High RPM RB's - Share Your Story

[Chopstick Tuner]

Hey folks, 

 

This thread is for the people who are (or previously have) ran RB's to decently high revs. I want to know the details to see what works, and what's worth it. Currently I have an Rb20det and curious as to what's an achievable rpm limit and what factors influence it. 

 

So what's your rpm limit, your build, what head work did you do, what turbo and boost did you run and at what point do certain size turbos begin to drop off etc etc

Share it all, curious to see how many of you are pushing 8k, 8500 or even 9k rpm and how your power and boost curves looked. Feel free to share dyno graphs. 

 

Cheers

[R_34]

Have an RB20 (currently sitting on a shelve), revved it to 8200rpm for around five years and it wasn't happy past 8000rpm but still pulled so i was using it past 8k regularly even if you could hear mechanical noises coming from the head. I don't know if it was the lifters not happy or valve float. I'd bet on the latter.

Decently sized higlflow turbo, 630cc injectors... just basic power upgrades and 20psi boost on E85 so nothing crazy.

A small chunk of a valve on the exhaust side decided to retire itself from the workforce and fly through the neighboring cylinders and the turbo for a better tomorrow.

Installed a broker motor and kept the revs to 7800rpm with the same setup, miss the 400rpm a little as the limiter is much more present, but motor didn't last long and wast extremely extremely rusty in the cooling jacket.

No graphs on E85, but I have one from the first motor on pump 98, 14psi/0.9b and stock airbox that showed 198 rwkw and 320Nm of torque. And the topic for RB20 dyno already exists so go find some graphs.

Stock limiter on an RB20 is 7600rpm, it's plenty enough with a good and decently sized turbo on it, don't go too big as the 20 quickly becomes a dog down low. 7800rpm was a nice sweet spot for me but my turbo was waking up late.

GT28 based turbo (2860RS/X2863) and the like, mid boost, stock limiter and enjoy. Street fun, decent power and powerband, reliable, can serve as a daily.

I'd say install springs in it i you want to rev it past 8k, especially with more than 12psi/0.8b of boost for peace of mind. The crank was decently balanced from the factory so not much to gain from that side, but mass from the rods and piston are a little all over the place. If you plan a refresh you might try to even things out on that side.

[Ben C34]

Budget and planed use aort of matter don't they?

 

Otherwise get in touch with Maatouks as they will build you something good for 10,000 rpm if you just give them a f**kload of money.

[Chopstick Tuner]

Budget is unknown hahah but I don't generally spare much expense with this car. Already have a pretty big shopping list of what I want to do with the engine to make a very fun, very reliable street car. Valve springs are inexpensive so I'm happy to buy them and already intend to, head will get checked over regardless, and will likely get aftermarket cams to try and improve the power curve. 

[BK]

The turbo power spread 90% determines the rpm limit - everything else is to support that limit - big camshafts and valvetrain, wild head flow etc.

You don't strap a turbo on that starts to fall off at 7krpm and continue to rev to 9k for example. Big revs generally mean big turbo.

[Chopstick Tuner]

On 18/04/2022 at 7:52 PM, BK said:

The turbo power spread 90% determines the rpm limit - everything else is to support that limit - big camshafts and valvetrain, wild head flow etc.

You don't strap a turbo on that starts to fall off at 7krpm and continue to rev to 9k for example. Big revs generally mean big turbo.

That's why I asked exactly that question in my post lol

[BK]

Is this a theoretical question or you just want big revs ?

If you want big revs - ideally have a very large turbo for your motor in question, large duration camshafts (minimum 272 duration) that come into their own at 8 9,10krpm, a head that is ported to flow hopefully 50% more cfm airflow than the stock casting, adequate seat pressure valve springs that can seat the valve at said rpm and have the lightest reciprocating mass bottom end ensembly that is practical (think titanium conrods with less than 1g weight difference and very light crankshaft with excellent balancing counterweighting etc.) All of this needs to be accounted for as crankshaft load goes up at square, so an upto 10krpm motor can turn to shit very quickly.

In practice a stock RB26 rev limit can be 8000rpm- 8500rpm completely unopened, so what do you define as high revs ? I say RBs over 9000rpm is above the norm but actually not that hard to achieve up to 9k.

