High RPM RB's - Share Your Story

[Chopstick Tuner]

On 20/04/2022 at 9:02 AM, GTSBoy said:

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.

Thanks for the feedback. The anecdotal evidence about different ways of building one of these motors is what I've been chasing, hence the kinda vague post (keen to see a variety of setups, why they were built a certain way etc) but allow me to try to clarify where I'm aiming. 

1. So my RB20 is never gonna make any big torque down low, it's simply not torquey enough compared to a 25, this is why I'm curious to see the pros and cons of getting one over 8k rpm, and whether anyone has managed a half decent power band by revving out higher (or if it simply moved it up higher). 

2. Motor won't be stock when all is said and done, it's gonna be over built internally for the power its gonna make, feel free to judge that decision but it's getting rebuilt and updated anyway so why not forge the pistons and rods for the extra bit of money is my thinking, along with making things more reliable (oil system, trigger kit etc) 

So the plan is obviously engine rebuild, standalone ecu, Garrett turbo (or similar quality, running maybe 14psi of boost or more depending on the power it makes), high mount manifold, ext gate, bigger rail, injectors, new intake plenum on stock runners most likely etc etc. As for the head I had planned valve springs and a freshen up/check over, but unsure on what cams, or whether to port etc. Which is part of what brings me here. 

 

3. Don't get me wrong I'm keen on an Rb25det, but I would do all the exact same work to it regardless so I've been (and still am) tossing up the idea of forking out the extra cash for the extra capacity. Trying to get a good picture of just how much shorter an Rb20det would fall compared to an Rb25det performance and driveabilty wise. A fun, bulletproof street car is the goal, not chasing a 500hp beast, if that helps. 

 

And as much as I love rotaries that's not gonna happen hahah

[GTSBoy]

On 4/21/2022 at 3:22 PM, Chopstick Tuner said:

1. So my RB20 is never gonna make any big torque down low, it's simply not torquey enough compared to a 25, this is why I'm curious to see the pros and cons of getting one over 8k rpm, and whether anyone has managed a half decent power band by revving out higher (or if it simply moved it up higher). 

8K is a walk in the park for a stock RB20. I simply raised the rev limit on mine (Nistune) to 8300 and ran it hard for years. Stock turbo though.

9k is not hard. Just need springs, and maybe consider the lifters as a potential weak point. Making strong power up there is, of course, a matter of cams and porting and so on, as I said before.

On 4/21/2022 at 3:22 PM, Chopstick Tuner said:

Garrett turbo (or similar quality, running maybe 14psi of boost or more depending on the power it makes), high mount manifold, ext gate,

Doing all of this, on a forged motor, and not planning to run 22+psi is a waste of time. You need boost and you need lots of it to make power on an RB20. With E85 you should probably be considering 30+ psi.

On 4/21/2022 at 3:22 PM, Chopstick Tuner said:

Trying to get a good picture of just how much shorter an Rb20det would fall compared to an Rb25det performance and driveabilty wise. A fun, bulletproof street car is the goal, not chasing a 500hp beast, if that helps. 

An RB20 is not a good motor for the street. By the time you have them up into the 250rwkW region, you have lag, lag, lag, lag, nothing, then more nothing, then.......wheelspin. As a track engine, kept right up on the boil, more acceptable.

For street use, I would seriously not be looking too exceed 200rwkW on a 20, to try to keep it more useful. But even that still matches the description in the paragraph above. I went RB25 and the thing actually accelerates before boost arrives, simply from that tiny bit of extra capacity. A 3L would be even better.

If I was stuck with an RB20, I would twin charge it. Screw compressor blowing through a turbo. Make it act like a 3L, then rev like a 2L. I think I might have said this before.

[Chopstick Tuner]

On 21/04/2022 at 5:46 PM, GTSBoy said:

8K is a walk in the park for a stock RB20. I simply raised the rev limit on mine (Nistune) to 8300 and ran it hard for years. Stock turbo though.

9k is not hard. Just need springs, and maybe consider the lifters as a potential weak point. Making strong power up there is, of course, a matter of cams and porting and so on, as I said before.

Doing all of this, on a forged motor, and not planning to run 22+psi is a waste of time. You need boost and you need lots of it to make power on an RB20. With E85 you should probably be considering 30+ psi.

An RB20 is not a good motor for the street. By the time you have them up into the 250rwkW region, you have lag, lag, lag, lag, nothing, then more nothing, then.......wheelspin. As a track engine, kept right up on the boil, more acceptable.

