Rb 25/30 - What are the advantages?  

BRISBANE EPOXY FLOORS

20% extra capacity

BRISBANE EPOXY FLOORS

spools up turbos 1000rpm sooner than rb25 (think its 1000rpm, maybe 500)

GHOSTY

an unopened rb25 with a 3037 equiv. turbo and supporting mods will comfortably make 400hp. do you want more than 400hp? if the answer is no then 25/30 is not for you. and if the answer is yes then 2j is a better choice anyway.

180sxy

Bullet proof bottom end but as ghosty said its really something you'd only do if your chasing big hp. 2jz conversion would be more expensive imo

GHOSTY

You reckon? I've heard a lot of horror stories of guys who've spent big bucks getting their 25/30's going only for them to have serious complications later down the track, where's stock 2j bottom end can handle 600-700hp. just seems like the smarter (cheaper) way to get there.

180sxy

From what Ive seen its cheaper, significantly cheaper even if your doing the work yourself . But then Ive seen competent people building these engines and yes I have heard the horror stories, but who hasnt when dealing with any 20/15/10yo import motor (with who really knows how many k's sometimes) pushing High hp/kw.

2jz hands down is the best motor but it is expensive motor itself then all of the parts you need to make it fit into *not a toyota* it becomes even more expensive.

gutless

The horror stories aren't because of the bottom end, they are because 30DET is a hybrid motor and you should'nt let some small workshop build an engine that was never released.takes proper engine building skill to build one that doesn't break.
2j can apparently go 800hp stock unopened. A high k rb30 can withstand 600hp unopened.



To OP
the advantages of 25/30 are:
Quicker spool
a lot more torque
Power made much lower in the rev range
strong bottomend


At the minimum when building these engines you will pay 5500 to have a bottomend completely prepared(properly)
but then you have head preparation,turbo,manifolds,piping,computer,injectors ,fuel pump and all the other shit.
Basically this isn't some willynilly option over just putting a 25 in your 180
Are you breaking 25's left right and centre or do you want to have something a bit different?
Either way you will have to dig deep.

Hope this ramble has helped.
Good luck with your 180.

drunk_chicken

rb30et

09ONE

At a bare minimum, you also have to remember the extra torque, the fatter torque and power curve, the ability to have the same powerband but rev the engine 1,500rpm, the fact that 4th gear roll ons at 140km/hr are insanely fun!



Maybe he wants 400hp and full boost by 3000rpm?
Maybe he wants to shift his power and torque curve to the left?
Maybe he wants do everything a 25 can do except in the next gear up?
Maybe he wants to have a built engine not a startup warranty from an importer?
Maybe he wants to "keep it in the family" and not have his exhaust on his inlet side and his inlet on his exhaust side?

So I MAYBE a little biased, but seriously it's a bit of work to do a 2J conversion. Also gearbox and clutch dramas and if he has mods on his RB25 they transfer over to the 30DET. No re-wiring the car, no new ECU etc etc.

Ghosty needs to go for a drive in a twincam 3L Nissan. There is a reason why my car when it had 368rwhp was quicker then the equivalent vehicle with ~440rwhp. You do understand the concept of "average" power?

ItsIHavok

Thanks for all the replys guys.

This would be the first 25 i have dropped in. I had a forged SR that popped after extensive work so i dont want to waste money going down that road again.

I want to have a nice cruiser that will hit 400 to 450 on the street but for dyno days ect can make close to 600 kinda thing.

Gutless: If i were to forge the 25 and do all the extensive work needed to make that power would i be better off spending that money on the 25/30?

Also are there different 30 bottom ends or are the ones on ebay/Here for $150 $200 the ones to use?

Could anyone send me in the right direction to get this built if i go ahead with it?

