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  1. #1

    RB20 / RB25 / RB26 Engine Swap Links

  2. #2

  3. #3
    On Vacation Walperstyle's Avatar
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    Nov 2002
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    Copied this from the link because if any of these links go down, we could loose valuable documentation

    Many of you have your views on the SR vs. RB engine swaps. I can not speak from experience on the SR swaps, but I can on the RB swaps and I can provide information that may change the way you think.

    I get extremely aggrivated reading about how people say the RB swap is too expensive or that it is too hard to do, or that you can't find parts, because all of that is not true.

    The RB series engine is the soul of Nissan. It is the strongest engine ever built by man. The Nissan Skyline block is among the only blocks in the world never to have been blown. It has sustained over 2200 HP with nothing being done to the block.

    The RB engines are also light for their size, having similar displacement to the KA24DE motors, they weigh relatively the same. After removing the AC condensor they are practically the same.

    A common RB engine can be purchased through anyone that buys and imports engines. I can get the RB20DET, RB25DET, and RB26DETT clips for little cash. The RB20DET clips run just $2250, RB25DET clips just $3000, and the RB26DETT clips are close to $5,000. Match that price against their potential and you have a winning combination, especially when people want $2750-$3500 for a SR20DET clip.

    Another common mistake is thinking the RB engines are solely AWD, though this can be done simply (when having a clip) in a 240SX, it is not the case. (and to mister know it all who thinks that there aren't AWD 240's or in Japan the Silvia/180, think again!. Ever heard of the BlueBird? Came with 231HP stock and a top mount intercooler...AWD tranny and was in the 180SX rally cars???) The two most popular for the swaps are the RB20DET and the RB25DET which both came with RWD transmissions (unless you have the GTS-4 which came with AWD and the RB20DET engine).

    Now, as far as power goes, the common red top SR20DET pumps out a good 275 with the stock turbo. The RB20DET pushes up to 350 easily with the stock turbo, the RB25DET pushes easily to 400 with the stock turbo, and the RB26DETT pushes up to 500 with the stock turbos. The torque on the RB engines (the stuff that really matters since hp is an imaginary number derived by torque and rpm) is also greater on the RB series engines. Better torque, better speed.

    Installation on the RB engines is relativey the same as the SR20DET's. They both use the stock engine mounts and stock tranny mounts on the 240SX, however all that has to be done on the RB series engine for the tranny mounts to line up, is to dis-assemble the tranny mount, turn it around, and re-assemble it. The only difference here on installation is that the RB engine is longer, so the stock engine fan cannot be used without radiator relocation (this is why you get dual power fans)($100) and you need to have a new driveline made ($400).

    As far as parts go on these engines....they are both from Japan!!! That means all parts are ordered from Japan!!! Anyone that carries Trust (Greddy), HKS, Blitz, Apexi, or whatever, has access to these parts. I myself am a dealer in these parts, both new and used. Just as well, the stock parts on the car are easy to come by. The RB20DET and RB25DET both use the same clutch as a non turbo 90's model 300ZX. They also use the same oil filter!

    Now when comparing the two....SR20DET clip for $3,000. RB20DET clip with driveline and fans - $2750, RB25DET clip with driveline and fans - $3,500. Come on people, which makes more sense? A SR20DET has rarely, if ever, been taken over 1000hp. I believe the strongest made was around 600HP by Signal. The RB engines have been taken over 1000HP as a daily thing in Japan. Which engine has more potential? Just think about it and equate the costs, you'll see that by putting a RB engine in, you can have a much faster car.

    Also, I have a RB25DET in my 240SX...I was one of the first to do it. I run a 12 in the quarter mile at stock boost (7psi) How many SR20's can come close to that being stock??? Absolutely none.

  4. #4
    On Vacation Walperstyle's Avatar
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    copied to preserve documentation incase link goes down

    Q: What is required to make the RB25DET fit into a 240SX?

    A: All that is needed is the clip, driveline, tools, patience, and parts for extending/crimping wires.

    Q: Do the RB parts interchange with any US-Spec Nissan cars?

    A: Yes, in fact, the RB25DET uses the same clutch as the 300ZX Non-turbo. It also shares the same spark plugs, oil filter, and ignition coils.

    Q: What extra parts do you recommend with the swap?

