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Re: Gearbox
[Re: bojke]
#1589943
07/12/2016 22:43
07/12/2016 22:43
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Joined: Oct 2010
Posts: 549 Bulgaria
Ferrarist
Enjoying the ride
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Enjoying the ride
Joined: Oct 2010
Posts: 549
Bulgaria
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Alfa 156 2.5 diff is 3.9.....20VT is 3.1......for me the better option is Lancia Kappa 20VT GBox - 3.45....and it's direct fit.....
20VT - Alfa 156 2.0 - Alfa 156 Mid-Engined RWD - Locost 20VT
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Re: Gearbox
[Re: bojke]
#1589972
08/12/2016 10:11
08/12/2016 10:11
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Julien
Unregistered
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Julien
Unregistered
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Hi guys.What do you think about gearbox with shorter gear ratios like one from Alfa 156 2.5?I just bought Quaife diff and i have dilemma if i should install it in Alfas gearbox with little shorter gear ratios then original 6 speed Coupe gearbox.Honestly i do not need top speed i just want to make my car accelerate even better.My turbo is GTX3076 and its laggy as you all know,so maybe shorter gear ratios will help a little bit. I don't think that shorter gears will make you faster if lag is your problem : big turbos usually need heavy loads to spin : the longer the load is, the faster the turbo will spin. If you are just looking to have a better match between speed and rpm (for example going 4500rpm at 50mph instead of 3500rpm) then a shorter ratio will help with getting the jump faster. On a long run, the acceleration will still remain the same
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Re: Gearbox
[Re: bojke]
#1589983
08/12/2016 11:50
08/12/2016 11:50
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Joined: Feb 2006
Posts: 5,390 Essex
Trappy
Forum is my life
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Forum is my life
Joined: Feb 2006
Posts: 5,390
Essex
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bojke, can you post up your dyno graph? I've got these ratios for the 156 V6 spd 3.937 3.500 2.235 1.520 1.156 0.971 0.816 Using your dyno plot, I'll show you a power to speed graph across all gears and calculate the performance before and after As I always say though, simply fitting shorter gear ratios won't improve acceleration. You'd have to tailor every single ratio to suite the power curve to get any real benefit from it.
F****** b****** thing...
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Re: Gearbox
[Re: bojke]
#1589984
08/12/2016 12:08
08/12/2016 12:08
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Joined: Oct 2008
Posts: 192 Serbia
bojke
OP
On a journey
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OP
On a journey
Joined: Oct 2008
Posts: 192
Serbia
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I do not have dyno plot unfortunatelly because i am currently abroad. My plan was to increase a little rpms in lower speeds where the car is mostly used. I love to cruise on low rpm,but in real life i use the car around a city mostly. I just do not need 200 mph top speed.
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Re: Gearbox
[Re: bojke]
#1589998
08/12/2016 16:13
08/12/2016 16:13
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Joined: Oct 2010
Posts: 549 Bulgaria
Ferrarist
Enjoying the ride
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Enjoying the ride
Joined: Oct 2010
Posts: 549
Bulgaria
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Yes but Kappa is 5 speed gearbox? Yes.....is your 20VT using 5 or 6 speed GB??? You can fit 6speed GB but with few mod's......
20VT - Alfa 156 2.0 - Alfa 156 Mid-Engined RWD - Locost 20VT
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Re: Gearbox
[Re: Nigel]
#1590337
14/12/2016 14:36
14/12/2016 14:36
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Joined: Feb 2006
Posts: 5,390 Essex
Trappy
Forum is my life
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Forum is my life
Joined: Feb 2006
Posts: 5,390
Essex
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Trappy - it would be interesting to see the effect on the stats of changing the gear ratios on my car (as you know, we've played around with my stats so that they are now VERY close to proven dragstrip figures) I’ve already run the calculator over your car with 5spd, 6spd and Alfa 2.5 V6 gear ratios and, lo and behold, it’s makes next to no difference to acceleration. I’ve been saying this on here for years but it falls on deaf ears (much like the grip vs tyre width thing). All that matters is the power available due to gearing at the particular speed. A better way of explaining the reasons for this might be to show a graph of (bhp@wheels-drag/tonne) against speed. I’ll send the spreadsheet over to you to have a look yourself and see what I mean. Gearing can be used to make this curve as smooth as possible and remove the dips between changes, but shorter gearing overall just shifts this effect around. All this torque multiplying effect is irrelevant. If gearing could give you the perfect smooth curve (cars like a remapped Audi TTRS do this – have a look) then you have maximised the acceleration.
F****** b****** thing...
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