DeusEx Posted August 6, 2004 Share Posted August 6, 2004 Hey Guys, At the risk of being tared and feathered i just wanted to see what sort of experiences you guys have had with the above engines in to a Z. Now i know that the 25 can be tuned way past the 20 (obviously) but in a standard guise, with perhaps an aftermarket intercooler etc, how will the two react to slight modifications. As i understand it a business in Brisbane has alot of experience with these conversions, the price difference is about 1k (5k for RB20 conversion and 6k for the 25). As im not going to be chasing a 10sec quarter, i want something that is daily driveable, whilst maintaining some urge. Is the price difference worth it if im not chasing big HP numbers? Are there any advantages one has over the other (aside age and Cubes) Thanks Guys Quote Link to comment Share on other sites More sharing options...
stony Posted August 6, 2004 Share Posted August 6, 2004 Now i know that the 25 can be tuned way past the 20 (obviously) but in a standard guise, with perhaps an aftermarket intercooler etc, Save some money and throw a decent size turbo on a rebuilt L motor and you will get more performance from a slightly modded L motor then a rb 20 or 25 with just an intercooler. Just my 2 cents. Quote Link to comment Share on other sites More sharing options...
DeusEx Posted August 6, 2004 Author Share Posted August 6, 2004 Well i was gonna do that, but after talking with some people i was told that the gain would be 20-40 HP max. I am getting 167 N/A (Triple Carbs) at the moment, so spending 2-3K on a turbo, hardly seems worth the money. But if it can be done decently with 1-1.5k, well thats a big difference But im open to opinions Quote Link to comment Share on other sites More sharing options...
cheftrd Posted August 6, 2004 Share Posted August 6, 2004 What Stony is trying to say is for the money it's going to cost you to swap in the RB 20 or 25, the same money spent on the L will kick the stock RB's butt. And......at the risk of offending those with RB20's (I've been building RB's since they came out), the 20 isn't worth spitting on. When the RB20 was all to be had, we were swapping L motors into the R31 skylines and pitching the RB20. The cost is small to bring the L28 to 3 liters and all the RB20 mods in the world won't make up a 1000cc deficit. With an efficient turbo system, at around 17 pounds of boost you will double your power, so you're looking at around 150hp gain, not 40. If you're going for the "wow" factor of having an RB in an old Z car. Stick with the 25. I don't know about elsewhere, but in Japan, people will laugh at you for swapping in an RB20. No joke. Matt Quote Link to comment Share on other sites More sharing options...
DeusEx Posted August 6, 2004 Author Share Posted August 6, 2004 Yeah i can see what your saying, and your info on the RB20, while suprising, is worth thinking on. Im not all for the new engine in old Zed thing (doesnt mean i dont like them, just means its not all i ever think about), my aim is to have a strong, reliable, economical (off boost) engine for daily driving. Will the 3ltr Turbo give me this? Also, as i am in australia we dont have easy access to L28 Turbo parts as the 280z(x) Turbo was not offered to us, so access to these parts are tricky at best. In australia a half cut Rb25 will set me back under 2k USD (around 3 here), so they are not that expensive for what they offer. Thanks Quote Link to comment Share on other sites More sharing options...
kalium99 Posted August 6, 2004 Share Posted August 6, 2004 . I don't know about elsewhere' date=' but in Japan, people will laugh at you for swapping in an RB20. No joke. Matt[/quote'] Yeah, but that's not because RB20's are bad. It's because its a classic car which is revered with an almost 'god-like' status, and the RB20 is a common sedan engine which. It's just sacralige for the japanese to put an engine which every second man and his dog own, into something as prestigous as the Zed. Quote Link to comment Share on other sites More sharing options...
akeizm Posted August 6, 2004 Share Posted August 6, 2004 3k, thats for an auto isnt it? Quote Link to comment Share on other sites More sharing options...
ZROSSA Posted August 6, 2004 Share Posted August 6, 2004 I would go to the junk yards and pick up a rb30 turbo from a c/dore. So you dont get the 4v head. You would still get 100 hp per lt. easy. and it should have gear box and every thing atached. A;so the locals should be able to service it. Douglas Quote Link to comment Share on other sites More sharing options...
zxgts-4 Posted August 7, 2004 Share Posted August 7, 2004 I'm with Douglas, Aus6K buys alot of other options probably with change left over. RB30 turbo is the obvious, rebuilt & bored 3.1lt as opposed S/h RB25. Even a GM 3.8lt V6 with 5 speed would come in around that sort of money and that would kick arse. You could even do Lexus 4lt V8 with 5sp Supra box in that price range. RB30 has definately been underated, given its cheap availability in Aus. Good luck with your project no matter what you choose. Neil Quote Link to comment Share on other sites More sharing options...
mjfawke Posted August 7, 2004 Share Posted August 7, 2004 As I have an RB20DET in my 240Z.... The big advantage of the RB20DET is cost. A bare RB20DET is ~ $1300Au, while an RB25DET is ~$3000 Au. I spent the money on fitting the RB20DET, and when it eventually smokes I could drop an RB25DET into the hole and only have to change the computer. I couldn't rebuild an L series for the money it costs to buy a complete low Km RB20DET. As for power - there are at least two cars (not Z's) in Aus getting over 200kw at the wheels on stock internal RB20DET's with reprogrammed factory computers. None of the tuners in Aus will run an RB25DET over 10psi because the computer will detonate the motor. Not an issue in my 1970Z, because I can ditch the factory management, but cars built after 1 Jan 1971 have to use the factory management that matches the engine (in NSW/ACT at least). About the only reason I would go for an RB25DET would be for the Neo motor (206kw from factory). Quote Link to comment Share on other sites More sharing options...
