Should I run an RB20DET?

[BobsYourUncle]

*puts on flame suit*

 

I'd like to think this isn't just another "I want an RB, can I do it for $10.50?" thread.

 

Today my mind wandered to the thought of putting an RB20DET in my 240z, and the more I thought about it, the more sense it started to make. I want my car to be a daily, take me to work and back vehicle, so reliability and fuel economy are coming into this somewhat.

 

I know everyone would usually say go the rb25, but my 240z project is already engineered in Qld for an rb20det (it's benny's old car). I've currently got an F54/N42 L28 with triple DHLA40s in it, but triples probably aren't the best choice for what I'm after (or are they??). It was engineered with stock brakes , but now it's got hilux fronts and r31 rear discs.

 

I guess my question is, doing most of the work myself, can I do this conversion for $5k or less? And is it worth it? I figure I can get an engine, gearbox and loom package for around $2k, then I've got to budget for mounts, tail shaft, cooling, piping, modified/custom sump, fuel pump, surge tank, new fuel lines... anything else? I'd run the stock ECU and stock internals, I'm not looking for crazy performance...

 

I suppose the alternative is to inject my L28. I suppose $2k or so would go a long way in this regard. Would installation complexity be that different? Fuel efficiency and power would still be worse though...

 

I'm after opinions as well as facts, any input would be helpful

[nizm0zed]

As as simple answer id say no, dont bother with the RB20. You'll have a much nicer driving car if you spend that money on the L series.

The RB20 is pretty much on its edge with minor mods anyway, and it doesnt make any power unless you rev it right out.

Its torque that makes a car fun to drive on the street.

HOWEVER! Its allready engineered for a RB20 so it makes it an easy swap. Bear in mind, for the engineers cert to still apply, it has to be TO THE LETTER of whats on there, so stock brakes and all. Anything else will require re-engineering. At that point, your better off to go with a RB25 or RB30 (and maybe RB25 head on it later) Or RB26 if you have lots of money.

 

I think you really need to asses EXACLTY what parts you allready have, or can get within your budget, Or look at what that same amount of money will get you if you mod the L series.

fwiw, I got quoted $500 to tune my Haltech from a rough base tune into a fully driveable car.

Add on $1200 for a Haltech platinum sport, $400 to set up your fuel system (pump, lines, clamps, reg)

Use a L28E manifold and a nice set of injectors ($400?) and your off and running.

[luvemfast]

I'd stick with L series.

 

[Zedman240®]

Any engine you choose with EFI will be great to drive.. My L24 has a pretty lumpy cam (74') and with the EFI, have driven to work and back several days a week while I was getting my other "car" roadworthied. But my system will set you back around 5K depending on what you buy new or used. If you want everyday smoothness, a 280zx manifold will work well but for any spirited driving, would need to me modified. I did have a NA RB25 and that was great to drive; smooth and quiet. If you come across a Rb engine for next to nothing, I'd go that way.

[zzzzed]

Hmm I have the rb20det out of your car which I bought from Benny. The l28 that you have used to be mine. for what you want it for I think the rb20 is an good choice. It will be good on fuel and have just enough power to be fun to drive. They make just over 200 hp in stock form and with a with a few mods they can wake up quite well. I had one in a r32 skyline that suprised many a v8 commodore bogen. Plus they are a little stronger than the rb25 as they don't have the ring land issue. But saying all that I will be looking to upgrade to an rb25 in the future for a bit more fun

[jamo240]

I have a 73 240Z that originally had the L24, which I then turbocharged with a draw thru Stromberg carby (more power, but less refinement). Then I put in an injected turbo L28 with 400HP which went like a cut cat, but sounded and felt like the truck engine that it is. I now have a RB25DET at around 500HP, but probably less torque than the L28. THe RB25DET installation would have $15k of parts in it, and if you added the labor, closer to $30k. So why did I do all that? It wasn't for the power....in an 1,100kg road car, what can you do with 500HP that you can't do with 400?