Thanks
Chris

gutless

if it were me and i had the option to be building a 25 to make 600hp, i would definately go 30DET. more useable on the street with less lag,more torque,improved "average" power like 09ONE said and all around just a stronger engine. from what i understand, if you can make a 30DET for 600, it has the potential for 1000.


yeah the 30 bottom ends come from R31 Skylines and VL commodores(Australian and new zealand Domestic) and some nissan patrols.series 1 R31 RB30 blocks do not have the oil and water galleries for being turbo'd but that is easy fixed by getting some drilled. nothing wrong with using a VL Block but i would personally seek out a nice series 2 or 3 R31 Block for the build.


wouldnt have a clue of who to send you to. im sure a few boosters will have some reputable names to share. just make sure they specialise in RB Hybrids and have a good reputation. this is something that needs to be researched and planned out to the enth degree. cut no corners and use the best parts.
Gavin woods comes to mind for building mean engines.

if you decide to go 30det, i would suggest selling the 25 as a whole package and just buying another 25 head for the build for 250 bucks. that way you will make the maximum money back on your 25 instead of taking the head off and having a $500 block to sell off.
or alternatively you could buy a 26 head, but that will cost around 1200-1500 bucks with covers and no plenum(iirc). its something i would do because its a better head,looks awesome and is RB Royalty. heads up,you can fit 26 covers to a 25 with ease but thats a dirty trick to play i believe.
hope this helps.

p.s bit of a heads up on what i plan to build in the future. RB34DETT (26/30 stroker) 3.4L stroker kit comes from spool imports for $5500:). they did some tests between a 30DET they built and a 34DET using the same internals and turbo(only difference being the stroker kit). 34 spooled up sooo much quicker making 60% more torque at 4000RPM and making just over 150KW more at 4000RPM. stroker kit already comes with pistons and rods, so it seems pretty fuckin cheap for the kit when you factor in not having to spend money on pistons and rods on top. bare in mind only a few are still in the build around australia(that i know of) so once again you would need a fuckin good builder to trust with this project but yeah definately a sweet engine to have built.

tas_ae71

my impression of a rb30e was that it didnt want to rev and was not really a performance orientated motor. is the crank even fully counter balanced being that it was only ment to rev to 5500 or something pathetic?

if you want 600hp i do think your looking in the wrong place. i maybe a little byas but any RB other then a 20 seems pretty weak from what i have seen. id def be going down the 2jz route. they really are not expensive anymore.

also another point is, why do you want to make 600hp on a dyno then 400hp on the street? seems a bit odd. thats a fair difference, also one thing you want to bare in mind is 400hp will still be drivable on the street but 600hp will require even larger injectors, larger cams, more agro clutch etc so it will be shitter to drive on the street. often large injectors will struggle delivering small amounts of fuel and run like a dog, combine with with really big cams its going to be a pig on the street and off boost. you may very well end up with a dyno queen with a number plate. that gets beaten on the street by a civic

gutless

1:True, whats your point? we aren't talking about an RB30E. we are talking about a twin cam hybrid using an RB30E block, a block that is stronger than a 26 block.

2:A 30DET can safely rev to 7,500RPM using the stock crank, or with some work to it:10,000RPM(RIPS NZ).

ItsIHavok

as Gutless has said 2Jz is just a money pit. To get the power i want out of a 2jz along with the costs of the motor gearbox and putting it in my 180 would be insane. I do love 2Js but i think RB is the way to go for this setup.

The 450hp on the street is so its still an easy car to drive and on a low boost setting. Then when its time for a dyno day i can just amp the boost up and make max HP.

I think im going to go with your idea Gutless of selling the 25 and buying a 30et bottom end then going to find a 25 head.

The idea of putting a 26 cover on is a sneaky little trick lol. I will keep that in mind hahah.

Thanks again for all your help =)

gutless

GHOSTY

I have passengered in Camo's 32 at QR, it was swell.

Unless you can do a lot of the work yourself, I don't think you'll be getting much change from $10k drive in drive out to have a 25/30 built properly with all the bells and whistles, not that you would want to take any shortcuts that could jeopardise it any way when you're outlaying that sort of cash..

Drifters are the cheapest kents around which is why I asked if OP was after much more than 400hp, because that can be achieved quite cheaply and safely with a 25, turbo, cams etc.

gutless

you wont.

09ONE

That would have been sweet!

But seriously on the street is where you realise just how much low down / midrange a 30DET has over a 25. Gives you a "real life" idea of how the engine feels i.e. acclerating up hills in 5th gear at 60km/hr, taking off in 2nd, dordling through those shit small roundabouts in the back streets in 3rd gear, over taking on the freeway in 5th with a twitch of your big toe etc.