DeusEx Posted August 9, 2004 Author Share Posted August 9, 2004 So getting more power out of the RB20 is a simple as configuring the ECU? The only reason i wanted to go an RB25 is because its just a more powerful motor out of the box. And because i know someone who is getting an RB20 in there Z and i need to stay on top Quote Link to comment Share on other sites More sharing options...
AgentZ Posted August 10, 2004 Share Posted August 10, 2004 I am just dreaming, BUT RB30DETT! THis would be great, I will find a post on making one of these Quote Link to comment Share on other sites More sharing options...
Guest 240Zdragon72 Posted August 11, 2004 Share Posted August 11, 2004 I'm kinda in the same boat. Putting a 4 cylinder in a 6 cylinder car would be going backwards. I feel very strongly about building the L motor with the turbo. You would have to do minor tweeking, and maybe some fabbing to get it to work. Just one other thing....Is the RB25 the same swap as a RB26? Would you have to change anything, or maybe fabb something? I would really like some advice on this. I'm about to get a RB25 practically dropped into my lap for nothing. Thanks. Quote Link to comment Share on other sites More sharing options...
DeusEx Posted August 11, 2004 Author Share Posted August 11, 2004 4 cyl? Whos talking about 4 cyl? RBs are a 6....... Quote Link to comment Share on other sites More sharing options...
mjfawke Posted August 12, 2004 Share Posted August 12, 2004 So getting more power out of the RB20 is a simple as configuring the ECU? The only reason i wanted to go an RB25 is because its just a more powerful motor out of the box. And because i know someone who is getting an RB20 in there Z and i need to stay on top There are a few places that have experience with re-tuning these. Basically the ROM is replaced with a socket so you can swap the ROM's. There are a number of ROM editors for the RB series of engines that let you play with the mapping. Real-time editors on the dyno are the better way. AFAIK, the RB25 computers have one-time programmable processors... Quote Link to comment Share on other sites More sharing options...
akeizm Posted August 12, 2004 Share Posted August 12, 2004 So getting more power out of the RB20 is a simple as configuring the ECU? The only reason i wanted to go an RB25 is because its just a more powerful motor out of the box. And because i know someone who is getting an RB20 in there Z and i need to stay on top There are a few places that have experience with re-tuning these. Basically the ROM is replaced with a socket so you can swap the ROM's. There are a number of ROM editors for the RB series of engines that let you play with the mapping. Real-time editors on the dyno are the better way. AFAIK' date=' the RB25 computers have one-time programmable processors...[/quote'] So, you could reprogram a rb20 ecu to run on an rb25? Quote Link to comment Share on other sites More sharing options...
Guest 240Zdragon72 Posted August 15, 2004 Share Posted August 15, 2004 4 cylinder...6 cylinder....2.0 liter...2.5 liter... It is still going backwards!!!! So what is the outcome of your argument? RB20...RB25.....IS THE SWAP THE SAME AS FOR A RB26!!!! Quote Link to comment Share on other sites More sharing options...
akeizm Posted August 15, 2004 Share Posted August 15, 2004 I'll be goin the 25 over the 26 because of the price difference. Quote Link to comment Share on other sites More sharing options...
stony Posted August 15, 2004 Share Posted August 15, 2004 4 cylinder...6 cylinder....2.0 liter...2.5 liter... It is still going backwards!!!! So what is the outcome of your argument? RB20...RB25.....IS THE SWAP THE SAME AS FOR A RB26!!!! Go to the search button and type rb26 and then select 6 cylinder forum if you use all forums you will get way too many returns. I got over 220 in just the 6 cyl forum alone. some may not answer your question but i know for sure the answers are there Quote Link to comment Share on other sites More sharing options...
stony Posted August 15, 2004 Share Posted August 15, 2004 4 cylinder...6 cylinder....2.0 liter...2.5 liter... It is still going backwards!!!! So what is the outcome of your argument? RB20...RB25.....IS THE SWAP THE SAME AS FOR A RB26!!!! in general yes. you will still need to fabricate a a tranny mount. you can use the rb20 Z31 mounts to bolt the motor in or use the mount available from a few members here to set it as low as possible. you will have hood to intake manifold clearance issues with the rb20 or 25 if you use the z31 mounts. if you get a rb20 tranny get the driveshaft from the same car you get the tranny from, same goes for the rb25. you will also need the flange that presses into the diff of whatever car you get the tranny and driveshaft combo from. after the engine mounts, and tranny mounts are done and driveshaft installed there is no specific reciept. there is no kit for this swap so basically the intercooler, fuel system, and anything else involved with the swap is up to the swapper. Quote Link to comment Share on other sites More sharing options...
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