240z Rb25det - Engine Build-up

[Brycey]

Hey guys, I’ve been doing alot of reading and searching on here in relation to building RB25's up, but I thought I’d be annoying and make my own topic asking for advice..

Basically, I’m getting into the final stages of my (thoroughly over-due, over-extended) 6 year project, its a 1973 Datsun 240z that I’ve put a RB25DET into. The engines arrangement, driveline, suspension, brakes and electrics are all sorted, its just time for the internal engine build and body work..

Here's what i have (in relation to the engine..)

S2 RB25DET (Standard internals)

GT3040

Full exhaust (external gate, dump pipe etc etc)

High Mount manifold

Q45 AFM

Plazmaman intake plenum

740cc Nismo Injectors

Bosch 044

Power FC

FMIC with all the plumbing

my question is.. what now? any specific recommendations to get the best out of what I already have or should I just go down the normal road of adjustable cam gears, forged pistons and rods etc etc.. and not only that, if there’s any tips on stuff like oil cooling etc..

also any recommended shops! I’ve been eyeing off Pryce Engines (in Newcastle) for a while now as they have a pretty good reputation, but I’m open 

my expectation is to get some serious power, but also some degree of reliability as it will more than likely be driven on the road more than the track (although I’ll be doing my best to be on the track as much as possible.. ah the dream)

Any seasoned advice or opinions are more than welcome :-) ill post up some pictures tonight when i get home for reference sake..

[t_revz]

theres a few threads about q45 AFM`s and some say good and most say go Z32 AFM. i guess see how you go. also see sydneykid`s posts about oil control for race engines. im rebuilding my engine now too and looking at following some of his advice such as oil return from back of head back to sump but not all of it as mine doesnt make it to the track that often.

goodluck with the datto!!!

[Brycey]

yeah mate i remember back in the day when i was first shopping around for parts there was the big debate about the Z32 vs Q45 (and i guess there still is..), but the main conclusion that i could find was that if a Q45 was available then go for it (mainly due to the larger mouth i believe), or go 2 Z32's, which seems a bit silly.. either way i think that side of things is relatively sorted but the oil management stuff sounds pretty interesting, ill have to check it out

[The Dan]

Q45 AFM

Power FC

my expectation is to get some serious power

As above. Z32 would have been better.

Don't know what a GT3040 is but if you are referring to a GT3082, then 320-350rwkw is about the most you will get. We have found the PowerFC to be rather good for mildly modified RB25's but once you get over about 300rwkw they seem to not get very good results.

I would change it out for a Wolf V500 or a Link G4 or a Vipec

[The Dan]

theres a few threads about q45 AFM`s and some say good and most say go Z32 AFM. i guess see how you go. also see sydneykid`s posts about oil control for race engines. im rebuilding my engine now too and looking at following some of his advice such as oil return from back of head back to sump but not all of it as mine doesnt make it to the track that often.

goodluck with the datto!!!

Most of the information there is very outdated.

You will get better results by drilling out the oil return holes in the block and head. Forget the drain in the back of the head as it's a waste of time and think carefully about the oil supply and how much oil you will need if it's a street car. If you cruise around at 3000rpm on the highway and have a single 1mm restrictor fitted, then say goodbye to your valvetrain.

If it's going to spend more time on the street then the track you should not restrict the oil so much but instead put in a double catch can with a return to the sump. Anyway a bit off topic sorry.

There are a couple of Q45 AFM's, you have to make sure you get the right one from what I have heard. They ditched the Q45 and PFC and put in a Haltech E11 into Noels RB25, instantly made about 50hp more at the wheels.

[Brycey]

As above. Z32 would have been better.

Don't know what a GT3040 is but if you are referring to a GT3082, then 320-350rwkw is about the most you will get. We have found the PowerFC to be rather good for mildly modified RB25's but once you get over about 300rwkw they seem to not get very good results.

I would change it out for a Wolf V500 or a Link G4 or a Vipec

Most of the information there is very outdated.

You will get better results by drilling out the oil return holes in the block and head. Forget the drain in the back of the head as it's a waste of time and think carefully about the oil supply and how much oil you will need if it's a street car. If you cruise around at 3000rpm on the highway and have a single 1mm restrictor fitted, then say goodbye to your valvetrain.

If it's going to spend more time on the street then the track you should not restrict the oil so much but instead put in a double catch can with a return to the sump. Anyway a bit off topic sorry.

