Max Boost On Stock Rb30 Bottom End?

[leeroy_25]

I am sure it's been answered before but I cannot find it! Also I have an interesting statement regarding this point. I was guessing around 1.5bar would be max boost on a Stock Rb30 bottom end. I am running RB26 head by the way. So nice compression. What do you say?

Some one said this to me...

'The boost thing, its funny, people worry too much, and to be honest, its not much about the strength of the internals, its about the quality of the mapping.

The increased pressure is nothing, say another 15psi boost in the cyls, 2bar rather than 1bar say. When it comes down to it, cylinder pressure on a most performance engines are 10-11bar standard, boost as a pressure itself does nothing too scary. Its exactly how these race diesels run 150psi+ because the cyl pressure isnt the issue, its the pressure when it dets.Det increases the cyl pressure to silly amounts, and thats what breaks things, 2bar is as safe as 1bar if there no det, just mappers in the UK seem to try and make things right on the limit of det, lean and advanced as poss, and granted that gives maximum power for the boost, but it also blows it up the min something goes out of peramiter!Safe fuel and ign settings, and you would be suprised what you can safely run.'

I can see the point to some extent but surely there is a limit which will be determined by the engine internal strength and static compression ratio.

Thoughts please.

Thanks

Lee

[CEF11E]

if you have a stock bottom end here are my rules to give it a decent lifespan

1. No leaner than 11.8 to keep tempratures down and supress the chances of knock

2. Keep your timing below 19deg at and above peak torque. it's plenty of timing to make big power wth a long stroke, big turbo and large cubes. this will also prevent knock if your afr's are no leaner than above

3. keep your rev limit set to no higher than 6800. rb30's dont like high revs. the psiton speed in an RB30 is around 16% higher in a 30 than it is is a 20 as the piston has to travel further top to bottom of stroke.

as for boost, limit it to 17psi if your comp ratio is close to 8.5:1 or 300rwkw whatever comes first. rod and piston strength becomes an issue over this level.

remember boost is compounded by compression. so if static is 100 psi then 100psi +15 psi of boost will not mean 115psi don't have a calc but would be more like 170psi

cheers!

[VB-]

where did you pull this magic 19* of ignition timing from? every motor is different, that would be far too much in some cases.

you can also run more than 17psi in a stocko RB30, been done heaps of times (probly into the hundreds when you look at VLT's)

[CEF11E]

19 deg is based on running 98ron fuel with no more than 17psi in a twincam rb engine.

i should know what i am talking about i have tuned over 30 of them

not trying to start a war, just giving my personal experience.

and you can run more boost but he asked what would be reliable.

[leeroy_25]

Thanks for the replies guys.. Good info I reckon and I did ask for reliable! Next question I have is I have heard plenty of people saying you can run a stock bottom end up to 600bhp flywheel power (including some big tuners!). So how does that effect things.. I was hoping to get 550hbp plus don't want to get too close to the max! Let me know what you reckon. Regards the pistons and rods obvioulsy being a weak link.. I have balanced mine and am going to get them peened. Was also thinking of ceramic coating the piston crowns or seeing if I can get some Hypereutectic ones that will drop straight in place of my OEM non-turbo pistons and give the correct compression without having to machine the block down. i.e around 8.5:1? Do you know if such a piston exists and if it's worth my while? I guess the stock pistons will be the first thing to let rip?? am I right? or will boost bend the rods first?

I was going for possibly ARP Rb25 or stock RB25 head bolts and ideally some better Rod boltd. I gather it's SR20 ARP ones I need?

Was not planning on doing the mains bolts though..

Let me know your additional thoughts and thanks for the time and info.

Lee

[MBS206]

If you're pulling it down, and rebuilding, don't put stock gear back in.

Put in good H beam rods, good set of bearings, and some forged pistons.

Then if you really want to play it "safe" stick to the same rules as have been stated above, and you should easily get 10+ years from it.

