High RPM RB's - Share Your Story

[Chopstick Tuner]

On 19/04/2022 at 7:53 PM, BK said:

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

Thanks will do, examples like this is what I'm looking for. For the likes of an Rb20det I'm not sure how well something like a 3071r (just for size example) would spool, or perhaps smaller. Be interesting to see if anyone has made any decent response improvements with say twin scroll manifold and better cams 

[GTSBoy]

On 4/19/2022 at 6:01 PM, Chopstick Tuner said:

For the likes of an Rb20det I'm not sure how well something like a 3071r (just for size example) would spool, or perhaps smaller.

Too small for the rev range you're talking about. Do the maths on the torque that you'd expect/want the engine to be making, multiplied by the revs (north of 9k) and that's your power number. That gives you your turbo flow requirements.

There's no point in revving it high if it's not making torque up there. If you're not making >350Nm.....

[Murray_Calavera]

I found something that might be of interest to you, its not an RB20, but I think it might be of interest because its a similar capacity turbo car that revs to about 10,000 RPM. Power comes on about 6,000 RPM. Seems to be around what your looking for. 

I hope you've got the budget though, the turbo on its own is about $6,000.

 

 

[Chopstick Tuner]

Appreciate the feedback although I think you've missed what I wrote before. 8000 to 9000 is where I said I'd like to be if feasible (not trying to get to 10k because that's a lot of extra work), but the hpa video is interesting since it made power from 6k to 10k, then perhaps it seems possible to make power from 5k to say 8500 or even 8250

[Chopstick Tuner]

On 19/04/2022 at 10:15 PM, GTSBoy said:

Too small for the rev range you're talking about. Do the maths on the torque that you'd expect/want the engine to be making, multiplied by the revs (north of 9k) and that's your power number. That gives you your turbo flow requirements.

There's no point in revving it high if it's not making torque up there. If you're not making >350Nm.....

Fair point. Roughly what rpm would you say a turbo this size would Max out at? 

[Predator1]

On 20/04/2022 at 8:12 AM, Chopstick Tuner said:

Appreciate the feedback although I think you've missed what I wrote before. 8000 to 9000 is where I said I'd like to be if feasible (not trying to get to 10k because that's a lot of extra work), but the hpa video is interesting since it made power from 6k to 10k, then perhaps it seems possible to make power from 5k to say 8500 or even 8250

8-9k is achievable on a basic RB anyways. But if your turbo is falling off at 7, then there's no point in revving it any higher. Mines fully built, and I only rev mine to 9.

[GTSBoy]

On 4/20/2022 at 4:37 AM, Chopstick Tuner said:

Fair point. Roughly what rpm would you say a turbo this size would Max out at? 

So....the genuine GT3071 is good for something like 500 engine HP, maybe a smidge less, and on a small engine like an RB20, almost certainly less rather than more. At 9000 rpm your engine needs to be making 400Nm (!) of torque in order to make that much power. If you want peak power at 9500, then you only need to make 375Nm.

So, realistically, despite what the other guys are saying (for reasons I will get into below**) there is actually no "what rpm would you say a turbo this size would Max out at?".....so long as the engine configuration is flexible. By "engine configuration" I mean the cams, porting, compression and so on that determine where it wants to make peak torque and how high it will be able to rev.

** If you're talking about a mostly stock engine, like the other guys are mostly basing their statements on, then yes, you need to match a turbo's capacity to what the engine can use at the stock rev range, or only slightly more. It's all the same calculation - how much boost and mass flow rate of air from the compressor map against what torque the engine will need to make at your anticipated peak power revs, and whether it is then possible to make that torque from that much boost. If the engine can't make that much torque, then the turbo is not a good match. If the engine can make that much torque at that boost, but the turbo can't flow enough (or is actually too large and perhaps running inefficiantly) then the turbo is also not a good match. Doing this from first principles is quite difficult, which is why most people just work from anecdotal evidence, ie "this engine did X with turbo Y", and then extrapolate from there.

[Komdotkom]

The elephant in the room here is the $25k gearbox to go with a $500 motor.

As someone who has spent an unwise amount of money on an RB20 to make it semi decent, build a dirty 30 and enjoy life.

[Ben C34]

On 4/20/2022 at 5:42 AM, Chopstick Tuner said:

then perhaps it seems possible to make power from 5k to say 8500 or even 8250

On 4/18/2022 at 9:06 PM, Chopstick Tuner said:

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

going round in circles a bit. 

what do you really want from the car? Why are revs the main focus at the moment?

[admS15]

Convert to 13B BP or PP. Problem solved, endless revs and the noise, that delightful noise..

[Lithium]

On 20/04/2022 at 11:46 AM, admS15 said:

Convert to 13B BP or PP. Problem solved, endless revs and the noise, that delightful noise..

Can confirm, a mate has a 500whp bridgeport 13B R32 GTS-t and it's hilarious fun

Edited April 20, 2022 by Lithium

[GTSBoy]

On 4/20/2022 at 8:00 AM, Lithium said:

Can confirm, a mate has a 500whp bridgeport 13B R32 GTS-t and it's hilarious fun

This is very interesting to me. In that....."how can I make my car both better and worse at the same time?" kinda way.

[Lithium]

On 20/04/2022 at 12:25 PM, GTSBoy said:

This is very interesting to me. In that....."how can I make my car both better and worse at the same time?" kinda way.

Haha, well the old engine was an RB20 so realistically there isn't much that is worse going to a 13B aside from reliability.  

[GTSBoy]

On 4/20/2022 at 8:41 AM, Lithium said:

aside from reliability.

Yes, that is definitely the "worse" thing I was talking about.

[Lithium]

On 20/04/2022 at 12:44 PM, GTSBoy said:

Yes, that is definitely the "worse" thing I was talking about.

To be fair that hasn't actually been an issue, it's been running for near a decade (granted, no daily haha) and I went for a hoon in a few months ago so I assume it's not THAT bad.  The engine is likely to get pulled to put in a 20B for awesome as opposed to necessity

[Komdotkom]

Why no quad rotor? Twice as reliable.

Perhaps.

But epic sound!

[Lithium]

On 20/04/2022 at 2:00 PM, Komdotkom said:

Why no quad rotor? Twice as reliable.

Perhaps.

But epic sound!

20B is a LOT cheaper to build and easier to install, and in some ways the sound may make people second guess what's in it as well.  Hopefully with a decent matched turbo it should be peppy enough

[Komdotkom]

On 20/04/2022 at 12:11 PM, Lithium said:

20B is a LOT cheaper to build and easier to install, and in some ways the sound may make people second guess what's in it as well.  Hopefully with a decent matched turbo it should be peppy enough

They make great power too, a mate has a 20B S4 RX-7, but even used motors are fetching huge dollars now.

But they don't sound like a 4 rotor. I've always wanted to this to my 240z but I've already got enough projects.

 

[Lithium]

Maybe an unpopular opinion, but I prefer 20B sound 80% of the time.  26Bs sound great when NA and at full revs, but 20Bs sound good all the time

 

[r32-25t]

I completely agree, the 20b just has its own sound and it’s much nicer then any other rotary 

The 13b sounds like shit and the 26b just sounds like 2 13bs running at the same time