    A: I recommend getting dual power fans to help with cooling, a Walbro 255LPH fuel pump to supply sufficient fuel, a new air filter for better breathability, NGK Iridium spark plugs for better spark and more HP, a decent sized downpipe and exhaust for better breathability and airflow, a new clutch for longevity and better grip, and a LSD so you are not burning rubber all the way down the track.

    Q: Where can I get aftermarket support for the RB?

    A: Aftermarket support can be found through me for both new and used parts. Other places are starting to stock parts for the RB swaps such as After-Dark Tuning. Other companies that carry brands such as Greddy, Apexi, HKS, and Blitz can order the parts for you from Japan.

    Q: What modifications are necessary to the 240SX?

    A: To make the engine fit properly with stock mounts, you will have to accomodate a few things.

    1) As with any turbo swap, you will need to cut holes for intercooler piping.
    2) You will need to shave (using a dremel or similar tool) a small portion of the turbo manifold that connects to the downpipe. This is necessary for steering rack clearance and does no harm as long as you do not shave too much off.
    3) You will need to make approximately a 6" cut of the hood skeleton to achieve hood clearance (which isn't visible from outside the car).
    4) You will need either a RB25DET driveshaft or a custom one made to fit the RB25DET engine.

    Q: How difficult is the swap?

    A: The swap, in my opinion, is fairly easy. Anyone who knows how to take something apart and put it back together again can do this swap. It is a simple plug and play with a few small modifications that are listed above. This was the first swap I ever attempted with no prior knowledge of how to swap engines.

    Q: How difficult is the RB25DET to wire?

    A: When I wired my car, I kept my 240SX interior harness (runs dash, headlights, tail lights, etc...) and got rid of the KA engine harness and ECU. I replaced that harness with the engine harness and ECU from the RB25DET. I then had to extend wires for the Gauge cluster and Ignition so that they would reach the LHD side of the car. I then integrated 5 wires from each of the harnesses ignition systems and made a power terminal where both harnesses were attached at the front of the car so that they would each receive power.

    Q: Is it true that you have to cut into the firewall or extend your front end?

    A: No, there is no need for cutting into the firewall or extending the front end. If you wish to use the stock engine fan that attaches to the fan clutch assembly, you will have to re-locate your radiator or extend the front end. This is why I recommend power fans for extra cooling.

    Q: Can you use the Stock RB25DET mounts?

    A: Yes, the stock engine mounts are bolted to the stock crossmember which shares the same bolt pattern as the KA crossmember when bolting up to the 240SX chassis. The tranny mount can be used, but must be taken off and flipped backwards. After you do this, you should add a spacer 1.5" thick made out of anything such as wood, metal, plastic, rubber, etc... as long as it will not collapse.

    Q: What do you use for cooling the RB?

    A: I use my stock 240SX radiator and haev no problems. The RB radiators can be used, but modifications must be made for it to fit into the 240SX as it is about 2.5" higher than the stock 240SX radiator. If you are worried about overheating problems, fluidyne radiators are a good option.

    Q: What are advantages of the RB25DET over the SR20DET?

    A: The RB25DET is an inline six built of practically a bullet proof block. It can handle more boost than the SR in stock trim. It is also capable of a lot more HP than the SR and has a lot more torque to start out with. The average black top SR puts 181-185 HP to the Rear wheels, whereas the average RB25DET puts 240-248 HP to the rear wheels. Simple upgrades on the RB can get you over 400 RWHP and with the right tires can put you into the 10's for the 1/4 mile if you boost and tune correctly.

    Q: Is the RB25DET a reliable engine?

    A: Yes, if it was not reliable, do you think Nissan would have put it into their signature car...the Skyline? It is the engine series out of their best cars and is daily driven in Japan.

    Q: Would the RB25DET make a good daily driver?

    A: Mine makes an excellent daily driver running low 13's to mid 12's on street tires. It handles well and has great acceleration. Think about this: are Corvettes good daily driving cars? They have over 300HP and are fairly lightweight for their size and design.

    Q: What kind of gas mileage can the RB25DET get?

    A: My car got 28-30 mpg highway and 25-26 in town before I fried my turbo. I am not sure if this is average for these engines or if mine just runs exceptionally well.

  5. #5
    On Vacation GranMastrDrift's Avatar
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