Debating on RB20/RB25...

[TurboB15sentra]

I'm sure that this has been beaten to death.. but, I'd like to hear from some people who actually have RB's in thier cars... making some decent power. I'd like to make around 400-450whp on pump gas.. I'll be using a standalone to run the car.. so, tuning is in my hands. I'd like to have the exta .5 liters of displacement.. but, the RB25 is double the price of what a RB20 goes for. Is the RB20 capable of making 450whp with... say.. a SC61? I know the RB25 will do it.. I'd like to see some dyno charts if anyone has any.. of both engines..

Travis

[drift freaq]

I'm sure that this has been beaten to death.. but, I'd like to hear from some people who actually have RB's in their cars... making some decent power. I'd like to make around 400-450whp on pump gas.. I'll be using a standalone to run the car.. so, tuning is in my hands. I'd like to have the exta .5 liters of displacement.. but, the RB25 is double the price of what a RB20 goes for. Is the RB20 capable of making 450whp with... say.. a SC61? I know the RB25 will do it.. I'd like to see some dyno charts if anyone has any.. of both engines..

Travis
Travis I do not have a dyno chart of my engine yet. Though I do know I am very close to 300 whp. I know of a Skyline GTS-T in Australia that pretty much had a very similar setup as I have . It dyno charted at 280pws which is basically just over 300 whp. Thats on a bone stock internal RB25 with a stock turbo , 3inch exhaust and downpipe, Greddy or Greddy style intake manifold, PowerFC and a boost controller with a FMIC. If you were to add 440cc injectors(with mod for top feed) or 550cc injectors and a turbo upgrade you could easily get into the 400 whp HP neighborhood IMHO. Now you still have more room to play as well and your internals are still stock.
With a RB20 you will turn out somewhere in the 350hp range but thats with turbo upgrade and a number of other bolts. Its up to you. Yes the RB25 will cost double in price compared the RB20 but your power potential is more than doubled again IMHO. My feeling is if your going to do it at least do the RB25 but I admit I am biased towards it :D

[SilviaNinja240]

go 25 if you want 400-450, you can do with with a 20, but its a bit of a hasstle. You can get there a little easier with a 25 with probably less monkey work too AND with less stress on the engine.

[andrewmp6]

im going with a rb25 if you got the money do it too

[GREENTONE]

Both Are Cool , And There What You Make Them . So Take Witch Comes Easier To You . I Would Be More Impressed With The 20 Making 400 Then The 25

[TurboB15sentra]

I might just go with the stock RB25 for now.. and upgrade it a little at a time. I can either do a RB20 with bolt-on's/bigger turbo... or a I can do a stock RB25 for now.. Since the 25 has more potential.. I'll probably end up doing that.

There's always the VQ35 option too... ;)

Travis

[GREENTONE]

I Seen A Vq30 Once And It Was A Good Strong Car And I Have Never Heard Of Another One , So If You Go 35 That Would Be Chill . The Rb20 Is So Cheap Though And Compared Bang For Buck On Fact. Specs Its A Great Option . Plus If Your Like Me You Will Do Either And Only Decide Then To Get A 26tt After All Or Buy A S15 Off The Boat . Its Safe To Say No One Is Ever Happy In The End You Want More

[GREENTONE]

There A Kid In Angola , Ny ( I Was Told About ) That Has A Rb26 Complete Set And Wants To Trade It For A Sr Swap Completed Because He Cant Get It In Or Wired , I Will Try To Find Out And If He Wants To Dump It I Will Let You Know . There Is No Market For 240sx Parts In Wny , I Own The Only 3 I Have Seen In My Shops Area , Thats Why I Am Trying To Sell My Stuff On The Forum

[ca19det]

i would go with the RB25 if you have the casha nd dont plan on doing ti all at once (upgrade slowly)

or buy the 20 and get the parts needed at once with the extra cash.

there are allot of RB powered cars locally, from S chassis cars to old 70's datsuns and mazdas, allot fo them are making really good power (350whp+)out of RB20's (which are about $500 USD locally) with customised intake manifold, upgraded t3/t4 turbo, injectors and safc, real backyard scrap performance, but it works..

the RB20 gearbox is crap, the more i think of it get a RB25, i have been looking for one locally for a while, but not finding any manual ones, and i now found a gearbox and no engine lol..

[anotherblusi]

Get the RB25 or stick with the SR20. Imo The trouble in finding parts and paying higher prices is worth it for the RB25, but not for the RB20. Not to mention the weak aftermarket support for the RB20. Seriously my one motto for everything is "never settle". I know if had settled for another motor, I would always regret not saving up a little more and getting the motor I really wanted.

