Jump to content
SAU Community

Recommended Posts

he guys , latley ive been debating on wether to rebuild my rb20 or go the rb25 conversion. its been hard trying to find an rb25 with all the other things like gearboxes and turbos, all that shit. anywaz ive been told to rebuild the 20 and get the head flowed ect. ive got around 8 grand to play with and im in perth. wats the go with rebuilding rb20's . i want the car for the street daily driver and for abit of fun on the track aswell. any info of any kind would be appriciated

simon :)

Link to comment
https://www.sau.com.au/forums/topic/131626-rebuilding-a-rb20/
Share on other sites

stock bottom end is good for about 400hp but to be safe I would be changing to forged pistons. ROSS make custom pistons for the RB20DET and they will set you back around $1500 including rings.

I would definately consider the porting you mentioned as every little bit helps with the 20's. You should also have the rods resized to ensure correct fitment and lose the chances of spinning a bearing easily. 8 g's is not really going to satisfy the budget once you get right into it. You should do cams, injectors, AFM upgrades while you are at it and make sure you have a clutch that will do the job. The RB20 gearbox will not last long at 200rwkw so you should also budget for an RB25DET box and fit it at the same time.

8k you have to play with?

RB25 conversion mate.

If you had a larger turbo etc etc already i'd say stick with the RB20.

But its pretty standard, so any cash you spend it going to better you regardless.

IMO Rebuilding the 20 and then doing a turbo will cost you more than an RB25 conversion, keeping the stock turbo and getting a PowerFC or similar.

RB20 box will be fine with a stock RB25 without a drama, even upto (give or take) 250rwkw in my expirience.

And that will be under 8k quite easily without having to do the gearbox. Which could even allow you to get a larger turbo for the RB25 + injectors/AFM 6-12 months down the track if you save a tad more :)

  • 2 weeks later...

If you run good gearbox fluid, a sensible clutch and dont drive like you belong in a padded room then an RB20 box is fine up to 240-250rwks. It will go bang sooner or later, but my old thing is still tracking well after 180,000kms so its not unheard of. Some die straight after a power hike, so if it doesnt go in the first month or so you may be able to cheat death.

The big question is what are you wanting to do with the car and what can you so yourself?

8k is a lot of money. If your RB20 is happy at the moment, then i would grab a 2530, remapped ECU and be on your way for around $2500. Spend the rest of your money on big nights out and driving the car at the track with a good 210-220rwkws.

If you really want to spend the 8k, then its a lot of money if you can do things yourself, not a lot if your paying a workshop. You would be looking at around 3.5k for a mechanic to do the swap for you. You will need a Pfc and you will make around 200rwkws with a turbo that may go bag at any time.

So say 3.5k for work, 3k for engine and gearbox and driveshaft...it leaves you with a bit of money to play witha high flow turbo etc that will net you around 240rwkws.

RB25 is a good building block, but its a lot of money for that bit of extra low end grunt. RB20, well i wouldnt personally even crack the motor. Just throw a big turbo on it and go have a ball driving it. Be careful even with cams. I have ummed and arred so often with cams, but am concerned about losing even more grunt under 3,500rpm for that little bit of extra top end. I want cams more for the low to mid, and ppl have raised concern over me losing low end so havent bothered.

Which ever way you go, plan it well as you can, and get as many fixed price quotes as possible from ppl that have done it before and know what they are on about. You can do a turbo and ecu upgrade in 2 days. I can see an RB25 transplant taking 2 weeks.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • I came here to note that is a zener diode too base on the info there. Based on that, I'd also be suspicious that replacing it, and it's likely to do the same. A lot of use cases will see it used as either voltage protection, or to create a cheap but relatively stable fixed voltage supply. That would mean it has seen more voltage than it should, and has gone into voltage melt down. If there is something else in the circuit dumping out higher than it should voltages, that needs to be found too. It's quite likely they're trying to use the Zener to limit the voltage that is hitting through to the transistor beside it, so what ever goes to the zener is likely a signal, and they're using the transistor in that circuit to amplify it. Especially as it seems they've also got a capacitor across the zener. Looks like there is meant to be something "noisy" to that zener, and what ever it was, had a melt down. Looking at that picture, it also looks like there's some solder joints that really need redoing, and it might be worth having the whole board properly inspected.  Unfortunately, without being able to stick a multimeter on it, and start tracing it all out, I'm pretty much at a loss now to help. I don't even believe I have a climate control board from an R33 around here to pull apart and see if any of the circuit appears similar to give some ideas.
    • Nah - but you won't find anything on dismantling the seats in any such thing anyway.
    • Could be. Could also be that they sit around broken more. To be fair, you almost never see one driving around. I see more R chassis GTRs than the Renault ones.
    • Yeah. Nah. This is why I said My bold for my double emphasis. We're not talking about cars tuned to the edge of det here. We're talking about normal cars. Flame propagation speed and the amount of energy required to ignite the fuel are not significant factors when running at 1500-4000 rpm, and medium to light loads, like nearly every car on the road (except twin cab utes which are driven at 6k and 100% load all the time). There is no shortage of ignition energy available in any petrol engine. If there was, we'd all be in deep shit. The calorific value, on a volume basis, is significantly different, between 98 and 91, and that turns up immediately in consumption numbers. You can see the signal easily if you control for the other variables well enough, and/or collect enough stats. As to not seeing any benefit - we had a couple of EF and EL Falcons in the company fleet back in the late 90s and early 2000s. The EEC IV ECU in those things was particularly good at adding in timing as soon as knock headroom improved, which typically came from putting in some 95 or 98. The responsiveness and power improved noticeably, and the fuel consumption dropped considerably, just from going to 95. Less delta from there to 98 - almost not noticeable, compared to the big differences seen between 91 and 95. Way back in the day, when supermarkets first started selling fuel from their own stations, I did thousands of km in FNQ in a small Toyota. I can't remember if it was a Starlet or an early Yaris. Anyway - the supermarket servos were bringing in cheap fuel from Indonesia, and the other servos were still using locally refined gear. The fuel consumption was typically at least 5%, often as much as 8% worse on the Indo shit, presumably because they had a lot more oxygenated component in the brew, and were probably barely meeting the octane spec. Around the same time or maybe a bit later (like 25 years ago), I could tell the difference between Shell 98 and BP 98, and typically preferred to only use Shell then because the Skyline ran so much better on it. Years later I found the realtionship between them had swapped, as a consequence of yet more refinery closures. So I've only used BP 98 since. Although, I must say that I could not fault the odd tank of United 98 that I've run. It's probably the same stuff. It is also very important to remember that these findings are often dependent on region. With most of the refineries in Oz now dead, there's less variability in local stuff, and he majority of our fuels are not even refined here any more anyway. It probably depends more on which SE Asian refinery is currently cheapest to operate.
    • You don't have an R34 service manual for the body do you? Have found plenty for the engine and drivetrain but nothing else
×
×
  • Create New...