R33 Rb30 Conversion

[Sydneykid]

yes, but its 2k for rims and tyres when a diff change will cost $500 odd...

(ontop of 10k+ spent on other mods )

I am not suggesting you change your wheels, unless you have 14" ones.

That would make the gearing shorter anyway and you want longer don't you?

If you have 16" wheels, then you most likely have 225/50/16 tyres, which give the same roilling diameter as 245/45/17's.

Cheers

[Bl4cK32]

no probs then longer gears for me.

With petrol prices the way they are and the long trips i do, the lower the rpm at 60 and 100km/h the better

[R32 TT]

I am not suggesting you change your wheels, unless you have 14" ones.

That would make the gearing shorter anyway and you want longer don't you?

If you have 16" wheels, then you most likely have 225/50/16 tyres, which give the same roilling diameter as 245/45/17's.

Cheers

Ah see now I'm glad this came up. Its been a question on my mind for a while since I see GTR's running 245/45/17's yet they came out with 225/50/16's..

correct me if I am wrong but isn't it calculated like:

225 * 50% = 112.5

112.5 x 2 = 225mm overall tyre height (top and bottom)

then add 16*25.4 = 406.4mm overall rim diameter

to reach a total of 631.4 diameter wheel.

Whereas for a 245/45/17:

245*45% = 110.25

110.25 x 2 = 220.5

plus 17*25.4 = 431.8

makes an overall diameter of 652.3mm

So it looks like the 245/45/17 is about 20mm (or nearly an inch) bigger in diameter...

Though I suppose this won't change the ratios a great deal... it will lift the height by another 10mm?

How do you get 808 revolutions per kilometre??

Isn't is more like 480ish?

[Sydneykid]

Ah see now I'm glad this came up. Its been a question on my mind for a while since I see GTR's running 245/45/17's yet they came out with 225/50/16's..

correct me if I am wrong but isn't it calculated like:

225 * 50% = 112.5

112.5 x 2 = 225mm overall tyre height (top and bottom)

then add 16*25.4 = 406.4mm overall rim diameter

to reach a total of 631.4 diameter wheel.

Whereas for a 245/45/17:

245*45% = 110.25

110.25 x 2 = 220.5

plus 17*25.4 = 431.8

makes an overall diameter of 652.3mm

So it looks like the 245/45/17 is about 20mm (or nearly an inch) bigger in diameter...

Though I suppose this won't change the ratios a great deal... it will lift the height by another 10mm?

How do you get 808 revolutions per kilometre??

Isn't is more like 480ish?

808 revs per MILE, sorry I used the US tyre tables

Your calcs are correct, the true comparison is 225/50/16 = ~245/40/17

I always use the manufacturers tables, as not all 245 tyres are actually 245 mm wide.

For example Yokohama A032R's in 235/40/17 's are 239 mm wide and 245/45/17 are 243 mm wide.

And not all 40 series tyres are 40%, I have measured 38% on a number of occasions.

For Bl4cK32............

Lower rpm does not always = lower fuel economy

You may move out of the engine's maximum efficiency zone

That means more throttle is required for the same torque output which = poorer fuel economy

cheers

[Cubes]

Driving the R32 RB30DET with its std 4.363:1 diff ratio really does feel buzzy.

If that makes sense.

Its like the car doesn't have time to use the torque of the motor to accelerate the car and really get that turbo working as you flick through the first couple of gears so quickly.

This really becomes apparent when driving a mild VLT making roughly the same power. The VLT's are roughly the same weight as an R32 so it IS a good comparison as to how the low down torque and mid range acceleration would feel.

All though the vlt could do with a slightly shorter diff ratio it really does work damn well. I wouldn't be worried with a 3.9:1 ratio in an R32 at all, if anything it will make it easier and quicker to drive at low speeds.

Currently first gear simply buzzes, its like all you want to do is get in to second gear asap as to get that turbo working so it makes some torque to accelerate the car.

The VLT I am refering to was running 225 50 16's, but damn it really did feel good, apart from the noticable lack of revyness due to the sohc head, it really felt like it didn't want to rev past 4500rpm.

My experience was the higher diff ratio (lower numerically) is much more rewarding to drive, from a performance perspective.

A car that is buzzy gets annoying and frustrating.