[leeroy_25]

Good advice but if I could afford to go with forged rods etc I wouldn't have started this post.

I am on a budget and it is my first build hence my option is to not go crazy and see what I can get from a stock based motor. R.I.PS sell rebuilt stock bottom ends as good for 600bhp. (approx 460rwhp I guess?) I am upgrading components I can afford to, like acl bearings rod bolts and getting the rods balanced and peened. The motor won't need to last 10 years! but to see 2 or 3 years from it i'll be happy! It won't often get track use or hard driving as it will be a fast road toy.. But on the occassion when I want to use it properly it will get used! I am a mechanically sympathetic kind of person as I understand how it all works so I tend to drive the motor with that in mind. I am not setting out to max the boost and rev the nut's off it constantly and blow it up!

So I guess I am aiming for something like 340-350rwkw if my maths is about right?!

I would like to know more on the boost front though. Will 1.4bar (20psi) blow it apart? 17psi seems quite low although I appreciate the pistons were not intended for a turbo application!

Just want to be realisitic about what I can achieve at the end of the day and what I need to get there!

Cheers

Lee

[MBS206]

Good advice but if I could afford to go with forged rods etc I wouldn't have started this post.

I am on a budget and it is my first build hence my option is to not go crazy and see what I can get from a stock based motor. R.I.PS sell rebuilt stock bottom ends as good for 600bhp. (approx 460rwhp I guess?) I am upgrading components I can afford to, like acl bearings rod bolts and getting the rods balanced and peened. The motor won't need to last 10 years! but to see 2 or 3 years from it i'll be happy! It won't often get track use or hard driving as it will be a fast road toy.. But on the occassion when I want to use it properly it will get used! I am a mechanically sympathetic kind of person as I understand how it all works so I tend to drive the motor with that in mind. I am not setting out to max the boost and rev the nut's off it constantly and blow it up!

So I guess I am aiming for something like 340-350rwkw if my maths is about right?!

I would like to know more on the boost front though. Will 1.4bar (20psi) blow it apart? 17psi seems quite low although I appreciate the pistons were not intended for a turbo application!

Just want to be realisitic about what I can achieve at the end of the day and what I need to get there!

Cheers

Lee

Take it from me mate.

If you're on a budget now, you need to slow the build, built it once, build it right.

DO NOT shortcut, or skimp out on things.

Buy the good brand name gear, and forge it right away.

If you really want to do it cheap, go buy a stockpile of RB30 blocks, and don't worry about rebuilding or breaking them...

[CEF11E]

Take it from me mate.

If you're on a budget now, you need to slow the build, built it once, build it right.

DO NOT shortcut, or skimp out on things.

Buy the good brand name gear, and forge it right away.

If you really want to do it cheap, go buy a stockpile of RB30 blocks, and don't worry about rebuilding or breaking them...

that's some good advice right there

stick to 270rwkw with a stock bottom end if you dont have the time or money to replace it

speak to sydneykid about this combo and its reliability at power levels. he has extensive knowlege

[Gts-t]

Im hoping for 300rwkw from my stock rebuilt bottom end running a 3076R at 1bar

From talking to SK i should be able to do it give or take a few kw's depending on the dyno and the day of course

[leeroy_25]

How do you get hold of SK on here?? I tried pm a little while ago and his box was full! I had some specific questions for him!

Only point I noted is I could run my stock RB26 and see the same power. I thought the point of going with the RB30 was for more power and torque? I could spend the money on my RB26 bottom end that my RB30 stock end cost and cme away with more power if that the case? When I started looking into this Tuners like RIPs and other guy's were saying 600bhp flywheel was achievable? Now it seems this isn't the case at all?

Cheers

Lee

[MBS206]

How do you get hold of SK on here?? I tried pm a little while ago and his box was full! I had some specific questions for him!

