bj928
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| posted on 28/6/07 at 04:38 PM |
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i'm stuck on what ratio, need advice please
Right, some if not all of you will know me as the nutter with the viper engine, well, i need to order the crown wheel and pinion and i'm stuck
as to what ratio to order, its a ford mustang irs 8.8 in the back so the ratios are
2.45
2.73 the one i was after but been adviced against but i would still like it if its ok.
3.08
3.27
3.55
3.73
4.10
tyres on the back will be 295/30 18, or 17 if it makes a difference, but would like 18"
weight of car 900kg ish
t56 gear ratios
2.66
1.78
1.30
1
.74
.50
max rpm = 6000
engine is dodge viper 8.3 v10, 550hp ish, 575Ib/ft ish ( been remapped so don't know exact yet but about this )
the t56 isn't the best gearbox for fast gearchanging, so thats why i like the idea of the 2.73, gives 61mph in 1st and 160+ in 4th, leaving the
5th and 6th as just cruising gears, it may pull 5th i don't know
the question is, will the 2.73 be to tall even with all the power, don't want to bog down in first, whats the chances of it pulling in 5th at
all.
over to the experts
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JoelP
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| posted on 28/6/07 at 04:44 PM |
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if first gets you to 60 at 6000rpm, then even idling is giong to be 6 or 8 mph, which might be annoying in slow queues. Id aim for lower gearing and
then just set off in second if you wanna avoid a slow change, but each to his own. 
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Volvorsport
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| posted on 28/6/07 at 04:49 PM |
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have you driven a std viper ?
that would give an indictation of what you might require .
youll spin the wheels whatever with bugger all weight over the back
www.dbsmotorsport.co.uk
getting dirty under a bus
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bj928
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| posted on 28/6/07 at 04:58 PM |
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a viper is geared for 49mph in 1st and weighs in at about 1600kg, so i guess at only 900kg ish 61mph in first would be an ok gear, of doesn't it
work like that!!!!
if i get stuck in traffic i'll just have to pump the clutch a bit.
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matt_claydon
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| posted on 28/6/07 at 05:00 PM |
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Agree with Joel, go for a fairly normal 1st and pull away in 2nd if you don't want to change. Two cruising gears seems excessive - if you
don't think it'll pull in 5th then it certainly won't in 6th!
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smart51
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| posted on 28/6/07 at 05:12 PM |
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quote:
Originally posted by JoelP
if first gets you to 60 at 6000rpm, then even idling is giong to be 6 or 8 mph, which might be annoying in slow queues.
The Viper idles (and pulls strongly, even in 6th) at 500 RPM. 60 MPH at 6000 RPM (will the viper do 6000?) is 3 MPH at idle. Plenty.
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britishtrident
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| posted on 28/6/07 at 05:12 PM |
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Not going to make any difference what ratios you use --- all academic as on road tyres you will get so much wheel spin in the lower gears it will be
uncontrollable.
Sometimes less is more.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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ERP
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| posted on 28/6/07 at 05:56 PM |
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A Standard Viper won't hit 60 in first.
And general concensus used to be that you should change in the 5200 rpm (or less) range, because power starts to tail off above that point (although
it's not exactly wimpy even there). Most of what makes a viper though isn't 0-60 time it's 30 to 100+, flooring a viper in 2nd gear
at 2000 rpm is really a very impressive experience.
Bear in mind a viper has wheels that are 13 inches wide on the back, and you'll still spin the wheels through multiple gears if you don't
take care with the throttle.
They also pretty much define throttle on oversteer, I don'y know anyone with a viper who hasn't spun it on standard roads by touching the
throttle too early going around a bend.
I sold my Viper 4 or 5 years ago, so I don't know what the current gen ones are like.
[Edited on 28/6/07 by ERP]
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matt_claydon
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| posted on 28/6/07 at 06:00 PM |
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quote:
Originally posted by smart51
The Viper idles at 500 RPM. 60 MPH at 6000 RPM is 3 MPH at idle. Plenty.
Sorry to be picky, and it's pretty academic anyway, but surely 60mph at 6000 is 5mph at 500 ! 
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mark chandler
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| posted on 28/6/07 at 06:13 PM |
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With that much power you may be better off working the other way, something like 1500rpm in 6th trundles along at 70.
The point about speed at idle is very valid, nothing worse than constantly playing with the clutch at very slow speeds, I would treat it as 5 speed
with crawler gear !
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bj928
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| posted on 28/6/07 at 07:13 PM |
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quote:
Funnily enough two of us had a startlingly similar conversation about the viper engined car that was on display @ Newark show recently, that while you
can never have enough power on the one hand, there are times when you will start encounter issues getting such amounts of power to the tarmac.
that was my car @ newark that i'm building, i was the big guy with lots of hair,
done some more ratio testing on an online gear ratio program thing, and the viper is said to top out at 195ish, to get there with the ratios and tyres
it is running it has to do the last 20mph in 6th as 5th tops out at 176mph, that means it runs out of puff at about 4500 rpm in top, god that thing
must have some torque to pull a .5 gear at those speeds.
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big_wasa
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| posted on 28/6/07 at 08:38 PM |
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Yep looked at that  High-light of my day that.
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Blakey_boy
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| posted on 28/6/07 at 09:01 PM |
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Just a pointer but is the T56 box able to take that amount of power?.
I would have advocated using a TKO600 BUT, I could be wrong.
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bj928
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| posted on 28/6/07 at 09:12 PM |
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quote:
Originally posted by Blakey_boy
Just a pointer but is the T56 box able to take that amount of power?.
I would have advocated using a TKO600 BUT, I could be wrong.
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bj928
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| posted on 28/6/07 at 09:12 PM |
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quote:
Originally posted by Blakey_boy
Just a pointer but is the T56 box able to take that amount of power?.
I would have advocated using a TKO600 BUT, I could be wrong.
i hope it will take the power, its what dodge fitted to it in the factory, and if you do a search you will find its stronger than the tko600 (as far
as im aware ), guys in america are putting 1000+hp through the factory viper t56 box and its taking it. its even got a viper logo cast on the box to
show its a genuine top spec box.
[Edited on 28/6/07 by bj928]
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ERP
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| posted on 28/6/07 at 09:28 PM |
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quote:
Originally posted by Blakey_boy
Just a pointer but is the T56 box able to take that amount of power?.
I would have advocated using a TKO600 BUT, I could be wrong.
There are a lot of different variations on the T56 with wildly varying max opowerlevels, but the one with the 0.5 6th gear is the factory Viper unit.
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