violacleff Posted May 26, 2005 Share Posted May 26, 2005 So I ran across this link on the web http://forums.freshalloy.com/ubbthreads/showflat.php?Board=UBB9&Number=67789925 and I got to wondering, if one is shooting for 450-500 rwhp, would the uprades necessary to reach this on an rb25 exceed what it takes to get there on an rb26 after purchasing a front clip? Here's what I can come up with so far (lets assume for both these motors, motor mounts, Injectors, Stand alone ems, fuel pumps, and fmic) RB26: Extra initial cost, Bigger turbos, extra 5 speed, z-31 oil pan, more expensive exhaust and intercooler plumbing. RB 25: Bigger turbo, custom intake, aftermarket header, Bigger Turbo, ext wg. Did I miss anything here (major) Assuming the info on the site is reliable, both cars retain stock head and block. But if you want, we can do arp head studs on the rb25 just to play it safe. For those who are more knowledgeable on the price this stuff, I'm wondering which would end up cheaper, would there be a large price gap between the two? I don't really care about future upgrage potential. Just the cost to get to where I mentioned above. Quote Link to comment Share on other sites More sharing options...
Guest JAMIE T Posted May 26, 2005 Share Posted May 26, 2005 You'll need an oil pan for the '25 also. That's a hard one. I do like saying I've got a GT-R motor. Kinda ricey sounding but it's about as far from ricer as it could possibley be. Quote Link to comment Share on other sites More sharing options...
240Z_Master Posted May 26, 2005 Share Posted May 26, 2005 You'll need an oil pan for the '25 also. That's a hard one. I do like saying I've got a GT-R motor. Kinda ricey sounding but it's about as far from ricer as it could possibley be. Nothing sounds cooler than saying Twin Turbo either (if you decide to keep both turbos). Other than that, the RB20DET Oil Pan and Pickup are fairly cheap... Intially the RB25DET is cheaper because you dont have to dish out the amount for the Tranny. The standalone is not needed if you wanna use the stock wiring. Everything about both of those motors are obvious. If you havent figured things out alredy you should take a look around the forums for more in-depth considerations. Quote Link to comment Share on other sites More sharing options...
violacleff Posted May 26, 2005 Author Share Posted May 26, 2005 I suppose you both may have missed what I was really going for in this post, but to clarify, I really don't care about "whats cooler to say I have" or "what looks cooler under the hood." I would have posted on a honda forum to find that out. Also quoc, I already mentioned the tranny in my post. As far as the oil pan goes, I took that info from stony's sticky who said quote "if you go rb25 you do not need to change the oil pan." This might be old misinformation that I have not yet caught up on. This post was merely for a hp to dollar analysis up to 450-500 rwhp. BTW, I have read all rb posts on this site. Quote Link to comment Share on other sites More sharing options...
fl327 Posted May 26, 2005 Share Posted May 26, 2005 it will always cost to be the boss. Quote Link to comment Share on other sites More sharing options...
Cal Poly Zmanaustin Posted May 26, 2005 Share Posted May 26, 2005 My buddy owns a shop in Northern California and his answer to your question is RB25. He is doing the RB25 swap for his personal car after weighing those same decisions. I have not personally done either swap, but have read a ton about it and talked to some of my gearhead buddies about it. The general consensious is the RB25 is a cheaper swap. If you want to go beyond 500hp then it can be argued a bit more. Also, someone with good fabrication skills and high comfort with the wiring it becomes less of a cost issue and more of a time issue, because the RB26 is clearly more difficult. If you are not doing all your own fabrication and install work then the cost will obviously go up significantly. With that said IMHO based on my knowledge of this swap the RB25 is still the cheaper route. Good Luck, Quote Link to comment Share on other sites More sharing options...
violacleff Posted May 26, 2005 Author Share Posted May 26, 2005 As far as wiring goes, it ought to be similar with both if you're using a stand alone right? I'm assuming noone is using stock ecu with this goal as I mentioned in the o.g. post Quote Link to comment Share on other sites More sharing options...
Guest JAMIE T Posted May 26, 2005 Share Posted May 26, 2005 No, I didn't mis-understand your post. I was stating my opinion of ME and my car and engine. I am pretty sure you still need the Z31 200ZR oil pan with the RB25. The Skyline still uses a front sump afterall. For the '26 to make 500rwhp you'll need to get the stock turbos upgraded to steel or inconel wheels. That, injectors, and a boost controller will put you at 500rwhp. You can even use the stock ecu with a programmer like F-Con. Stony's '26 made 400rwhp with the stock turbos. He was limited to 14-15psi with the stock turbo's. If he could have run 23-25 psi(steel or inconel turbo wheels) it would have made 500 rwhp. The only thing I know about '25's it that they ARE cheaper to begin with. The water pump, cam gears, timing belt and a couple other items are interchangable with the '26. The bonus of the '25 is that the front cut will come with the correct tranny. No need to drop another $500-1000 on a proper trans. When I bought Stony's motor, I got the proper trans with it. So, I lucked out. Or PAID for it depending on how you look at it. The post you linked to indicated a heavily modified RB25. The turbo was said to be good for well over 600 hp. The manifold was art in metal. A manifold of that quality will cost a grand. I think the answer is mute. My suggestion would be to start with the best one you can afford. If you can afford $3700 for a stock RB26 with no trans then buy one. If you can afford $2500 for a RB25DET with trans, then buy one. Either one will make 500 rwhp. The '26 will live forever on stock internals at that level, I don't know about the '25 Quote Link to comment Share on other sites More sharing options...
