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Discussion Starter #1
Hello,

Im looking to do an RB conversion for my S13. Im thinking RB20DET because there cheap and RB25DET. The RB26 is out of my price range. I have searched but cant find much info about the RB20 other then people swapping them for RB25's, the gearboxes are weaker and i need a MHG to up the boost.
Any advice on the following questions would be much appreciated. It will be for road use only.

1) What advantages and disadvantages does each engine have.

2) What power can the standard internals of each engine take.

3) Which would be the cheapest option be for around 300bhp.

4) which would you recommend

5) Anything else that ive missed

Regards.
 

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bla
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Id go for the rb25det if i was you.. There not that much nowadays... Theres a few threads of builds up in the project section...
 

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As shane said ^^^

The RB25 can handle about 500bhp on std internals and is very easy to tune to 300bhp.
 

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Discussion Starter #5
Thanks lads for your advice. Does the RB25DET suffer from any weakness or disadvantages like bottom end trouble. Is there anything i should do to the engine befroe fitting to the car, im only aiming for around 300bhp atm. It does seem like it has a pretty solid engine and box and even for the sound alone would be worth it.

Regards.
 

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If your only going for 300hp i'd stick to the CA18. Way way cheaper as you already have one to start from and easy to get a reliable 300hp out of.

I've gone down the RB25 route as i want a reliable 450hp and although the CA can do this its going to be very peaky and the gearboxes break consistantly at anything over 400.
 

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Discussion Starter #7
If your only going for 300hp i'd stick to the CA18. Way way cheaper as you already have one to start from and easy to get a reliable 300hp out of.

I've gone down the RB25 route as i want a reliable 450hp and although the CA can do this its going to be very peaky and the gearboxes break consistantly at anything over 400.
My CA needs to be rebuilt "surprise surprise" and if doing that it would be built with forged pistons, pauter rods and aiming 350bhp but have the option for more, i already have Z32 AFM and 444's but as you said the gearbox's are not realiable at that power.

Thats going to cost £2500 parts and labour for a full rebuild so i think its a better option for an RB25 conversion because its going to be more realiable, better gearbox, internals can handle more power, its a great platform with loads of potential and at the end of the day, a RB25 S13 is going to be worth loads more then a fully rebuilt forged CA.
 

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Good thinking Kouki, i really dont think you'd regret putting a RB25 in.
 

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Its true what you say but it will cost alot more than you think! It sure has for me! lol But then that depends on how you spec an RB. to get 300hp you wont have to do alot!:)
 

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Discussion Starter #10
Is the RB25 prone to any top or bottem end engine failure or would it be rare to have to rebuild them. Has many people had to rebuild them at any stage.
 

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There a very strong engine, there not prone to any real problems.

I've been running 400+bhp for over 3 years now with no probs.
 

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bla
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Seriously not alot.... LOL For 300/350bhp, you wont see a problem if its a healthy engine :)
 

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Discussion Starter #14
I Believe the bearings are common problems on a tuned RB every 30 or 40k due to oil supply. :confused:
 

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bla
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Never heard of that...... I have heard it has a weak bottomend just like the s13 but never heard of any one having problems with them..
 

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I Believe the bearings are common problems on a tuned RB every 30 or 40k due to oil supply. :confused:
On 500+bhp engines yeah the bearings on the std engine can be an issue and on 350+bhp a bad mapped engine will let go on rings and pistons quite easy but lets face it what engine wouldn't.

But in all honesty in all my years of tunning and all the different cars i've had i've NEVER know an engine like the RB25 that can take so much abuse and punishment at my level of tune and still be so forgiving and reliable.
 
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