rb motor series, which is 'better'

[sclay115]

in all reality, the initial cost of the rb20 is much less than that of say an rb25 or 26. but is it a better motor in the long run? can it build as much power as the above mentioned motors? i am trying to decide on a motor for my project, and i have full freedom as far as space constraints, so that is not an issue, in the end i'd like to see near 500rwhp, and i'm getting the feeling that an rb20 just isn't going to do it. anybody have any thoughts on this?

steve

[NISMO_RB25]

Please use the search button before asking these hugely debateable questions.

Getting to 500 HP is usually going to require a built bottom end. with RB20 I doubt you could get that far without it. with an RB25 and 26 it is possible, but you are pushing it, and your tuning better be perfect.

[sclay115]

yah i tried the search, as that's what people usually mention, but didn't seem to come up with anything decent, but i'll give it another go.

[HybridOne]

with the money you spend on an RB26 you could get an RB20 and upgrade it to higher HP. So your looking at the same dollar amount but instead of the stock 26 you have a built 20. Not to mention, the 26 swap is just a pain in the ***....it's possible, but no fun. And i lean towards 20s insted of 25s. either one is ok though.....the 26 IN MY OPINION is just to say you did it.

[lyon23]

yah i tried the search, as that's what people usually mention, but didn't seem to come up with anything decent, but i'll give it another go.

hey sclay since you're in orlando go see my friend rolo at central florida turbo...he tuned fitos car (rb25neo) to 587hp.. he's got another rb25 they're doing at his shop right now go talk to him about the swap..tell him leo with the rb20 from jacksonville sent you.

[NISMO_RB25]

i thought fito's RB blew up and that is why he went to the 26, but I could be thinking of someone else.

[sclay115]

wait so if i were not to crack the motor open, and just build upon the stock bottom end, would i be better off with a 25 or 20? i was reading up on it, and it seems the 25 can support more power. or is the .5 capacity really not worth it. considering the great difference in price, it would seem logical to get a 20 if i could get the same power out of it.

[mkory]

And i lean towards 20s insted of 25s.

Why's this?

[Carl H]

rb20's ownz.they rev fast and are a blast to drive.rb25 seems to me like it was designed for ppl who liked low down power, like the average person who likes to step on the gas and go, where as the rb20 is a bit peakier than the rb25 due to the .5l less displacement as well as the 8.5:1 cr.for ppl that dont mind waiting a sec for crazy power then the rb20 is the way to go.my .02

[rb240sx]

I agree, I would rather have a 20, I put a aluminum flywheel on mine and it screams, I love it, an rb25 cant rev as much as a 20. has more rotating mass.

[mkory]

Do the rb20's rev faster maybe because they come stock with a lighter flywheel? I can't imagine any other reasons why it'd rev faster.

I'm getting an rb installed sometime here in the next few months, and I can't decide which to get. a 20 is $3,000 installed and a 25 is $4,200. This price would be a stock clip swap, putting a completely stock rb into my car, just like it came out of the skyline. A street swap is available too, the rb20 costing $4,000 and I'm not sure about the 25.

[OKCA18DET]

why would u want 500+ hp for a daily driver?i mean basic boltons will get u into the 13's but thats even less then 300hp hell less the 250, if i had 500 hp in my car there's no way i would drive it "every" day but thats just me and if i were to spend as much for a built rb20 lets say 4K id rather swap in an LS1 or something crazy then slap some juice on it and call it a day

[mkory]

Nah... I really wanna go rb, and for as low as 3k installed I can't hardly pass it up. No work on my part, just give them the word and drop it off.

[JonPowell]

Do the rb20's rev faster maybe because they come stock with a lighter flywheel? I can't imagine any other reasons why it'd rev faster.

The RB25 flywheel is actually lighter thant he RB20(Thanks Brian)

There is about a 4-600 RPM difference in between the RB20 redline and the RB25 red line... It takes 10 PSI boost to get 210HP on RB20 and 7 PSI to get 250HP on RB25.

There is no replacement for displacement.

That is why there are stroker kits for the RB26 to go 2.7 or 2.8 liters...more displacement=more power. that is why Nissan Z-Tune Rb26DETT uses a 2.8 displacement and the 400R did the same.