Only point I noted is I could run my stock RB26 and see the same power. I thought the point of going with the RB30 was for more power and torque? I could spend the money on my RB26 bottom end that my RB30 stock end cost and cme away with more power if that the case? When I started looking into this Tuners like RIPs and other guy's were saying 600bhp flywheel was achievable? Now it seems this isn't the case at all?

Cheers

Lee

Lee, think of it this way.

Power (HP/KW) is = RPM, * Torque / Constant.

Or in simple terms, RPM * Torque (We don't need to worry about the constant whilst now working numerically.

Now, you make the same power from your RB26 to a RB30 right.

But your RB26 is being revved to 8000 - 9000RPM. Most of us rev the RB30 to an ABSOLUTE, maximum 7500RPM, Mines only going to be revved to 6500RPM... Yet, I'll make the same power... What does this mean... I'm actually producing more torque, and therefore, will have a quicker car.

People need to learn to give no shit for peak power. It's all about the torque curve.

Torque curve from an RB30 RULES the RB26 Torque Curve.

Edited January 3, 2009 by MBS206

[R.I.P.S NZ]

How do you get hold of SK on here?? I tried pm a little while ago and his box was full! I had some specific questions for him!

Only point I noted is I could run my stock RB26 and see the same power. I thought the point of going with the RB30 was for more power and torque? I could spend the money on my RB26 bottom end that my RB30 stock end cost and cme away with more power if that the case? When I started looking into this Tuners like RIPs and other guy's were saying 600bhp flywheel was achievable? Now it seems this isn't the case at all?

Cheers

Lee

Lee, I'm telling you, 600bhp frpm a stock internal RB30 bottom end is so easy its not funny, we have them 5 and 6 years old making more than that and 10s in a heavy 4wd GTR from them is also no big deal, one I built and sold to a R34 GTR owner in UAE has been safely tuned to 650whp at 1.4 bar/7000rpm.

The boost and the bhp (to a point, which is WAY above 600bhp) won't break it, poor setup, mapping or excessive rpm may do though.

We just ran an 8.36 with a stock block and stock crank pulling nearly 10,000rpm, don't under estimate how good stock parts can be and don't let anyone tell you a RB30 "doesn't rev" its just rubbish.

Rob

[leeroy_25]

Thanks RIPs

This is goning to be interesting to see what replies get posted now!!

I was always planning on limiting my rpm to about 6750... absolute max 7000rpm.. but I prefer to play safe and tune it so the power comes in a bit lower down.. Clearly too many revs will kill a motor! I am trying my best to give it it's best shot of surviving well by balancing evyerhting in the bottom to the finet point! My rods are all within 0.1 of a gram.. Just gone for peening. Next I am debating whether to ceramic top the pistons or if that's not going to be much of a benefit? Also I don't know how much valve clearance is in the RB30/RB26 setup? i.e will a thick coating in the valve cutouts in the pistons mean the valves collide? I would imagine not? I know this is a subject Sydney Kid probably has good experience with! But From what I gather he doesn't get on here much these days.

I know you won't want to give too much away.. but CAM wise. would you stay stock.. run mild poncams or step 1 hks? Reason I ask is I always wanted to go Poncams if anything as they maximise the lift with nt too much added duration. Which I gather will keep the power low down the rev range. Now I just got offered a low mileage pair of HKS cams. 264/272 setup Step ones.. so less lift than I was after.. but what woud you reckon?

Anyway.. I have another post on that on here!

Cheers for the reply.

Lee

[Adriano]

I wouldn't have bothered with the stock rods, as by the time you do all that work it ends up costing the same as some aftermarket ones. The coating on the pistons is about .1mm, so it wont effect piston-valve clearance.

[leeroy_25]

Hey Adriano.. maybe the rod work would cost a bit.. That is if you can't do it yourself and has a mate who does shot peening!! In that case why not!?

Thanks for the clearance info.. That's cool. I best get the pistons prepped!

Lee