Can You Put A Rb26 Gearbox On An Rb20

[Bullet32]

Im not sure I am following this thread right...

Viper_R32 - Youre saying that because you had a turbo failure, you want to put another RB20DET into your R32?

Why would you do this?

If you buy another used RB20 you will have no guarantee that it hasnt had the crap flogged out of it, you may have the same problems that youre having now, or worse!

If you are planning a re-build on the RB20 that you have why waste the money of buying another RB20? Taking the car off the road for around 6 weeks might sound like a pain in the ass but it could save you over a thousand dollars in the end...

Also, if you have a buggered RB20 gearbox why not have it re-built with a stronger gear set while the engine and box is out...?

If you buy a used RB25 box youre looking at about $1,500 at least and there is no guarantee that it will be in good condition. If you spend $2,000 on a new stronger gear set for the box you have then you will know that it is brand new and very strong.

If youre looking for a "budget" build up then why not look for a decent R33 Gtst front cut with low km's and transplant a good condition RB25DET with gearbox, wiring and computer into the car for around $5,000? - Thats what I did and I have never looked back.

If I have read this all wrong please let me know, Im just confused as to why you would waste so much money on unessecary things....

[CeJay]

You can run the rb25 on the rb20 ecu as well. Mine is.

[Viper_r32]

well, i looked at rebuilding the rb20 and it worked out to be at leased 7 grand, which was just way to much. and i couldn't justify a rebuild unless i was going to strengthen the engine, which would cost at leased 10 grand, once i had put all the rb26 gear i wanted into it (conrods,crankshaft etc.).

then i thought about an rb25, and a engine and gear box package is like 3 grand and once i put it in the car and cut and balance the tail shaft that takes it to around 5 grand, and then there is still no guaranty the engine will be in good condition and how long it will last. plus I'm not sure how easy it is to connect all the current exhaust and inter cooler piping.

my curent engine was pumping out 300kw at the engine and just over 200kw at the wheels, which i was happy with. plus Nick tuned my ecu and the setup was perfect. if i drop a stock rb25 straight in it will not produce the power i want straight off the bat. and i don't want to spend money doing up an rb25 and having to have the ECU returned. plus Nicks in Queensland now and i don't know of anyone else i could get or trust to tune it.

another option is bolting my inlet manifold and exhaust manifold which includes my current hi flowed rb20 turbo. I'm not sure how my current turbo would respond running on an rb25 block, i don't even know if my current inlet and exhaust manifolds would bolt on to the rb25 head. this would mean including my current ECU and electricals (in other words swap the rb20 head and block with an rb25 head and block). this would be like fitting a different crack and boring the engine out, and my current ECU tuning in theory would probably only require a light tune? so this is still an option

CeJay how did you set up your 25? if you are using the RB20 ECU are you using any other rb20 components or parts (manifolds, etc.)

another thing that concerns me is all my inlet piping, the piping for my pod filter, the blow of valve, the intercooler is all custom piping. and if i cant use this or have to pay to get it modified, it just don't know whether it would be worth the cost or the hassle.

replacing it with another rb20 seamed the simplest road to take. the reason my current engine died is because it has done nearly 200,000ks and it use to be used on the track and the old saying is that about 4 hours of hard thrashing on the track is almost like 10 to 20,000ks of daily driving. a replacement rb20 with only 70,000ks that has been flow tested with a compression and oil pressure tested is only $800 with 3 month warranty. i can have the sump pulled of and the bottom end inspected, have an n1 oil pump put in, a new watter pump, and a strengthened oil pump collar and have it all installed for just over 3 grand. and i know that i will have all the power i had without having to do anything to it. plus i get to keep my old engine and slowly build it up later on if i want to.

and with all the other things that need fixed like new seats, new shocks, and a decent stereo (since my last one got stolen) i just cant justify spending more money.

so this is my logic,

but i do appreciate your advice and I'm keen to hear more about what you think.

I guess it depends on what ill will take in total to put an rb25 engine in, piping, ecu tuning, new turbo, and i have read that the wiring loom can be a pain in the ass. and despite how much i have enjoyed working on cars, to be honest with you I'm just not into doing the work myself as much as i used to. after rebuilding two engines myself on previous cars and all the time spent over the last 10 years with all the headaches i just don't have the patience to do the work my self any more and would rather pay someone else to do it, only prob is i having the cash to pay someone else to do it!

but hey let me know i still haven't made any definite decisions and i still have 3 more weeks before i have the cash to go ahead with it all, so let me know I'm up for any ideas, but as you can see I have been putting allot of thought into it

i tell you one thing though if i had 13 grand i would be buying a nice new n1 rb26 long stroke i saw!

