RB20 or RB25?

[MKIV]

Having a tough time trying to decide a set up for next year. I currently have the stock RB20DET and have a goal of 400whp for next year...

So, what now?

Do I build the RB20 and do a big single and enjoy a low displacement rev happy motor...
Or do I swap in the RB25 and enjoy the extra displacement?

Keep in mind this is my daily and I'll be very happy with 400whp.

[Phillyb]

I was basically in the exact same boat as you, my rb20 blew a headgasket and a bunch of other things were starting to break down so I was wanting to buy a rb25 for a replacement. Ended up just getting a new low km rb20 instead. But if you have the extra money to do a 25 swap I'd say go for it.

[AaaronF]

I think most guys Rollin with an rb20 are in the same boat. I would absolutely love to have an extra .5 liters of displacement, but I just can't bring myself to do it. With a set of Poncams and a turbo upgrade on your rb20, you'll get a bunch more ponies, but I don't think it will bring you anywhere near 400 whp. If you can afford it, and can find one, I would go with the rb25. That being said... Nothing wrong with rockin' a bitchin 2.0L

[Skym]

With GT3076R turbo, equal length exhaust manifold, fuel system upgrade (255lph-300lph fuelpump, 550cc injectors, Z32 MAF), ECU, clutch, etc, you can get close to or 400whp with RB25, RB20. Just at what boost level, where in the rpm it reaches full boost would be the difference between the RB25, RB20. RB25 has the benefit of VVT, capacity which can help to get turbo to full boost earlier in rpm.

For example with RB20DET in Canada -

http://www.youtube.com/watch?v=X_mibuiFSuk

With R32 chassis, can use R32 RB25DE head (same sensors as RB20DET head, so can use stock RB20DET loom, stock RB20DET ECU) with upgraded valve springs, RB30 bottomend, GT3076R turbo on stock R32 RB20? exhaust manifold, fuelsystem, ECU retune, clutch, RB25 gearbox or 300ZX gearbox with bellhousing adaptor plate, etc. Some fit RB20DET camcovers so it looks factory, but produces 400whp (ultimate sleeper) with a lowish boost level. But the height of engine gives it away that it's a RB30.

[GTRADDICT]

RB25. No brainer

[whiteboy87]

rb25 for sure. just make sure you have a bundle of dough to get it where you want it. im still completing my swap and its been almost a year since i began tearing the 20 out and collecting my 25 parts..... with that said I have built up a tonnn of bolt on goodies like holset hx35w, equal length top mount exhaust manifold, 680cc injectors, lightweight flywheel, act 6 puck clutch, forward facing intake mani, q45 throttle body, q45 maf, ebc, along with rebuilding the head with poncams, new springs, guides, seals..... its the age old saying choose two: fast, reliable or cheap. im going to be putting 400whp down for sure, my only weak point is going to be the bottom end...but with a good tune i shouldnt need to worry. plus if the bottom end pops im starting a rebuild on another bottom end i got for 200 bucks

[esh]

400 whp with an rb20 is pushing it...300 whp is the sweet spot. I don't think an rb20 tranny would appreciate that much power so at least an rb25 tranny would be a good idea. Probably best to get the whole rb25 setup instead.

[MKIV]

400 whp with an rb20 is pushing it...300 whp is the sweet spot. I don't think an rb20 tranny would appreciate that much power so at least an rb25 tranny would be a good idea. Probably best to get the whole rb25 setup instead.

This is what I was told by many and I think going by this, I'm going to do the 25. Overall seems like a better setup.

Thanks to everyone!

[r33_gtst]

Rb25 with bolt ons and turbo will get you past your goal
My rb25 is a stock block, runnin 492 rwhp
Scrap the 20 and go for the 25.

[Supraclean]

Make it easy on yourself go the rb25 route. Be careful has the rb25 are known to have (more senstive) piston rings/ engine failure once a fair amout of boost is thrown at them. If it was me Id build up the bottom end on the 25 and go from there.