[wootwoot]

ka24de can do 400whp on pump pretty easily ;)
I would go for the rb25 no matter what, rb20 is strictly a budget engine in my eyes. Honestly, getting the rb26 would really be the way to go. You claim to be getting standalone, you do NOT need the engine harness at all. You could buy a rb26dett motor, z32 transmission (z33 even if you're a baller), and a rb25 oil pan. Twin gt28r's could produce 450whp on pump gas at around 1bar theoretically.

[BigVinnie]

Don't own an RB, but wouldn't it just be more logical to get the RB25DET?
RB20 is obviously an older engine, and I don't see those engines competing to well up against 2jz's and RB25's, overall the larger displacement of the RB25 would be better for boosting and power.
But what ever floats your boat.
I see people buying RB20's for being economical, and overall they should be fun for high reving.

[deep in silvia]

if you cant do the rb26 then just get the rb25. everyone that i have ever talked to that whent with the RB20 wish they would have got the RB25.

[rossfashow]

i want an rb25 over my sr20

[Destructo]

KA is a better engine. It pulls harder and is more upgradeable. plus it wont make the car only good for dounuts when you mess up the weight distrobution.(Saracstic:ya someone had to say it.)

[SilviaNinja240]

I might just go with the stock RB25 for now.. and upgrade it a little at a time. I can either do a RB20 with bolt-on's/bigger turbo... or a I can do a stock RB25 for now.. Since the 25 has more potential.. I'll probably end up doing that.

There's always the VQ35 option too... ;)

Travis


I think he already made up his mind guys.

[Neb456]

I would go with the RB25 why ad weight and not displacement? Just doesn't make sense...

[TurboB15sentra]

I have made up my mind, actually.. ;)

KA24DE build up..

Custom 9.2:1 CP pistons
Crower H-beams
ARP head/main studs
Cometic gasket
Stock cams
Custom sheetmetal intake manifold
SS-Autocrack top mount manifold (re-TIG welded)
Precision SC61 turbocharger
750cc injectors
FI-R fuel rail (my own CNC'd design)
Mallory FPR
Walbro 255lph HP
Enthalpy ECU
Z32 MAFS
3" DP and exhaust
JWT clutch/pp

And, I'm debating on whether or not to do the Z32 TT Auto trans swap...or maybe a Z33 6spd swap. From looking at it.. the Z33 trans actually looks easier to set up. But, since this car will be mostly for drag.. the auto trans is very appealing.. especially since it can hold 500whp in stock form.

Travis

[andrewmp6]

i dont like the ka rather have a rb since i want a torque monster

[wootwoot]

750cc's wont be big enough
Stock cams are NOT going to cut it
SSAC manifold is for budget not for high power
Auto tranny for only 500whp? Silly.

Are you actually serious about this?.....

[Hitawall]

i pondered all these ideas , and it always comes back to the fact the sr20 and ca18 is balanced for the 240 . the rb's are great option for being different but you get the same power with an sr20 for less money and it will keep you at 50/50 weight to get it moving and dialed in right . it does seem we are a dime a dozen but i still have the only one in my city so just think ! if the hoods closed it looks the same . good luck with wich ever and the vq kinda sucks 180hp and all custom brackets driveshaft ext....

[TurboB15sentra]

750cc's wont be big enough
Stock cams are NOT going to cut it
SSAC manifold is for budget not for high power
Auto tranny for only 500whp? Silly.

Are you actually serious about this?.....

750's/Z32 will make right at 500whp safely..It's been done before
People have made over 500whp on stock cams/intake manifold
Yes, it's a cheap 4-1 short runner manifold.. I've made more power on log manifolds.
Yes, the Z32 TT trans will hold 500whp stock.. it's been done before

Am I serious? Here's my last S13..

http://myspace-548.vo.llnwd.net/00363/84/53/363633548_l.jpg
http://myspace-363.vo.llnwd.net/00326/36/34/326384363_l.jpg
http://myspace-747.vo.llnwd.net/00367/74/70/367430747_l.jpg

I think I've got enough experience to know what I'm talking about buddy..

Travis

[TurboB15sentra]

i pondered all these ideas , and it always comes back to the fact the sr20 and ca18 is balanced for the 240 . the rb's are great option for being different but you get the same power with an sr20 for less money and it will keep you at 50/50 weight to get it moving and dialed in right . it does seem we are a dime a dozen but i still have the only one in my city so just think ! if the hoods closed it looks the same . good luck with wich ever and the vq kinda sucks 180hp and all custom brackets driveshaft ext....