For street use, I would seriously not be looking too exceed 200rwkW on a 20, to try to keep it more useful. But even that still matches the description in the paragraph above. I went RB25 and the thing actually accelerates before boost arrives, simply from that tiny bit of extra capacity. A 3L would be even better.

If I was stuck with an RB20, I would twin charge it. Screw compressor blowing through a turbo. Make it act like a 3L, then rev like a 2L. I think I might have said this before.

That all does make sense. I have seen a couple of good setups but also many that have a whole lot of nothing, then bang full boost at like 5k, which doesn't sound ideal lol. The ones I seen that I liked though had nice set ups, including one boosting hard at 4k all the way to 8k, which I'd be stoked with but may well be a lot of work just for that power band. 

Cheers for the insights btw. 

Selling an Rb25det in need of a rebuild? 😂 

Because if I could find one at the right price I'd be keen lol

Edited April 22, 2022 by Chopstick Tuner

[Roy]

Having played with my old RB20 for years. These days a 20G is relatively small but was plenty of turbo for 8,500rpm. The secret for me actually making power at that rpm was tye Plazmaman inlet manifold. The std inlet manifold meant that power fell over after 7,000rpm

It lost a bit of torque and response...but all in all since I was willing to spin it the moon I didn't mind too much. That said I did go back to std these days years later

 

When going E85 and more boost the engine was perfectly happy with 8,600rpm rev limit. I shifted based on power curve so used all the revs in 1st and 2nd but generally shifted earlier 3rd to 4th etc as it was still in the meat of the curve.

So my view is a 450hp external gate turbo for airflow, a plenum to help top end is all I needed for good spread of power using revs. It was perfectly reliable for the longest of times and only died in peak hour traffic when a radiator hose split under the plenum and I cooked the headgasket trying to get out of melb cbd with steam over the bonnet Still drove it for 12 months and on a skidpan bumped the limiter to 10,00rpm for giggles. Still didn't kill it and drove home. But skidpan with no load due to wheelspin isn't a real high rpm test

 

If I was serious about making it more bullet proof then my advice is a good oil pump, underdrive ps and water pulleys so you don't overspeed the gears and cause cavitation. Valve springs too....I have Tomei solid lifters that I never installed as never had too...but some baby 256/9mm cams and lifters with the springs can't hurt. But I tried several cams in my RB20 and std always worked best so is very easy to over cam an RB20...part of the reason I never installed the Tomei solid lifters and cams is I could find a sub 250deg cam with >9.0mm lift

It's stoopid that RB20s aren't $600 wrecker motors any more as I'd love to becstill playing with them

 

 

[Chopstick Tuner]

On 18/05/2022 at 2:23 PM, Roy said:

Having played with my old RB20 for years. These days a 20G is relatively small but was plenty of turbo for 8,500rpm. The secret for me actually making power at that rpm was tye Plazmaman inlet manifold. The std inlet manifold meant that power fell over after 7,000rpm

It lost a bit of torque and response...but all in all since I was willing to spin it the moon I didn't mind too much. That said I did go back to std these days years later

 

When going E85 and more boost the engine was perfectly happy with 8,600rpm rev limit. I shifted based on power curve so used all the revs in 1st and 2nd but generally shifted earlier 3rd to 4th etc as it was still in the meat of the curve.

So my view is a 450hp external gate turbo for airflow, a plenum to help top end is all I needed for good spread of power using revs. It was perfectly reliable for the longest of times and only died in peak hour traffic when a radiator hose split under the plenum and I cooked the headgasket trying to get out of melb cbd with steam over the bonnet Still drove it for 12 months and on a skidpan bumped the limiter to 10,00rpm for giggles. Still didn't kill it and drove home. But skidpan with no load due to wheelspin isn't a real high rpm test

 

If I was serious about making it more bullet proof then my advice is a good oil pump, underdrive ps and water pulleys so you don't overspeed the gears and cause cavitation. Valve springs too....I have Tomei solid lifters that I never installed as never had too...but some baby 256/9mm cams and lifters with the springs can't hurt. But I tried several cams in my RB20 and std always worked best so is very easy to over cam an RB20...part of the reason I never installed the Tomei solid lifters and cams is I could find a sub 250deg cam with >9.0mm lift

It's stoopid that RB20s aren't $600 wrecker motors any more as I'd love to becstill playing with them

 

 

That looks like a good power curve, a lot of RB20s I saw were out steam before 7500 tbh, and usually not making anything before 5k, hence the topic lol 

Cams and a plazmaman intake were among the many things on the shopping list, but still in two minds over whether to build it for a 8500ish rev limit or use a different motor. People don't really like 20s, so finding examples of similar builds isn't very easy, people just say buy a 25 😂 

Cheers for the response tho, good info. 