Correct.

My parts list was over $15K

Also will agree with 600hp 30DET's are more than streetable

gutless

I can't wait

GHOSTY

Yeah I definitely agree about the street showing the difference, the only compareable thing I can relate is when I went from an rb20 to an rb25 in my last 180, the difference was incredible. And that feeling of awesome (putting your foot down and actually going somewhere) makes me hate my sr20 (current engine) everytime I drive it on the road haha. But I have stuck with the sr20 this time round simply because I do recognise the weight balance is a lot better than in my last rb silvia.

180sxy

Exactly

SN33ZY

sorry to hi jack the thread but it thought i would save starting a new one and is a similar topic

ive just purchased a vl with an rb25det in it and im keen on building a 600+rwhp setup

it has standard internals, greddy copy plenum and fmic, t04e turbo with stainless t3 hi mount manifold, 630cc injectors, 3" steel mandrel exhaust and 3" stainless fmic piping, vlt 5speed, 3.9 diff gears with a locker, wolf v500 ecu, 38mm external gate, drift bov and probably a few more bits

i was thinking of selling the engine and turbo and using the existing parts on a new 25head/30et block... along with a spool imports forged rebuild kit, acl bearings, n1 water pump, hi volume nitto oil pump, arp main and head studs, hi volume sump,head worked and fitted with some type of cams adjustable cam gears good spring etc all with a garrett t51r turbo and bigger injectors and twin 044s with a surge tank rb25det box and twin plate clutch...

this car will barely be on the street but will be regoed for cruises and some friday night street duties
any comments ticky tips or suggestions with parts and turbos stuff would be good as i am new to rb engines

gutless

This thread was a question about the differences between a 30DET and a 25DET. you haven't even asked a question.
Advice would be just the same,don't cheap out at all and use the best parts. and im thinking there would be a more suitable turbo to run 600hp through other than a T51R SPL turbo,sounds like an invite to the lag-show.

B Unit

Agreed on turbo size. Check out a T04Z, should be able to hit the power you want on a 3L engine and be more responsive.

E.Honda

why not lean on a standard rb25 bottom end. just make sure you keep it in a safe state of tune. i seem to recall a certain blue vh commodore making over 680rwhp from a standard bottom end r34 neo motor!
it's not just rb motors you have to choose from nowadays. seriously the vq25 and vq30 det's are awesome grunt machines for reallly low$$$ lately. they will be the next 2 jays in the coming years!(you read it here 1st!)

SN33ZY

haha yeah forgot to add that part in.
-is the 25det capable of a reliable 600hp build or is it way too expensive to bother?

-also what exactly is involved in fitting the 25 head to the 30 block? i was once told galleries didnt match up and had to be filled or something or is that the 26?

-would the parts i have mentioned be a solid reliable start to a 600hp combo or would i need better quality/performing bits?



what sort of flange does this turbo run? will it fit my stainless t3 hi mount manifold?

gutless

If you have the money to be making a 25DET make 600hp,then you should just build the 30DET,reap the benefits and not end up throwin a rod or something.

There is more than enough information on the internet about the process of building an RB30DET. check SAU or Calaisturbo. and please don't make a thread on here asking that question.

Those parts sound pretty decent for a strong build

B Unit

I have a feeling that they are a T4 flange unfortunately.

L32

Message ovl00 on here he build one from scratch with the help of camo that ghosty speaks off i believe the cost is great

SN33ZY

can you purchase a weld on flange to swap them on your manifold or turbo even? or is it not worth bothering?

only reason i say this is because i have a few mates who are boilermakers and could do it for me for a six pack or something

SN33ZY

only reason i asked is because i want to build the engine myself to save funds and haven't had an rb before or looked into a 25/30 and you boys seem to posses this knowledge already and could save me the hassle of searching forums full of half truths

180sxy

Dude just look on sau there is so much info on this topic there

gutless

SAU is a highly moderated forum dedicated to skylines and skyline engines. they have all the info you need with no half truths or bullshit.