Rb20Det Max Power

[eightsixboy]

full boost at 4-4,500rpm on a standard high flow seems realy laggy, my 25/35 is on full boost before then

I am just guessing, ill actually have a proper look tonight, prob closer to 3.5-4k. Definently all in by around 4k, but as with any rb20 nothing really happens regardless of aftermarket turbo before about 4.5k. Its comes down to tune aswell, i know that once i get cam gears and a retune with a decent tuner then i'll prob gain maybe 5rwkw and be even better in the lag department.

I don't know the exact specs on my tubro as i bought the car with the work already done but i'm guessing its prob got the same response as a standard rb25 turbo, feels somewhere in between the vg30 and a standard rb20 turbo.

Either way i think that unless this guy wants to spend mega money on the 20 a hks 2530/2535 or the 3071 is prob best, no way your gonna get around 260rwkw with standard inlet and on 98ron, i'm prob wrong lol but 230 seems to be a good number for a 20 without spending mega bucks.

Only reason i havent gone a 25 is due to not wanting to getting defected for it, nothing wrong with having a 220rwkw 32 that looks standard under the hood.

Edited May 1, 2011 by eightsixboy

[Kris..]

standard inlet is fine for over 400 rwkw

anyone else here using a 25/35 on an rb20? im fairly dissapointed with mine, comes in hard at 4000rpm but runs out of puff at around 6500rpm, is this normal?

are my cams not matched to this turbo? HKS 264 8mm

Edited May 1, 2011 by Kris..

[Roy]

Yeh, you seem to lose a bit of the powerband by falling off boost and power over 6,500rpm.

Also, you can easily get 260rwkws with std inlet and 98ron. My car sees the track so my tune always has 4 deg taken out of them for when the oil and water gets up to 100+ deg C. Like I said, running 100ron was more an insurance thing for when it went to the track. I ran it on 98 fuel for about 6 months after shell removed their 100ron from the boswer...NO PROBLEMO So the 100ron was for insurance. Now that I have a plenum I need the 100ron as the engine is far more sensitive to the amount of ignition then engine can take. So it is prone to detonate unless I have the 100 in there to make about the same power

[zebra]

Yeh, you seem to lose a bit of the powerband by falling off boost and power over 6,500rpm.

Also, you can easily get 260rwkws with std inlet and 98ron. My car sees the track so my tune always has 4 deg taken out of them for when the oil and water gets up to 100+ deg C. Like I said, running 100ron was more an insurance thing for when it went to the track. I ran it on 98 fuel for about 6 months after shell removed their 100ron from the boswer...NO PROBLEMO So the 100ron was for insurance. Now that I have a plenum I need the 100ron as the engine is far more sensitive to the amount of ignition then engine can take. So it is prone to detonate unless I have the 100 in there to make about the same power

Thats very weird, maybe uneven airflow causing a couple of cylinders to run leaner than the rest?

[swirto]

t04e .57 turbine .50 compressor ?????????????

[eightsixboy]

standard inlet is fine for over 400 rwkw

anyone else here using a 25/35 on an rb20? im fairly dissapointed with mine, comes in hard at 4000rpm but runs out of puff at around 6500rpm, is this normal?

are my cams not matched to this turbo? HKS 264 8mm

Hmmm ok, i always thought the inlet manifolds on the 20's were shit, maybe i was thinking of the redtop or something. Just weird how you rarely see a 20 make more then 230-240rwkw, i know not wanting to put a massive turbo on is a big reason due to lag but if the std inlet is not a restrition then whats holding these motors back? 25's seem to make more power easier, mate at work has almost 300rwkw with a unopened motor, just a 3076 (i think) and the usual supporting mods, i know been a 2.5 over a 2 littre helps but still.

Yea sounds weird if the 2535 is running out of puff after only 6.5k, should be good almost to redline. I think even the smaller 2530's are good till about 7k then they fall of.

Might have something to do with the cams, your not running cam gears are you?

Edited May 5, 2011 by eightsixboy

[Wheezy]

Hmmm ok, i always thought the inlet manifolds on the 20's were shit, maybe i was thinking of the redtop or something. Just weird how you rarely see a 20 make more then 230-240rwkw, i know not wanting to put a massive turbo on is a big reason due to lag but if the std inlet is not a restrition then whats holding these motors back? 25's seem to make more power easier, mate at work has almost 300rwkw with a unopened motor, just a 3076 (i think) and the usual supporting mods, i know been a 2.5 over a 2 littre helps but still.

Yea sounds weird if the 2535 is running out of puff after only 6.5k, should be good almost to redline. I think even the smaller 2530's are good till about 7k then they fall of.

Might have something to do with the cams, your not running cam gears are you?

RE the RB25, Ignoring the obvious capacity differences...

A much larger bore will give it more torque, along with a way better flowing head...it goes with out saying.

The redtop 20 also appears by reports to flow better than the silvertop, along with slightly more aggressive cams...

My biggest regret is going for the front facing plenum, standard is more than adequate for 99% of the RB20's out there.

I really dont see anyone making more power out of cam gears in a 20, more so a little fatter midrange, and not a huge difference in response, perhaps on a snappy 2860 it would be a different story.

[Sarumatix]

+1 2860RS is a great choice for RB20 street driven .

[Nee-san]

Because they are too big for a 2ltr motor.

Even a GT3082 is too big IMO.

tell that to the evo guys

[zebra]

2.4L 4G63 > RB20

[Wheezy]

tell that to the evo guys

RB20 has such a small bore and stroke should it be compared to say a 1.4/1.5L DOHC 4 banger.... in terms of stroke and bore?

