RB20DETT TwinTurbo2Litre

[Option1Garage.com.au]

Hi all - I am Paul from Option1Garage and I built the R31 with the twin turbos pictured above - Just goin to go through and tell the truth about some of the questions on this thread - Ricky from Fantasy did not have alot to do with this car except for the plenum and injector upgrade - He did not build it .

Was it a completely std RB20. Did it end up blowing up at that hp????

A single RB20 turbo is bigger then a GTR turbo, so you woudl expect GTR turbs to be a bit more responsive ???

Throw a 75 hp shot at Nitrous on it, and for a backyard tinkerer you would have a mid-low 11 sec drag engine, turbs/manifolds/piping/nitoris costing less then 3k:)

yes it was a completely standard jap import motor and it was never expected to hold out at 18lb ...... The car has since had a set of cosworth forged pistons fitted and head recoed but other than that motor is std spec - It ran 12.2 @18lb boost with the motor dying , has never been back to the track since but i think a high 11 sec pass would be a reasonable guesstimate with the fresh motor - and no it doesn`t need nos ..... holds good boost between gears or it wouldn`t run that sort of time would it ?

[Option1Garage.com.au]

Bit more background on the R31 - it was a project that we came up with to see what sort of power we could get from a std RB20 without spending a fortune - with just bolt ons . So we bought the R31 , cheap car to put it in , made sure it was a base model for less weight .

I made up the manifolds , dumps , intercooler piping etc all myself from scratch - has 3" dumps into 4" engine pipe then back to 3" over the diff and out . The manifolds were kept as short as possible the idea being to keep good exhaust flow into the turbos . Originally it was set up with the turbos , Haltech E6K ECU , PWR front mount with tanks from Fantasy , fuel pump upgrade and Malpassi Reg - other than that completely standard . In that spec it had approx 320 rwhp @ 13 lb boost and ran a flat 13 sec 1/4 in complete street trim - we were pretty happy !

The car was a great sleeper .... had alot of fun on weekends on the Gold Coast with it till it got known . It ran in this spec for a year with an 8000rpm rev limit with no problems at all .

Edited March 1, 2006 by Option1Garage.com.au

[Jago]

Was it a completely std RB20. Did it end up blowing up at that hp????

A single RB20 turbo is bigger then a GTR turbo, so you woudl expect GTR turbs to be a bit more responsive ???

Throw a 75 hp shot at Nitrous on it, and for a backyard tinkerer you would have a mid-low 11 sec drag engine, turbs/manifolds/piping/nitoris costing less then 3k:)

that's what my setup is, twin GTR turbos. Lag city mate, full boost at around 6500rpm. Ask Sproosy, he'll tell you how laggy it is

Pulls like a steam train though, and has some squat in her too

[robots]

Hmmm. Someone here mentioned about 1000cc turbo engine. Getting a turbo from it and running them in twins on rb20. My guess woud be suzuki ihi from k10a engine came in wagon r. Or daihatsu K3-VET - 1.3 litre 4-cylinder, DOHC, 16-valve EFI turbo, CB70 - 1.0 litre, 3-cylinder, DOHC, 12 valve EFI turbo. This will be cool for low-rev torque.

[`nigno]

Seen this done on an Sr20 with Garret GT17's... was in an escort and it was more to practise fabrication than actual practicality.

I suggest having a look at those turbos though

[Jago]

SR20 and RB20 are like comparing apples and oranges. As for the T17's, would be a serious downgrade and will cut your power significantly. It's all about floooowwwwww

[Hella Flush]

just after reading this thread doing some surfing for new parts... found these pups...

manifolds to install rb26 turbs on rb20 (turbos not included)

could be yours id say for about 500 landed here in 7 days if anyones keen

[R31Nismoid]

So... that means you have stuff for sale?

[Hella Flush]

no... re-read what i said... its up for auction...

do you really think im in japan atm? no...

[Jago]

in my opinion i think custom manifolds are a main in the arse. Having the adaptor plates lets you bolt on any manifold suited to the RB26, so long as it fits . Except, you do have the extra cost of the RB20 AND RB26 exhaust manifold gaskets.

[fantasy]

Hey Paul,

I wasn’t looking to offend. Sorry if I did so. No porkies said here. I stand by what I have said. I made a point of saying what I had done on the car. We both spent many hours working on that car when it was in my shop. And I did do everything I said including redo the IC pipes. Lifted the cooler at the same time. Remember?

