R33 Rb30 Conversion

[Sydneykid]

The bathurst GTR's had a thicker block than ur normal rb26dett, they kept cracking the normal RB26 blocks and it was only making approx 600hp.

The one and only genuine N1 block that I have looked at (and had ultrasonically tested) has thicker cylinder walls. This seems to have been accomplished by casting the water jackets smaller. The outside of the block looked the same as normal:cheers:

[Skyrine-Dave]

my compression ratio came out at 9:1, how is that going to affect me on this motor?

[Cubes]

What pistons did you use?

9:1 is nice.. The quench is setup like factory?

Zero deck height?

[Skyrine-Dave]

rb25 wiseco forgies, the batch i were larger than previous batches so my CR was high. then used a 2mm head gasket and its now 9:1

[Cubes]

I used Domed 87mm RB25 Wiseco forgy's, decked the block .020" and ended up with a CR of 8.2-8.3:1.

My calculations on paper said that I should have ended up with a static comp of 9.2:1 HOWEVER after the physical measurements & dummy assembly that was far from being true. This is why it is so important not to buy from a catalogue.

Which ones? Were they custom or out of the catalogue?

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While we are talking about Forgy's..

I've discovered I have a little piston slap while its stone cold.

I was watching a CA18DET that had forged internals on the dyno, I heard the same slight strange noise from that. I asked what the noise was and was told it is slight piston slap.

The CA18DET was one of Nisspeed's cars (Who builtup Whatsisnames and a few other tough RB's). What suprised me was that the CA18DET was slapping while it was warm. I suspect large bore clearances due to the amount of boost that was needed to make 200rwkw from the poor ol' 1.8ltr.. heheh

I suspect I have the slight slap when stone cold due to the larger bore clearances that were setup.

I said to the engine builder that I may be running hard stints around Mallala and may even run up to 24psi.

He said the Wiseco specs were to make the clearance larger if you are using the motor on the track or 24psi. So he did so...

[Skyrine-Dave]

the pistons were catalogue rb25 forgies brought thru Trev, JNR24

compared 2 sets side by side, same part numbers, mine were just larger :S

cant complain now, whats done is done. Just need to sort out alot of shitty things before i can put the motor into the car

[Cubes]

So the dummy assemble gave you the 9:1?

Not to worry... ditch the 2mm headgasket and drop a set of big cams in it..

Its best not to have a huge quench with a high static comp as its an invite for detonation.

What did the comp ratio work out to without the 2mm headgasket?

What was the deck height?

[the phantom]

Hey Joel,

Do you know what piston clearance was machined into your setup?

I've finally had my first mechanical malody on the RB30DET. I was expecting the engine to grenade but its turned out to be the turbo. The rear shaft support bearing looks like it completely disintergrated and either blew out the exhaust or fell into the oil return into the sump. With only the front bearing the whole shaft assembly wobbled itself to destruction with both wheels rubbing and grinding themselves on their respective housings...the result...great clouds of smoke remeniscent of the old formula 1 turbo days. Needless to say I quickly turned around and shut it down.

As an aside...I have previously stated that the turbo was an SB8005A. Well in taking a closer look and knowing more now than 3 years ago, it is actually an SB8006, part # 70177-14 (the engraved cover helps ! ) That means it had the 82mm GT40 series compressor wheel, not the TO4S as previously thought, mated to a GT30 60mm turbine. In consideration to the Garrett performance catalogue, this appears to be a GT30R with the larger GT35R compressor wheel, even though the core part numbers are still different. This makes me less worried about using the proper GT35R with its larger turbine in the new build.

[discopotato03]

Phantom , when does the GT35R go on ?

Thanks A .

[Cubes]

Phantom,

I'm running a 0.004" piston/bore clearance for what they state as track and or 24psi+.

General street use of under 24psi & no track they recommend a 0.003" clearance.

I figured i want to be able to push it hard up at Mallala and not worry about a piston locking the motor and throwing a rod.

The piston slap is really quiet when cold, you have to really listen and know what you are listening for otherwise it sounds a little like a slightly noisy top end. To hear it you have to lift the bonnet and put your head down near the exhaust side.

Warm up.. I generally idle it for 30secs-1min while I buckle up and put my wallet etc in the glovebox.

Then literally idle off short shifting and light throttle until water temp is up (~1-2km's) then I drive it normally for another 5-10minutes to wait for the oil temp to come up and oil pressure drop.

---

The RB25DET oil pump gives me quite a bit more oil pressure and much earlier in the rpm over the rb20det oil pump. When cold I get oil pressure up around 7kg or in the middle of the 8 and the line under it.

Once warm oil pressure sits slightly above the first mark which is around 2kg then as soon as you slight raise the rev's oil pressure is up slightly over the 4, once reving its up slightly over 6.

lol got a bit off the track there....

[Clint32]

phantom what size rear housing were you running and what was your power and boost? cheers

[the phantom]

discopotato03....unfortunately time isn't readily available and since I preffer to do all the work myself it will probably be somewhere within Q2 next year before the new engine is ready I dont want to throw a nice brand new turbo on an old engine even though its tempting.