You are always going to have very different behavior not only due to the amount of cylinders due to engine characteristics such as the above, is it fair to compare such things just on capacity alone? I am not completely sure how to look at

[Nee-san]

2.4L 4G63 > RB20

Yeah, but a 4g63 comes from the factory as a 2.0 Litre, with what I would consider to be a shit bore and stroke ratio.

As to the comment above, this is somewhat true, but having a short stroke with a substantially larger bore is in my eyes a better philosophy towards engine design then an IMO inferior undersquare setup.

This leads me to believe that the difference is in the head.

[The Dan]

I have fit a couple of the 2860RS (Disco) to RB20's, the dyno overlay from before to after showed a complete line trace in boost response, then the disco just kept making more power where the standard turbo started to turn. Made about 220-240rwkw in both instances

EDIT: I forgot to mention, that was with a Sonic turbine housing which makes it about a 0.73 A/R instead of the 0.86 standard form

[zebra]

Yeah, but a 4g63 comes from the factory as a 2.0 Litre, with what I would consider to be a shit bore and stroke ratio.

As to the comment above, this is somewhat true, but having a short stroke with a substantially larger bore is in my eyes a better philosophy towards engine design then an IMO inferior undersquare setup.

This leads me to believe that the difference is in the head.

Yeah, but most of the guys ive seen running GT35's etc are also running strokers.

Nothing wrong with undersquare turbo motors, if NA than being Oversquare has its advantages in a race motor.

[Nee-san]

Yeah, also true Zebra,

Have a mate who is into evo's, he's forever showing me dyno plots of various turbos etc and you think "f**k on only a 2L we must be doing something wrong" but then you realise they are rollin' 30psi deep with 2.4 - 2.6 litres and E85 Lol. (on a yankee dyno )

there are arguments for and against but I still think that all the positive facets of an over-square bore/stroke ratio carry over to a charged setup, an example would be de-stroking the BMW E30 engine to 1.5 litres for use in their grand prix program.

[R31Nismoid]

tell that to the evo guys

We aren't talking bout 4g which is a big pot four... We are talking RB20 which is a small pot 6.

The 4g has a bit more development than the late 80s RB20. They can take a GT30 quite well and are much more responsive. Part head, part bottom.

A stock 4g will make 200-210 on the factory turbo and be on much sooner than the RB20. It's not a fair comparo either way.

SR20 are similar, they take a bigger turbo better as well.

Yeah you need 20psi+, but you would with a RB20 as well.

its either 230rwkw, or 270rwkw with turbo options that still leave the car useable. forget plenums etc, as several results suggest you only go backwards by spending 1200... Not a good return.

[Lithium]

Yeah, but a 4g63 comes from the factory as a 2.0 Litre, with what I would consider to be a shit bore and stroke ratio.

As to the comment above, this is somewhat true, but having a short stroke with a substantially larger bore is in my eyes a better philosophy towards engine design then an IMO inferior undersquare setup.

This leads me to believe that the difference is in the head.

I disagree with most of this. RB20s are stupidly short stroke, rod/stroke ratio is what really matters and 4G63 have awesome rod/stroke ratios and have both torque and the ability to rev - partly as a result of this. One of my mates has a track car with a 2litre running a GT3582R with .82a/r hotside and the car is perfectly useable with it, I think a lot of it is the fact he can rev the crap out of it and be heavy on the throttle without fear of going from lag to no traction and back again relentlessly.

RB20s lose a lot of torque probably partly to do with this, and don't do too much to make up for it - so you really have to put a lot of work into making up for it... hence this thread being so tricky. With most 2litres it'd just be a case of "get a GT3076R/GT3582R" or something like that and all would be fine.

[toffy]

I disagree with most of this. RB20s are stupidly short stroke, rod/stroke ratio is what really matters and 4G63 have awesome rod/stroke ratios and have both torque and the ability to rev - partly as a result of this. One of my mates has a track car with a 2litre running a GT3582R with .82a/r hotside and the car is perfectly useable with it, I think a lot of it is the fact he can rev the crap out of it and be heavy on the throttle without fear of going from lag to no traction and back again relentlessly.

RB20s lose a lot of torque probably partly to do with this, and don't do too much to make up for it - so you really have to put a lot of work into making up for it... hence this thread being so tricky. With most 2litres it'd just be a case of "get a GT3076R/GT3582R" or something like that and all would be fine.

i disagree with the rb20 does'nt rev statement , every one i've ever owned had bounced off 8.5krpm for as long as i've wanted it too ... and wanted more

[Lithium]

Where did I say they can't rev?

[Roy]

All the people on about torque etc, at what rpm it makes power etc...all fair comments and points. The fact that the RB20 has such a short stroke means they have very low loads and forces on bearings so you can rev the hell out of them and the piston speeds and loads are not that high so the rpm issue is mostly with the heads.

The R31 chassis wise was not a huge improvement in performance over the DR30, in fact it was heavier and took some time to come to terms with the extra weight in Grp A speak. The area where the R31 improved greatly over the DR30 was the RB20 over the FJ20. Typically the FJ20 is far more popular for performance, but with regards to usable performance and tracability the RB20 was seen as an improvement over the FJ20 for racing. The more linear power band and tractability made it the better race engine, especially in the wet where the FJ20 was like the Sierra with its on/off power delivery.

So those hanging crap on the RB20 for being laggy, not spooling big turbos etc may be true. But it also means that in a rwd car it wont fry tyres if you are really concerned about going quick. I remember all too often following R34 GTT and R33 GTS25ts on circuits where I just plant my thing and get great power down and traction whilst all the RB25 and SR20 Silvia lads are fryign tyres with wheelspin losing that jump out of the corner. So there are trade offs where I wish I could have a bit more at light throttle and lower revs...but its all a trade off.