Im a new 240 owner but a long time nissan lover, im interested in an rb20 swap but from what i have been reading on this forum and on 240sxforums.com some of the information seems somewhat contradictory, Im confused as to weather the cross-member needs to be swaped for a rb20 swap or weather that is just somthing that has to be done for a rb25

If you have an s13 (probably s14 also) you will need to swap the crossmember out for the HCR32 (R32 skyline GTST)crossmember, but preferably the A31 (cefiro) crossmember.

yes the RB engines do sound sweet. where the SR sounds like a WRC car the RB sounds like a le mans car

i would save up the extra money for the 25

perpetual gyro wrote:I have done research in this area. I realize their both the same displacement but you also got 2 more pistons, plus it's much cheaper (w/ clip) than the highly-demand SR. And as night pointed out, it's only about 100lbs heavier, and has [roughly] 35 more hp at the wheels...so please explain why you would choose the SR over the RB instead of just spitting out opinions. Thanks.

Hey night,really? I would of thought that the RB had more torque. Can you please explain to me why? Thanks bro.

I'm new here, so I'm not sure if this has been said already, but here it goes. The reason for the difference in both torque and power is the same. The SR20DET has only four pistons, but it has the same displacement as the RB20DET with six. Therefore the SR20DET has larger pistons/cylinders. This will give it more torque. Simple physics P = F/A Which is to say The greater the area of the piston the more force a given pressure is exerted on it. This force is directly proportional to the torque. While conversely, the smaller pisons of the RB20DET give them less inertia, allowing them to move up and down faster.

Sorry to bring this thread back up, but I developed a dilema and a question to go with it.

If I understand correctly the SR20DET's power is measured at the crank, but the RB20DET's power is measured at the wheels?

In other words... What are the crank HP and TQ ratings and the wheel HP and TQ ratings of both engines?

both at the wheels

Is it a second hand engine? Is it full stock? Have things been added or taken away?

Also at least for The numbers I have for the skyline they are in PS not HP.

R34 RB25det 206ps or 203.18

http://www.mr2ownersclub.com/converter.htm

that is exactly what I mean...

I know the (S13) SR has (at the crank) 205hp and 203lbs/ft. and your numbers sound about right, night. Calculating around a 20% power loss through the drivetrain, which is more or less a standard for RWD cars.

My question is...What about the RB20? 215hp and 193lbs/ft and that is measured where? Wheel or crank?

i didnt read through this, so I dont know if its been mentioned. The rb20 has a major disadvantage over the sr20;It has the same displacement but 2 more cylinders, which means a 50% increase in rotating mass inside the engine. This will effect the power both engines can make.

There are definately upsides to the rb20 swap, but I figured I'd mention that since I doubt anyone else had thought of that yet.

NightXCZ77 wrote:The RB20 also has a smaller piston size and lesser stroke which gives it less capacity to make torque against the SR engine, however, with the RB26 crank and rods you're RB20 can be a killing machine.

Night

wouldnt that make it an rb24? I think that's a waste of time, better off getting a newer rb25, which would probably cost less/same.

you could probably find a used 26 crank and rods for less than the cost of a set of 8.5:1 pistons that you would need to put into a 25 to make decent boost with that

why not get the motor the RB26 crank is attached to and quit half-steppin:thinker The RB20 is a great engine, tough as nails but your about done at 400hp, want more? go RB25 or RB26

of course the 26 is NOT an easy swap. thanks to the twin hair dryers hanging off the left side of the block. i figure the 25 is good since its still a single turbo and easy to swap but is limited due to the 9:1 CR

themadscientist wrote:why not get the motor the RB26 crank is attached to and quit half-steppin:thinker The RB20 is a great engine, tough as nails but your about done at 400hp, want more? go RB25 or RB26

L

NightXCZ77 wrote:Mad - don't mean to deter you in any ways, but the average black top SR I've seen on a dyno only produces about 185 whp and the average red top about 168....far from 205 and 220.

Night

Used motors right? plus the figures that guys throw around are metric HP which is less than SAE. The Dyno runs here at the wheels jive with what the cars are listed wheels in Metric HP so these are wheel figures. The HP figures you are stating sound right in line when taking into account the two contributors I mentioned.

hmm its starting to get confusing as im new to the engine swap world of nissans but i was thinking of either an sr20 , an rb20 or a rb25 so i have come up with the conclusion that i will get a 92 fastback se and go blacktop sr20. and we shall see an s14 with an rb25 in about 3 years from now

themadscientist wrote:Used motors right? plus the figures that guys throw around are metric HP which is less than SAE. The Dyno runs here at the wheels jive with what the cars are listed wheels in Metric HP so these are wheel figures. The HP figures you are stating sound right in line when taking into account the two contributors I mentioned.

yes, and the end result is the rb swaps have 20-60hp more, depending on which ones your comparing.

jmillheiser wrote:of course the 26 is NOT an easy swap. thanks to the twin hair dryers hanging off the left side of the block. i figure the 25 is good since its still a single turbo and easy to swap but is limited due to the 9:1 CR

well if your looking under the hood from the front, like most people would consider it, it would be on the right side cheif.