The RB26 is the peak of Nissans technology at the time, that is the reason to use it...because it just plain rocks the house.

with the money you spend on an RB26 you could get an RB20 and upgrade it to higher HP. So your looking at the same dollar amount but instead of the stock 26 you have a built 20.

This may be true but witht he extra stress on the parts from higher boost/lower displacement it may not last as long as an RB26 at the same HP level. Stock RB26 motors are at the extreme low end of the power potential, esentially de-tuned for street use.

I agree, I would rather have a 20, I put a aluminum flywheel on mine and it screams, I love it, an rb25 cant rev as much as a 20. has more rotating mass.

RB25 cant rev as high cuz it dont need to...again...whats 600RPM when you lose .5 displacement and 40HP? People pay alot of money to gain 40HP.

Choose whatever engine YOU want and forget what everyone else says.

I say if you got the green the 26 is the way to go...alot more responsive to mods, alot more wow factor and alot better starting point.

If you aint got the green the RB20 is a good motor and has alot of potential also....just takes MORE money to get where you want...in the end you will probably spend the same amount.

[Miata Master]

This is my .02 on the which rb to use. a lot of this is agreement with jon.

26 WOW factor but over priced for the added power/potential but if you can get the green then yes.

25 the way to go. extra 25% displacement over rb20. beeffier trans. tougher stock bottom end. still has good support.

20 only if it is all you can afford. maybe if you are building a drift/auto and want the 6 instead of the sr20/4. it is lighter than 25.

as far as how fast something revs if the rb20 gets to 6500rpm in the time it takes the 25 to get to 5500rpm the rb25 will still be pulling harder b/c of the extra hp/torque. once again my .02

I have an rb25 almost went 20 and will be building up a KA soon too.

[mkory]

Miata... Any regrets on not going with a different rb over the 25, or are you happy with your choice?

Jon what you're saying makes a lot of sense, and is making me lean even more toward the 25 over the 20. .5 displacement seems like a lot more when you think of it as 25% more, but then again, the price for me between the 20 and 25 is 33%. lol... still deciding.

[Miata Master]

When I ran out of money doing the 25 I was kicking myself for not going 20 but not anymore. I didn't want to spend money building up a 20 then changing to a 25 for the added potential. also 25 will be a newer engine. But I still love rb26

[mkory]

Yeah, I'd love to go with a 26 if I could. I'm still gonna need to check on the price, but considering the motor costs as much if not more than the motor+install of the 25, and install is harder, I think it's gonna be way out of my price range. Now I just need to find an additional $1,500 and I'll be all set.

[JonPowell]

Think about this....RB25 with a Blitz LM air filter and Blitz Realize TT exhaust(empty cat) made 255HP at the wheels stock boost(7 PSI)

What are you going to have to add to the RB20 to get 255 at the wheels and is it going to cost more than the RB25 with exhaust & airfilter(you are gonna do this to the RB20 anyway so I think the prices cancel each other there.)

For me its no choice, .5L extra displacement, newer motors, VTC, stronger trans lower boost and more power all leads me to the 25...Plus with the recent developments of 580HP at the wheels on stock internals means that most people will never need to upgrade pistons & such.

RB26 with ~700CC injectors, stand alone & nice big FMIC will make 400HP at the wheels....so engine, + ~$1000(ECU) + ~$500(injectors) +~$600(IC) makes 400HP...I doubt that an RB20 plus $3000 and the mods listed above could put 400 to the ground and be a consistent daily driver.The extra boost required will make it tough on everything inside the motor and the headgasket.

The RB20 is a great motor....for its time period. Nissan fazed it out in favor of the RB25 for a reason...its just plain superior. Sorry to piss off everyone but its the truth. Same as the RB25 got fazed out for the NA VQ35...its just superior. 280HP, larger displacement and no turbo lag. if I could get ahold of a cheap VQ35 I would put it IMMEDIATELY into my 280Z...hands down...then turbo it!!!! HA HA HA HA HA

[RMiller]

RB25 for 4200 installed is a steal. An absolute steal, as long as it runs the way it should. Like people keep saying, displacement is your friend. Whoever preaches about small displacement, high revving motors as being the end all, be all, is probably comparing their 2.0 turbo to a Pontiac Grand Am or, at most, their big brother's 5.0 fox body. I'd take a LS1 over a rb26, 2jz, etc. most days of the week. My foot communicates so much better with an n/a than with a turbo, and people that have driven good n/a powerplants will feel the same way.