Edited December 28, 2007 by Viper_r32

[Viper_r32]

We'll i did some more research today and phoned up a few places, to get an idea on prices.

an late model r33 half cut with manual box and 3 months warranty is $4,500 and to drop the engine in is $1500 plus all the rewiring which is between $500-$1000 depending on how long it takes.

so its a total of $6500 - $7000. and then i would still want to replace the oil and watter pump.

or have another rb20 installed with new oil and water pump for just over $3000. which leaves me cash to put in new seats and coil overs and stereo gear.

i just don't think i can justify spending nearly 7 grand in an engine swap. i know it would be a crap load cheaper if i did the work myself, but with my Muscle disability i shouldest even be thinking about it!

[CeJay]

CeJay how did you set up your 25? if you are using the RB20 ECU are you using any other rb20 components or parts (manifolds, etc.)

another thing that concerns me is all my inlet piping, the piping for my pod filter, the blow of valve, the intercooler is all custom piping. and if i cant use this or have to pay to get it modified, it just don't know whether it would be worth the cost or the hassle.

I guess it depends on what ill will take in total to put an rb25 engine in, piping, ecu tuning, new turbo, and i have read that the wiring loom can be a pain in the ass. and despite how much i have enjoyed working on cars, to be honest with you I'm just not into doing the work myself as much as i used to. after rebuilding two engines myself on previous cars and all the time spent over the last 10 years with all the headaches i just don't have the patience to do the work my self any more and would rather pay someone else to do it, only prob is i having the cash to pay someone else to do it!

but hey let me know i still haven't made any definite decisions and i still have 3 more weeks before i have the cash to go ahead with it all, so let me know I'm up for any ideas, but as you can see I have been putting allot of thought into it

i tell you one thing though if i had 13 grand i would be buying a nice new n1 rb26 long stroke i saw!

I bought the car as is, but it appears to be running all the rb25 running gear, ie IM etc etc. Nick could probably explain it better to you, but I'm pretty sure its running a normal rb20 loom. I'm a novice to all this stuff myself, but I'm more than happy to drop the car over one day for you to have a look at the setup. The install was done by Power Garage Testarossa in Japan. It appears the main thing they've done during the changeover is rechip the ecu to run the 25.

Also Nick would have a rb25 map to base your rb25 tune off as well if you took that route, as I had mine retuned by him as well. Myself I'd go the rb25 route.

If you end up getting a rb25det half cut and it's awd and you don't want the box, I'd be interested in that meself. You might be able to get a 25 halfcut cheaper than 4500, and you could sell at least some of the bits back off it that you don't need.

[Bullet32]

Ok then, some more friendly advice for you Viper_R32

The RB25DET and RB20DET are almost physically the same, if youre using a low mount turbo with the standard T3 flange your dump pipe will bolt straight on.

If you wanted to use the exhaust manifold and turbo from your RB20 they will also go straight onto an RB25 as both manifolds have the same flanges. You wont need to change the head.

As for your front mount kit, the only thing you have to change is - you will need to have a small outlet welded onto the inlet pipe for the wastegate actuator, this is the only difference between the RB20 and RB25 cooler kits (apart from the general shape) I use an R32 Gtst intercooler kit on mine and I have an R33 RB25 in it.

The water pump for both engines is a the same and Im pretty sure the oil pump is aswell, so if you already have an aftermarket one you can still use it on an RB25.

A tailshaft will only cost $500.00, I had mine made custom with all new uni's and a brand new front yoke, the balance is near perfect and it is a lot stronger than a standard 2 piece.

If you buy an R33 front cut you can request to have it come with a test sheet just like the one that you would get with the RB20 that youre planning on buying.

The good thing about a front cut is that it comes complete with computer, wiring and gearbox so you dont have to worry about sourcing these things later.

Trojan, ESP or even Intune Auto Electrics will all be able to install the wiring and computer without to much hassle, the looms arent that different.

"my curent engine was pumping out 300kw at the engine and just over 200kw at the wheels," - How did you work that out? If you were making that kind of power at the engine you would have been making an easy 250 - 260rwkw if not more, your drive train shouldnt soak up anywhere near 100kw, even with an older gearbox, tailshaft and diff you should only notice a drop of 30 - 40kw from the engine at the most.

