Jump to content
SAU Community

Recommended Posts

i still can't really see any point to using forged pistons in a street car. but each to their own, the extra $600 or so for the build might help you sleep at night anyway, if so it's money well spent i reckon.

we'll see how long my casties last and what power i put down with them reliably anyway, might help some people see the light :)

p.s. had my first run with a fastish car on the weekend - "200rwkw" 180sx down the gold coast. anyway murdered him through 2nd and 3rd - even with the laggiest turbo known to man. i really need a tune too.

hey!

I got casties in my rb30 too. did you change the rod bolts at all? because mine are stock also.

How much power have you made ??

Mine was tuned to 16psi only because i am too scared of breaking the engine. if i was game id run it to 22psi and roll off another hundred hp at the rear wheels at least.. but yeah im scared of the cast comming to pieces or something lol

tell me the details of your engine ?? will be interesting for my next power up :O

You want a 0 deck clearance. At top dead center the piston is flush with the top of the block.

sounds good, you have been there done that so all the info is pretty helpfull

whats a formula to work out comp ratio and what ratio were your pistons ideally, had they been in an rb25

hey!

I got casties in my rb30 too. did you change the rod bolts at all? because mine are stock also.

How much power have you made ??

Mine was tuned to 16psi only because i am too scared of breaking the engine. if i was game id run it to 22psi and roll off another hundred hp at the rear wheels at least.. but yeah im scared of the cast comming to pieces or something lol

tell me the details of your engine ?? will be interesting for my next power up ;)

No i didn't bother changing the rod bolts. Have you ever heard of rod bolts breaking on an RB30? cause i hadn't :P

i have only a vague idea of what power my engine is making as it's still running an RB25 base map for the time being. as i mentioned, it REALLY needs a tune. but i'm not going to bother yet, not until my blower is on the engine and piped up.

basically i have a built RB30DET with custom manifolds and a GT40 turbo with 1.34!!! rear housing at the moment. it was all built to run as a twincharge with an Eaton supercharger, hence why the rear housing on the turbo is so large. it's still remarkably good to drive though, even with RB25DE cams and no tune the top-end power is astounding.

Just spent over an hour reading this thread.. tired as hell. sorry if i missed it but if the RB25/30 conversion is done, can a R33 gtst power FC tune it all up or do you have to go with another type of comp?

yeh mate i run gts-t pfc with my 30det

got mine back yesterday, has a very mean "serious business" exhaust note haha.

No boost as yet until it's run in, but even so definatly has more balls than the n/a i drive daily.

Just itching to get some boost into it though. :devil:

head restrictors

does anyone have a pick of the hole i have to weld up and the the one i have to put the restirctor in

also when do i get one of these restrictors

pete

There are 2 oil feed galeries in the block that mate up to matching galleries in the head. They are between #2 & #3 and #4 & #5. Block the rear one and restrict the front one. A piece of brass rod drilled to the right size hole works well as a restrictor.

:( cheers :D

got mine back yesterday, has a very mean "serious business" exhaust note haha.

No boost as yet until it's run in, but even so definatly has more balls than the n/a i drive daily.

Just itching to get some boost into it though. :(

good to hear gav, about time! Can't wait to see it!

Easier to tap the rear for a grub screw or put a solid piece of brass in to plug the hole - than to weld it up.

head restrictors

does anyone have a pick of the hole i have to weld up and the the one i have to put the restirctor in

also when do i get one of these restrictors

pete

Just a question regarding pistons and compression ratio stuff for this conversion. Cubes I think stated a page or so ago that the compression height for a rb30 normally was 1.26". Now the CP pistons for the conversion I got have a compression height according to the spec sheet of 1.28". So my understanding is that the piston will actually sit .020" (.5mm) outside of the bore when at TDC. Is that correct?

They reckon with a 1.2mm (.048") headgasket you should get about 8.3:1, now this worked out in my calcs if the head cc's up to about 64cc. If your head cc's up about 62cc then i think i worked it out to be about 8.5:1CR. I just want to check the formula here so hopefully im working this out right.

CR = 1pot vol+head cc+deck height cc / head cc+deck height cc

So if the piston sits .020" outta the bore then I should take that away from the headgasket thickness im running or plan on running and work it out from there...eg if i used a 1.5mm gasket, minus that .020" i would use 1mm in the equation to work out the CR, even though Im using a 1.5mm gasket.

Does that sound correct? Or have I confused myself here?