fl327 Posted May 26, 2005 Share Posted May 26, 2005 In the end a $1200.00 difference is just that. RB26 is a detuned race motor, nuff said. Quote Link to comment Share on other sites More sharing options...
stony Posted May 26, 2005 Share Posted May 26, 2005 HMMMM i dont ever recall saying you dont have to swap the oil pan on a rb25. What i do remember is that the rb25 requires no oil pan modifications where the same pan for the rb26 requires extensive mods to fit on the motor. the rb20 from a z31 in japan will bolt right in without changing the oil pan. So in short if you bolt in a rb20 from a z31 you dont need to change the oil pan. but either the rb25 or 26 will both require a different oil pan. Sorry if i mistated that somewhere. If you could post the link from where you got that i will go back and correct it. Quote Link to comment Share on other sites More sharing options...
violacleff Posted May 26, 2005 Author Share Posted May 26, 2005 Youre right stony, I was wrong. I misread the info. It was a specific modification that had to be done with the rb26 whereas everthing from the z31 to the rb25 was bolt in. My mistake Quote Link to comment Share on other sites More sharing options...
cheftrd Posted May 26, 2005 Share Posted May 26, 2005 It really depends on what you intend to do with the car, as well. If you truely intend to stay around 450 (smokin' in an S30), and it's just a cruiser with a little track duty, there's nothing wrong with the RB25. You'll need cams to make it breath beter, though. You can also get away with a T3/T4 hybrid that will bolt to the stock exhaust manifold, too (you may need an additional flange and longer bolts as a spacer, though). Above this level, though, and you really have to squeeze this motor for minimal gains. The last Rb25 I tuned was running TEC3, 272 cams, GReddy intake w/Q45 throttle, and T66 Garrett turbo on a Trust manifold. It made 501hp at 1.5 bar. This is the absolute limit for the stock bottom end. Any ping at this level, and the piston ring lands are going south for the winter (25 and 26). By comparrison, another of my customers has a 26 with close to the same mods, 272's, SDS EFI, and pistons (stock bore and compression) and rods for abuse insurance. Stock throttles and modified Nismo GT LeMans turbos on Veilside manifolds. 1.5 bar put this engine at over 700hp. That's the 25/26 difference. If you do intend to go higher, 200hp for $2000 is CHEAP. Quote Link to comment Share on other sites More sharing options...
slownrusty Posted May 26, 2005 Share Posted May 26, 2005 Great post Chef! 501@1.5bar....cripes....I would love that... Yasin Quote Link to comment Share on other sites More sharing options...
Wedge Posted March 22, 2008 Share Posted March 22, 2008 Sorry for bringing that old thread up but i wanted to thank you guys for the info because i wasnt sure what engine to start with . And it may be a good info for new guys wondering the same thing . Quote Link to comment Share on other sites More sharing options...
fast-datsun Posted March 22, 2008 Share Posted March 22, 2008 UNDER 500HP the RB25 is the best $$$ swap with the SR20 in SECOND place. We have ALL the parts for YOU DIY swap give us a call if yoooou have questions of e-mail info@mckinneymotorsports.com Quote Link to comment Share on other sites More sharing options...
triple B Posted March 24, 2008 Share Posted March 24, 2008 it takes more to get the RB25 over 500 the RB26 gets there quickers out of the box. Quote Link to comment Share on other sites More sharing options...
240Z_Master Posted March 25, 2008 Share Posted March 25, 2008 it takes more to get the RB25 over 500 the RB26 gets there quickers out of the box. Something about a twin turbo I hear? Quote Link to comment Share on other sites More sharing options...
eh? Posted March 25, 2008 Share Posted March 25, 2008 it takes more to get the RB25 over 500 the RB26 gets there quickers out of the box. Please explain how. Quote Link to comment Share on other sites More sharing options...
240Z_Master Posted March 25, 2008 Share Posted March 25, 2008 Please explain how. The RB26 has stronger internals. Quote Link to comment Share on other sites More sharing options...
Careless Posted March 25, 2008 Share Posted March 25, 2008 Please explain how. simple. most importantly, the head designs are different enough to make it easier or more reliable to pack more air into the cylinders on RB26 than on the RB25. anyone and everyone knows that developing horsepower means developing an efficient engine head. add the stronger internals, a big single turbo, put some ARP rod bolts and head studs + metal headgasket, and you have what Boozt3d had. 680whp on a stock shortblock (no rod bolt upgrades) Quote Link to comment Share on other sites More sharing options...
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