To the point: RB25 > RB20. More displacement, stronger everything, incredibly awesome stock turbo, newer, better.

[Nameless EJ6]

Jon Powell, you have spoken. I agree, as usual. :p

[mkory]

I've gotta go with the 25... but that 1,200 cheaper 20 keeps trying to pull me back with its price. Don't worry fellas, I won't let it.

[rb240sx]

If I am not mistaken a rb25 has 9.5:1compression and a rb20 has 8.5:1compression. The rb25 has a sorda vvt and a 20 doesn’t.I have heard of and seen rb25's not take boost as well as a 20. Yea there is no replacement for displacement but the compression factor is there as well, I haven’t done it but if this info is correct than I would love to see a rb25 run 15 p.s.i and last a month. I have ragged on my rb20 since the day I installed it with not 1 problem and I mean some serious ragging, I don’t have a rev limiter if that says anything. I like the 20 just because of revs, not so much as power bc/ when a 20 hits its power ban it hit's hard, a 25 kinda gets into it alot slower than a 20. Meaning a 20 has more kick and but it has just as much potential as a 25.

[rb240sx]

correction the rb25 has a 9:1 compression

[Joe]

If I am not mistaken a rb25 has 9.5:1compression and a rb20 has 8.5:1compression. The rb25 has a sorda vvt and a 20 doesn’t.I have heard of and seen rb25's not take boost as well as a 20. Yea there is no replacement for displacement but the compression factor is there as well, I haven’t done it but if this info is correct than I would love to see a rb25 run 15 p.s.i and last a month. I have ragged on my rb20 since the day I installed it with not 1 problem and I mean some serious ragging, I don’t have a rev limiter if that says anything. I like the 20 just because of revs, not so much as power bc/ when a 20 hits its power ban it hit's hard, a 25 kinda gets into it alot slower than a 20. Meaning a 20 has more kick and but it has just as much potential as a 25.

what the hell are you talking about

the 25 is a power monster. it goes from idle all the way up. has a ton more potential than the 20 beause the turbo is bigger, and better, not to mention more displacment. the 25 does not "get into power" slower, it makes more low end power and more peak power. so where does that make a 20 faster in the power band. a RB25 will easily hold "15psi" if you upgrade the injectors and turbo. 450whp daily driven with a good tune is absolutley realistic with stock internals.

how is compression a factor? its a .5 difference.

and whoop de doo the rb20 revs higher, the 25 dosent need RPM to make power. its a superior engine, plain and simple.

also, id put a rev limiter on your engine, its just plain retarded not to have one. whats the point? your stock turbo dosent make power above 6500 anyway. RPM does not equal horsepower.
Modified by Kamin at 3:48 PM 3/27/2005

[JonPowell]

If I am not mistaken a rb25 has 9.5:1compression and a rb20 has 8.5:1compression. The rb25 has a sorda vvt and a 20 doesn’t.I have heard of and seen rb25's not take boost as well as a 20. Yea there is no replacement for displacement but the compression factor is there as well, I haven’t done it but if this info is correct than I would love to see a rb25 run 15 p.s.i and last a month. I have ragged on my rb20 since the day I installed it with not 1 problem and I mean some serious ragging, I don’t have a rev limiter if that says anything. I like the 20 just because of revs, not so much as power bc/ when a 20 hits its power ban it hit's hard, a 25 kinda gets into it alot slower than a 20. Meaning a 20 has more kick and but it has just as much potential as a 25.

Translation:

"I couldnt afford an RB25 and want to justify the Rb20 in my own head."

[DriftingisLame]

I didnt know people argued the rb20 comparing to the rb25...

[Wulfgang]

Translation:

"I couldnt afford an RB25 and want to justify the Rb20 in my own head."

LOL! No doubt about it, the decision must come down to money. I love my RB20, but there's no way I would have an RB20 if I could have afforded an RB25, or better, an RB26.

A VQ35... now that would be nice. On car-part.com, looks like prices for decent VQ35s start in the mid $2k range. Someone with decent fab capability should do this. Probably $5-6k installed if you could fab up everything yourself. Might be able to run dual exhaust too, if you make a new fuel tank.

[mkory]

So... guys... will I really be $1,200 happier with the 25?

[eh?]

that size differece plus the .5 ltrs is worth it in my opionion