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34Gtr Diffs In A 33Gtr?.

rockabilly
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rockabilly Rising Star

rockabilly

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one for the ratio guru,s.lol i am contemplating fitting r34gtr diffs in my 33gtr. anyone done it. i have done the maths and keeping the 33 box and std ratio,s it gears it almost identical to the hks 6 speed box, 1-4 speeds at 8k are vertually the same. one the hks 5th is .83 and 6th is .79 i think so no real difference to me..

i did the maths of the two boxes.

hks 6 speed in a 33gtr with 4.11 @ 8000rpm

1st 55mph

2nd 87mph

3rd 120mph

4th 149mph

now 34 diffs in a 33 with std 33 box @ 8000rpm

1st 54mph

2nd 96mph

3rd 134mph

4th 174mph

i run and rb26/30 with 660 lbs of torque @ 5500

done lots of searches but everyone puts a getrag in a 33 or 33 diffs in a 34...

the main reason behind this is to lower revs on the motorway, most trackdays i go to are 300 miles plus round trip.

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R31Nismoid Grand Master

R31Nismoid

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By lowering the revs, and stretching the ratios you will hurt acceleration. Obviously gear change point also affected, how much hard to say.

I can get over 600km+ to a tank on the freeway with 370rwkw, so i cannot see how you'd need to change diff gearing for economy.

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zebra Grand Master

zebra

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Isnt the 34 diff ratio 3.6:1?

Also iirc the GTS-4 has a longer 5th gear than the others (due to its 4.3:1 diffs), could throw the GTS-4 5th gear in your gtr box and keep the 4.11:1 diffs

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rockabilly Rising Star

rockabilly

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i be interested to know if 5th is taller on the gts-4 .. anyone confirm this?.

r31 nismoid..600km wow.

i get 220 miles from a full tank on a motorway journey thats sitting at 90mph with the odd burst to 150 lol

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R31Nismoid Grand Master

R31Nismoid

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i be interested to know if 5th is taller on the gts-4 .. anyone confirm this?.

r31 nismoid..600km wow.

i get 220 miles from a full tank on a motorway journey thats sitting at 90mph with the odd burst to 150 lol

Just drive off boost mate?

I went to Syd & back few months back - 900km or so one way.

Sitting on 120km/h the entire way too, just not jumping onto boost and light accel.

I reckon i could get 700 if i really tried as i got to around 640 and pulled into the servo as i was close to the light coming on for sure.

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zebra Grand Master

zebra

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i be interested to know if 5th is taller on the gts-4 .. anyone confirm this?.

r31 nismoid..600km wow.

i get 220 miles from a full tank on a motorway journey thats sitting at 90mph with the odd burst to 150 lol

There is your problem lol

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rockabilly Rising Star

rockabilly

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lol. fair piont, trouble is with that damn gt4094r its nearly always on boost.lol light throttle at 3000rpm and above an you have a bar of boost, and i mean light, slightest hill ..lol

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KiwiRS4T Grand Master

KiwiRS4T

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I plan to do this on my Stagea. have a 3.545:1 front diff - they are very common as people buy RB26s to put in their GTTs or s14s etc etc and so throw out the front diff and weld up the sump but the rears are not so common. As you say a lot of GTRs swap their 3.545 for the 4.1 but all the examples in my area have been of V-spec ones with the active diff rather than the straight mechanical one. Perhaps you should try to get a drive of an R34 to see if you like the effect first in situations other than on the motorway.

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GTRNUR Grand Master

GTRNUR

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There is your problem lol

I agree.

I've been messing around with my economy tuning a lot lately, and basically fuel consumption increases exponentially with speed. My light load cruse injector pulse with is about 2.2ms at 60km/h, 2.6-2.7 @ 80-90km/h and around 3ms at 100km/h. I managed about 8.3lt/100km on the last long drive including some exuberant driving. I have tried setting up the ecu map for a higher speed cruse at 120ish but fuel economy goes down hill quickly. From memory 120km/h was about 3.4ms.

Also, engine response under track driving conditions suffers because you end up with a lean spot in the middle of your map at the new higher cruise RPM.

I think that to get away with your idea of taller diff gears, you will need to lower or widen your engines torque range. So more mild cams or vcam, and possibly higher compression (not what you want to hear after a rebuild). If your cam timing could be optimised to make peak torque much lower in the rev range, the engine will also be able to be tuned leaner for the lower RPM.

Just another thought too keeping in mind one of your previous posts, but R34 diff gears would take you in the wrong direction with regard to keeping up with the evo's while accelerating out of the corners.

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rockabilly Rising Star

rockabilly

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cheers guys thanks for the input, ref bringing power on earlier, we have the motor apart at the moment for checking, going spend some time dailing the cams in spot on and have also got my rear housing back after being modified, car wont be on the road for a few months yet but i will report back when it is with the findings..lol

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SkylineSky Rising Star

SkylineSky

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i be interested to know if 5th is taller on the gts-4 .. anyone confirm this?.

r31 nismoid..600km wow.

i get 220 miles from a full tank on a motorway journey thats sitting at 90mph with the odd burst to 150 lol

you want to have power and economy as well.... leave it in the shed..

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rockabilly Rising Star

rockabilly

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cheers guys, i think one of the main issues is the link g4 takes a tps reading for the map, we are going to use the map sensor option and try that.it would make sense, when i exit it a corner on track i will floor it, this then gives 100duty to the ecu and injectors, whereas using a map sensor input to the ecu as the boost builds so does fuelling..thoughts guys?....

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zebra Grand Master

zebra

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cheers guys, i think one of the main issues is the link g4 takes a tps reading for the map, we are going to use the map sensor option and try that.it would make sense, when i exit it a corner on track i will floor it, this then gives 100duty to the ecu and injectors, whereas using a map sensor input to the ecu as the boost builds so does fuelling..thoughts guys?....

I thought it was supposed to be via MAP, unless you are still running teh ITBs where it should then be via TPS with MAP correction.

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