Advantages And Disadvantages Of An Rb30det?

[Freeman]

Ive been reading heaps about how to build the RB30DET, the guide, topics, turbo choice etc, and i just want some more information about this engine. Mainly, what are the advantages and disadvantages over the Rb25det? Pretty much all i know is that boost would come on earlier due to the extra 500cc. Can they be revved as hard? If built by a proper workshop, can they be as strong and reliable as an rb25? Whats an average figure to get one of these engines fully built and into your car (if anyone has previous experience)? So basically, the advantages and disadvantages of building one of these engines. Also any other information anyone thinks would be interesting, thanks

Luke

[Sweet T]

Slow reving, bad harmonics to much torque for standard gearbox

stick with the RB25 to me they're a lot better suited

[R31Nismoid]

Just a few points for you (which are in the RB30 thread im sure of it)

1) you dont need to rev them, thats the best part

You wont need to rev it past 7000rpm anyhow.

2) bad harmonics - poppy c0ck - related to number 2

3) Search, this information about the "pros" are all covered.

Sydneykid has posted a LOT of info, do him some justice and dont make him search for his own posts.

4) As for power they make - how long is a piece of string really.

5) Anything can be as strong and reliable in the RB series if built properly

There is no "advantage or disadvantage" in my view.

- You build a motor to what your needs require

- What characteristics you want

- What your budget allows.

[Freeman]

R31Nismoid - thanks for your advice. But why do you say 'you dont need to rev them - thats the best part' if there is no advantage or disadvantage in your view? And i just asked if they can be as strong, because Nissan never brought out the Rb30det, its parts from two different engines so i figured it may have some weaknesses. And for characteristics i want? Not sure, thats why I'm asking what this engines' are!

[R31Nismoid]

As in you dont need to rev them like mad to make good solid, and broad power

[Dahtone Racing]

i think wat R31Nismoid is trying to say is you dont need to rev em as hard as an RB20/25/26 to make the power because they have the extra displacment.

IMO this is always better, the higher you rev the engine the more stress your putting on it.

strength wise, i cant see it being any weaker than an RB25.

they can be alot cheaper to build than an RB25 too.

mine has cost me probably close to 10K in parts and machine work

all labour has been done by myself except for head assembly, balancing and machine work

[Guilt-Toy]

I got a RB30DET and im from Newcastle too. The best thing about having the combo is that you can be lazy behind the wheel..

Who needs to change gears when you want to go around round abouts or turn into side streets etc.. just keep it in 5th gear and slow down to 900rpm and drive off with no worries

[Sydneykid]

I will keep this short..............it's just repeating what I have said numerous times.

Remember

BHP = Torque X RPM

Advantages

Say you want 650 bhp, the RB31 will achieve it at ~7,000 rpm the RB25 will need ~8,400 rpm. The cost in components (particularly valve train) is multiples higher for 8,400 rpm than it is for 7,000 rpm. The wear and tear on the up & down and round & round bits is much higher at 8,400 rpm than 7,000 rpm. For 7,000 rpm, you don't need the agressive camshaft profiles that you need for 8,400 rpm. This means more low down (below boost rpm) torque.

Then you need to consider the drive train components, to be as fast accelerating as the RB30, the RB25 will have to launch at higher rpm. This means stronger clutch, tailshaft, drive shaft diff etc. Plus, to use the 8,400 rpm properly, you will need to shorten the gearbox ratios (not cheap) or the diff ratio (still not cheap). None of this is necessary with the RB30 because it doesn't rev any higher (to make the power) than the standard RB25 did.

An RB30 is simply a long stroke RB25/26, the bore is the same. OS Giken make a 3 litre, HKS make a 2.7 litre stroker, Trust make a 2.8 litre stoke and bore. These are the big gun engines, the workshops know that extra capacity brings rewards. We are lucky that RB30's are so common (doors), easy to get and cheap. Last year we exported 5 X RB30DET (DETT) to UK and USA race teams, they also understand the advantages of 20% more capacity.

Dissadvantages;

Well you are going to spend a lot of money to get an RB30 to rev as high as a forged RB26. But if you do, it is going to make some serious power.

No block mounted oil squirters, they can be fitted, with some difficulty. Although ceramic coating the piston crowns and oil retention coating the piston skirts has proven to be just as effective.

Tight balancing is required, the RB30 is not a "long stroke" engine, they are almost perfectly square (86 mm bore and 85 mm stroke). So it's not as bad as the high rpm lovers would have you believe.

