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Rb20det Vs Rb25det

migs

By migs,
in Engines & Forced Induction

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migs Enthusiast

migs

Posted
Posted

ok i have an RB20DET in my ride as we speak

was thinking about running some mods on it

or upgrading to an RB25DET or RB25DET-NEO what you think

whats the pros and cons with the RB20DET, RB25DET & the RBB25DET-neo

currently my rb20 is running

*Stock rb20 motor

*300zx 45v3 t3 turbo

*10-12 psi boost

*TurboXS boost controller

*Blitz bov

*Blitz LM 3" intercooler

*2.5 intercooler piping

*3" free flow stainless exaust

*Custom RB26 side mount intake manifold

*Upgraded ecu ( flashed\remapped )

*Fidanza 4.3 ceramic clutch kit

*NGK iridium spark plugs #7

*Walbro external fuel pump

Was going to upgrade to......

*Rebuild with Genuine Nissan complete engine kit

*Genuine nissan piston rings

*Garrett GT3076r or hks GT3037pro-s

*Xo2 exhaust manifold

*Sard fuel press reg

*550cc injectors

*AEM water/meth injection kit

*Greedy E-manage ultimate or haltech unit (TRY TUNE TO ABOUT 18-20PSI)

*Map sensor setup

*Wide band o2

*Cometic metal head gasket

*ACL race bearings

*ARP head bolts

*HKS timing belt

*Oil cooler

*Oil rerun lines from head to block

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https://www.sau.com.au/forums/topic/342842-rb20det-vs-rb25det/
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Truffles Community Regular

Truffles

Posted
Posted (edited)

Really depends what your goals are. How partial are you to your RB20?

Usually in these circumstances it's easier to drop an rb25 in. By keeping the Rb20 you'll always be behind the '8 ball', given that the extra 500cc is a 25% increase over the stock rb20.

Depending on your power goals, I'd personally take a rb25 if you can do it cheap enough.

Edit: was also going to say I hate mods going to waste. But a lot of yours could be applicable to an rb25 set-up. Now is as good a time as any to make this decision. Before you spend money for specific rb20 components

Edited by Truffles
R31Nismoid Grand Master

R31Nismoid

Posted
Posted

Factory RB25 you can do 280rwkw safely (about the limit IMO).

A RB20 @ this power level will be quite laggy, however the RB25 isn't "too" bad. Its basically where the compromise point is.

But as asked, depends what you want mate.

Use of car? Motorsport? Response required? Drag? what? :verymad:

GTScotT Grand Master

GTScotT

Posted
Posted

As stated, it really does depend on your goals. There is a thread I think all RB20 owners should read before giving up on the motor.

http://www.skylinesaustralia.com/forums/Bo...20-t330619.html

Personally Im not an RB25 fan boy. I think the lag limitations of the RB20 keep it grounded as far as usable and reliable power goes. I personally am a fan of Roy's results, and I think a 260rwkw RB20 with delivery like his would be an excellent motor.

Maybe consider going down the TD06 route before you give up on your RB20, at the end of the day you can transfer your turbo kit over to your new motor should you decide to go RB25 later.

More TD06 info here:

http://www.skylinesaustralia.com/forums/Le...tml&hl=td06

Rolls Grand Master

Rolls

Posted
Posted (edited)

get a 25 you will never look back, it is sooo different to drive, more low down power, can make more power before getting laggy and even then you still have more off boost capacity so it isn't as bad.

VCT is a godsend and makes it so much nicer to drive as well, I would never ever get an rb20 again, they sound amazing but that is it, I think I'd go an SR20 before an RB20.

Ive had 2 rb20s and 1 rb25 with a highflow turbo and the difference is night and day.

If you have an R32 you can reuse half the stuff anyway, intake etc, use the rb20 ecu and get a nistune module, eboost street so you can retain the VCT and you can use all the old sensors, means you don't need a half cut, just the raw motor, might need to change a few things like throttle body but that is it.

Edited by Rolls
battery Mentor

battery

Posted
Posted
get a 25 you will never look back, it is sooo different to drive, more low down power, can make more power before getting laggy and even then you still have more off boost capacity so it isn't as bad.

VCT is a godsend and makes it so much nicer to drive as well, I would never ever get an rb20 again, they sound amazing but that is it, I think I'd go an SR20 before an RB20.

Ive had 2 rb20s and 1 rb25 with a highflow turbo and the difference is night and day.

If you have an R32 you can reuse half the stuff anyway, intake etc, use the rb20 ecu and get a nistune module, eboost street so you can retain the VCT and you can use all the old sensors, means you don't need a half cut, just the raw motor, might need to change a few things like throttle body but that is it.

yeh i dunno about this personally i think rb20's are highly underrated and very usable up to the 250kw range, i'd never remove a running one for a 25.

when my last rb20 blew a headgasket i went engine hunting, i already had a rb25 box in the car so i got a rb25 engine cheap and dropped that in.

now both of these engines were running stock turbos with 1 bar of boost the rb20 would be around 160kw and the 25 was making 193kw.

the 25 was a decent upgrade but if i had a 25 turbo on the 20 i dont think the gap would of been all that great.....

i also think its crazy to rebuild a perfectly good running engine but if your deadset on doing a rebuild i'd be looking at a 25/30 build for the 3L's of fury!

JonnoHR31 Grand Master

JonnoHR31

Posted
Posted

peak power may be similar but the 25 will be much quicker on the street.

imo, get yourself a 32 25de head, bolt it to a 30e block and throw on a gt30. can re use all your silvertop loom etc that way and nistune the ecu

Rolls Grand Master

Rolls

Posted
Posted
the 25 was a decent upgrade but if i had a 25 turbo on the 20 i dont think the gap would of been all that great.....

i also think its crazy to rebuild a perfectly good running engine but if your deadset on doing a rebuild i'd be looking at a 25/30 build for the 3L's of fury!

below 200kw the difference isn't that much, but when you get closer to 250kw the difference is massive, drive both and you will see what I mean, an rb25 making 250kw has more punch down low than a stock rb20, it really is night and day.

joeyjoejoejuniorshabadoo Grand Master

joeyjoejoejuniorshabadoo

Posted
Posted
300rwkw on an rb25det won't last very long...

many cars on here say otherwise...

i've been running ~300rwkw for almost 2 years now on stock internals as have a heap of others

bubba Grand Master

bubba

Posted
Posted
i also think its crazy to rebuild a perfectly good running engine but if your deadset on doing a rebuild i'd be looking at a 25/30 build for the 3L's of fury!
imo, get yourself a 32 25de head, bolt it to a 30e block and throw on a gt30. can re use all your silvertop loom etc that way and nistune the ecu

Unfortunately the OP is in Trinidad/Tobago and they don't have RB30E's over there.. I've been telling him to build a 30 for ages ;)

tm_r33 Experienced

tm_r33

Posted
Posted
300rwkw on an rb25det won't last very long...

whats your reasoning for this? i beg to differ. in fact if u ignore the pistons for the most part, 25 and 30 internals also a farely strong. u may drop a bearing at 300kw but thats due to the fact they are old and f**ked anyway.

and to be honest i havnt seen too many problems with the 25 pistons its usually the australian 30et pistons. (stock vl turb pistons had a tendancy to 'melt' lol)

not having a dig just curious. you may have seen some fail and i just havnt come across it yet.

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