R33 Rb30 Conversion

[retrotec]

This ones for the guys with 32 and 33 gtst's. What (lower) diff ratio would be more suitable considering VL rb30's 3.45 and R33's 4.11 ratios.

How could the manual speed sensor signal be corrected?, recalibrate the speedo signal/voltage?

[Sydneykid]

We use 4.3 to 1 ratio diffs. Jaycar have an electronics kit for speedo correction. We use the GTST speedo gears (they have 4.3 to 1 diff ratio) in the gearbox and the speedo drive.

[Cubes]

I went for a spin in a friends VLT and vice versa today.

I actually quite liked the power delivery, gearing and turbo matching of a VLT running a 2.5" exhaust, FMIC & 13psi.

Turbo spool differences.. High gear 1500rpm full throttle mine will make 12psi pretty quick. The VLT didn't. It required around 2000rpm on board to get boost being made. On the road I noticed the VLT started pulling hard from around 3500rpm and actually went pretty well.

Taking the VLT man for a spin first thing he said was. "It doesn't have time to 'Use' the torque" I feel he hit the nail on the head.

The stock turbo made peak torque at 2000rpm. Giving the car a little stick its always up over 3500rpm, simply because of road speed.

Power drops off after 4950rpm and really there is no point reving past as the short gears have you selecting the gear at peak power then accelerating with power dropping rather than gaining like it should.

In other words, a stock rb20, 25 or even RB30et turbo is really a bad match for the RB30DET with the Skylines gearing.

Open up the hot side as to improve top end (over 5000rpm) VE and have the 3ltr reving to 6000-7000rpm and the gearing will be a good thing. Possibly a new gen VG30DET turbo?

As I am a full time student I make the money to 'waste' on the car during holidays. I may pick up a cheapy Vg30DET turbo, throw it on and see how it goes until I get the big mofo turbo on.

It was nice to be in a car that you can actually wind out the gears a little. Something I haven't felt for a long time.

The RB30DET with the stock turbo's on it really does feel like Diesel Powahhhh. lol

Very much like my parents 2003 Nissan Patrol 3.0TDI.

They have since traded it in for a Landcruiser V8 auto, which suprisingly goes damn hard. Very punchy off the line.

[StockyMcStock]

i still can't beleive you even bothered to get the 30DET tuned at all with an RB20 turbo, but i guess you just wanted it running ASAP which is understandable. as a comparison, a friend of mine had an RB30DET and he was using a TO4E with a big front wheel (can't remember exact specs) but get this: the rear used a 1.33 a/r. the turbo was off a big HP rotor, but the 30DET spooled it to 20psi by 4000rpm. boy did that thing have some stink in it.

in short, you can run quite a large turbo off these buggers and still get decent spool time. of course, being 3 litres, high compression and twin cam, you probably won't even notice that it's off-boost most of the time.....

in a few weeks i'll throw up some pics of my engine in this thread, you guys might be interested to see just how far i am going to reduce lag

[RB30-POWER]

3.7:1 are great with these motors.

Stacks of torque, any diff gearing lower then that (higher numerically) is really a waste, unless you can spin it to 8k.

3.7:1 allow 100km/h at around 6k or so in second gear on my brothers R31 with the 25/30DET.

Although i think the 3.45:1 in my 30ET VL are preety good as well, the 3.7:1 give a slight advantage down low, without sacrificing the top speed available from each gear.

Gearbox ratio's may be a little different in the R32/R33 so you would have to take that into consideration as well.

[Cubes]

From memory gearbox ratios are fairly close between the rb30/25/20 box's.

I've always toyed with the idea of a 3.7 or 3.9:1 diff ratio.

What diff ratio do the GTR's run? 3.9? It rings a bell for some reason.

[TTT]

CUBES - Have you considered getting a second hand cheap turbo from a Rotary of some sort?

I'm pretty sure they have rather large exhaust wheels even on the stock cars.

I'm sure it won't be a direct bolt on but they are fairly cheap and might work out a better option than the VG30 way..

just a thought.. not sure if it's a good one though... hehehe

[Cubes]

The VG30DET turbo is capable of 200rwkw.

Are the rotary turbo compressors capable of flowing this much air?

I had a mate with a 13B T in a little RX3 many years ago. 200rwkw was made with a highflowed turbo.

The exhaust side may be capable but is the compressor side?

[TTT]

not sure..

I'm sure a quick search through AUSrotary forum would find the answers.

like I said..

it was just a thought.