[Roy]

 

On 5/19/2022 at 11:35 AM, Chopstick Tuner said:

That looks like a good power curve, a lot of RB20s I saw were out steam before 7500 tbh, and usually not making anything before 5k, hence the topic lol 

Cams and a plazmaman intake were among the many things on the shopping list, but still in two minds over whether to build it for a 8500ish rev limit or use a different motor. People don't really like 20s, so finding examples of similar builds isn't very easy, people just say buy a 25 😂 

Cheers for the response tho, good info. 

Problem with 20s is nobody uses decent parts. A few mates had RB20s with HKS2530 turbo that weren't bad....but it's a small bore small stroke engine. A small turbo makes for a little nicer torque but you would be shocked by how little the TD06 gives away just driving around under 3,500rpm. My car was clearly quicker as after 5,000rpm I was making >40rwkws more.

The natural benefit of the 20 is small light pistons, short stroke all meaning low piston speeds etc for lower stress bottom end. Smaller, lighter valves meaning easier for springs to control at high rpm. And i call hog wash to small valves that dont flow....look at the ratio of valve area to cylinder displacement of RB20 vs SR20 and you will see why RB20s can make a lot more power on std cams

I found the secret to RB20s is a good exhaust manifold, ideally 6 into 2 into 1. These days I reckon a 7163 on 22psi and E85 with good quality twin scroll manifold would be pretty fun. With the Greddy manifold on my 20 it drove real nice off boost, better than std.

Now not saying they are superior yadda yadda but you need to know and play to the strengths of the RB20. They rev and handle boost with strong std pistons and rods and low loads to crank and bearings. 

Again, going by the tech and size of the TD06-20G then an EFR 7163 is going to be more responsive, make more power and flow more. I feel that general wheel size is max id run on a 20. Suspect you can pull 8,500rpm and have good average power over a 4,000rpm power band. If that works then cool...if it doesn't fit the recipe then with used prices of engines these days it's going to get more expensive 

Won't need cams, lifters, headwork etc. I'd spend the money on oil pump and 8f you are going to track it and be at high revs for sustained period then underdriven pulleys are a good idea imo.   I'm betting on e85 it will make 320-330rwkws on std internals just with good cooler, exhaust and ex manifold. I'd leave the std inlet and only if you find it falls over then throw something like a plazman on. I have gone back to std inlet and making 380rwkw now so std plenum can flow.  But old combo of 2l and turbo fell over hard. Doesn't seem to do it with the extra flow of ported RB25DE head with twin 2860-5s and extra (dirty) 500cc. Also run a different diff ratio now (4.1 was 4.3)

 

Truth is between the two set ups posted the 20 only clearly loses out after 210km/h with additional hp and torque with longer final drve making it able to pull an extra 30km/h down the straights at places like Phillip Island and Sandown

[Chopstick Tuner]

On 19/05/2022 at 6:08 PM, Roy said:

 

Problem with 20s is nobody uses decent parts. A few mates had RB20s with HKS2530 turbo that weren't bad....but it's a small bore small stroke engine. A small turbo makes for a little nicer torque but you would be shocked by how little the TD06 gives away just driving around under 3,500rpm. My car was clearly quicker as after 5,000rpm I was making >40rwkws more.

The natural benefit of the 20 is small light pistons, short stroke all meaning low piston speeds etc for lower stress bottom end. Smaller, lighter valves meaning easier for springs to control at high rpm. And i call hog wash to small valves that dont flow....look at the ratio of valve area to cylinder displacement of RB20 vs SR20 and you will see why RB20s can make a lot more power on std cams

I found the secret to RB20s is a good exhaust manifold, ideally 6 into 2 into 1. These days I reckon a 7163 on 22psi and E85 with good quality twin scroll manifold would be pretty fun. With the Greddy manifold on my 20 it drove real nice off boost, better than std.

Now not saying they are superior yadda yadda but you need to know and play to the strengths of the RB20. They rev and handle boost with strong std pistons and rods and low loads to crank and bearings. 

