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Rip - Rb25

MissJuz

By MissJuz,
in Victoria

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Roy Grand Master

Roy

Posted
Posted
Currently running a r32 na diff ratio 4.3 i think. Is that the uber torquey one from na nissans?

Even with the RB25 in there i would have been seriously considering dropping the diff ratio, now that you are going to have Ben's Special Sauce under the bonnet, i would 100% be dropping the diff ratio. Mind you it may just mean you now take corners in 3rd rather then 2nd depending onb how the turbo and engine combo responds. But would still think a diff change is warranted (Remember i said "think" :D )

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Roy Grand Master

Roy

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There isn't a massive difference between a 4.3 and a 4.11 - I'd be leaving it where it is given the big snail on the side.

In road speed to rpm there may not be a massive difference.

But the diff multiplies torque. So considering he was borderline with the std RB25 then its only going to be worse with the higher torque figure of the engine. The only benefit may be that the new motor has a nicer torque curve (expected) so doesnt have the big torque hit that the chassis/suspensio/tyres has to cope with. But the diff still multiplies torque and will only make traction more difficult.

I would be backing off the diff ratio personally. Will certainly help on corner exits where you will be able to grab more throttle and ride the torque and get out of the corners, which helps corner speed and boost on corner exit. 9 times out of 10 you will go through a corner quicker if you carry more throttle in say 3rd then you would in 2nd at higher revs having to be more delicate with the throttle application. 9 times out of 10 :D

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Adz Experienced

Adz

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Posted

Yeah good thinking man.

The 25 box countered the 4.3 diff but now with the torque increase it might be time to go a bit taller. I will see what the power delivery is like. All i know is that when I grab 5th with the 25 box the car feels like its standing still. 5th feels really long but now that we cut the rear bar off its at least 30% beter in 5th.

Ill see how it feels with the new motor.

Also we have now offically gone to RE55 265/35/18 all round.

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Al Grand Master

Al

Posted
Posted
In road speed to rpm there may not be a massive difference.

But the diff multiplies torque. So considering he was borderline with the std RB25 then its only going to be worse with the higher torque figure of the engine. The only benefit may be that the new motor has a nicer torque curve (expected) so doesnt have the big torque hit that the chassis/suspensio/tyres has to cope with. But the diff still multiplies torque and will only make traction more difficult.

I would be backing off the diff ratio personally. Will certainly help on corner exits where you will be able to grab more throttle and ride the torque and get out of the corners, which helps corner speed and boost on corner exit. 9 times out of 10 you will go through a corner quicker if you carry more throttle in say 3rd then you would in 2nd at higher revs having to be more delicate with the throttle application. 9 times out of 10 :(

Wise words there Brisby; couldn't agree more :)

I have attached a comparison between my 25 and 30 set-up. The 30 has a bigger turbo (530hp compared to 380hp) so on the same engine, bottom end torque would be less; but look at the attached graph and note how much torque is gained at 90km/h, in 4th gear.

post-1811-1213164788_thumb.jpg

Double the 25 set-up! and this is in run in tune.

But i have to admit this is VERY tractable and does not tend to kick the arse end out unexpectedly/violently (in a straight line anyway). Keep the foot 3/4 buried and the wheels start squealing at about 5000rpm, in second gear; But you have better, wider tyres.

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Roy Grand Master

Roy

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Posted
Yeah good thinking man.

The 25 box countered the 4.3 diff but now with the torque increase it might be time to go a bit taller. I will see what the power delivery is like. All i know is that when I grab 5th with the 25 box the car feels like its standing still. 5th feels really long but now that we cut the rear bar off its at least 30% beter in 5th.

Ill see how it feels with the new motor.

Also we have now offically gone to RE55 265/35/18 all round.

LOL, this is so cool. I know Period Pain (Will go back to being Big Red when it stops locking brakes, throwing PS Belts, shearing oil pumps ie head aches etc etc) has been in the build a long time. But it is great to see a whole lot of quick development going into the car and things actually happening and changing.

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R31Nismoid Grand Master

R31Nismoid

Posted
Posted

How about tell your friend to ring? Or wait for an update...

Anyhow - i have a 4.3 i believe too, its not too bad but i wouldnt mind a 3.7 or something to keep me in the power longer and even for road duties

Im doing silly RPM @ 100... 3000 or something :wub:

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