The VQ sucks? 300hp/265tq with the VQ35.. I put one in a Sentra, and the car ran 12's on a stock motor, stock exhaust, manifolds, intake.. etc.. The VQ is a badass motor.. It's not always about peak power.. ;)

Travis

[TurboB15sentra]

i dont like the ka rather have a rb since i want a torque monster

The KA is known for it's Torque.. It's a 2.4 liter.. the RB is a 2.5 liter..

[TopClassGarage]

The KA is known for it's Torque.. It's a 2.4 liter.. the RB is a 2.5 liter..

But its silly to say, dont forget about an extra 2 cyc. Torque is nothing with your down 2cyc. :Ownedd:

[TurboB15sentra]

Displacement is displacement... Sure, the RB25 might have better total mass flow.. but, it's not THAT big of a deal.. I'll sacrifice 10ft lbs of TQ to save 2500-3000 dollars.

Travis

[wootwoot]

The only reason an rb would produce more torque is because of it running a smaller turbo in relation to its displacement allowing quicker spool. The earlier you have full boost the higher tq you will have

[TurboB15sentra]

Well.. the RB25 is going to produce more total mass flow over the KA.. even if the KA was a 2.5 liter.. the RB would still outflow it.. simply, beacuse it has 2 more intake/exhaust ports.

Travis

[BigVinnie]

The only reason an rb would produce more torque is because of it running a smaller turbo in relation to its displacement allowing quicker spool. The earlier you have full boost the higher tq you will have


From what I understand it is the amount of fuel dumping to ignition timing that effects torque numbers........
RB will naturally produce more torque from being an inline six.
But in the power to displacement ratio the KA doesn't fall far behind in power potential from having a stroker crank. The longer stroke makes up the power in half the rev it takes the RB.
Overall the RB has a much stronger bottom end to achieve higher HP numbers.

[wootwoot]

Put a big turbo on either motor and they lose most of their "torqey" characteristics. Your peak torque on turbo motors is when the turbo reaches full boost. I'm kind of confused what you meant by the fuel/ignition timing thing you're saying

[BigVinnie]

Put a big turbo on either motor and they lose most of their "torqey" characteristics. Your peak torque on turbo motors is when the turbo reaches full boost. I'm kind of confused what you meant by the fuel/ignition timing thing you're saying


EXAMPLE:
A KA24det (lets say T25) that uses a OEM ECU will usually run torquey (209hp 229FT lb.s/torque), this is on a bone stock ecu, and lets say an SAFC.
Timing needs to be retarded on boosting. Retarding the timing increases torque and kills HP. The stock ECU also runs more on the richer side of fuel dumping than leaner (mostly for smog reasons and lowering NOX emissions).
Retuning the ecu's A/F ratio's, and TTP can correct the KA's performance to provide more HP than torque as provided through most tunes that you see from enthalapy (just an example).
My point was the majority of the power that you think is torque produced by the turbo, is really just a really bad tune from the ECU. Engine management allows you to play with the power band, not the turbo. Turbo's just MAGNIFY power in the power band.
Appoligize for using the KA as an example, but it is what I usually work with.

[wootwoot]

No apologises needed, any example would have worked absolutely fine. I understand what you are getting at now and agree but still stand by my peak tq is made at full boos. I dont think you are arguing against that point though or in anyway with it.

[andrewmp6]

who ever said a rb is heavy its only 130 pounds over the ka take off the a/c and ditch the pop ups youll make up for that 130 easy pick whatever engine you like and can afford

[revat619]

and fwiw, most of the weight difference in the RB lies in the tranny, which is pretty much in the center of the car. So it doesnt make that big a difference if any with handling.

For your power goals and what you're building the car for, i would suggest an rb25/26 or 1jz/2jz. A KA can do it, but you're putting a lot of stress on the motor. With the big 6 cylinders you can make that power easily on stock internals. Oh and automatic rb and 1j/2j clips can be had at a fairly cheap price. Let me know if you need help sourcing one. :bow:

[skatanic28]

The VQ sucks? 300hp/265tq with the VQ35.. I put one in a Sentra, and the car ran 12's on a stock motor, stock exhaust, manifolds, intake.. etc.. The VQ is a badass motor.. It's not always about peak power.. ;)

Travis

ive seen pictures of a similar swap somewhere, definately seems like a nice combo. im not sure how common those swaps are, maybe it was even yours?

good luck on the next build!
make sure you have enough brake master cyl clearance with the ssauto mani and an sc61.

[ca19det]

nice choice TurboB15 - i think you should look at some 96lb/hr injectors and maybe even stand alone (used E6k or something) so you can have a little more room/controll/possibilities and not need scott to fine tune things for you if you change or upgrade your setup. that way you can switch to direct fire etc..

and why not use something bigger like a GT40R or soemthing and make ~700whp and do a modified Z32 tranny with 4k stall and the works ;)

keep us updated