Clint32...1.06 rear housing, ~250rwKW, 1 bar

[Cubes]

Is there any reason you are building up a new motor?

The only issue I am concerned about is the amount of kms the bores will last for with a .004" clearance. Especially being a daily driver.

Time to buy a little Micra.. lol

[the phantom]

Hey Joel,

The spec sheet I got with my Arias forgies also specifies .004", but regardless of intended use. Interestingly it also says that with "Pro-Coating" you can reduce this to .002", which is within the factory spec (upper end) of an RB26DETT. I have yet to assertain what this is but I assume its the typical oil attracting skirt coating and a ceramic crown coating. All of this can be done for a few hundered bucks in Melbourne. I guess if you can deflect as much heat as possible from the crown, and/or use piston squirters less expansion wil occur allowing a tighter clearance. It would be interesting to put a piston in an oven to 2-300 degrees and see exactly how much they expand with a micrometer, although I have no idea what the typical skirt running temperature would be. I doubt it would be much higher than this or else the oil would carbonise pretty quickly.

As for the new engine build....I want to push the envelope a bit higher...aftermarket rods/pistons/rb26 head etc. to the tune of about 600bhp. I'm hesitant to push my standard internal 75000 km RB30DET to such levels without at least a freshen up, even though it still seems ok, but I want rock solid reliability, without the threat of meltdown all the time. I'm also currently implementing something very time consuming in design and construction.....RB30DETS. Working on it seperately still allows me to drive the Skyline everyday.

[Alf]

its now 9:1

That would make the low end very drivable.

What are you doing about the cooling side of things?. Driving in peak hour traffic in brisbane on a hot summers days will surely test the cooling system esp. with your engine specs.

[Cubes]

Thats quite interesting to know Phantom.

If I were building a street RB30DET I would most certianly stretch to get the coating.

It will only extend the engine life. Piston slap is well knowen to reduce engine life.

Phantom, when the motor goes all together could you post what deck height, how much you had to deck the block, comp ratio and the rest of the specs?

Reason being is when selecting pistons I had trouble with the off the shelf range. Basically they either had a really low comp ratio but good quench or a really high comp ratio and good quench.

I tried getting some specs from Arias but wasn't very successful.

Some km life numbers of a .004" clearance if any one has any?

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Alf... Long gone are the days of Big V8's with big lumpy cams where daily driving was affected.

[Skyrine-Dave]

big 3" PWR aluminium radiator and 2x thermo fans.

With my rb20det i could turn the thermos on and keep water temp <80deg in stop start traffic.

[the phantom]

will do, Joel

[discopotato03]

I agree getting the CR right with pistons flush to the deck is not easy , with the interest in this conversion I'm surprised no ones had specials made . Nizpro has been doing these for ages so does anyone know if they do a piston that suits the std rods , block and four valve heads . Another avenue could be the OS Giken three liter pistons if they're available at a sane price , though if they suit RB26 rods the gudgeons are surely 22mm . It may be possible to run the pistons slightly proud of the block but less than the thickness of the head gasket , this will be limited I guess by the piston to valve clearence and the compression height of the pistons ie how much off the block safely to achieve it . So depending on valve lift approaching top center it may be possible to squeeze in 8.5 - 8.6 to 1 with off the shelf pistons . Joel you have mentioned the ideal squish height or thickness , I'll have to measure my 26 head but the step into the combustion chamber is huge compared to an FJ20 so may work ok ?

My cooling system will use the viscous hub WP fan , I like the idea of the constant airflow through the rad keeping a reserve of slightly cooler water in the core so that the thermostat can controll the jacket temperature . LOL I have never been totally sold on a part time cooling fan and some like me reckon the thermos don't pull enough air anyway . Just my two paseos worth .

Chow for now A .

[mark99]

Joel, the piston slap you refer to earlier in the CA 18 is more likely the top ring land of the piston touching the bore. As a general rule, piston noise when the engine is cold is as you said, the skirt making a little noise just when cold, wich should go after warm up, unless the piston to bore cleaance is massive, ie worn out... piston noise when warm will generally be the top ring land touching, wich can be made worse if the piston to bore cleaance is opened out a little (due to more rock). This can occur when the top ring land is not machined small enough comparative to the skirt size. Its very interesting to look at different piston manufacturers differing designs in this area. there is a general rule of thumb amount smaller this area should be, .008" - .009" per inch of bore. If the top ring land is not this amount smaller, it will become too big as the piston crown begins to heat up and contact the bore, this produces no noise when cold and then begins to make noise as the engine warms up.... if the engine is pulled down slight scuff marks will be seen on the top ring land.Ill bet the pistons in the CA 18 were wiseco, they tend to run fairly large top ring land diameters, ie small difference in skirt to ring land size. So if the clearance was opened up a little on set up, it could put it right on the border of touching... Hope all that makes sense and is of some help...