Tech@EPR Posted December 17, 2009 Share Posted December 17, 2009 Hello folks. Im normally in the VG realm of engines the majority of the time but fell into a deal for an RB20DET for $100 and figured I'd go through a full tear down/rebuild on this particular engine. I did several searches on here and did find some good info but nothing concrete enough to tell me what is and isn't First off. What are the pros/cons between the RB20 and RB25? Besides the fact of displacement obviously. Secondly..why are so many ppl in favor of the RB25s vs the 20s? It would seem that regardless of overall displacement the RB series engines while in variance still make expendable power and are easily modified once built. I am fully aware of displacement values and how it affects power and so forth but overall have there been 500-800rwhp RB20s? Do those of you who have swapped the RB20 build these up to any stature to make good power? I have no problems soaking in information but I just need to have someone steer me in the direction of the info or can show me some ins and outs of the series. I've built a few RB26s but they were pretty straight forward for what the customer had and wanted done. For this engine i"m looking to put down 600-800rwhp out of this RB20 (if applicable) thanks for your time. Quote Link to comment Share on other sites More sharing options...
Midnight-280Z Posted December 18, 2009 Share Posted December 18, 2009 RB25 Pros Newer Easier to attain more power in it's stock internal form N-VCT (Nissan Variable Cam Timing) Beefier Tranny Better head design than the 20 Stroker kits available More torque RB25 Cons More expensive Lame Turbo (Better than the 20 though) 7,000ish Redline Weak piston ring lands Harder to tune than the RB20 Side Feed Injectors RB20DET Pros 8,000 Redline Cheaper Easier to tune than the RB25 RB20DET Cons Head doesn't flow as well as we would like Lame turbo No N-VCT Harder to get more power in stock internal form Weaker tranny than the RB25 Older Makes almost the same HP as a SR20DET out of the box 270CC injectors (stock) Sure there's more to both engines besides the obvious, but this is a start. Quote Link to comment Share on other sites More sharing options...
mr jdm Posted December 18, 2009 Share Posted December 18, 2009 If your going to spend the kind of money to make 500-800 whp. Why are you thinking about going with the weakest option as far as a motor goes. 700whp. Your looking at a gt42r = 2g turbo, and a exhaust manifold that will cost 2g. 4 grand for only two components, if you that kind of money. Definetly go with a rb26, or no less than a rb25. Quote Link to comment Share on other sites More sharing options...
Tech@EPR Posted December 18, 2009 Author Share Posted December 18, 2009 are the heads interchangable between the 25 and the 20? Honestly...the money going into this engine isn't going to be too much. But overall it seems that most don't like to use the 20 because its baseline is quite weak. Thats ok honestly because im doing a full build and then selling the engine off. The engine itself will be built with a lot of key points being addressed. The one other thing I had a question on was the oil pump. Do these have issue like the other RB engines? Thanks so much for the information. Clear cut and dry. Quote Link to comment Share on other sites More sharing options...
chrism Posted December 18, 2009 Share Posted December 18, 2009 I put an RB20DET in my 75Z. Other than a couple of bolt on things like a chipped ECU, 440cc injectors, sard regulator, little bit bigger turbo, I have no plans to dump any more money into it. It's just a DD and I get 32mpg at this point. If you go to 300RWHP or more, you are going to have to change out the stock clutch also. Stock is going to burn up. That alone could cost way too much. Quote Link to comment Share on other sites More sharing options...
sileightygx Posted December 18, 2009 Share Posted December 18, 2009 even after all the weaknesses you got it for $100? with a few bolt ons it is not a bad engine, and you can make power with it. even if puts down the same power as an sr20det it does have a better valvetrain design compared to the sr20det. since you are going to sell it off after building, i am sure someone will buy it. Quote Link to comment Share on other sites More sharing options...
Ben Posted December 19, 2009 Share Posted December 19, 2009 600-800rwhp you say? I'm assuming these are 'dynojet' numbers, but even so, that's still upwards of 350rwkw. What driveline are you planning on using for those kinds of numbers? A stock gearbox (even a 25DET one) will not tolerate any abuse at those numbers, you'll be using a triple-plate clutch, custom 3" tailshaft, 300ZXT axles etc. etc. You say that the money going into the engine isn't going to be 'too much', but a 300+rwkw RB20DET is pretty bloody serious, and will need to spin to some ridiculous rpm number to generate that kind of HP level. If you want that kind of power, reliably, then you're talking about a built RB26DETT, not a full-house one, but not a stock one either (poncams, headwork, forged, bigger oil pump, injectors, HKS-GTRS or a decent single), plus all the supporting mods (PowerFC or other full EMS, pumps, the list goes on...) I don't think you'd get change from $7kUSD On the other hand.... Almost every other R33 in these parts is turning around 200rwkw, my auto RB25DET Stagea puts down 150awkw, and that's with some pretty minor mods (exhaust, mappable AFM and boost, shift kit, and RB25DET NEO SMIC). 200rwkw is easily doable in a '33 - but not with the stock turbo (they just spin too hard and will eventually fail at those numbers). You won't really see much over the 190rwkw mark on an 'unopened' RB20DET. Some food for thought - drop into the Skylines Australia forums and have a look around at what people are up to, the RB's can make excellent, reliable power, but it's not free! Quote Link to comment Share on other sites More sharing options...
