rb20 vs rb25

[skidmark]

which one is stronger the rb25det or the rb20det

i know the rb25 has more tourqe and can produce a bit more power

but which one can take more punishment

and how streetable is the rb20 over 200 to 250 rwkw

[R32-GTR-89]

Been in a 250RWKW Rb25 , they are pretty much top end powerhouses.. RB20 has not as much Turbo lag .. dont forget your setup may very. if you want topend powerhouse go for RB25 instead of Rb20..

[skidmark]

i more whant to know which one is stronger

i always thaught the rb20 had more lag

but i have never driven a rb25 to find out

[R32-GTR-89]

in what way you thinking stronger ? as more potential ? RB25 offcourse.

[skidmark]

stronger as in which one will wear out quicker i have heard the rb25 have proplems with their ring lands up around 250 rwkw

[Kinks]

I tend to think the RB20 is "stronger" as in you can lean on it more. RB25's can have ring land problems with upped boost + detonation. Both are strong, overengineered engines though!

Given the RB25 is half a litre bigger it's obvious you can get more power and more torque from it.

Personally I like the character of the RB20. It seems to enjoy revving a bit more than the 25, and IMO sounds just a bit better.

a 200rwkw+ RB20 will have a decent sized turbo on it so it'll be pretty flat until it comes on boost and then it'll rocket off. Just bargain on having a 2L motor at low RPM. It won't be fast until you get up it, so it depends on your definition of "streetable". If you don't mind on/off behaviour and will drive it around off boost then that could work. If you want something in the middle though, it gets to be a bit of a pain. Even in my car it makes too much fuss trying to accelerate at a medium pace - it really wants to have the throttle nailed so it can do its thing

[skidmark]

thanx man thats the answer i was looking for.

Im about to satart a project so i was looking to find a cheep engine ither rb20 or rb25 and build it up while im still running my stocker rb20det

i supose it dont matter to much about strengh coz i was going to run fourged pistons and rods any way and more than likeley balence to handle 9000rpm just trying to make a choice on which one to go for

btw its in an r32gtst

thax guys

[PRO_32]

So what did you decide on???

Im about to do the same with 25t into 32 sick of no torque peaky engine there's to much fuss trying to get decent power out of them. Id say it's more economical to do a 25t conversion then build that up way more power, more easily extracted have to lean on the 20t too much for any real kinda numbers.

[R32-GTR-89]

if i were doing up a R32 GTS-T ( i am in 6 months ) . id put her 5spd and 2.5ltr .......

the rb20 is hard to get real power figures out of her.. but then again.. personal preferance

[skidmark]

yeh im leaning towards the rb25 most hardwear bolt bolts from one to another any waylike torbos and ect

so I can still get the rb20 pumping whill im building the rb25 block might even stroke the rb25 for even more torque or maby an rb30 with an rb25 head ahhh my brain hurts

:sadam: :boobies2:

[nmcmahon83]

Shorter stroke on RB20 generally means increased reliablility, but i'm not too familiar with the RB20/RB25 debate.

[PRO_32]

Extra rev's needed to make the power would wreck that reliability advantage.

What your budget??

rb25/30 hybrid id want atleast 15K to do it right after all is done.

If the 25t is not enough for you why not just to get 26??

just some thought...

[skidmark]

good point on the 26 conversion i guess im getting a bit exited over possible mods for i would be happy with 200 to 250 rwkw and as my origonal question was

how streetable is an rb20 at this kind of power say compared to the 25 engine is the dollar value worth the conversion for the tourque gain? :boobies2:

[PRO_32]

for roughly 3.5 to 4k you can have an rb25 supplied and fitted.

Then you have a solid platform for a very quick streetcar.

250kw from rb20 would be a slow of boost and when it does come onto boost traction or lack thereof would be a major hinderance. Thats assuming you do end up getting 250rwkw out of the rb20 dont count on doing it cheaply around 10k and then you really have nowhere to go.

Once again depends on your driving style and budget. There's not too many 250kw rb20's on the street it would definately get respect..

my 0.02

[RBsileighty]

I tend to think the RB20 is "stronger" as in you can lean on it more.  RB25's can have ring land problems with upped boost + detonation.  Both are strong, overengineered engines though!

Given the RB25 is half a litre bigger it's obvious you can get more power and more torque from it.

Personally I like the character of the RB20.  It seems to enjoy revving a bit more than the 25, and IMO sounds just a bit better.