There are a couple of Q45 AFM's, you have to make sure you get the right one from what I have heard. They ditched the Q45 and PFC and put in a Haltech E11 into Noels RB25, instantly made about 50hp more at the wheels.

Thanks for that mate, the turbo is the Garret GT3040R (with the 500hp rating), which is quite similar to to GT3082, but keep in mind my parts (although new) are a few years old due to delays in the project..

300rwkw is a pretty good target, especially in a car that's a pair of socks over 1000kg, my plan was to always aim above 300rwkw. i gotta admit that i went through a dud PFC and then through hell to get a brand new one so im not sure if im ready to give it up just yet, but a 50hp gain from chaining AFM and ECU seems pretty incredible!

im very interested in the oil related stuff as its all relatively new to me, i had a custom catch can made that looks like quite an effective design, but ill have to see once the thing is rolling .. nothing is off topic if its about making my engine better! haha

[Brycey]

oh and i gotta admit, my knowledge is a couple of years out of date, so im quite happy to be schooled

..considering the stage that i'm at, is it worth getting an RB30 bottom end?

Edited August 25, 2010 by Brycey

[simpletool]

Std internals + GT3040 is usually a mis-match. What A/R is the turbine housing?

What are your expectations? What is your mid-range goal? Peak power goal? Do you want a monster or something genuinely quick and more usable?

I'm not one of the experts but if you've only a got a 240Z shell to push around then you'd want a nice linear midrange with 550 to 600Nm max coming in as early as possible. The GT3040 adds more lag for no gain on a stock internal engine. I'd swap it straight-up for a GT3076 w/0.82 rear (normal GT30), run 17 or 18psi coming on full at under 4000rpm and be happy. Will the chassis benefit from much more than 260-270rwkw?

Assuming you are ~1200kg then a RB25 would already behave like a 3.0L in a R33/R34, just with more revs and power up top. 550Nm in 1200kg is like 640Nm in a GTST! Having even more torque on that light rear end sounds like a recipe for no traction and slower speeds.

[The Dan]

Std internals + GT3040 is usually a mis-match. What A/R is the turbine housing?

What are your expectations? What is your mid-range goal? Peak power goal? Do you want a monster or something genuinely quick and more usable?

I'm not one of the experts but if you've only a got a 240Z shell to push around then you'd want a nice linear midrange with 550 to 600Nm max coming in as early as possible. The GT3040 adds more lag for no gain on a stock internal engine. I'd swap it straight-up for a GT3076 w/0.82 rear (normal GT30), run 17 or 18psi coming on full at under 4000rpm and be happy. Will the chassis benefit from much more than 260-270rwkw?

Assuming you are ~1200kg then a RB25 would already behave like a 3.0L in a R33/R34, just with more revs and power up top. 550Nm in 1200kg is like 640Nm in a GTST! Having even more torque on that light rear end sounds like a recipe for no traction and slower speeds.

My experience with the 3076 is that it's doughy as all shit and with a 0.82 rear, no where near coming on full at 4000.

Not sure what stock internals has to do with making power either? Aside from obvious things like lighter piston. But there is nothing special a forged piston is going to do to spool up a turbo really

[PaulosECR33]

thats awesome that is pretty much the exact same setup im in the process of building , but in r33, i would much rather a 240.

i went a .63 rear housing on the 30/40 as i am looking for responce in the long run

[The Dan]

thats awesome that is pretty much the exact same setup im in the process of building , but in r33, i would much rather a 240.

i went a .63 rear housing on the 30/40 as i am looking for responce in the long run

Just remember that with a 0.63 rear, you will choke it in the top end. I I wouldn't expect it to make power past 7000rpm and it will cap out at about 300rwkw

[PaulosECR33]

Just remember that with a 0.63 rear, you will choke it in the top end. I I wouldn't expect it to make power past 7000rpm and it will cap out at about 300rwkw

thanks for the advice the reason i went for the .63 was that i am leaving the limiter as is and am aiming for 280 - 300 rwkw with supporting mods and a good tune.

From the reseach i have done the .63 will give good response while the motor is unopened, any advice would be great.

i can still change the order as it is going through my work the other options i have is .82 and 1.06 which obviously the 1.06 is way to big.

