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RB25de or L28? best bang for your buck.


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#1 matsdat

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Posted 27 December 2009 - 03:33 PM

Hi guys, i am looking into replacing my L24 in my 240z, its not original so no need to keep it. What are your opinions, in terms of the power gained vs the money spent, on a RB25de transplant compared to an L28? Turbo is out of the question due to engineering. From my research it seems that the RB25de halfcut is the way to go, similar power to a mildy rebuilt and worked L28 with tripples or good su's, modern gearbox, no need to rebuild engine/gearbox (i would need to do this with an L28) or source good carbis, and reliable. So is it purely the extra effort involved in fitting an RB and keeping with the zed heritage that makes people go for an L28 rather than an RB? I appreciate anyones opinion, i like both engines but am not sure what path to take. Thanks. 

#2 waxhead

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Posted 27 December 2009 - 03:48 PM

L28 all the way
its there you dont have to do the sump mods as well as buy the conversion kit
It will not need to have a mod plate

#3 Lurch ™

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Posted 27 December 2009 - 03:54 PM

L28 is cheaper to get the HP out of.
It also produces more torque for the $ spent ($ for $).
Zedman240 (Dimitri) knows all about this.

Turbo is out of the question due to engineering.

Hate to burst your bubble but you'll have to Engineer the RB in the Zed to make it legal.

In any case, it sounds like you've made the decision to go RB, so why are you asking us?

#4 matsdat

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Posted 27 December 2009 - 03:56 PM

It will need an inspection but no engineering required so virtually no cost impact. Whilst the fitting kit is required, a rebuild of both engine and gearbox, maybe even carbis would be required to the L28 to get the same power a standard RB25de would produce out of the box. At least i think this is the case. My gearbox is knackered so this is part of my equation also.

I understand that the rb would require more work and hassle to get in and legal, but im not too worried about that, more so interested in the kind of power the two make for the cost.

#5 matsdat

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Posted 27 December 2009 - 04:03 PM

L28 is cheaper to get the HP out of.
It also produces more torque for the $ spent ($ for $).
Zedman240 (Dimitri) knows all about this.
Hate to burst your bubble but you'll have to Engineer the RB in the Zed to make it legal.

In any case, it sounds like you've made the decision to go RB, so why are you asking us?


Decision hasnt been made yet, just after some helpful info. I have neither an RB engine nor an L28 and would be happy to go for the L28 and rebuilt gearbox if i could get the same amount of power out of it for the money it would cost to purchase and install an rb25de and gearbox from a halfcut.



#6 zzzzed

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Posted 27 December 2009 - 04:03 PM

+1 l28

#7 NZeder

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Posted 27 December 2009 - 04:18 PM

The first question is how much HP are you looking at? Then the next question is what is the budget?

If you want around 200HP at the wheels then either can deliver this and the L28 is easier to install to get this vs) mount kit, custom headers (assume you want headers not the stock iron item)

The cost of triple you might see as an issue then the come back from that for the RB is a good ecu replacement is the cost of the triples. Headers for the L6 are easy and available, an L28 with a/c, power steering pumps etc instock form are 170hp at the fly so cam, carbs and header and you are most of the way there.

RB25DE have issues too. The rear mounted sump are NLA for nissan so that will need to be custom (there is your cost of the L28 forget the cost of the RB 1/2 cut). The early heads (none NEO) have hydrallic lifters so revs are limited by this. The later NEO are like the RB26 heads and solid lifters but the ports are not the same as the 26 or early 25's.

I am installing an RB into my zed (RB26/25 hybrid one to become 26/30 hybrid) but can't compare to all the other L6 powered cars I have owned as the engine is still on the stand but an L28 would have been cheaper for the same power IMHO

Cheers
Mike

#8 Zedman240®

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Posted 27 December 2009 - 04:45 PM

After having an RB25DE in my zed, stock except for the EFI system and throttle bodies, power was at 120KW at the wheels. Biggest limiting factor in that motor was the camshafts. A rear sump now would be difficult to find but the easiest way I think would be to source a sump from a GQ model Patrol (and pickup) and modify that. It's already a rear sump but wayyy to deep. Clears the ground by approx 2" installed. If I was to go the RB way again, I'd go for the turbo. Best power/$ improvement over stock L series. A pair of cams for a NA RB, you are looking at around $1000 compared to an L series one at about $300. The RB will cost more in the end with around the same amount of HP. As Nzeder explained, a set of headers for a RB in Australia, is very hard to come by. I've done the searching! Custom made one's would be the easiest or a trip to Japan for some Fujitsubo headers at $2000..
You could always make a triple Weber manifold and source some carbies and install them but you will have to find an ignition system that can work without a distributor; RB engines have the CAS sensor on the front. MSD I think make something that will work but from memory that alone is approx $500.
I've gone back to the L series because a) Its the orginal motor
                                                      b) I miss the sound of a healthy angry L!
Whichever way you go, it will cost.