Of cause I did not build the whole car. I fabricate performance parts. I am not and engine builder and have never led anyone to believe so. On the same token you did not build the whole car either.

I had driven the car and found it disappointing for the power it made. I have also seen it get beaten by many cars with less power.

My opinions on this kind of set up are my opinions. Just because I don like twins setups on small capacity engines does not mean I don’t like the people that chose to run them.

Phil is a good lad and you where a good mate at the time.

Doesn’t matter anyway it was like a million years ago now.

Roy,

I had a quick read back through and I pretty sure I’m in agreements with everything you had said on page six.

Sincerely,

Fantasy.

[discopotato03]

Hi Roy , yeah out muscling an FJ20 with an RB20 would be very difficult . The FJ was a pretty good combination of bore and stroke (89 x 80) and rods were 140 odd mm between centers . The big bore means you can fit larger valves in the chambers before they come close to the bores . The FJ20 being a production engine a had wider included angle between the inlet and exhaust valves than say a Cosworth BDA which makes for a deeper chamber - more steeply angled chalet roof shape . compact chambers are supposed to have anti detonation advantages and its easier to make CR alterations with piston crown variations .

The world changes dramatically when you go to six inline cylinders . The I4 has a flat plane crank so the number of crank degrees between cycles or power strokes is 180 deg . The I6 is more like two I3's joined together and the crank phasing is 120 deg between cycles . Now the RB20 has 6 333 odd cc pots compared to the FJ's 4 497 cc pots so the 4 clinder with generate greater power from its larger pots . The power cycles have less overlap being 180 vs 120 phasing so theres going to be less time for the next and last cylinder to interfere with its induction and blow down phases .

You would have to know my opinions on the whole split pulse/twin scroll turbo set up and an interisting thing is that the TS system works a little better on an I4 than an I6 . This is because a TS I4 has 2 cylinders venting into each side 180 crank degrees apart where an I6 has 3 cylinders into each side 120 degrees apart .

There probably was good marketing reasons for going with an I6 - 6 always sounds more than 4 even if the cubes are the same so good for marketing a sporty car . Depending on a few things an I6 can be a smoother running engine than an I4 so some say this adds "sophistication" to the vehicle . To a degree I like big I4's but packaging them and having nice bore/stroke and rod/stroke ratios seems to be one the manufactures want to baulk at . Such is life .

As for TT's on an RB20 thats a big ask . I'd prefer the twin scroll single turbo system because it works out simpler - TT's on an RB20 is not really economic because the RB26 manifolds don't bolt up and I think the effort to make it work tip the balance in favour of the TS system . To go either way properly would not really be viable unless the user had to stay with the RB20 and could not use an RB25/26/30 .

To make an RB20 strong means to have more air forced into its cylinders earlier and have the absolute minimum of exhaust manifold pressure but with reasonably good turbine response . This is all about raising the volumetric efficiency of the thing earlier in its rev range to make usable torque before its limited breathing abilities become the limiting factor .

The Budget . Spent ~ 2300 on a FullRace manifold/~ 1600 the turbo/? the waste gate/? the plumbing and get it all fitted . So for something up to ~ 5 + grand is anyone interested ?

Cheers A .

[HR31DRFT]

oK, i reckon you gonna spend alot of time and money bustin your ass 2 put on a twin setup on a rb20... Then realise it was a bad idea.

Go a 25 with cams, inj, turb n good tune.

And a 25 box 350-400

Rb20's are sh!t.

Blown 3 of them.

[GeeTR]

I sure do know your fiendish obsession with TS Trying to provoke some counter thought here.

You speak of the pulse phases in I4 and I6, but end it with “less time for the next and last cylinder to interfere with its induction and blow down phases” Is this to say turbo V12 and such aren’t efficient? Can one quantify when pulses occur too rapidly and start blowning down, or weakening others, would single pulses per 360 be optimum?

HR31DRFT - You've blown 3 of them? Damm, they must be sh_t!!

[HR31DRFT]

Yeh havnt had a good run with 20's

Building a killer rb now. RB30/26 Yeh gurl

its gonna be a sure @ss spanker

[discopotato03]

Thats not straightforward question . Yes the faster you turn an engine the closer "time" wise the pulses become . From a mechanical point of veiw it doesn't change no matter how fast you turn it . The crank pins will always be the same number of degrees apart .