My car is putting down 230rwkw and 550nm on a safe tune, which is more than enough to have a lot of fun with, if you have a highflow turbo, big exhaust, front mount, boost control - you should easily see over 200kw at the wheels from an RB25DET, you will however need programmable engine management or an air fuel controller if you have larger injectors or if you want to play with the AFR's

The only reason that I would lean more towards the R33 RB25DET is because the amount of power and torque available from doing simple mods is far greater than what you get from an RB20DET, I have had both engines in my car and I wouldnt go back to the RB20....

Just my opinion though, if youre partial to RB20's then go for your original plan.

[Viper_r32]

"my curent engine was pumping out 300kw at the engine and just over 200kw at the wheels," - How did you work that out? If you were making that kind of power at the engine you would have been making an easy 250 - 260rwkw if not more, your drive train shouldnt soak up anywhere near 100kw, even with an older gearbox, tailshaft and diff you should only notice a drop of 30 - 40kw from the engine at the most.

well its pumping out 210kw at the wheels at 15psi as for the engine figure that may not be accurate. i worked it out by finding the ratio between the original power at the engine and the original power at the wheels and then used that ratio to work out how much i was making at the engine from my rear wheel figure. i thought it would have been close as I've heard you can lose up to a 3rd of your power down the drive line, but the may not be the case. it was just a guestament so i'ts prob wrong.

as for changing to an RB25, i can see why it is worth it for the extra torque, but to me the killer is the cost. i was already making 210rwkw on the rb20 and although the extra 20rwkw would be nice i just cant justify spending another 3 grand on top of what it would cost just to drop another rb20 in. if i had the cash i would do it, but there are so many other things that need to be fixed. i worked out a list of every thing i need, and using the rb20 engine the total came to $7,500. i just cant justify spending $10,000 or more when i could buy another r32 for that. but when you think about it you could prob buy another r32 for $7,500

Edited December 31, 2007 by Viper_r32

[Scooby]

For good measure, the GTR also has it on reverse.

reverse synchros!!?? so THAT'S why when i put my 32 into 6th gear there's no crunching but it slows down a lot...

Gotta say I'm with Mick, his RB25 conversion is a cracker and looks OEM, ditto Bluprint's R31 with the Neo. Due respect to your desire to hot rod the RB20, but I really think you'll do better from a bang/buck perspective doing what they did. If your RB20 is going OK then sell it and put the money towards an RB25 half cut. It will go well even on the stock ecu with some boost tweaks.

An N1 oil pump is not a neccessity for the street, and unless you have a baffled sump and increased capacity will add to the potential for oil starvation. Also the N1 water pump is designed for low cavitation at high rpm, not for moving water at low speeds when you generally need it most in a street car.

My 2c

Cheers

Edited January 4, 2008 by Scooby

[Viper_r32]

Ok guys, I have been thinking about going for the rb25 but I need to know some things, I've tried to call Nick but he seems to be very busy.

If you are running the rb25 engine with the rb20 ECU, dose this mean that you are not running it with the NVCS (Nissan variable Cam System)?

If I’m going to swap to a 25 I can’t see the point unless I swap the turbo over from my rb20 because its steal ball bearing and handles a lot more boost than the stock turbo 25 turbo

Plus my rb20 engine was already making the same power the rb25 would if I did a straight swap. so I don't see the point of going to the RB25 unless I use my current turbo.

The only issue I have is the stock 25 ECU, I don't know if it will run correctly with the new turbo.

If I use the rb20 ECU, it could be reprogrammed to run the RB25 but would this mean that I could not use the NVCS?.

I know I could go a Power FC, but the conversion is going to cost enough as it is and i just couldn't afford it.

I all ready have an Apexi AVCR for boost so, I need to work out my options.

[CeJay]

Mines got a 33 25det head on it, has the vct port, but is not running it. But I also appear to have tomei cams in my car. You'd have to ask nick if you could run vct on the 32 ecu. check this thread as well

http://www.skylinesaustralia.com/forums/Rb...25-t155917.html

Don't see why the ecu wouldn't handle a different turbo, I initially had a normal rb25 neo turbo on mine, now have a slide rb25 hi flowed turbo, ran fine on both, just had to have a remap to run better on the current turbo (getting another remap done, due to some small issues). Your going to need another remap to run the rb25 anyway if you decide to take that route.