#9 PeterAllen

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Posted 27 December 2009 - 07:58 PM

If you simply want 'bang for bucks' then I suggest go outside the square and consider an LS1.

$3000 = 250kW (335bhp) standard engine, 6-speed box, loom, etc.

That equates to $325 per 20bhp increase (I'm subtracting the original L24 151bhp and calculating on the mere 184bhp increase).

There is probably another $3000 to install it... engine mounts, radiator, extractors, etc... but if you have to do that with other alternative engines then don't include it.

Unquestionable reliability and parts/service available all over Oz.

If you want to stick to Nissan then ignore all the above.

#10 gav240z

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Posted 28 December 2009 - 04:44 AM

I think the problem with engine swaps is that people assume they will be a straight forward HP upgrade with no hassle and it will only cost $x in total.

The reality is often far from the truth. Just ask any project manager what can go wrong, will go wrong :).

Problems with engine swaps:

1. You will need to get it engineered. This will have to comply with emission standards and may be forced to upgrade brakes and other mechanical items depending on your state.

2. Buying a half cut with a low km motor does not mean trouble free motoring. You may end up buying an engine that needs a lot of work or a rebuild (so back to square 1).

3. If you are fitting the motor yourself it might work out cheap depending on how handy you are with fabrication work and mechanical work, but don't forget all the little pieces ad up, especially if you with with genuine parts.

4. Being pulled up by the boys in blue will involve a lot more hassle and your car could be more easily defected for little things. It will depend on where and how you drive your car.

5. If you are not handy with electrical work you will need to pay an auto electrician to wire it up. Although I'm sure with enough time and effort and help from other forum members you could get their on your own.

So provided you get through all the red tape, install the motor correctly, you will still be sitting on stock HP for the RB25de. As the others mentioned cams are more expensive as are other parts.

My vote is to rebuild your L24 / L28. The displacement is far less important than the head, camshaft and intake, exhaust mods you do. In fact I prefer the way the smaller motors rev to the L28.

A stock L28 block does not rev as nicely, although it produces more torque which is good.

If I was going to build an L-series on a budget here is what I would do first.

  • 240z SU carbs (rebuilt with minor mods for better flow) mounted on port matched intake to cylinder head
  • N42 head with larger SS valves
  • Stage 2 Port Work with Camshaft Profile to suit
  • Electronic Ignition mapped to camshaft profile also

From there you could decide on gearbox, rear end ratio. If you wanted to invest in a set of triples (who doesn't? :)), bore / stroke the block.

If going NA and chasing bigger HP as Peter Allen said a V8 is probably the way to go.

Also an L-series Z will probably retain slightly more value in the long term and is pretty easy to work with / on.

You don't need buckets of power in an early Z to have a quick car. All this really depends on your budget and HP goal as Nzeder stated.

#11 RB30X

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Posted 28 December 2009 - 08:40 AM

If you simply want 'bang for bucks' then I suggest go outside the square and consider an LS1.


I'm with Pete on that one. LS1's are a mental engine with nothing more than a tune and some bolt on's. Cheap to buy, get it engineered and never have to tune it or muck around with it again. To be dangerously honest, apart from making the wrong sound, they would be so much cheaper "if you were only after bang for buck", compared to the same amount of engineering and tuning and turbo accesseries and expensive things like cams for a jap six. An LS1 may have been a plan for my car early in the game as far as bang for buck goes but then you realise that isn't what its all about.

Ask yourself a few Q's.

Do I want NA?
Do I want an inline 6?
How much power do I want?
Where do I want to use that power?

#12 matsdat

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Posted 28 December 2009 - 09:59 AM

Thanks guys, I appreciate all your opinions. It gives me a lot to think about.