A V12 like any other multi cylinder engine will be affected by how its manifolds are designed . If every inlet and exhaust tract is completly seperate then its cylinders won't be robbed by the others . In a turbo application obviously the exhausts have to be ducted into a turbo or turbos , I'm not quite sure of what their firing order is and to be optimul the exhaust manifolds would have to be designed around that . Possibly four turbos and four three branch manifolds may work but I somehow doubt the firing order would make the groupings right . Older aero engines like Merlins and Griffons used mechanically driven multi stage rotary compressors so exhaust was no issue .

The V block configuration changes everything again compared to an inline one . Usually a V engine has its inlet ports facing the middle and obviously the valley cover becomes the inlet manifold . The exhaust ports face outwards so you'll have two six port exhaust manifolds . How they get around exhaust pulse timing I'm not sure . The only V12's and V16's I've had anything to do with are locomotive diesels and they have the exhausts in the middle and airboxes on the outsides of seperate cylinder heads . These things are slow reving ie around 900 for a GM or 1100 for a GE and as you could imagine throttle response is very slow compared to anything automotive . Getting OT but nowdays the Americans are opting for V12's with larger pots to develop their 43-4500 Hp and the advantages are a lot less moving parts and a shorter possibly lighter prime mover .

Manufacturers have lots of reasons for deciding on how many cylinders and in what configuration . Their last consideration is what we as petrol heads can get out of it . All they want is cheap clean and economical - mostly .

Cheers A .

[GeeTR]

Hey Disco, sorry, my question was meant to be non straightforward

I'm not convinced by your argument that larger capacity, less often slugs of gas (from a I4) are more effective to moving a turbine then smaller capacity, more often slugs (same capacity I6) I cannot think of any reasoning either way, so am interested in how you get yours

Cheers

Edited October 4, 2007 by GeeTR

[LedZepLen]

cams will help a tiny bit.

Increase the capacity to 2.4L with the stoker kit availible from JUN and others. Put an RB30 bottom end on the motor will be much cheaper.

will a rb30 crank fit right inside a rb20det and work with existing rods??

[discopotato03]

GeeTR 500cc pots are ~ 1.5 times the size of 333cc pots so more power per cylinder and a greater slug of gas going into the turbine housing each time .

Most production engines use plenum type single throttle inlet manifolds and the fours induction events don't overlap as much as the sixes . On the exhaust side you only have two cylinders venting into each side of the divided twin scroll manifold and housing every two crank revolutions . Its the phasing of the fours flat plane crank pins 180 degrees apart vs the sixes 120 degrees apart that makes a difference manifolds wise .

A thing to note as well is that some parts of an FJ20ET make it in a higher state of tune than an RB20DET , the cams are a bit hotter at 256 deg by ~ 8. something mm lift and their ports are reasonably big by production engine standards . In std trim the FJ's smallish T3 turbo uses a larger turbine than an RB20 and the early ones had a 0.63 A/R turbine housing which would be nearly as big internally as the VG30DET's ball bearing type turbine housing .

Also I mentioned the FJ's large bores (which can fit large valves) so are an advantage . Most of todays current 2L fours are used in east west apps ie CA18 and SR20 so the blocks have to be short along the crank centre line , this forces smaller bores and longer strokes which is fine for shopping trolley cars but not the best for all out power . From memory RB20's have 78mm bores so valve size and valve lift is probably limited .

A few manufacturers made larger capacity fours such as BMW's I think E30 M3 (LHD only) with good bore/stroke and rod/stroke ratios and I reckon they would have been very strong in turbo form . Porsche had a 3L I4 but it may have been N/A and 2 valves per cylinder in std form . Nissan does do a KA24DE but it's 89 x 96 bore/stroke make it not a real high crank speed thing . Twin scroll systems on those are supposed to be capable of making VERY strong torque without many revs - perfect for fast road and why people out here don't do them up is beyond me . Perfect for the S13/14 and they fall in with the right manifolds because thats what US spec S13/14's get std .

Another 2c spent , cheers A .

Edited October 8, 2007 by discopotato03

[klys]

which twin scroll would you recommend for an RB20? I've been wanting to do a Twin GT-SS on my 2.2L RB20 .. but I'm starting to wonder if I shouldn't stay clear of the complexity the TT will bring.

I've seen Twin scroll turbos in subarus.. and I'm guessing an I6 would be a good engine for this type of turbo.

Thanks

A friend sugested a Garett GT3076R... I know it's not a TS system but seems to be rated for the power I want .. with an .83 A/R