RB20 turbo VS RB25 turbo

[linedriver]

i was comparing my skyline to my friends skyline the other day, and it seemed the only real difference was just the turbo we have on our cars. mine is the stock RB20 turbo while his is the RB25 turbo. anyways, for comparison sake, at 4500rpm in 3rd gear, his car seemed to pull away quite a bit quicker then mine. he hasnt dynoed his car yet, but my car dynoed at 195whp with just an intake and exhaust. anyways, ive tried searching, but i only got so far in the search, but is the RB25 turbo significantly different compared to the RB20 turbo in terms of spool speed? my only guess at the time was that at 4500rpm, we were both fully spooled, but he had more boost over what i had. that really got me thinking whether or not my turbo is actually on its last legs as well despite still spooling pretty good

[Skym]

These are the rough specs on stock RB25, RB20 turbo's -

Stock RB25 turbo

Compressor
48mm inducer x 66mm major compressor wheel in a .60 A/R compressor
housing.

Turbine
51mm inducer 43mm exducer in a .5 A/R turbine housing

RB25 turbo is rated at 300hp.

-----------------------------------------------------------------------

Stock RB20 turbo

Compressor
42mm inducer x 59mm exducer in a .50 A/R compressor housing.

Turbine
51mm inducer x 43mm exducer in a .4 A/R turbine housing.

RB20 turbo is rated at 250hp

----------------------------------------------------------------------

As you can see the RB25 turbo has a slightly bigger exhaust housing A/R, compressor housing, compressor wheel.

[linedriver]

as far as the compressor housing/wheel goes, if its bigger, wont it take more time to actually spool up?

a lower AR in the exhaust side would mean a slightly faster spool time, so i guess both turbos will somewhat balance out in the end. im starting to think my motor is getting tired after 18 years, then again, its the only time ive compared mine to another skyline

[Skym]

As far as I know exhaust housing A/R, exhaust wheel size affects the rpm where turbo produces full boost. Of course ECU tuning can affect rpm where turbo reaches full boost (bigger turbo) by roughly 500 rpm earlier if the ignition, fuel maps on ECU are adjusted.

RB25 turbo will move more air on compressor side, which means a lower boost level to achieve the same power level. Also has less beating of air at higher rpms which creates less heat on intake side.

Do a compression test, then wet compression test if compression is low. Compression test can help to determine if engine is ok or not.

It's recommmended that RB engines be refreshed around 100,000km (high rpm use). Basically that's with new rings, seals, gaskets, bearings, head studs, studs, etc.

[89Baysideblue]

i was comparing my skyline to my friends skyline the other day, and it seemed the only real difference was just the turbo we have on our cars. mine is the stock RB20 turbo while his is the RB25 turbo. anyways, for comparison sake, at 4500rpm in 3rd gear, his car seemed to pull away quite a bit quicker then mine. he hasnt dynoed his car yet, but my car dynoed at 195whp with just an intake and exhaust. anyways, ive tried searching, but i only got so far in the search, but is the RB25 turbo significantly different compared to the RB20 turbo in terms of spool speed? my only guess at the time was that at 4500rpm, we were both fully spooled, but he had more boost over what i had. that really got me thinking whether or not my turbo is actually on its last legs as well despite still spooling pretty good

its more then just a turbo?

~ 2.5L ,more displacement
~ 2.5L more free flowing
~ Turbocharger, ceramic as the RB20DET aswell.

just a few, but theres a whole lot more then just a simple turbo.

[linedriver]

~ 2.5L ,more displacement
~ 2.5L more free flowing

we are both running RB20's

[89Baysideblue]

i was comparing my skyline to my friends skyline the other day, and it seemed the only real difference was just the turbo we have on our cars. mine is the stock RB20 turbo while his is the RB25 turbo. anyways, for comparison sake, at 4500rpm in 3rd gear, his car seemed to pull away quite a bit quicker then mine. he hasnt dynoed his car yet, but my car dynoed at 195whp with just an intake and exhaust. anyways, ive tried searching, but i only got so far in the search, but is the RB25 turbo significantly different compared to the RB20 turbo in terms of spool speed? my only guess at the time was that at 4500rpm, we were both fully spooled, but he had more boost over what i had. that really got me thinking whether or not my turbo is actually on its last legs as well despite still spooling pretty good

this^
..and the caption to this thread is RB20 VS RB25?

[linedriver]

this^
..and the caption to this thread is RB20 VS RB25?

that is the only real difference in our cars other then the brand of exhaust and intakes we have

[mcfly]

truth be told both turbos suck
the neo rb25 turbo is the only semi good.

rb26 turbos also suck if they are ceramics

[J-Ran]

its more then just a turbo?

~ 2.5L ,more displacement
~ 2.5L more free flowing
~ Turbocharger, ceramic as the RB20DET aswell.

just a few, but theres a whole lot more then just a simple turbo.

both cars have rb20s, one has an rb25 turbocharger on the rb20 engine, he wants to know the difference between the turbochargers, nothing to do with engine.

I believe if you search there is a thread somewhere that has all the specs for all turbos that came on cars from the nissan factory (rb26 20, 25, sr20, etc...)

[linedriver]

both cars have rb20s, one has an rb25 turbocharger on the rb20 engine, he wants to know the difference between the turbochargers, nothing to do with engine.

I believe if you search there is a thread somewhere that has all the specs for all turbos that came on cars from the nissan factory (rb26 20, 25, sr20, etc...)

ive actually searched and found that particular thread. i was trying to see if anybody else compared both the turbos while bolted onto an RB20 and seen a significant difference in the RB25 turbo in comparison to the RB20 turbo while running their respective wastegates.

[89Baysideblue]

ok....so RB20/25/26 engines are all same blocks by what you say, then i can slap the 26 head on my 25DET and turbocharger from the better of the 3 variants right?

lol

[Skym]

I think there's a 2psi difference between RB25, RB20 actuators (wastegate is located on the back of turbo).

[judasentinel]

Steven, I will give you my example. When I had an RB20DET engine in my car, it was completely stock. The RB20DET is a more rev happy engine than an RB25DET when compared stock to stock motors. The stock RB20 turbo was good, but I wanted more power. So I had Harvey install an RB25 turbo on my motor, and that made a huge difference. The RB25 turbo is a better turbo than the RB20 turbo. I saw a power increase of around 10-20 hp by just changing the turbos, but this is around 2 years ago. I would suggest that there are quite a few turbos out there (and I can source one out for you if you want) that will give you a lot of power gain and they wont drain your pockets. Leave those who say, "go for HKS or GARRETT"......I am running the XS Power turbo without any problems and I push my car enough to see if it would break down. And it hasn't.

Skym, the wategates for both turbos are in the front (at the compressor side). And it's correct that RB25 turbo produces more power at the same level of boost than the RB20, due to its ability to push out more air at any point in time.

[Skym]

The bulb part is called the actuator and has a actuator arm that is connected to the wastegate (flap part) on back of turbo (internal wastegate).

Some call bulb part the wastegate actuator, like in this link below -

http://www.deepsouthtuning.com/index.php?manufacturers_id=10&osCsid=55a9ee4321bc5250f499f4f76b22fbde

I presume people see the wastegate word, so call it a wastegate.