Myself ? I have 8500RPM limits across all our RB26 because that's what the combinations support without falling off power.

[Chopstick Tuner]

Well I'm curious as to what others have set their limit to, and how they went about it and came to that conclusion. 

With regards to turbo and cam sizing, this is the info I'm trying to gather. Sure I'd love to rev to 9k, but if my Rb20 lags like hell until 5 or 6k then it's probably pointless lol and vice versa with boosting at 4-4.5 but topping out at 7500. 

I'm deciding things for my build and want to achieve a good wide power band, if I can do that and hit a 9k rpm limit then great, if it ends up being a better option to aim for 8000 or 8500 then that's cool too as long my goal is achieved. 

 

So, feel free to share specs, stories, whatever 👌

 

P.s I know the question was open ended but 10k is not a goal of mine lol but if anyone has hit it, feel free to tell us

[BK]

On 18/04/2022 at 9:06 PM, Chopstick Tuner said:

I'm deciding things for my build and want to achieve a good wide power band

Good wide power band and RB20 is usually not in the same sentence. Cost wise it'll be better to ditch the RB20 and go for a capacity increase.

[GTSBoy]

RB20 can be made to rev to 10K without too much trouble, although the hydraulic lifters can be hard to convince to play along. They are 30 years old.

The best solution is to twin charge. That way you get the engine to act like it is a 3L at lower rpm and rev like the short stroke 2L that it is up high, with a big open turbine housing to unload the exhaust pressure.

A 10K RB20 is otherwise a 6-10K engine. There is no lag down low, because there is no going down there. You stay above 6 or you suck.

[r32-25t]

Be interesting to see an rb20 with 10:1 compression ratio and then shove a decent sized turbo on it and let it rev

[Amaru]

On 4/18/2022 at 9:36 PM, Chopstick Tuner said:

Well I'm curious as to what others have set their limit to, and how they went about it and came to that conclusion.

9000rpm because that's what the data sheet for the HKS Step 2 2.8L stroker kit says it'll do - and the engine seems happy doing it 🤷‍♂️ N1 block, stroker kit, 272 cams, some mild head work, makes around 540awkw on E85. Engine's been solid, cops a beating with "2 stepping" and flat shifting sequential but it's getting retired to a more sedate street car life shortly to make way for a 10,000rpm 3.2L. 

 

[Chopstick Tuner]

On 18/04/2022 at 11:27 PM, GTSBoy said:

RB20 can be made to rev to 10K without too much trouble, although the hydraulic lifters can be hard to convince to play along. They are 30 years old.

The best solution is to twin charge. That way you get the engine to act like it is a 3L at lower rpm and rev like the short stroke 2L that it is up high, with a big open turbine housing to unload the exhaust pressure.

A 10K RB20 is otherwise a 6-10K engine. There is no lag down low, because there is no going down there. You stay above 6 or you suck.

The last part interests me lol even though I have no intention of hitting 10krpm, but I mean if I could have ample boost and power between 5k and 9k rpm? Then why not, I'd be happy with it lol

With regards to the inevitable comment about buying an Rb25 for the low down torque, considering my plans for the car regardless (rebuild, lots of new parts, update it some and tidy it maybe respray) are going to cost a lot, I'm not keen on dropping 5 or 6k on a stock Rb25 just for extra torque low down. Keen on the idea of building a good street Rb20. 

Like i said before, why not stick with the Rb20 engine(s) I already have and aim for good power from the 4500-5000 mark up to 8500-9000 rather than that extra torque below 4k to top out at 7500 

[Murray_Calavera]

Are there any setups in the 21 pages of RB20 dyno results pages that interest you? 

 

[Chopstick Tuner]

On 19/04/2022 at 5:58 PM, Murray_Calavera said:

Are there any setups in the 21 pages of RB20 dyno results pages that interest you? 

 

Considering about 90% of them are a decade or more old (different set ups and parts to what's available/what I'll be running now) and I found most were revving to 7500rpm, not all that relevant to my question

Edited April 19, 2022 by Chopstick Tuner

[BK]

On 19/04/2022 at 5:09 PM, Chopstick Tuner said:

Like i said before, why not stick with the Rb20 engine(s) I already have and aim for good power from the 4500-5000 mark up to 8500-9000 rather than that extra torque below 4k to top out at 7500 

Why are you assuming an rpm top out at 7500 on a non RB20 engine ?

