Built rb20 or stock rb25?

[krystalized_jdm]

Now that I have some cash flow this winter

I'd like to do some visual + performance mods.

Visual is already cared for at this time, so here comes my question.

This is 100% opinion based, not spec based.

Option 1:
Keep current rb20 and add the following. (the ones marked with ** I already have)
- Upgraded coils
**exhaust
- ecu
- front mount
**Intake

+ other possible mods?

Option 2:
Buy a stock rb25
w/ no mods other then the exhaust/intake


In my opinion, but I don't know if all of the work would be worth it in the end.

What is your guys' opinions?

[magular]

to be honest i have those mods on my sedan rb20 and its not much of mods, i also got new manifolds so its really good flow everywhere with new rad and oil cooler so everything is in check temperature wise. but go rb25 for sure. you will significantly feel the torque difference, plus the turbo is a tiny bit bigger, it can handle a few more psi, but rb25 will be better stock then rb20 with the mods. positive of it. but others might say other wise.

my buddy is giving me his rb25 turbo and i will have it set for 13 with the new manifold, stage 1 ecu tune, and it should be ok. probly not even 200 whp lol. rb25 is much better idea also for down the road and as far as i know everything is interchangeable, so it wont be a headache, except the ecu's are different or the rb25 ecu doesnt plug in the rb20 harness. not sure exactly whats the mix up but thats the only hickup i heard of.

[DynamiteQC]

I bought a 25 with trans and I don't regret it. Later on , if you want to have more power, you have a pretty good base setup that have everything to handle it.

stock rb25 , stock fuel system , frount mount , air intake , n60 maf , exhaust and stock turbo at 16psi ( not recommended for daily driving) made 263whp on a mustang dyno. not bad for 3000$ part and labor ( engine/trans + engine swap + custom driveshaft/mount).

Tuner said the engine with good stock internal can handle 450-500 hp ( not whp I suppose)

[DynamiteQC]

to be honest i have those mods on my sedan rb20 and its not much of mods, i also got new manifolds so its really good flow everywhere with new rad and oil cooler so everything is in check temperature wise. but go rb25 for sure. you will significantly feel the torque difference, plus the turbo is a tiny bit bigger, it can handle a few more psi, but rb25 will be better stock then rb20 with the mods. positive of it. but others might say other wise.

my buddy is giving me his rb25 turbo and i will have it set for 13 with the new manifold, stage 1 ecu tune, and it should be ok. probly not even 200 whp lol. rb25 is much better idea also for down the road and as far as i know everything is interchangeable, so it wont be a headache, except the ecu's are different or the rb25 ecu doesnt plug in the rb20 harness. not sure exactly whats the mix up but thats the only hickup i heard of.

a friend of mine on a rb20 with n62 maf, walbro pump, gtr injector , frount mount , exhaust , air intake , rb25 turbo made 220whp.

as for the ecu on mine , I reused the rb20 ( rb25 is crap and cannot be tunned).

[knate]

Go rb25 if it's a choice... as far as wiring a rb25 where a 20 used to be, it's suppose to be easier than a sr into a 240. with the 25 you will have way more low end because of the added displacement, and more potential. Rb25 and rb20 turbos are limited by the same thing... the ceramic exhaust wheel max boost you can safley run on them is around 14 psi (from what i've read). Either way the ( safe boost limit is the same) only difference is the 25 turbo is a bit bigger.... So at the same boost level as a 20 turbo, the 25 turbo is flowing more air. Plus no rb20 that i know of came with vtc... whereas a rb25 series 2 does ( playing with that can contribute immensely to your midrange... ie "powerband"). As far as ecu most people with a tuned 25 use a chipped rb20 computer for a series 1 ( ie no cam control). Or a chipped z32 for a series 2 ( ie has cam control). Or a nice standalone system that can do both. Also not as many things are as easily interchangeable as what one would like.

Bash away
.Nathan

[Skym]

RB25DET has VVT, boost control (stock ECU + solenoid in engine bay), 0.5 more displacement, longer stroke, higher compression which helps with pickup. This is helpful when trying to spool bigger turbo's (more hp). But with RB25DET gearbox you have less room in R32 tunnel (need gearbox oilcooler on racetrack) and adding weight to car (I think was something like +30kg + extra weight of engine). This would affect how car is setup with suspension. Higher compression limit's boost level you can run.

RB20DET has a thicker block (higher resistance to cracking), smaller, lighter 78mm pistons, conrods (lighter internals = more reliable at higher rpm due to less load on conrod bolts, crank, bearings), lower compression (can handle higher boost levels) and responds well to smaller turbo upgrades. It's main weakness is the oilpump drive on front of crank. Can run external oil pump or rebuild engine and fit aftermarket crank collar.

Faster car = better power to weight.

With RB25DET you are adding slightly more hp, but also adding weight with gearbox, engine that cancels out it's advantage.

With RB20DET you are adding weight with FMIC (some FMIC can be up to +20kg), but adding power with FMIC (can be up to 23hp more with 1.5psi increase in boost level). Power to weight doesn't change by much.

On RB20DET FMIC, boost controller, fuelpump + adjustable FPR, ECU tune, BOV mods, upgraded clutch, 3" exhaust from turbo are the basic boost up mods for 330hp at engine at 14.5psi which would improve power to weight. Then add engine oilcooler to keep oil temps down (oil temps affect engine bearings, turbo bearings) and 1.2mm, 80.5mm metal headgasket for reliability (or rebuild with metal headgasket, ACL bearings, oilpump drive upgrade).

