Rb20det Stroker Motor

[johan.p.g]

i was planning on doing it the otherway round 20 crank and cons in a 25 block what i wanted to know was is the small end bearings the same for a 20 and a 25 also

does any1 have the conrod lengths and piston hights (small end to top) for both 25 and 20

[signalpuke]

i was planning on doing it the otherway round 20 crank and cons in a 25 block what i wanted to know was is the small end bearings the same for a 20 and a 25 also

does any1 have the conrod lengths and piston hights (small end to top) for both 25 and 20

RB20 - Std Rod Ratio 1.743

RB25 - Std Rod Ratio 1.694

RB26 - Std Rod Ratio 1.65

RB20DET - 78mm Bore/ 69.7 Stroke,

RB25DET - 86mm Bore/ 71.7 Stroke

RB26DETT-86mm Bore/ 73.7 Stroke

20 conrod length 121.5 rod journal bearing 45

25/26 conrod length 121.5 rod journal bearing 48

30 conrod length 152.7 rod journal bearing 50

Hope that helps, by swapping the 20 crank in the 25 you will destroke the motor, and have a smaller rod journal bearing, but the R/S ratio will improve to that of the RB20, you may need custom pistons though. Overall displacement will be 2055.651316787177cc

Edited January 3, 2007 by signalpuke

[signalpuke]

This is a handy calculator

http://golenengineservice.com/calc/calcci.htm

[Rolls]

Just out of curiosity why would you de stroke it when you could buy a cheaper rb20 block with everything already in it?

[Roy]

I think the idea is to use the short revy stroke of the RB20 with the volume you get from running 86-87mm bore. If you can work out the piston deal (pin heights) then its a great wasy of getting a rev crazy 2.4L

I have also thought about the poor mans budget RB20 stroker where you get the unloved RB26 crank and rods out of an R32 GTR and use them with the std pistons (Again pin heights etc????) You get very little increase in displacement, but you dont have to modify the combustion chambers etc etc as is the case if you go the 3-4mm overbore. The extra stroke from the RB26 crank will give you more torque accross the rev range.

[Jago]

i hadent heard about using a rb25 crank and rods. ive only ever heard about using rb26 items.

using RB25 items gives you an RB23, whereas RB26 crank and rods as well as the right sized pistons gives you an RB24

[signalpuke]

On another forum that I frequent quite regularly there is a discussion going on about rod/stroke angles, and there is a lot of good information that really applies to all motors. May be of some interest to some of you K20A.org Spoon Motor thread

And here is a cool piston speed calculator

Edited January 6, 2007 by signalpuke

[Jago]

well. Im still umming and arring about it all. Sofar allot of the results i've seen have been VERY dissapointing. A car for sale at UAS with an RB24 is only making 287rwkw, i've heard of others making around this power. For the ammount of cost involved to do it, and only getting figures that small, well it makes me want to change my mind and go RB30DETT. But when watching DVD's etc, of cars down the 1/4 in Japan, some RB24 engined cars are running in the 10's

Oh yea, and having seen the results the HPI demo car gave, well, that was laughable.

[johan.p.g]

RB20 - Std Rod Ratio 1.743

RB25 - Std Rod Ratio 1.694

RB26 - Std Rod Ratio 1.65

RB20DET - 78mm Bore/ 69.7 Stroke,

RB25DET - 86mm Bore/ 71.7 Stroke

RB26DETT-86mm Bore/ 73.7 Stroke

20 conrod length 121.5 rod journal bearing 45

25/26 conrod length 121.5 rod journal bearing 48

30 conrod length 152.7 rod journal bearing 50

Hope that helps, by swapping the 20 crank in the 25 you will destroke the motor, and have a smaller rod journal bearing, but the R/S ratio will improve to that of the RB20, you may need custom pistons though. Overall displacement will be 2055.651316787177cc

thanks for that although i think that some of ur details are a bit out as the cons for the 20, 25 and 26 are all diff

i think u miss understood i would be replacing the both the conrods and the crank which would give me a capacity of 2429.2419391773424cc

a bore of 86 and stroke of 69.7 im also planning on using rb30 pistons if i can just need 2 check the small end sizes as this will decrease the compression ratio so i can run high boost

[Roy]

well. Im still umming and arring about it all. Sofar allot of the results i've seen have been VERY dissapointing. A car for sale at UAS with an RB24 is only making 287rwkw, i've heard of others making around this power. For the ammount of cost involved to do it, and only getting figures that small, well it makes me want to change my mind and go RB30DETT. But when watching DVD's etc, of cars down the 1/4 in Japan, some RB24 engined cars are running in the 10's

Oh yea, and having seen the results the HPI demo car gave, well, that was laughable.