#13 dat2kman

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Posted 28 December 2009 - 10:57 AM

my two bob's worth,
Ok so you dont want to go turbo, Licence requirements? Dunno, but if you did, consider a SR20DET set back close to firewall, great weight balance and overall car weight reduction, You can get up to 400 hp at flywheel ( reliability??) without pulling them apart, and over 500 with a "built" motor.
There's your horsepower!
Ok less torque but the benefit is less overall weight.
260DET in here did a FJ20 turbo mod, quite mild tune, it went very well, and at least it is all Nissan, like a SR.

I am doing a SR det into an old skool Datsun Fairlady convertible ( 1967) and wont even bother with external mods to motor, mind though finished weight will be approx 850kgs.
Having been mucking around with old racecars for a while, HP isn't everything, it does help, but weight is your enemy bigtime.

Anyone here done weight comparos between L28, RB25DE, LS1??

SR20DET with box is 222 kgs
RB25DET with box is 300kgs, and it sticks well over front axle centreline
Gee, thats like sticking  a Dimitri under your bonnet between to radiator and the fan !!!!!

#14 Ben

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Posted 28 December 2009 - 11:24 AM

You mention that turbo is out due to engineering. That's certainly applicable to the RB25DET, but with the L28, it should not be so.

I have in my possession a Certificate For Exemption stating that my car is a'ok with a 'standard' L28ET (and some other details like my brake conversion). My father had an Approval In Principle for the RB25DE, but it has lapsed and who knows if he'd get it again...

Now that's not a precedent, but it is an indication that you should be able to do an L28-turbo conversion without engineering.

What's more important, is that the 240Z is an ADR26 compliant vehicle - which in SA means that you can turbocharge the original motor without any regulatory obligations aside from maintaining the original PCV system.

So...
Your cheapest 'upgrade' providing you can tolerate some engine downtime would be to turbo your L24.

It took me 6-months to turbo my L24 in 1997, including auto gearbox mods and brake upgrades. From memory the was about $4k - including ECU, turbo, manifolds, exhaust, intercooler, pumps and tuning. We managed to double the standard rwkw and triple the rwtq with 12psi of boost :)

I also have some bits (and experience) you could use if you decide to go that route.

#15 PeterAllen

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Posted 28 December 2009 - 11:30 AM

LS1 and t56 adds only 15 kg to a standard 240Z. It's an all alloy block and when set back in the engine bay the extra weight is all over the rear wheels.

Gavin made an important point I missed. With an LS1 you will need big brakes to pass engineering.

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#16 Glen

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Posted 28 December 2009 - 01:42 PM

Out of interest, how far would 3K get you with a tired L28? Using SU's... How much HP would you see at the wheels? I know its an age old question but i wouldn't expect much for 3K starting from scratch with a L-series.

BTW 170HP was when they rolled off the line, in my case, 32 years ago, These are good motors but i doubt it's still producing 170HP at the fly. 

I still think the RB30t is the cheapest way to get decent HP but as Dimitri said, you dont get that wonderful note.


#17 zzzzed

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Posted 28 December 2009 - 01:57 PM

dont forget the vg30et is exact same motor as the rb30et but in a v fashion.This means you can use the same computer and injectors for both motors Nistune has remaped computers available to suit.
Also you would be able to get the weight more central with the vg30et
I think thease motors are way overlooked for a conversion possibilitys


#18 waxhead

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Posted 28 December 2009 - 02:21 PM

Makes me wish the rb26det head could be cut in two and fitted to my vg33e pathfinder

#19 nizm0zed

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Posted 28 December 2009 - 03:02 PM

dont forget the vg30et is exact same motor as the rb30et but in a v fashion.
I think these motors are way overlooked for a conversion possibilities


arent they known for catching on fire????
They copped a bad rep from the Z32 300ZX, but its more because they are a complete POS to work on in that application

Makes me wish the rb26det head could be cut in two and fitted to my vg33e pathfinder


With enough money, im sure its possible.

#20 zzzzed

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Posted 28 December 2009 - 03:28 PM

arent they known for catching on fire????
They copped a bad rep from the Z32 300ZX, but its more because they are a complete POS to work on in that application

With enough money, im sure its possible.


they caught fire because because of there dodgey injectors which leek. this can be remedied by replacing them with rb30et injectors
they are only hard to work on because of all the extra crap the put all over the engine bay in the 300zx  i have replace the heads on my old 300zx and it wasnt that hard





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