[magular]

that is some pretty sweet info, even i will be will using this to my advantage. but you could always keep rb20 trani with rb25 motor which means trani wont be heavier, and it fits obvi. but depending on how much power you will run the rb20 might not last i suppose.

[krystalized_jdm]

Love the responses, espcially skym. Always blows the responses right out of the water.

Thanks guys, keep em coming.

[S13Jordie]

right now im trying to decide between the two as well. I am leaning towards a 20 solely because i can get a full r32 clip which i can use all the parts from or sell them to 240 owners ( brakes, crossmember ect ect.) and make some money back .

now Ive ridden in cars with 500+ hp rb25's and they are a riot. but realistically i am not going to ever need that much power.

a responsive 300 hp revvy rb20 is what i am aiming for i think


" its better and more fun to drive a slow car fast than a fast car slow"

-Jordie

[krystalized_jdm]

Well said, I just don't want to dump 2 grand into my engine, to realize I could have got the same hp out of a stock engine.

I'm leaning more towards the rb20 now. Considering the engine is still pretty mint and very low kilo's (92k, had 78 whjen i bought)

[TruJDM]

Skym is right on the money. With my rb 20 I installed pon cams, "high flowed" rb25 turbo, FMIC, and supporting fuel upgrades (injectors, pump etc) and 3" exhaust I made 332 whp @ 15lbs

[Skym]

I know of a custom car that weighs around 600kg and has 170hp (Hayabusa engine) and laps same racetrack slightly quicker than a R33GTR with around 1500kg, 700hp. You can either increase hp or lighten car to improve power to weight ratio. When you think about it, with RB20DET engine you can get car into 1000kg area (with carbon doors, trunk lid, etc, maybe under 1000kg). Old school Japanese cars were about power to weight and weighed under 1000kg.

Lighter car has it's advantages, better under brakes (less weight to pull up, less brake wear thus less brake pads changes and this has been proven in endurance racing and on the custom car mentioned above, where I think brake pads last a whole season), better handling (less weight for springs, bushes, chassis, etc to deal with), etc.

Lotus build their cars with good power to weight (under 1000kg and small amount of hp from engine) and really good handling and heavier supercars (cost more) struggle in the corners yet the lighter Lotus doesn't -

http://www.youtube.com/watch?v=6nfK41KvzTE

So it's nothing new, but how SR, RB20 engines / chassis are meant to be modified for better performance. You have to realise, more hp = less reliability. I would rather have a car that's lighter, low hp from engine and has less stress on everything thus last's longer (have more fun with it) and can out corner a supercar.

[Skym]

Also when you look at a boosted up R32GTR vs R32 GTS-T in Targa (where handling matters), GTR with bigger capacity RB26, etc is heavier with more hp (over 400hp at engine) and GTS-T is lighter with less hp (around 330hp at engine) -

http://www.youtube.com/watch?v=fgD5j52ltFA

Then on racetrack with 330hp -

http://www.youtube.com/watch?v=f74NM5236zw

Only thing that car lacked was a engine oilcooler which resulted in it's bottomend bearing failure (did heaps of laps, Targa stages before engine failed).

GTR's advantage (bigger capacity engine, more hp) is in a straight line where it can use the hp, as shown at Bathurst vs V8 (GTR had 640hp and V8 had around 500-550hp) -

http://www.youtube.com/watch?v=VQOIXiXmLd4

But take the straight line out of equation and it's not as quick. Also the 4wd gives GTR advantage in wet weather (can keep dry pace when ground is wet) and has grip when tyres wear (problem that the rwd GTS-R had in racing and had to pit to change tyres). That is something a rwd RB25DET powered car doesn't have (4wd).

[markdett]

Stock rb25 ftw. Friend runs one in a r33. Gtx3583r and the supporting mods.

Makes 480hp at the rears. If it does decide to pop 1500aud and there's a new stocker for him!

[r33_gtst]

Bone stock rb25
Bolt on's, holset hx40 @ 20 psi = 492 rwhp 364 lbft @ 7,500rpm
Full mod list is in my YouTube video.
First is a dyno video. Second is an all around video
Had this set up two and a half years, 35,000 km and daily use 8 months of the year.
Compression test this summer was 165-170 psi across the board
Been smashing thru the gears for over two years at 20psi tuned rich and the motor is still healthy.
RB25 FTW alright!

I have outrun many cars on the highway. Top end power is scary fun.
3rd 4th gear pulls are a shiit ton of fun
Jaguar, Porsche, BMW, Audi...
I am yet to see a set of tail lights. But then again I havent raced heavily modified cars
Bee R* rev limiter allows 6k launches at full boost and awesome firework display.
These motors effin dominate and I haven't even built it yet

http://www.youtube.com/watch?v=B0Y6uH4Qb8w&feature=youtube_gdata_player

http://www.youtube.com/watch?v=y_ImDsveHpE&feature=youtube_gdata_player

This is the turbo I want.
Garrett gt3076R
Will be the upgrade from my holset.
And with a built motor I can see this being a response monster.
And this is a pretty mildly mldified rb25

http://www.youtube.com/watch?v=diryh7d5rbc&feature=youtube_gdata_player

http://www.youtube.com/watch?v=mz_M5gnIXnM&feature=youtube_gdata_player

RB25 has bigger displacement, vvt, just as capable as the rb26 and has a solid rock transmission.
Bolt on's and tuning and it's good to go
Built and specifically modified: deadly