Final Drive Gear - 3.5 vs 3.9
#41
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Originally Posted by sentry65
you'd have to change the individual transmission gears non-proportinally to actually create a rpm change from gear to gear compared to the stock tranny gearing. The final drive only multiplies everything one final time as a whole
the change in gap you're talking about doesn't change when you change the final drive. the only thing that changes is the accelleration, theoretical top speed in each gear, and the frequency you will shift during a given distance
the change in gap you're talking about doesn't change when you change the final drive. the only thing that changes is the accelleration, theoretical top speed in each gear, and the frequency you will shift during a given distance
I think you misunderstood my point.
#43
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Originally Posted by mario60185
who cares about thes technical mumbo jumbo? It makes the z faster...period. Only time i would think twice is if i was going to go turbo with big horsepower.
#47
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Originally Posted by sentry65
it definetly helps your top end accelleration. You really feel the difference in 6th gear when cruising on the highway. It's no longer a lazy gear
Overall I think the 3.9 gears are one of the best bang for the buck mods out there for the 350Z. I really could care less about 1/4 mile times. I got the gears for overall performance. I have had mine for a year now and love them.
#48
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Originally Posted by Dave B
Has anyone actually proven this with a timeslip though? The acceleration through each gear is quicker, but there is more shifting going on and/or the gearing may cause the engine to run through the powerband too quickly in 1st and 2nd.
#49
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Originally Posted by mario60185
Let me rephrase......its faster through turns, so maybe not for a dragstrip.
#51
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Originally Posted by Dave B
Has anyone actually proven this with a timeslip though? The acceleration through each gear is quicker, but there is more shifting going on and/or the gearing may cause the engine to run through the powerband too quickly in 1st and 2nd. If adding gears was the answer, then why stop at a 3.9? Why not a 5.0? It is very possible to overgear a car. With the VQ35s fat and wide powerband, it's not remotely as dependant on gearing as something like a 3.0 VTEC V6.
I think its mostly designed for road-racing and auto-xing, for more responsive power bands and such.
#52
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I suppose that matters if you only drive your car at the drag strip or if you have a magazine journalist reviewing your car's 0-60
otherwise everything else is faster. If you're going to drive up to 165 mph, you have to shift 5 times no matter what. Your rpms are still going to be higher in each gear which puts you higher in the torque/hp band in addition to the 10.6% gearing multiplication punch
otherwise everything else is faster. If you're going to drive up to 165 mph, you have to shift 5 times no matter what. Your rpms are still going to be higher in each gear which puts you higher in the torque/hp band in addition to the 10.6% gearing multiplication punch
#53
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Originally Posted by Nismo 350z
The 3.9FD will help acceleration through all the gears. It doenst matter if u are on a drag strip or on a track.
unless you have this mod and have tested it why do u think your so smart? people have shown there 1/4 times werent any faster, thats what were discussing genius.
#54
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Originally Posted by Mathys
There is no cheaper option for a 3.9 FD than going for the Nismo 3.917 for +-1300$?
http://z1auto.com/prodmore.asp?model...ne&prodid=1726
16 sets coming end of the month, still have a few sets left
#55
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Originally Posted by Z1 Performance
Sure there is:
http://z1auto.com/prodmore.asp?model...ne&prodid=1726
16 sets coming end of the month, still have a few sets left
http://z1auto.com/prodmore.asp?model...ne&prodid=1726
16 sets coming end of the month, still have a few sets left
Just ordered the 3.91 gears, great price. Thx for the info
#56
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Final Gear RPM formula: FYI
Tire diameter will also have an effect on a vehicle's final drive ratio. As tire diameter changes, so will engine rpm at a given speed. This can be demonstrated this with the simplified formula: rpm = (mph x final gear ratio x 336*) / tire diameter (*the constants of time, pi and distance have been simplified and replaced with 336). For example, given 65 mph, a tire diameter of 30 inches, and a final gear ratio of 4.10, the engine speed will be approximately 2,984 rpm--(65 mph x 4.10 final gear ratio x 336) / 30-inch diameter tire. If we reduce the tire diameter to 25 inches, the engine speed increases to 3,581 rpm. By installing shorter tires, the vehicle will accelerate as though it has a 4.73 (higher numerically) gear without the expense of gear swapping.
Tire diameter will also have an effect on a vehicle's final drive ratio. As tire diameter changes, so will engine rpm at a given speed. This can be demonstrated this with the simplified formula: rpm = (mph x final gear ratio x 336*) / tire diameter (*the constants of time, pi and distance have been simplified and replaced with 336). For example, given 65 mph, a tire diameter of 30 inches, and a final gear ratio of 4.10, the engine speed will be approximately 2,984 rpm--(65 mph x 4.10 final gear ratio x 336) / 30-inch diameter tire. If we reduce the tire diameter to 25 inches, the engine speed increases to 3,581 rpm. By installing shorter tires, the vehicle will accelerate as though it has a 4.73 (higher numerically) gear without the expense of gear swapping.
#57
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Originally Posted by quint1
Final Gear RPM formula: FYI
Tire diameter will also have an effect on a vehicle's final drive ratio. As tire diameter changes, so will engine rpm at a given speed. This can be demonstrated this with the simplified formula: rpm = (mph x final gear ratio x 336*) / tire diameter (*the constants of time, pi and distance have been simplified and replaced with 336). For example, given 65 mph, a tire diameter of 30 inches, and a final gear ratio of 4.10, the engine speed will be approximately 2,984 rpm--(65 mph x 4.10 final gear ratio x 336) / 30-inch diameter tire. If we reduce the tire diameter to 25 inches, the engine speed increases to 3,581 rpm. By installing shorter tires, the vehicle will accelerate as though it has a 4.73 (higher numerically) gear without the expense of gear swapping.
Tire diameter will also have an effect on a vehicle's final drive ratio. As tire diameter changes, so will engine rpm at a given speed. This can be demonstrated this with the simplified formula: rpm = (mph x final gear ratio x 336*) / tire diameter (*the constants of time, pi and distance have been simplified and replaced with 336). For example, given 65 mph, a tire diameter of 30 inches, and a final gear ratio of 4.10, the engine speed will be approximately 2,984 rpm--(65 mph x 4.10 final gear ratio x 336) / 30-inch diameter tire. If we reduce the tire diameter to 25 inches, the engine speed increases to 3,581 rpm. By installing shorter tires, the vehicle will accelerate as though it has a 4.73 (higher numerically) gear without the expense of gear swapping.
Tire size: 245/40/17 (stock Z)
65mph*3.53 rear end ratio*336 / 24.7 tire diam (17") = 3121 RPM
Tire size: 275/35/20 (mod Z)
65 mph*3.53 rear end ratio*336 / 27.6 tire diam (20") = 2793 RPM
Tire size: 245/40/17 (stock Z tires)
65 mph*3.91 rear end ratio*336 / 24.7 tire diam (17") = 3457 RPM
Tire size: 275/35/20 (mod Z)
65 mph*3.91 rear end ratio*336 / 27.6 tire diam (20") = 3094 RPM
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