Again, going by the tech and size of the TD06-20G then an EFR 7163 is going to be more responsive, make more power and flow more. I feel that general wheel size is max id run on a 20. Suspect you can pull 8,500rpm and have good average power over a 4,000rpm power band. If that works then cool...if it doesn't fit the recipe then with used prices of engines these days it's going to get more expensive 

Won't need cams, lifters, headwork etc. I'd spend the money on oil pump and 8f you are going to track it and be at high revs for sustained period then underdriven pulleys are a good idea imo.   I'm betting on e85 it will make 320-330rwkws on std internals just with good cooler, exhaust and ex manifold. I'd leave the std inlet and only if you find it falls over then throw something like a plazman on. I have gone back to std inlet and making 380rwkw now so std plenum can flow.  But old combo of 2l and turbo fell over hard. Doesn't seem to do it with the extra flow of ported RB25DE head with twin 2860-5s and extra (dirty) 500cc. Also run a different diff ratio now (4.1 was 4.3)

 

Truth is between the two set ups posted the 20 only clearly loses out after 210km/h with additional hp and torque with longer final drve making it able to pull an extra 30km/h down the straights at places like Phillip Island and Sandown

Pretty interesting, I have always liked that it's a rev happy motor. That's impressive results from yours, and it's even more than my goals. I'm happy to have a reliable motor that loves the limiter, anywhere in the 300-400hp range. Wide range of power figures I know, but hp figures aren't the important factor in how fun a car is, that's just a general ballpark of other skylines I've driven that were heaps of fun. 

Don't get me wrong I'm still tossing up the idea of a 25 or 30, but for my goals I'm unsure if I want to spend an extra 4 or 5k before any refreshing, for a power goal the 20 is capable of. Most RB25 dyno sheets I see have a good power band starting between 3500-4000 up until usually 7500 or less. Which made me wonder if getting a 20 to be fun to drive from say 4500-5000 up to 8000-8500 was possible (and how people built their 20s), and if it was really much different or worse... enough to justify a new engine. But I probably asked it in the wrong way because despite trying to clarify a few times, it seemed people thought I wanted a 10k rpm motor, or a 600hp Rb20 🙈 which I don't. 

Plus it would be kinda nice to say the car has its original engine, not sure why. 

[iruvyouskyrine]

On 5/19/2022 at 6:08 PM, Roy said:

 

Problem with 20s is nobody uses decent parts. A few mates had RB20s with HKS2530 turbo that weren't bad....but it's a small bore small stroke engine. A small turbo makes for a little nicer torque but you would be shocked by how little the TD06 gives away just driving around under 3,500rpm. My car was clearly quicker as after 5,000rpm I was making >40rwkws more.

The natural benefit of the 20 is small light pistons, short stroke all meaning low piston speeds etc for lower stress bottom end. Smaller, lighter valves meaning easier for springs to control at high rpm. And i call hog wash to small valves that dont flow....look at the ratio of valve area to cylinder displacement of RB20 vs SR20 and you will see why RB20s can make a lot more power on std cams

I found the secret to RB20s is a good exhaust manifold, ideally 6 into 2 into 1. These days I reckon a 7163 on 22psi and E85 with good quality twin scroll manifold would be pretty fun. With the Greddy manifold on my 20 it drove real nice off boost, better than std.

Now not saying they are superior yadda yadda but you need to know and play to the strengths of the RB20. They rev and handle boost with strong std pistons and rods and low loads to crank and bearings. 

Again, going by the tech and size of the TD06-20G then an EFR 7163 is going to be more responsive, make more power and flow more. I feel that general wheel size is max id run on a 20. Suspect you can pull 8,500rpm and have good average power over a 4,000rpm power band. If that works then cool...if it doesn't fit the recipe then with used prices of engines these days it's going to get more expensive 

Won't need cams, lifters, headwork etc. I'd spend the money on oil pump and 8f you are going to track it and be at high revs for sustained period then underdriven pulleys are a good idea imo.   I'm betting on e85 it will make 320-330rwkws on std internals just with good cooler, exhaust and ex manifold. I'd leave the std inlet and only if you find it falls over then throw something like a plazman on. I have gone back to std inlet and making 380rwkw now so std plenum can flow.  But old combo of 2l and turbo fell over hard. Doesn't seem to do it with the extra flow of ported RB25DE head with twin 2860-5s and extra (dirty) 500cc. Also run a different diff ratio now (4.1 was 4.3)

 

Truth is between the two set ups posted the 20 only clearly loses out after 210km/h with additional hp and torque with longer final drve making it able to pull an extra 30km/h down the straights at places like Phillip Island and Sandown

I am doing basically exactly what you said. RB20DE + Big T4 exhaust manifold + EFR6758 external gate + crank trigger and good ECU + E85 + RB26 inlet manifold. It's 90% done although probably wont be finished for another 2 years if i know myself.