I am a big 20 fan myself, and for more or less the same reasons as these. I feel if I were to do anything other than a 20 it would be a RB26DETT with a RWD conversion (I have a S13 with the RB20 and my buddy has a S14 with a RB20). You could pick up a 26 unit out of a R32 and most likely produce the power levels you are looking for by turning up the wick on the boost a little bit. I'd imagine you could pick up the 26 for a good price where you are, since they are running for 3500-5500 USD for clips here in the states (depending on what year/model clip).

The 26 fad is really big here in the states right now. Shops are trying really hard to get a few examples of S-chassis cars with that motor in it at the moment. I am content on playing with the 20 while it is overlooked and priced low. The engineering aspect of building up a clean high reving, well powered (300rwkw) is more interesting to me than building a RB26 at the moment.

Back to your subject... I have never really liked the 25. The extra money you would put toward a 26 you would get returns several times over, in my opinion. The 26 is a well proven powerplant that has very high limits. My logic behind this, without any experience with the 26, comes from companies like TOMEI that will use a 26 crank (http://www.tomei-p.co.jp/_2003web-catalogu...35_rb25det.html) in their RB25 buildup of Phase 3... their highest level of building up a motor. This is not to forget many other owners who are able to pull exceptional, useable power out of this same motor. Well, enough of me blabbing on... this is my dollar twenty on the subject. Hopefully this helped a little...

[PRO_32]

Rbsil..

Few questions and opinions..

Did you swap the Rb20 with a ca18 or sr20?

What are your goals in building your car?

I would assume Drift.

The reason you stated for disliking the the Rb25 was that the 26 is better surely thats not logical.

Now if your building the 20 so you can pull a peak power on a dyno and say that's what a 2L can do, Thats one thing but if it's Average power across the rev range you want (which equates to a quick street/track car) then with similar mods the 25 will win everytime.

[skidmark]

i might just build up the rb20 as far as i can go on stock inturnals and then build up a rb25 short motor and swap all the hardware over

[RBsileighty]

Thats one thing but if it's Average power across the rev range you want (which equates to a quick street/track car) then with similar mods the 25 will win everytime.

I am not looking to be faster than anyone else. I am looking to build a RB20 the best I can build it up (even if it requires custom parts), and more or less like you said... get the most out of a 2L. Don't get me wrong, I do want a fast car, but I don't care if "guy X" can beat me b/c he has a RB25 and I don't. I will have another car down the road that can do this... not sure what though.

My car came with a KA24DE, which is a crap 4cyl truck motor over here in the states. There are plenty of people who will argue this point with me, but I really don't like driving the car with that motor in it. I would say my VQ35DE in my Pathy revs smoother than the KA does by a long shot. The car is being built for fun/track/drift/street, and it is not my daily driver. It is mostly a fun car that I can do a lot of things with...

Why would you say that a RB25 swap is better than a 26? The 26 seems to be a well sorted motor from the factory. He could probably pull his 250rwkw goal easily without much more than a solid turbo back, pod filter, and boost controller correct? It would be a reliable, basically stock motor at this power level would it not? I'm just not a big fan of the 25. It seems to be everyone's saving grace, and I think it gets a little more credit than it's due. The inicial investment may be more with a 26, but there is not a lot to change on the motor to get significant power out of it.

Excuse me skidmark, if this info is not useful to you we can continue our discussion in PM or something. Let me know... this is your thread/topic.

[Elithrar]

If you are going to 'build an RB20DET, you won't exactly need custom parts. Arias make forged pistons for the RB20, and my guess is that most of the major conrod manufacturers (Argo, Eagle) will also have RB20DET stuff available.

One thing I can say is that a forged-internal RB20DET would be something different and would be a good starting point for others looking at alternatives to an RB25 transplant.

[BenA31]

yeh im leaning towards the rb25 most hardwear bolt bolts from one to another any waylike torbos and ect  

so I can still get the rb20 pumping whill im building the rb25 block might even stroke the rb25 for even more torque or maby an rb30 with an rb25 head ahhh my brain hurts  

:sadam:  :boobies2:

yes RB30 with a RB25 is the go i reckon!! my mate is in the process of building one for his EH. I'm sure it would be alot better then any RB26 RWD conversion. if your into building engine conversons i believe the RB30DET is the best!!! not the RB30ET from a VL Turbo either.