Since this is centred around the RB20 now what turbo do you think is realistically going to achieve this on an RB20 ?

Be honest - what do you have in mind for a turbo to have a 4500 - 9000 power band on an RB20 now ? What range is good power to you ?

On 19/04/2022 at 6:17 PM, Chopstick Tuner said:

Considering about 90% of them are a decade or more old (different set ups and parts to what's available/what I'll be running now) and I found most were revving to 7500rpm, not all that relevant to my question is it? 

As suggested above have a good read of the RB20 dyno thread to gauge your expectations vs reality. The thread is still completely relevant as the RB20 is still and RB20 engine. You see why most are not revving their arses of to 9000rpm - because of the fundamental principle I raised about the turbo dictating the rpm range, and most of the turbos they're using are falling off power below 8000rpm. If you've gotta go a turbo that is capable of still making power at 9000rpm on an RB20 you have just shifted your whole powerband to the right haven't you ?, meaning you don't have that 4500 - 9000rpm power band you're after.

Turbos have definitely improved since then granted, so being the RB20 what it is an ideal turbo would have to spool relatively quickly with relatively low exhaust gas flow but not choke at the rpm you're talking about. An EFR or Precision would have to be the considerations I would think to even have a shot at achieving what you're after on a 20, butI suspect the results will still be underwhelming.

[Chopstick Tuner]

On 19/04/2022 at 7:08 PM, BK said:

Why are you assuming an rpm top out at 7500 on a non RB20 engine ?

Since this is centred around the RB20 now what turbo do you think is realistically going to achieve this on an RB20 ?

Be honest - what do you have in mind for a turbo to have a 4500 - 9000 power band on an RB20 now ? What range is good power to you ?

As suggested above have a good read of the RB20 dyno thread to gauge your expectations vs reality. The thread is still completely relevant as the RB20 is still and RB20 engine. You see why most are not revving their arses of to 9000rpm - because of the fundamental principle I raised about the turbo dictating the rpm range, and most of the turbos they're using are falling off power below 8000rpm. If you've gotta go a turbo that is capable of still making power at 9000rpm on an RB20 you have just shifted your whole powerband to the right haven't you ?, meaning you don't have that 4500 - 9000rpm power band you're after.

Turbos have definitely improved since then granted, so being the RB20 what it is an ideal turbo would have to spool relatively quickly with relatively low exhaust gas flow but not choke at the rpm you're talking about. An EFR or Precision would have to be the considerations I would think to even have a shot at achieving what you're after on a 20, butI suspect the results will still be underwhelming.

This forum can be a pain 🤦‍♂️ 

I'm just asking the question, to see if anyone has any real world examples of their RB's making decent revs, and to see what they sacrificed low down, and what turbos their running. So why ask me what turbo I'm gonna run? 

So if you have an example of one doing anything decent from the 4500 mark to 8000 or higher then I'm keen to see the set up, if not then chill, not every forum post has to be a keyboard contest where you use both extreme ends of my examples to argue (notice I have mentioned a FEW ranges, I didn't ask for a blueprint to make full boost 450hp from 4k to 9 or 10k rpm) 

 

I'm just posing a question, as part of my own research, to see if people have some more *detailed* descriptions of setups that worked. The whole point of the power band is what I'm asking. Relax. 

[Ben C34]

Haha, get angry mate.  Your question is so open ended and pointless,  the fact you can't see that is pretty funny.

On 4/19/2022 at 6:51 PM, Chopstick Tuner said:

This forum can be a pain 🤦‍♂️

 

[Chopstick Tuner]

On 19/04/2022 at 7:43 PM, Ben C34 said:

Haha, get angry mate.  Your question is so open ended and pointless,  the fact you can't see that is pretty funny.

 

Not angry but cool, good for you. 

 

R_34, GTSBoy had relevant feedback, and some of BK's info was very useful. Hardly a pointless question when these motors have been built a variety of ways and guys who've done/seen it can talk about the pros and cons. It's just a forum about car shit dude lol

But sure, get hostile on the internet if makes you feel good, you do you. 

[BK]

Genuinely trying to make you understand how it works.

Have a look at results for the Precision 5558 or 5858 on an RB20 to see if they are to your liking - they are out there