 

In a word....REFINEMENT. An L series can make plenty of performance, but an RB is a million times smoother. It's not just the engine either...the (larger) transmission and prop shaft and Uni joints deal with the torque much better and you get nothing like the vibration under hard acceleration...the RB sounds better too, and with VVT gives comparably good bottom end torque for an engine that also loves to rev. So, if you want refinement, go the RB, but you will struggle to do it for that budget, even if you keep everything stock.

 

If I was doing it on a $5k budget, I'd just do the L series up to a warm config (perhaps go an L28), and put your effort into simple enhancements that won't cost much. I wouldn't worry about injection...twin carbs will make plenty of power, as will triples, but they cost money to buy and keep tuned.

 

One of the most fun 240Z's I ever drove just had a warmed over carbied L28 and it had stacks of power for road use and was easy to keep running well and very durable.

 

If you go the RB20 you will have less torque than the L28 due to both capacity and the flow characteristics of a 4 valve head....you'll take the car backwards for road use, although it may be more refined if you do it well.

 

RB conversions go best when a fair bit of money can be thrown at them...if not, you'll get a better overall result enhancing the L series.

 

Regarding some of your questions...I can assure you enhancing an L series is nowhere near as complicated as installing an RB in a Z. There is quite a bit to it if you want a nice result.....sure you can shoehorn it in and have all sorts of things not work or fit properly, but if you want to do justice to the potential of the base engine, you need to do the installation thoroughly and attend to all the little details that take time and tend to cost money, even if a few hundred bucks at a time.

 

Finally...what's all this appeal of fuel injection??? Back when I was 19 and first bought my 240, it started up just fine with the carbies and ran plenty hard. Injection came along to deal with emissions, not make more power. If you've got an old car that doesn't need to meet emissions, stay with the classic look of carbies and enjoy using the choke lever on cold mornings!!

 

Cheers

 

Jamo

[waxhead]

If you going for an rb then go for at least an rb25 the rb20 struggles to idle they are that gutless

 

Fuel injection is more than just for emissions, remember they made carbs for emissions as well.

The good thing about fuel injection is you can have it all. nice and economical off throttle and then the delivery when you hit the loud pedal.

Sure you can get a carby engine to drive nice but your not going to get the same results you can get from efi, no way

 

[BobsYourUncle]

Ok, so so far the majority opinion is RBs need more more money spent to be worth while, and that on my budget the L28 is the way to go. Thanks everyone.

[zzzzed]

How can people say the rb20det is gutless. Fair enough they arnt as powerful as the bigger rb brothers. But compared to any stock l series I have ever driven. And I have driven a few. The rb20det would leave any of them for dead. The op is not after big power figures he just wants something that is einomical smooth and a little bit of fun. Sure he can make the l series faster but it will drink more fuel and won't be so smooth for a daily driver.

[BobsYourUncle]

but is the improvement worth it? The wiring for the rb20 is quite complicated, even using the stock ecu/loom, isn't it? hmm I don't know...

[waxhead]

The 25 bolts in place of a rb20 the rb20 has small ports that dont really flow that well in comparison. Its not just capacity you are picking up here but also alot more flow. i guess its like putting in a l24 or an l28 what would you fit.

[luvemfast]

People always bag the RB20DET, but doubt they've ever driven a good one before.

I once had a friends HR31 for a month or so, I was selling it for him while he was living in Japan.

Had a couple of mods and this thing flew!

Another friend took me for a drive is the, then new, VZ SS 6.0L manual and it felt slow when compared to the Skyline.

But the question is about what to do to the 240Z, my opinion is that the budget conscious should stick to the L series.

[benny]

The rb20 that was in the 240z was last dyno'd at 270HP atw. Hardly slow and only had minimal mods.

[waxhead]

but the rb25det puts out 250 at the engine with alot more torque. We have an rb25det std in an r33 drift car. it had aftermarket steaam pipe ebay exhaust manifold

kando dynmaics turbo.

front mount intercooler

high flowed injectors,

its making 437 hp at the wheels

Hardly an expensive engine to build as anything that you bolt on to an rb20 will bolt onto an rb25

the only difference in price is the purchase of the engine in this case its more expensive to buy the rb20det and you dont get the big gearbox like you do with the rb25 engine

 

Going on the calculator and giving the car 1100kg that works out roughly to be a flat 11 second 1/4 mile. I say roughly as there are man more factors than this. using the 287 hp gives using the same weight a 12.8 second quarter for the same money.

