2.4 Rb20 Stroker Or Drop An Rb25det In?

[legend01]

Yo Roy

[32DET]

Isn't the different noise experienced by the rb20 as opposed to the rb25 due to injector positioning? Not really sure, just thought i read that somewhere and i also remember reading in the HPI magazines during their rb24 build up that they thought the rb24 had a little more torque than a standard rb25.

If your willing to pay some extra money and encounter a few problmes along the way then go the rb24 and you will end up with a pretty cool engine setup that looks stock but has a little more low-down go but it would be alot easier and cheaper to just go the 25.

[WazR32GTSt]

rb20 ftw!

if money is no option, i'd say go the rb24 route.. no one here has the balls to do it, all i hear is "its too expensive"

well who has actually done it?

[RedDrifter]

  32DET said:

Isn't the different noise experienced by the rb20 as opposed to the rb25 due to injector positioning? Not really sure, just thought i read that somewhere and i also remember reading in the HPI magazines during their rb24 build up that they thought the rb24 had a little more torque than a standard rb25.

If your willing to pay some extra money and encounter a few problmes along the way then go the rb24 and you will end up with a pretty cool engine setup that looks stock but has a little more low-down go but it would be alot easier and cheaper to just go the 25.

I doubt the injector positioning would make the noise difference. I think it would be a number of things like the different compression, different cams specs, valves and bigger ports etc. As for the rb24 having more toque it is possible i guess as it would have a slightly bigger stroke than the rb25 but i would think it was due to a better tune .

If the intention was to build a new motor anyway then the rb24 would be the way to go.

I think if i was gonna go a rebuild I think the rb22 would be the way I go.

Personal pref i guess.

[Cubes]

  32DET said:

Isn't the different noise experienced by the rb20 as opposed to the rb25 due to injector positioning? Not really sure, just thought i read that somewhere and i also remember reading in the HPI magazines during their rb24 build up that they thought the rb24 had a little more torque than a standard rb25.

If your willing to pay some extra money and encounter a few problmes along the way then go the rb24 and you will end up with a pretty cool engine setup that looks stock but has a little more low-down go but it would be alot easier and cheaper to just go the 25.

Was their comparison between an RB25DET in an R32 to the RB24 in an R32 or an RB25DET in an R33 vs the RB24 in the R32. If the latter its possible the rb24 will feel as if it has more torque as the R32 is both lighter and runs a lower diff ratio.

The other possibility is that the R32 inlet runners and ports are considerably smaller than the RB25's, increasing velocity at low engine speed, this too improves low down torque but creates a greater restriction at higher airflow levels.

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[Roy]

You would still want to rebuild an RB25DE though wouldnt you? Ppl have problems with the valvesprings in them dont they when they turbo them?

Also what compression do they run, and are the pistons any good, or are the ring lands pretty pissy like std RB25 pitsons?

Think it could work well, but i dont think its a better option then throwing in a std RB25DET.

If you are going to rebuld an RB20, i still think some custom pistons for an 82mm bore, std rods and crank with a clean up of the combustion chambers and ports....would be a pretty decent thing for not too many dollars.

I still think a std RB25 is a pretty strong thing and ppl prematurely open them up. So if you only want a punchy streetable engine then it does take some beating...but does cost a few dollars to do. Especially sinc if i was doing an engine change i would put a new water and oil pump in. New timign belt and idler/tensioner bearings. New belts on the front of the motor...it all adds to the cost of an engine swap. Hell even engine oil, coolant and air con re-gas woudl set you back a few hundred...things to consider if your thinking about swapping out the RB20

[WazR32GTSt]

roy, i think you and i are about the only people on SAU that actually like their rb20!

[andylaurel]

i have driven a cefiro that sported a HKS built RB24 and i am pleased to report that these motors are infinately more torquey than a stock RB25. This is in my opinion, largely to do with the small port/valve size creating high intake velocity.

The motor was noticably bad about 6000 where it trailed off in power.

Building a 2.4 would be great fun, but how easy is it to find good, cheap virgin rb26 cranks?