[discopotato03]

Joel I think you'll find the VLT had the wide ratio ( ute pack !) gearbox option meaning shorter gearing 1-2-3 . Actually , got a copy of the Holden 3.0ET (Vol 6) manual that states MX7 ratios are 3.580 , 2.077 , 1.360 , 1.000 , 0.760 .

When used with the 38/11 (3.454) final drive the overall ratios are 12.367 , 7.175 , 4.698 , 3.454 , 2.625 . From memory the R32 GTST Manual uses a 4.36 final drive and the gearbox a 3.321 1st gear ratio making for 14.479 overall , 2nd 8.288 , 3rd 5.703 , 4th 4.36 , 5th 3.309 .

My master plan was to have the VLT's 1st gear ratio (overall) but with the closer ratio gearbox . So divide 12.367 by 3.321 which gives 3.724 as my ideal final drive ratio . I've yet to dabble in the later type short nose R200 differentials and have not heard of any with taller ratios than 4.0xx . The later Nissans were using larger diameter rims ie 16+ whereas the earlier types ie R30/31 , S12 , 280Z , Z31 were on 14's and 15's . I'm sure a look at tyre rolling diametres and available differentials should get me in the ball park for an R32 . I'll probably need to look into up a ratio (4.1 ?) and up a tyre profile to 60 series . The only GTST I see on a regular basis wears either 225/55's or 205/55's on the std 6.5x16 rims , can you tell me what is standard .

Cheers A .

[TTT]

r32 standard is 205/55/16x6.5 rims

r33 standard is 225/50/16x6.5 rims

r32 gtr is 225/50/16x8 rims

Z32 300zx is 225/50/16x7.5 rims

I think the R33 GTR wears 245/45/17x9 rims (I think)

[Fitzpatrick Speed Works]

GTR standard diff ratio is 4.11

GTS4 came with a 4.3.

I think you will find the rolling diameters on all these cars to very similar as the older cars have a taler sidewall on the tyre to compensate for a smaller rim. Tyres only come in a few select overall rolling diameter usually 570mm, 600mm, and 620mm... these are the common passenger car rolling diameter for example a 215/65/14 is the same rolling diameter as a 265/35/18. SO i dont think tyre size plays any key roll in the discussion of final drive ratios especially if people are just using a common tyre.

On another note a friend just finished a VL turbo I had some things to do with. The build was forged internal with a standard 25det head, custom plenum with 90mm throttle body, gt35/40 turbo with a .92 rear a/r all powered by a mcrotech. The car spools to 15psi ie run it by 3600RPM and made 476rwhp on only 14.5psi. With a 3.45 diff ratio and standard VL gear box the car is an animal all the way up to and including 3rd gear. I was very impressed with the power output considering the low boost and also the fact the head is untouched. I will try to find a dyno print out in the next week.

[Sydneykid]

Just saw the engine dyno sheet for one of our RB30DET's (RB30 + RB26) with GT35R at 1.3 bar made a nice 632 bhp.:headspin:

[retrotec]

3.7:1 are great with these motors.

3.7:1 allow 100km/h at around 6k or so in second gear on my brothers R31 with the 25/30DET.

Although i think the 3.45:1 in my 30ET VL are preety good as well

What kind of revs in 5th are we looking at on highways, 110, 120,130, and 140 ks etc.. ? (rb25det box, r32 16" rims n tyres)

[Cubes]

7000rpm in first in the R32 is around 50-55km/h..

Imagine changing up at 5500rpm. lol.

[StockyMcStock]

On another note a friend just finished a VL turbo I had some things to do with. The build was forged internal with a standard 25det head, custom plenum with 90mm throttle body, gt35/40 turbo with a .92 rear a/r all powered by a mcrotech. The car spools to 15psi ie run it by 3600RPM and made 476rwhp on only 14.5psi.

exactly the same boost level as what i'm going to be running, but i'll be using a larger turbo. amazing power out of the 35/40 at just 15psi, i didn't know they could push such numbers at so little boost!

[discopotato03]

The point I'm trying to make is I probably can't get a 3.7 to 1 ratio short nose differential to suit an R32 GTST so a 4.1 with a larger diametre tyre may go close .

About that .92ARR housing , is that a propper GT35 housing ?

Cheers A .

[retrotec]

The point I'm trying to make is I probably can't get a 3.7 to 1 ratio short nose differential to suit an R32 GTST so a 4.1 with a larger diametre tyre may go close .  

About that  .92ARR housing , is that a propper GT35 housing ?

Cheers A .

What about a 3.7 crown wheel for the 32 diff?

[discopotato03]

I'm not sure if such a thing exists . Does anyone know if the V8 Nissans used an R200 differential ?

Cheers A .

[Cubes]

How about the VG30DET Cima's, Leopards?