I know which car I would rather be in

 

http://www.asianautospares.com.au/index.cfm?Do=View.Product&ProductID=43

http://www.jdmenginedepot.com/jdm_engine_details/50/Nissan_RB25DET_Skyline_Swap

 

 

[nizm0zed]

there are people who will bag the RB20 because thats what they have heard other people say.

There are people who will defend it, because they have experienced quick ones, they do exist, you just have to spend a decent bit of coin to get to that.

Then there are practical people, who will say that on a budget, a RB20 isn't worth it.

 

I helped my brother put a stock RB20DE in his R31 skyline. Took a little effort to wire up but by no means difficult if you have the whoe stock loom.

Yes, it was a nice motor, starts and runs smoothly, reliable and easy to drive, but if you actualy wanted to get any 'fun' out of it, you had to rev it right out.

Its just a normal characteristic of a small capacity engine to have a smaller amount of torque, and its TORQUE that makes a car enjoyable on the street.

 

If you can get a worked RB20 with good power and torque figures for a real good price, then yea, its seriously worth looking at. Otherwise if you go the RB route, you may as well use a RB30 because they are a LOT cheaper and make a decent amount of torque too. Later on down the track you can then mod it or swap it for a RB25 for a real beast.

At the end of the day though, how refined do you really need it to be? Its a 40 year old car, it'll allways feel like a 40 year old car, your not going to be driving it to work and back 5 days a week are you? So if thats teh case, enjoy it and put in a motor you know will suit you and the car.

[Scoota G]

http://www.ebay.com.au/itm/rb20det-engine-Skyline-vl-r31-200b-180b-Bluebird-/190635573258?pt=AU_Car_Parts_Accessories&hash=item2c62c4000a

 

I think you should just do it. Now.

[waxhead]

The rb30 is king for sure, i am using one in my skyline. rb26/30 I was just concerned about the block height and that's why I didn't suggest it

 

[zzzzed]

That's a red top scoot. They are a bit ordinary

[waxhead]

I love the rocker covers. I would love a set of them

 

[BobsYourUncle]

Seems like one of the major hurdles for this conversion would be the sump/oil pickup... what's the situation there? Is anyone (locally) selling suitable parts, or would you need to go custom, or ship something over from the US?

[jamo240]

You can check out my thread on making an RB25DET sump in the engine section of this site...fair bit of information from me and others on sump options for Z's. In a nutshell, you can use the sump off an Australian delivered Nissan Patrol that had the RB30 engine in it...but they're hard to find. The one I made was based on one of these, but modified for increased volume and performance under lateral G conditions.

 

Cheers

 

[Wayne G]

Yes you should IMHO purely because it will be easy to upgrade to RB25 in the years to come using the smaller box. The z is light so if not driven like it is stolen all the time should be fine.  I have seen the smaller box in R32 with Rb25 DET with engine mods that lasted quite well with reasonable use.

http://www.ebay.com.au/itm/Nissan-patrol-Sump-and-pickup-rd28-rd28t-turbo-gq-Heaps-parts-view-my-items-/220949213107?pt=AU_Car_Parts_Accessories&hash=item3371996fb3

Confirm with others on site but I think it is the same. 

 

If you want to buy a conversion from Asian Autos in Slacks Creek I can assist and likely get you a deal from the owner.

[BobsYourUncle]

I think it's the sump of the petrol patrol that ran an rb30 that's used? Isn't the diesel rd28 sump quite a bit bigger?

[waxhead]

Yeah your right, the rd28 sump is deeper

it bolts on I used one when I was doing my conversion. You just have to cut the bottom off and weld a plate on.

Not hard at all

[BobsYourUncle]

I've been quoted $6500 to get an rb20det conversion done by a shop that's done it before, including supply of the engine (+ new belts, seals, plugs, water pump), custom sump/pickup, intercooler and piping, exhaust, mod plate...

 

Based on the research I've done I don't think I could do all that myself for less than $5k... I guess that's something else to think about.