[Sydneykid]

Driving the R32 RB30DET with its std 4.363:1 diff ratio really does feel buzzy.

If that makes sense. Its like the car doesn't have time to use the torque of the motor to accelerate the car as you flick through the first couple of gears so quickly.

This becomes apparently when driving a mild VLT making roughly the same power.

All though the vlt could do with a slightly shorter diff ratio it really does work damn well. I wouldn't be worried with a 3.9:1 ratio in an R32 at all, if anything it will make it easier and quicker to drive at low speeds.

Now first gear simply buzzes, its like all you want to do is get in to second gear asap as to get that turbo working so it makes some torque to accelerate the car.

The VLT I am refering to was running 225 50 16's, but damn it really did feel good, apart from the noticable lack of revyness due to the sohc head, it really felt like it didn't want to rev past 4500rpm.

My experience was the higher diff ratio (lower numerically) is much more rewarding to drive, from a performance perspective.

A car that is buzzy gets annoying and frustrating.

When talking 1st, 2nd or 3rd you have to look at the gearbox ratios as well as the tyre sizes and the diff ratio. With the RB31DET (R32GTST) on the road I only use first until the wheels rotate a few times, then shift up to second. Then use second to the speed limit and drop it into 5th. Beats most cars easily using zero boost. I also go 1 --> 3 --> 5 a lot, I hardly ever use all 5 gears on the road, they have so much torque and so little weight they carry high gears easily.

My rule is, if it's buzz'n change up

cheers

[Cubes]

When talking 1st, 2nd or 3rd you have to look at the gearbox ratios as well as the tyre sizes and the diff ratio. With the RB31DET (R32GTST) on the road I only use first until the wheels rotate a few times, then shift up to second. Then use second to the speed limit and drop it into 5th. Beats most cars easily using zero boost. I also go 1 --> 3 --> 5 a lot, I hardly ever use all 5 gears on the road, they have so much torque and so little weight they carry high gears easily.

My rule is, if it's buzz'n change up

cheers

Thats how I drive.. 1st to literally just get the car moving then straight in to second.

BUT.. If I want to drive briskly... well thats when it begins feeling buzzy from a standing start.

[platinum]

well just got mine back from its first tune - it's only running 7-8ish PSI on a stock turbo, but anyway it made 154rwkw - feels very nice, and funnily it definatly feels faster than it did before, maybe those extra torques Should also mention it's an auto not a manual.

Will do another few km's on it, and wind it up to 12 PSI or thereabouts, hopefully make a bit more. Few pics of the conversion:

[Cubes]

Very nice Gav.

Care to share a dyno print out with us?

Did u take note of where (rpm) it made the 154rwkw, or more relevant.. What rpm does it feel like it requires you to shift?

[platinum]

haha knew you would want a dyno print out - i'll scan it when I get home tonight

Best place to shift seems about 5500rpm, but it's probably being a bit limited by the turbo size I'd say.

Edited May 22, 2006 by platinum

[sky30]

I do agree with joel with the diff ratio not making good use of the RB30 torque, i also felt mine could do with slightly taller ratio.

Notice how nissan put a 4.11 ratio in the GTR (RB26) and R33 RB25)which had more torque than the R32 RB20 that uses 4.36. I think nissan got the right idea.

Im keen to see how the RB30 goes in my GTS4 which has a GTR 4.11 diff in it, will be interesting to compare it to my old GTS-t with the 4.363 diff.

[SirRacer]

hey platinum do you mind posting up some pics of how you have supported the cooler piping to the block

cheers

[platinum]

hey platinum do you mind posting up some pics of how you have supported the cooler piping to the block

cheers

Supported by gravity But yeah - it doesn't really need any support, although the pipe which runs along the bottom of the radiator is supported by a series of 'tabs' welded to it and the radiator support bar.

Edited May 22, 2006 by platinum

[platinum]

Very nice Gav.

Care to share a dyno print out with us?

here 'tis

[Cubes]

For those that are interested I've made a dyno spool comparison of the mine, sky30's and Ash's.

The reason mine jumps up sharply is it basically spools up instantly at that rpm, if shaun had loaded the car up at a lower rpm ~1500rpm it would have been a slightly better indicator of how it spools in the real early rpm.

I haven't attached bl4ck32's 218rwkw run as he doesn't have a print out.

