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Thread: 4.7 vs 5.1 FD in a SE-R tranny

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Posts: 1-10 of 44
2015-02-05 12:47:49
#1
4.7 vs 5.1 FD in a SE-R tranny
Changing from a 16ve tranny to an aftermarket FD on a regular SE-R tranny. However I'm undecided over the 4.7 or 5.1 FD.

The 4.7 will be very close to a 16ve at the end of the day, so I'm not sure if it justifies the cost. Here is the % difference compared to a 16ve ratios for each of the 5 gears:

99.1%
100.7%
102.6%
107.8%
107.8%

The 5.1 will be very different but I worry about the 1st gear and if these will be too short at the end of the day.

107.0% (aka 7% shorter 1st gear ratio)
108.8%
110.8%
116.5%
116.5%

Thoughts?
2015-02-05 13:43:59
#2
i suppose it depends what you doing with it. i have a 32v with 4.7fd, and just overlapped a 32a with 5.1, and theres not much in it. 2nd and 3rd are a bit shorter in the 32a/5.1

would not want to travel far in 5th but.
2015-02-05 13:47:10
#3
Originally Posted by sss4me
i suppose it depends what you doing with it. i have a 32v with 4.7fd, and just overlapped a 32a with 5.1, and theres not much in it. 2nd and 3rd are a bit shorter in the 32a/5.1

would not want to travel far in 5th but.


What do you mean by "overlapped"?

The car is just to have some fun on the streets and occasional 1/4 mile racing at the strip (without full slicks - it's still a street legal car)
2015-02-05 13:52:02
#4
Originally Posted by Doctor
Originally Posted by sss4me
i suppose it depends what you doing with it. i have a 32v with 4.7fd, and just overlapped a 32a with 5.1, and theres not much in it. 2nd and 3rd are a bit shorter in the 32a/5.1

would not want to travel far in 5th but.


What do you mean by "overlapped"?

The car is just to have some fun on the streets and occasional 1/4 mile racing at the strip (without full slicks - it's still a street legal car)


MFactory® Competition Products - Gear Calculator
2015-02-05 18:46:04
#5
Originally Posted by sss4me
Originally Posted by Doctor
Originally Posted by sss4me
i suppose it depends what you doing with it. i have a 32v with 4.7fd, and just overlapped a 32a with 5.1, and theres not much in it. 2nd and 3rd are a bit shorter in the 32a/5.1

would not want to travel far in 5th but.


What do you mean by "overlapped"?

The car is just to have some fun on the streets and occasional 1/4 mile racing at the strip (without full slicks - it's still a street legal car)


MFactory® Competition Products - Gear Calculator



Uhm yeah I know what the theoretical speeds are. Still doesn't explain what you meant by overlapped?

I'm interested in real world experiences of the 5.1 FD. Does it make the gears too short to be practical on the street...?
2015-02-05 19:12:18
#6
I think he means he "compared with the gear calculator" when he said overlapped
2015-02-05 19:55:20
#7
^^^^ thanks.

I didn't mean to come across agitated. It's late here...

Mfactory what's your thoughts on the 5.1Fd with the 32a ratios? Streetable? Will the 4.7 even be noticeable compared to the 16ve? The comparison to 16ve is in my original post up top....
2015-02-05 20:40:58
#8
Originally Posted by Doctor
Originally Posted by sss4me
Originally Posted by Doctor
Originally Posted by sss4me
i suppose it depends what you doing with it. i have a 32v with 4.7fd, and just overlapped a 32a with 5.1, and theres not much in it. 2nd and 3rd are a bit shorter in the 32a/5.1

would not want to travel far in 5th but.


What do you mean by "overlapped"?

The car is just to have some fun on the streets and occasional 1/4 mile racing at the strip (without full slicks - it's still a street legal car)


MFactory® Competition Products - Gear Calculator



Uhm yeah I know what the theoretical speeds are. Still doesn't explain what you meant by overlapped?

I'm interested in real world experiences of the 5.1 FD. Does it make the gears too short to be practical on the street...?


i had mine in just an average sr20de, and i reckon it was super fun. just running in my ve now with it.click the photo.

[URL=""][/URL]

another aussie put a 4.83par in a sr20ve.32a box



oh, and theres a lot of americans running 4.8's on their 32v's
Last edited by sss4me on 2015-02-07 at 03-07-39.
2015-02-05 23:14:41
#9
5.1FD is great for a street or circuit car, as long as you dont do many highway miles. 70mph Will be like 4000rpm. 1st gear will be very short, making it perhaps not so good for drag racing.

I have the 5.1FD, and I had similar concerns to you. I decided the 4.7 might not be worth the effort and cost (coming from a 4.4) but was cautious that the 5.1 may be too short for a daily road car. So I ended up fitting the 5.1FD along with taller 24.9" tyres to offset things and essentially make the gears a bit longer.

Months later, Ive since decided that the 24.9" tyre is too tall and I will be better off with a 24" tyre with the 5.1fd.

I say go for the 5.1FD, its great.
2015-02-06 09:12:27
#10
Thanks. I also feel like for the cost, I want a bigger difference than the 2.6% in 3rd gear with the 4.7. Downside is off course the useless 1st gear. I'm running 215/45/17 bridgestone RE11S's up front so I guess that's fairly tall.

The N1 box has near perfect ratios it seems. Long 1st and 2nd and then almost the same 3,4, as the 5.1 option and a longer 5th.
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