I am not 100% sure what the std rb30 comp height is to achieve a zero deck clearance.

The best way to know what comp ratio you will have is to buy your pistons last. Measure everything up then select what pin height etc you require.

I checked acl website and for a set of forged pistons for rb30et they stated on their spec sheet that the compression height is 1.261"

Im assuming the forged piston is just a copy of the std one and maintains all std specs. So 1.26" is pretty close to std.

Most of the pistons mentioned in this thread have different crown design/machining. Some are dished, some raised, some have small valve relief fly cuts, some have large ones. All of these affect the compression ratio.

Compression height is useless without knowing the dome cc's.

:) cheers :P

Most of the pistons mentioned in this thread have different crown design/machining. Some are dished, some raised, some have small valve relief fly cuts, some have large ones. All of these affect the compression ratio.

Compression height is useless without knowing the dome cc's.

:D cheers :)

how do we take the dome cc's into account when measuring the compression ratio

how would using the rb25 pistons also affect them when the block is decked to suit?

The discussion is piston selection for the rb30det.

First thing we need to do is select a suitable compression height which is 1.260". THEN we worry about the dome or negative done to achieve the comp ratio we are after.

Without a dome and zero deck clearance you will be running some where around a 7:1 comp ratio. :

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Similar Content

  • Latest Posts

    • Wideband is worth setting up if only for tuning purposes. I would not mess with the ignition system unless there's a misfire. HKS crank trigger is popular out here for the relatively easily sourced Denso crank sensor, not a bad idea to install as well regardless of power level on a standalone. Boost leak test is worth thinking about. Oil pressure sensor tied to a fuel cut isn't a bad idea either. Getting the tune figured out is a good idea. Without putting eyes on it and getting under it there's no way for us to tell you exactly what it needs but most likely you're down to the last 10% that will make a big, big difference in how happy you are with the car.
    • Doing a refresh of my 33 and can see a few websites stating they sell the entire main carpet for our cars, but they all have generic photos which is fine, i understand they are custom made to order.  Just seeing if anyone has got it done or had any experience with this, as i would only want to do it if the fit and finish was as good as oem https://carmatsdirect.com.au/products/moulded-carpet-or-vinyl-for-nissan-skyline-r33-1993-1998-coupe https://knoxautocarpets.com.au/moulded-carpets/nissan/skyline/skyline-r-33-1993-1998/
    • Any plans for E85? If so, add flex fuel sensor.   I'd probably add in the sensors I mentioned above if the Link will support using them for engine protection. With water pressure, you need to be able to effectively set it that "If temp > X, and pressure = atmospheric, shutdown" as at running temp, you should be able to read pressure in the cooling system. If pressure suddenly disappears, it means the water went some where, and this is a quicker reaction than waiting on water temp to go up (Which, can take a little longer than you'd like, considering it now has to wait for hot air to heat it up) Oil pressure, Oil temp, both would be on my list too if you're looking to add sensors. Wideband O2. And at least one EGT sensor. If you're feeling deluxe, put in individual runner EGTs. Single EGT sensor is more so forget about a specific number, get used to "What is normal EGTs", and then keep an eye on it, if it starts going away from "normal" it's a sign something is wrong (Also, things like the tune can still start going out of spec, but EGTs may not show it, for example one injector starts running leaning, so ECU richens everything up, now 5 out of 6 cylinders are rich, and running cool, with one cylinder lean and running hotter, so it's not perfect) Then there is your other things to look at non sensor related, but you may have already done, or have underway, and that would be things like building a sump for more oil, and better oil control under high G-Forces (Cornering, brakes, acceleration). Basically, the above is worth looking/thinking about, if the ECU can do protective stuff with it, and you continue to use it how you are (Drive it to the track, thrash it, drive home, repeat once every 3 to 4 months)
    • Can also confirm these work a treat for most balljoints and bushes. If you have access to a big rattle gun, they make the job so much easier and quicker, compared to using a socket wrench or shifter on the c-clamp 👍
    • Its sort of street but got used for circuit sprints on account of I never drive it on the road because I dont have the time to spare. So it usage was sits around for months at a time then gets driven either 50 or 250 kms to the track followed by 20 laps followed by 50 or 250kms home followed by stuck in the shed until next time. So yeah neither fish nor fowl. Just dont want to break it on the track as a preference. Hence the fairly short sensor/mod list. Probably more worried about it pinging itself to destruction more so than anything oil related.
×
×
  • Create New...