Like I said before happy to let you have a look at my engine bay.

[Bullet32]

Forget about running an RB25 on the RB20 computer, youre better off getting the 25 computer and loom in the half cut...

You might get the same outright power from an RB25 as your old RB20 but I will guarantee that you will get more torque, and its torque that pins you into your seat and spins wheels.

Your turbo will run just fine with the stock ECU, I had the stock 25 ECU in mine when I put my GT30/71 on it and the boost went from 9psi to 12psi at the manifold.

The standard 25 ECU has an "air/fuel tolerance" built into it that allows you to turn the boost up a bit (not a lot).

It will run a bit more rich than standard but thats better than lean.

FYI - RB25DET computers are "un-tuneable" you will need to have an RB25 computer chipped to change any settings... My advice is to just source a plug in replacement like a PFC or get an SAFC if you want to play with the AFR's - Did I use enough acronyms there?

P.S. > Thanks Scooby, I like my engine too

[CeJay]

Forget about running an RB25 on the RB20 computer, youre better off getting the 25 computer and loom in the half cut...

You might get the same outright power from an RB25 as your old RB20 but I will guarantee that you will get more torque, and its torque that pins you into your seat and spins wheels.

Your turbo will run just fine with the stock ECU, I had the stock 25 ECU in mine when I put my GT30/71 on it and the boost went from 9psi to 12psi at the manifold.

The standard 25 ECU has an "air/fuel tolerance" built into it that allows you to turn the boost up a bit (not a lot).

It will run a bit more rich than standard but thats better than lean.

FYI - RB25DET computers are "un-tuneable" you will need to have an RB25 computer chipped to change any settings... My advice is to just source a plug in replacement like a PFC or get an SAFC if you want to play with the AFR's - Did I use enough acronyms there?

P.S. > Thanks Scooby, I like my engine too

Why exactly would the rb25 ecu produce more torque for the engine? Seems a bit strange to me, from memory I think my 25 is putting out a fairly decent torque figure on the slide hiflow, but I'd have to look it up., and theres a fair amount of work involved I'd imagine to splice the 33 ecu into the 32 loom. People run rb30dets on rb20ecu's as well. I'd either keep the 32 ecu and get in remapped, or go the whole hog and get a PFC.

[Bullet32]

I didnt say that you get more torque from the computer I meant that you get more torque from an RB25 over an RB20...

Im saying that it is easier to use an R33 computer for an R33 motor.

The amount of work involved in splicing the looms is actually minimal as they're very similar, however if youre not an auto elec and you dont have a wiring diagram then it could be very hard for you.

If you get a front cut with the motor, gearbox, computer and loom like I did then the whole process is a lot easier.

[Viper_r32]

I didnt say that you get more torque from the computer I meant that you get more torque from an RB25 over an RB20...

Im saying that it is easier to use an R33 computer for an R33 motor.

The amount of work involved in splicing the looms is actually minimal as they're very similar, however if youre not an auto elec and you dont have a wiring diagram then it could be very hard for you.

If you get a front cut with the motor, gearbox, computer and loom like I did then the whole process is a lot easier.

yeah i know what you meant! i did understand that part (bigger displacement = more torque)

but after talking to Nick Danger about it he convinced me is isn't worth going to the 25, he said compared to the amount of torque I'm already making on my current setup, the extra torque would be hardly noticeable.

he said with my current setup if i was to do a straight swap to the rb25 with wiring lom ecu and all, it would most likely make less power than I'm already making, and i would most likely have to get a power FC to bolt my existing turbo or another after market turbo on. and adding up the cost at the end of the day its a hole lot of extra money that i don't have for a gain in power i don't kneed. so I'm going to go with swapping it out for another rb20 as it will only cost me about $800 plus $1000 for the install.

[Bullet32]

Your choice in the end, but I dont agree with "Nick" at all. Ive had both engines and both have been lightly modified and I know which I would prefer.

FYI - You only need a full computer replacement if you want to start playing with AFR's, Timing, RPM limits etc. or if you want to use larger injectors, you dont need a PFC to put an aftermarket turbo on.

But good luck with the build up anyway

[CeJay]

Yeah good luck with the build, I just thought since you already had you ecu remapped, the 25 wouldn't be a big leap, since you know nick as well. Keep us posted. an aftermarket turbo wouldn't be to hard to sort up with a decent remap on your ecu.