His little plain bearing MQT/Dynamic Turbochargers RB20 highflow makes 218rwkw on 16psi and it spools ever so slightly better than the vg30det turbo shown here.

I think if ash were to get an ebc on to his nice tight little actuator he may bring full spool in slightly earlier, which actually would look too bad.

Dial some more boost in and it should hold power a little better than the .82. BUT it is difficult to tell as sky30 is making a shiet load more power/airflow at that rpm so ash's power curve very well may follow sky30's rapid nose over.

I really do believe this rpm/airflow/velocity point is the limitation of the standard exhaust manifold.

Especially when you see blokes like 88sillouete or what ever his alias is running a nice exh. manifold, stock head, td06-20g and he flicks it to 7200rpm no problems.

Ash,

At 100km/h yours is making a bee's dick more power than a healthy R33 RB25DET running 13psi to make a total of 200rwkw, usual mods pfc etc.

80km/h you are down 18rwkw compared to the rb25det where as sky30 is the same..

So essentially... Sky30's RB30DET GT35r .82 will feel the same at 80km/h as an rb25det running the stock turbo at 13psi.

Impressive when you look at it like that.

60km/h... who knows, most likely they will be the same, if not the rb30det will have the upper hand as 60km/h is some where around 2000rpm.

If one was able to get the 1.06 holding power until 7000rpm I think it would be a rather drivable street car with a downlow (up to 3000-3500rpm) stock rb25det power delivery that simply becomes more and more insane as rpm's increase. I hope that makes sense if you visualise the power curve.

[Bl4cK32]

alrighty, time for me to get another dyno run done. Hold on for some new topend with new sparkies

[discopotato03]

I remember working out the overall ratios of VLT's and R32GTST's and I think the VLT set up is better for the RB30 engine . Yes the final drive is taller but the VL's intermediate ratios are shorter . The 1-2 gap in RB20 and 25 gearboxes is wider than the VL's though 2-3 and 3-4 are closer so innitially too much and then too little . I think they got the VLT right for its RB30 , it could be worth look at what the 300ZX used in the way of gearbox/diff ratios and wheel OD's .

The VLT box is probably getting hard to find and is supposed to have some minor differences with the slave cylinder mount and gear shift . I did a search on Navara VG30 boxes and they used the same ratios as the VLT (except shorter OD) so the gear set is around .

One of the wifes distant lations has a manual VLT quietly rusting away in a small central western town and I hope to get the box and bottom end when its beyond help .

Cheers A .

[gtst25]

Got to agree about the diff ratio saga. I'm a bit lazy at times and get sick of changing from 1st to second so quickly in my 250rwkw r33 gtst. Also when getting really under it it feels like it shoots through the torque band too quickly - you really don't feel the shove until second gear (just wheelspin)

Vl turbos seem so happy chugging away at just over 2000 rpm @ 100km/hr. I also don't think this is the ultimate ratio though - 3.7's or 3.9's in a vl seem perfect.

I wouldn't change the ratio until doing a rb 30 conversion though. Also changing into second @ 3000 or 4000 rpm every time you want to keep up with those torquey commodores gets a bit painfull for the syncros - I've never driven a nissan with a really ''nice'' second gear.

I use to go home and swap my r33 for my bog stock na vl 5 speed and it was a much more happier car to drive - got to love that rb30 torque.

Cheers

[discopotato03]

GTS25T there only ever was one production gearset out of Nissan I found that was on the money . That was from the Aust spec Datsun 260Z , 1st was 2.906 and second was 1.901 . It was really good to use and much easier on the baulk rings , just the thing for the old "Wonnie Bends" in the wet with the snap crackle and crash Detroit diff . The V8 Ford aircraft carriers never could catch me there .

Cheers A .

[Sydneykid]

From memory, when racing the VLT’s, they had an annoying gap in the gearbox ratios. Maybe it was 3rd to 4th where they would drop off boost on the gearchange. You couldn’t rev them hard enough in 3rd (due to the power drop off) so that they didn’t drop too low in the rpm into 4th. With the 225/60/15’s we couldn’t use 5th gear on any circuit other than Bathurst and Philip Island.

If someone has the actual VL gearbox ratios, I can overlay them on the Skylines ratios to show the differences.

cheers