The bottom line

The reality is if spend the same amount of money on an RB30 (as an RB25) it will make more power at lower rpm, cost less in maintenance and be more economical due to its greater low rpm (off boost) torque.

cheers

[paulr33]

After reading the RB30 thread over and over a few times I have found there are two main engine "setups" that come from the guide;

1) Complete RB30DET build: forged internals, bored, big injectors, cams, massive highmount, ecu, etc.

2) Budget box RB30DET build. Rb30e bottom, rb25de heat, a turbo manifold and ecu, any turbo and some good injectors

The RB30 thread has recently had a few versions that are a cheap build of the RB30 using standard run of the mill parts and run it till it blows up, then replace what has died. Cubes has posted this a few times and it appears to be a very cheap and alternate engine build to a $10k RB30DET engine setup.

Some references to the budgetbox RB30det

http://www.skylinesaustralia.com/forums/in...owtopic=104332#

http://www.skylinesaustralia.com/forums/in...=15420&st=3180#

http://www.skylinesaustralia.com/forums/in...=15420&st=3140#

So it doesnt' *have* to be a 10k engine build, heck when my 25t dies it will be going back in an rb30det

[N I B]

RB30 has the same bore and stroke as a Toyota 2JZ so it cant be to bad.

[Gts-t]

RB30 has the same bore and stroke as a Toyota 2JZ so it cant be to bad.

<{POST_SNAPBACK}>

Is the 2JZ not 86 x 86?

Also talking about the cheapie rb30det build, i have been thinking the same thing. At the momment im wondering what oil pump and water pump will do the job well, i am wondering if i should use the 120k rb20 item sor rb25 or 26 ones...

I have trade discount so i am thinking i will buy new rb26 items.

[Abo Bob]

One disadvantage when using an RB25 head - and one of the ones that dissuaded me when I went for a rebuild recently - is clearance.

AFAIK you need to either put a front facing plenum on or drop the sub frame. The first I couldn't afford or find, the second sounded dodgy to me.

If I ever have to rebuild again I will use an RB26 head on the RB30 bottom end though.

[R31Nismoid]

Mate of mine has a 25/30 in an R33 GTS-T.

Still had the stock plenum and all the piping that goes over the rocker covers of the motor down to the normal spots etc etc.

I dont believe clearance is a "major" problem. Just some smart pipe design

[fatz]

mmmm rb26 head ona 30

yea baby

im very exited!!!!!!!!

[Bl4cK32]

clearance isnt an issue if using the std ic pipng route.Cubes uses the std route and has no probs, where i have the "drivers side over the top of the radiator " route, and had trouble closing the bonnet.

Even for a cheap version it requires a pfc, bigger injectors, bigger afm, and a fuel pump. The std trurbo is useless (even highflowed) so a bigger one is needed.

Even as a chheap drop in it still requires a few supporting mods. Otherwise u will be putting it around trying not to hit a fuel cut etc...

[PHATR32]

i hear the only bad thing about rb30det's is the tourque likes to eat drivetrains? any truth in it?

steve

[Abo Bob]

Mate of mine has a 25/30 in an R33 GTS-T.

Still had the stock plenum and all the piping that goes over the rocker covers of the motor down to the normal spots etc etc.

I dont believe clearance is a "major" problem. Just some smart pipe design

<{POST_SNAPBACK}>

Was the strut brace still installed?

[Gts-t]

Was the strut brace still installed?

<{POST_SNAPBACK}>

Thinking the same thing as i really dont want to lose my strut brace.

Options are, lower the motor and probably still have to lose it, or try and find a front facing plenum to fit a r32 rb25de head. Anyone know of anyone who sells one?

Maybe R.I.P.S? Will the r33 greddy one bolt up. Headspin

[fatz]

torque is great

helps with burnouts in 3rd and 4th

[Bl4cK32]

Peoples, you can keep your strut braces. Its simply a matter of making new sections where they bolt onto the strut top.

You just offset the bar a little forward to clear the x-over pipe.

Im doing this soon as i get some steel :toolazy:P:

edit/ if you are doing the rb30det, you need to cut and weld the engine mounts, so dont say you dont have acess to a welder

PHAT32 - ive upgraded my driveline at the same time. I had the rb20det gearbox/diff, but am now running a os twin clutch, r33 box, nismo 2 way diff. Its now coming down to worn subframe bushes, old cheap shitty tyres that wear out due to my slightly imperfect wheel alignment setting.

If you start off with std gear (evgen in a r33/34) you will no doubt end up replacing all the wornout stuff that u do when upgrading any engine.

Edited February 8, 2006 by Bl4cK32