock rods.

A mate also ran his RB30ET to 470rwkw with WMI but a limiter @ 7k for a good 1.5years odd.

No issues with rods but did end up cracking a piston due to a failed alternator that resulted in lean out. :S

I went with forged pistons in mine as I figured cheap(ish) insurance and were a lot lighter than the factory cast.

Edited July 12, 2009 by SLAPS

[bubba]

There will be a reason you bent a rod and I'd be pretty sure you had a dud rod or another issue all together.

A friend has a RB30 with stock rods in a track gtst, he runs well over 500wkw/8000rpm and its been going for a very long time.

I still maintain that stock parts are incredibly durable if everything is setup and tuned properly and its highly unlikely you'd be hurting parts from power alone, there will surely be other factors.

My 240z engine with a totally stock, unfilled, non braced 2wd RB30 block with a stock crank running around 1400hp, 9500-10,000 rpm is WAY beyond what I was told by everyone was possible yet with extreemly carefull setup and tune it has been reliable and we intend to push them alot further yet with the ultimate goal being a 6 and 200mph on the same old stock block and crank and I genuinley think we'll do it.

Rob

What have you done to the "stock" crank?

[GT-RZ]

lol. stock means stock right? I would like to know too, hopefully without paying $$$

[proengines]

In all reality you can go a long way with std rods and pistons but honestly, if you pay someone to do everything properly you don't save a lot. Have a set of standard rods checked, new bolts fitted, closed and honed, pin bushes replaced etc and see what it costs. Then compare that to a cost of Spool rods, you might save $350-400, if that. Forged pistons will set you back maybe $700 more than a set of cast stock ones, maybe as little as $500.

Compare the price to re-ringing a set of 20 year old factory pistons and doing nothing to the rods and it might seem a big cost but if someone's going down that path the argument is pretty null anyway, the difference between doing it properly with cast pistons/stock rods and forged pistons/aftermarket rods is small. They might cost you $1000 extra but over the total price of the engine, it isn't a huge percentage for the piece of mind it gives you.