Power is largely a function of the turbo they put on it. In Japan there are RB24s with T88s running 10s. Put a 2530 on it and the same motor will make 230rwkws

[Wheezy]

legend01 how much boost were you throwing down the 20 for that power figure of 282rwkw?

Also what exhaust manifold and inlet manifold? Standard? Id love to know a bit more about your old setup

-Jez

[Jago]

Power is largely a function of the turbo they put on it. In Japan there are RB24s with T88s running 10s. Put a 2530 on it and the same motor will make 230rwkws

heh, i was thinking twin HKS 28 series or something if i went through with my stroker motor

twin turbo power -_-

197.7 rwkw @ 13psi on internally std RB20 (failing RB20 with a half shot turbo too), nuff said about twin turboing -_-

[huddy]

Power is largely a function of the turbo they put on it. In Japan there are RB24s with T88s running 10s. Put a 2530 on it and the same motor will make 230rwkws

guy in SA bought a 32 gtst from KANSAI with a RB23 in it. with a T78 - made 400+rwkw!!!

i also have a rb24 with a hks2530 making 240rwkw.

I know i could have more, but have sacrificed peak HP for more usable power for me with drift.

[legend01]

Hi Wheezy

22.5 psi, hks low mount cast mannifold and standard inlet all mods listed in the rb20 dyno thread .

[DJRIFT]

using RB25 items gives you an RB23, whereas RB26 crank and rods as well as the right sized pistons gives you an RB24

ahh i never new that. so can you pretty much just drop in a 25 crank and rods and get the rb23 or do you need to biuld the motor properly?

what was the final figures on the HPI rb24????? i never seen the final output. that car kinda pissed me off because they would say just slap in a gtr crank and rods and your done mate. they never tell you just how hard it all is. like how the block has to keep getting ground so the crank will clear the sides and so on. plus they buy all this brand name stuff from japan that is very hard to get in aus and say yea this is a grate mod if you can find the parts.

basicly final power output cant realy determine how good a motor is as like someone said before it is hugely govened by the turbo. but a stroker motor gives you torque and diferent engine charecteristics. torque wins races and spins the wheels better.

as far as strokers go thoe everyone seems to say rb30det are the best dolar for kilowat engine biulds.

[signalpuke]

thanks for that although i think that some of ur details are a bit out as the cons for the 20, 25 and 26 are all diff

i think u miss understood i would be replacing the both the conrods and the crank which would give me a capacity of 2429.2419391773424cc

a bore of 86 and stroke of 69.7 im also planning on using rb30 pistons if i can just need 2 check the small end sizes as this will decrease the compression ratio so i can run high boost

Do you happen to know the lengths? I dont have the actual pieces on hand, I found the info from aftermarket conrod manufacturers on the internet. I cant imagine the rods are that different, other than the bearing width, as it would make sense from a production standpoint

[R31Nismoid]

500rwhp/370rwkw is asking far too much from an RB20 that will be driven.

I couldnt begin to think the levels of boost required when you need well over 20psi to hit 400rwhp.

[johan.p.g]

Do you happen to know the lengths? I dont have the actual pieces on hand, I found the info from aftermarket conrod manufacturers on the internet. I cant imagine the rods are that different, other than the bearing width, as it would make sense from a production standpoint

i just read somewhere else that the rod lengths for a 26 are the same as a 25 and the diff is made up in the pin height in the pistons but i am sure the 20s cons are a diff length

also i found out that the pin diameter for a 30, 25, and 26 are all 21mm diameter if any 1 could tell me the diameter of the 20s that would be very useful

Edited January 15, 2007 by johan.p.g

[legend01]

RB20 rods are the same length as rb25 and 26 little end pins or gudgen pins also the same dia only differance is the big ends are smaller in the 20 rods .I had all three measured up for my rebuild just b4 xmas

Rb26 rod on the right rb20 rod on the left

Cheers Peter

[Wheezy]

500rwhp/370rwkw is asking far too much from an RB20 that will be driven.

I couldnt begin to think the levels of boost required when you need well over 20psi to hit 400rwhp.

Gibson HR31 comes to mind

RB20DET-R, GTS-R turbo (im guessing hi-flowed), lumpy as f**k cams, ported head, cosworth pistons

460rwhp @ 8,000rpm on 1.7bar (24.6psi) of boost

But I guess with a factoruy backed budget anything is achievable

In the end I dont think anyone who aims for this amount of power is looking for a streetable RB20DET, although Im keeping mine registered to have some fun....

*here it comes...DAMN STREEEEEEEEEEEEEEET RACERS

EDIT: thanks legend 01

Im going to be running the same turbo and exhaust manifold, a Jun intake plenum, 040 pump, 550 jectors, remapped ecu, and maybe cam gears, should get 260rwkw on 18-20psi with some luck

-Jez

Edited January 15, 2007 by Wheezy