[Roy]

Why did it fall over? My std RB20 with cam gears pulls well, even up around 8,000rpm. Tune???

[kwazza11]

My rb24 doesnt tend to trail off after 6k, infact it feels like the 7.5k limiter is cutting its lunch, and thats with stock cams, ports, and gears. once theres some cams in the mix it'll be a weapon!

personally i think the 24 is well worth it, sure it'll cost you 5k+ to do it properly but you'll have no problems after that if the tune is sweet. i've owned a 31 with a stock rb20 and my hr31 with the rb24 and 2871r and the 24 has more power everywhere, better to drive around town and just generally better behaved (especially since i change the leaking HG ). can't comment on a 25 though, never stepped over to the dark side..

Oh and you definately cant beat the sound of a 24 at full revs! especially with a good exh manifold, the HKS one sounds awsome but the Trust high mount gave me a horse stiffy everytime i wound it out.

Edited September 27, 2006 by kwazza11

[Cubes]

  Roy said:

You would still want to rebuild an RB25DE though wouldnt you? Ppl have problems with the valvesprings in them dont they when they turbo them?

Also what compression do they run, and are the pistons any good, or are the ring lands pretty pissy like std RB25 pitsons?

Think it could work well, but i dont think its a better option then throwing in a std RB25DET.

If you are going to rebuld an RB20, i still think some custom pistons for an 82mm bore, std rods and crank with a clean up of the combustion chambers and ports....would be a pretty decent thing for not too many dollars.

I still think a std RB25 is a pretty strong thing and ppl prematurely open them up. So if you only want a punchy streetable engine then it does take some beating...but does cost a few dollars to do. Especially sinc if i was doing an engine change i would put a new water and oil pump in. New timign belt and idler/tensioner bearings. New belts on the front of the motor...it all adds to the cost of an engine swap. Hell even engine oil, coolant and air con re-gas woudl set you back a few hundred...things to consider if your thinking about swapping out the RB20

When I origionally suggested the rb25de route I said one would have to change pistons, and yes valve springs will also need to be replaced with a $200-$300 set of GTR springs. Forgot about that one...

Its a little bit of the its a fresh motor or a second hand motor.... By all means the second hand motors do appear to be not too bad but personally I'd prefer a fresh motor and it shouldn't cost you more than 1k over the purchase price of a s/h rb25det.

[Roy]

Yeh, my problem is once you crack a motor, where do you stop? So in go the new pistons and valve springs, so there is a new head gasket, bearings, head studs, rod bolts etc. Or do ppl re-use things kiek head studs?

[Cubes]

I didn't reuse headstuds. They weren't terribly expensive but as you say... Where does one stop.

Stick with the rb20 and ram boost in to it I say.. When it pops throw another $500 RB20 in.

Rebuilding motors I worry about popping it. $500 cheap rb20 who cares, hammer it enjoy it.

[32DET]

haha yeah stuff the rebuild..spend the money on 8 rb20's and just hit the track!

I am definately going to rebuild my rb20 and bump it out to a 22 or 24 when the time comes because the dark side is a place i never want to go to

It came with that engine so i wanna keep it and see what it is capable of. Obviously there are other ways that will make much more power but im not after a 10sec car etc. just something fun and a bit different.

[Lukaz]

Awesome replys guys, I assumed $5k+ for a forged 2.4 setup, Ive already got cooler, pod, injectors, wolf3d ecu, full exhaust with dump pipe and fuel pump, so I figured stroke and turbo should see me close to those figures with little fuss?

[johan.p.g]

im thinking of going with the 24 as well but i want to use the 25 block out ov a r33 with variable valve timing and then the 2 litre crank and forged 2litre cons this chould give me a ridiculously high redline and a free revving tourquey engine the exact capacity will be 2429 with this combination

[johan.p.g]

im thinking of going with the 24 as well but i want to use the 25 block out ov a r33 with variable valve timing and then the 2 litre crank and forged 2litre cons this chould give me a ridiculously high redline and a free revving tourquey engine the exact capacity will be 2429 with this combination

[Roy]

If using the 2L crank how are you going to get 2429cc?