streeteg Posted December 21, 2009 Share Posted December 21, 2009 for 100 bucks you got yourself a winner no matter how you look at it. The 20 is a potent motor for some decent power. If you were really looking to make big power you would know that this motor wont do it without serious cash and you would just grab a 26. The fact that your asking this question implies (at least to me) that you want to know the potential. For 100 bucks I would rip this motor down all on my own and try to build it up---pistons/rods, headgasket, cams, 6boost manifold and a 30r. Keep the power at around 400whp all day so that your trans is hanging on (barely) and you have yourself a fun time. With as light as a Z is it should be plenty. Quote Link to comment Share on other sites More sharing options...
wax Posted December 21, 2009 Share Posted December 21, 2009 The head is not interchangeable between them as they have a different bore size the rb20det you cant even sell in Australia as they don't have alot of potential However rb30s are cheap here so i guess we live in the promised land I saw some guy putting a sohc rb20 in a car over here , not sure why you would want to hamstring your car that badly The sr20 makes more power and is lighter Quote Link to comment Share on other sites More sharing options...
PA240 Posted December 22, 2009 Share Posted December 22, 2009 The sr20 makes more power and is lighter I don't think this statement is totally true. The sr20 is lighter but can it really make more power? Quote Link to comment Share on other sites More sharing options...
Tech@EPR Posted December 22, 2009 Author Share Posted December 22, 2009 I don't think you guys get what I'm saying. I'm a machinist/engine builder for a living. I build Nissans specifically. I bought this RB as a project to build and get to know the RB lineup a bit more. I understand that the parts will be up there to some extent however I can machine a bunch of stuff myself and I can have parts made for me such as pistons/rods quite affordable. My goal is to research this engine to find all of its weak points and do my best to fix/resolve them while increasing efficiency. Overall...an iron block/aluminum head with a closed deck design will handle more power than an all aluminum block/head combo with an open deck. The materials are better and the platform is better for making power with an RB over an SR purely by design and composition. Even if this engine only makes 600whp it will be fine. I plan to build it to handle much more but Im not building this for myself or any car I own. Im just building this to build it and then sell it. Its a project. I own Z32s and race them primarily. RBs are fun to mess with and are interesting to me to build and get involved in. I'm quite confident that this RB20 will be able to handle any type of power a typical owner would dream of putting to it. Quote Link to comment Share on other sites More sharing options...
wax Posted December 22, 2009 Share Posted December 22, 2009 I don't think this statement is totally true. The sr20 is lighter but can it really make more power? Yes its true Quote Link to comment Share on other sites More sharing options...
chrism Posted December 22, 2009 Share Posted December 22, 2009 I plan to build it to handle much more but Im not building this for myself or any car I own. Im just building this to build it and then sell it. What do you think it's going to be worth when your done. Please post all the changes so we can see what you did. Lots of high def pics. Quote Link to comment Share on other sites More sharing options...
Ben Posted December 22, 2009 Share Posted December 22, 2009 I don't think you guys get what I'm saying. I'm a machinist/engine builder for a living. I build Nissans specifically.... The materials are better and the platform is better for making power with an RB over an SR purely by design and composition. ... I get it now , but I agree with what Wax said; if you want to stretch a 2.0L Nissan to breaking point, the SR will go further (as much as I think that they have some pretty ordinary design features, such as a single-row chain). But if it's just an exercise in learning and development, then go for it. Just make sure you get an ECCS motor, not a NICS one. (NICS was R31/Z31, ECCS was R32 onwards) Quote Link to comment Share on other sites More sharing options...
PA240 Posted December 22, 2009 Share Posted December 22, 2009 Yes its true haha. I love when people just make statements and pass them off as fact without any proof. Wheres your proof ? Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted December 22, 2009 Administrators Share Posted December 22, 2009 haha. I love when people just make statements and pass them off as fact without any proof. Wheres your proof ? No proof this time guy's. This is getting WAY off topic. Argue about it in another thread. Quote Link to comment Share on other sites More sharing options...
PA240 Posted December 22, 2009 Share Posted December 22, 2009 Ok. that's legit . So what are the differences between the rb20 and other rb's? In the r33 fsm the rb20 is normally explained along with the rb25. This leads me to believe they are very similar. Quote Link to comment Share on other sites More sharing options...
wax Posted December 22, 2009 Share Posted December 22, 2009 The rb20det head has alot smaller ports , in fact it flow about the same as the sohc rb30 head It also has a much smaller bore than the other rb series engine that share the same bore You could i guess weld up a rb25 head and recut it to fit the bore of the rb20 not sure how you would go with valves Quote Link to comment Share on other sites More sharing options...
PA240 Posted December 23, 2009 Share Posted December 23, 2009 why not fit the block to the head? How similar are the blocks other than bore? Quote Link to comment Share on other sites More sharing options...
Tech@EPR Posted December 23, 2009 Author Share Posted December 23, 2009 The rb20det head has alot smaller ports , in fact it flow about the same as the sohc rb30 head Do you have information backing that statement up? Quote Link to comment Share on other sites More sharing options...
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