5th Gear Rpm

[R TUNE]

I have a R32 GTST auto and will be changing it to manual soon,

At this point in time the over drive is at 3000rpm at 100km/h, i am wondering when i change to manual what the rpm will be at 80-110km as this is the avg speed i do driving around. i would prefer it to be around 2500rpm for 100km/h.

any one know of any aftermarket 5th gears that are in diffrent ratios or will i have to get a custom one made.

I have the stock diff too.

[SimonR32]

5th gear is around 3000rpm at 100km/hr for a manual with 4.3 gears

not 100% if the autos also have 4.3's but if they do you would be best off sourcing a 4.11 diff for lower rpm high speed cruising

[jiffo]

Mate at 2500 and 100kph, an Rb20 is simply dreadful.

Had this scenario in my Rb20/R31.

Hopeless economy and not happy until it's pulling 3000 but then you're way too fast.

Stick with the 4.3 or if you absolutely must 4.1

Nissan got it right.

[DarkRyda]

My RB25DE sits at about 2800RPM's @ 100 km/h 5th gear freeway cruising = ]

Edited August 2, 2010 by DarkRyda

[blind_elk]

Why do you think you need to be running that low in the rev range?

Nissan will have set the tune of the engine to be optimised with the gearing of the car. Changing the diff ratios will upset that balance.

[DarkRyda]

maybe he wants to save petrol

[bubba]

3.9:1 diff gears took my 5th gear @ 100kph down to about 2500rpm but that's with the RB30 (and a 25t gearbox, I think the ratios are a bit different) .. I agree that an RB20 at 2500rpm in 5th would be pretty gay.

[Spurdo]

yea the rb30 would still pick up good from 2500rpm, the old saying "no replacement for displacement" is mostly true.

if your simply after better economy on the highway then personally i dont think it'll happen, if you gear it down to 2500 or so then you'll find you have to spend more time on the gas to overtake (or you may even have to chop it down to 4th, also a good way to use more gas) and even at normal cruising, the rb20 wont maintain 100kph as easily, meaning the throttle needs to open further to maintain 100kph, injector duty cycles go up and fuel economy goes out the window. same reasons why you shouldnt use 5th gear at 50km/h. i'm sure you've tried that. it's shit.

like jiffo stated above, Nissan got it right. there are good reasons why most engines 2000cc and below do ~3000rpm at 100km in 5th gear, it provides optimal fuel economy and optimal driveability. the general rule of thumb for factory vehicles is the bigger the engine, the lower its rpm at any given speed, simply because it can (i blame physics).

and yea, factory diff ratio for auto r32 (2wd) is 4.3. factory manual diff 4.1

Edited August 5, 2010 by jonboy

[bubba]

and yea, factory diff ratio for auto r32 (2wd) is 4.3. factory manual diff 4.1

Factory manual 32gtst is 4.36:1, 32GTR is 4.11:1.

[Spurdo]

Factory manual 32gtst is 4.36:1, 32GTR is 4.11:1.

ahh yes. my bad. tits on a bull