[simpletool]

My experience with the 3076 is that it's doughy as all shit and with a 0.82 rear, no where near coming on full at 4000.

Not sure what stock internals has to do with making power either? Aside from obvious things like lighter piston. But there is nothing special a forged piston is going to do to spool up a turbo really

As in stock internal won't allow anymore power to be produced than a 3076 can provide > 300rwkw. Forged internal don't make more power, but they allow it to be made. Dyno graphs in the thread show plenty of GT3076 at fullboost before 4000rpm.

[Harey]

My experience with the 3076 is that it's doughy as all shit and with a 0.82 rear, no where near coming on full at 4000.

Just remember that with a 0.63 rear, you will choke it in the top end. I I wouldn't expect it to make power past 7000rpm and it will cap out at about 300rwkw

So what turbo do you recommend on a stock RB25? You seem to have just disagreed with all of them.

[The Dan]

As in stock internal won't allow anymore power to be produced than a 3076 can provide > 300rwkw. Forged internal don't make more power, but they allow it to be made. Dyno graphs in the thread show plenty of GT3076 at fullboost before 4000rpm.

Won't allow any more power to be produced?

The only difference between your stock engine making 300rwkw and your stock engine making 450rwkw is how good your tuner is.

[The Dan]

So what turbo do you recommend on a stock RB25? You seem to have just disagreed with all of them.

I haven't disagreed with any of the turbos mentioned. GT3082 (or GT3040 if you buy from GCG) is a good sized turbo for ppl wanting to make 300-350rwkw without too much fuss. I was only mentioning the capping out thing with the 0.63 rear so he was aware that it will do this. There is nothing wrong with that turbo on a stock 25 though.

The 3076 in external gate form is not too bad but in order to get it to 300rwkw you MUST choose the 0.82 rear. If you aren't going to rev your stock engine over 7500 (which is a good idea to keep it alive longer) then the 3082 with the 0.63 is a perfect match. You cap it down in power a little but you make up for it in better response.

Other turbos to choose would be GT2871 if you want to make around 250rwkw or the GT3071 for approx 270-280rwkw

Other brands of choice would be something like a TD06 20G 8cm which has pretty good response for that engine.

It also depends on what you want out of the car, response and power with a bit of a tradeoff or response and power with a lot of tradeoff on power or better power with a tradeoff in response.

[Adriano]

If it was my car, i wouldnt bother building the motor, just run it with the gear you have and see what you like and dont like.

Daniel, what can you attribute the extra 50hp from the ecu change?

[Harey]

If it was my car, i wouldnt bother building the motor, just run it with the gear you have and see what you like and dont like.

I agree, get it running as is. Heaps of stock RB25s making big power. Keep the money if you do have troubles one day and then build it if it breaks.

Awesome project BTW!

[discopotato03]

Now lets see , a hotted up RB25 in an early 70's 240Z . Before you go gangbusters have a think about what a 240Z Datsun is and its steering/suspension/braking limitations . Actually I strongly suggest you speak to Stewart Wilkins because he has had a long term interest in those cars mainly from a rallying perspective . I have seen many big dollar tear down to bare metal 240/260Z builds there and I wouldn't think there would be much he couldn't tell you about these old cars .

They start out with a very long structurally unsupported nose but a least they had rack and pinion steering unlike many cars of the era . They do have problems with bump steer and Stewart has had many custom parts made to fix most of the front end woes in Zeds .

ek think hes even had custom hubs made to take 5 x 114.3 stud pattern wheels , and CV/pod joint style rear axle shafts to replace the archaic uni and ball/splined std ones . They can do the conversion work with custom bits to fit GTR Skyline brakes too .

I'm pretty sure they told me that Zeds really need a good welded in roll cage to get a reasonably stiff shell becase std and at nearly 40 yrs old they move around like a cock in a sock .

I have seen pics of aluminium radiators and suitable intercoolers in the nose of a Zed but you don't have as much room as you would have in an R32 or 33 .

You obviously have a project in mind but in a way its a shame not to se a well built L28 under the lid of a real Zed and the triple 45s always created the essential growl in a hot 240/260 .

Cheers A .

Edited August 26, 2010 by discopotato03

[The Dan]

I'm pretty sure they told me that Zeds really need a good welded in roll cage to get a reasonably stiff shell becase std and at nearly 40 yrs old they move around like a cock in a sock .

For some that's not a whole lot of movement