Discussion
Whats the average top speed for a mini? (talk about loose question!)
I know this is diff dependant, and possibility of 5 speed boxs....
just a comparative list of diff ratios vs rpm in 4th and or any infomation of JackKnight 5 speed ratios is welcome.
This might sound really bad but diff ratios is the one area about cars i have never looked at or had anyone explain. I just seem to have missed that.
Oh and power wise 100bhp and 100ft/lb 1380cc ,webber 45dcoe.
Any thoughts knowledge is kindly recieved.
Gwiz
I suppose i really want to know what the maximum velocity of a standard mini running a tuned A-series engine is.....
I know this is diff dependant, and possibility of 5 speed boxs....
just a comparative list of diff ratios vs rpm in 4th and or any infomation of JackKnight 5 speed ratios is welcome.
This might sound really bad but diff ratios is the one area about cars i have never looked at or had anyone explain. I just seem to have missed that.
Oh and power wise 100bhp and 100ft/lb 1380cc ,webber 45dcoe.
Any thoughts knowledge is kindly recieved.
Gwiz
I suppose i really want to know what the maximum velocity of a standard mini running a tuned A-series engine is.....
i use this one as its pretty good - saves all hte head scratching with a pencil and paper!
http://www.guess-works.com/Gearbox/Technical/ratio...
http://www.guess-works.com/Gearbox/Technical/ratio...
baller11 said:
1293, 82bhp, 4.11 diff, 13" sportspack wheels, hiff44, a ton came at 5200rpm. I reckon i got 110 out of it, but never really pushed for more
if your running a 4.1 diff....13 inch wheels (assume 175 tyres)
assume a 4 speed box
assume 1.1 drops
100 = 7000rpm!
5200 = about 74 miles per hour
you must think you have the wrong diff ratio?????
I do like this calculation because it so accurate. It makes you realise how 'out' mini speedometers are.
My final drive is a 3.444
However I've modified the final drive ratio by changing the drop gears ratio to 0.958
(primary 24 teeth, idler 30 teeth and input 23 teeth).
You multiply the 3.444 X 0.958 and that gives you a new Final Drive of 3.299.
You then need to know how many revolutions a wheel and tyre combo will do in a mile. (see below for table)
For me its 165/60/12 will do 1047.27 revolutions in 1 mile.
Take your final drive 3.299 multiply that by 1047.27 = 3454.94
60000 divided by 3454.94 = 17.36mph per 1000rpm
You can then plot the Final Drive speed table for my car:
17.36mph x2 (2000rpm) = 34.72mph
17.36mph x3 (3000rpm) = 52.08mph
17.36mph x4 (4000rpm) = 69.44mph
17.36mph x5 (5000rpm) = 86.8mph
17.36mph x6 (6000rpm) = 104.16mph Beyond this your ears start bleeding
Here are some other Wheel/tyre combinations with their respective revolutions per mile to help you work out your own speed table.
145/70/10 1176.78
165/70/10 1078.47
145/70/12 1059.06
155/70/12 1030.71
165/60/12 1047.27
175/50/13 1058.82
In answer to gingerwizards original question and sticking with a "4" speed box (although 4th doesn't actually exist) A mini (a theoretical example excluding all other factors) running a ridiculous 2.760 final drive on 155/70/12 wheels & tyres would give 21.09mph per 1000rpm.
21.09mph x 2000rpm = 42.18mph
21.09mph x 3000rpm = 63.27mph
21.09mph x 4000rpm = 84.36mph
21.09mph x 5000rpm = 105.45mph
21.09mph x 6000rpm = 126.54mph
21.09mph x 7000rpm = 147.63mph
Fresh underwear please at those speeds in a mini!
My final drive is a 3.444
However I've modified the final drive ratio by changing the drop gears ratio to 0.958
(primary 24 teeth, idler 30 teeth and input 23 teeth).
You multiply the 3.444 X 0.958 and that gives you a new Final Drive of 3.299.
You then need to know how many revolutions a wheel and tyre combo will do in a mile. (see below for table)
For me its 165/60/12 will do 1047.27 revolutions in 1 mile.
Take your final drive 3.299 multiply that by 1047.27 = 3454.94
60000 divided by 3454.94 = 17.36mph per 1000rpm
You can then plot the Final Drive speed table for my car:
17.36mph x2 (2000rpm) = 34.72mph
17.36mph x3 (3000rpm) = 52.08mph
17.36mph x4 (4000rpm) = 69.44mph
17.36mph x5 (5000rpm) = 86.8mph
17.36mph x6 (6000rpm) = 104.16mph Beyond this your ears start bleeding
Here are some other Wheel/tyre combinations with their respective revolutions per mile to help you work out your own speed table.
145/70/10 1176.78
165/70/10 1078.47
145/70/12 1059.06
155/70/12 1030.71
165/60/12 1047.27
175/50/13 1058.82
In answer to gingerwizards original question and sticking with a "4" speed box (although 4th doesn't actually exist) A mini (a theoretical example excluding all other factors) running a ridiculous 2.760 final drive on 155/70/12 wheels & tyres would give 21.09mph per 1000rpm.
21.09mph x 2000rpm = 42.18mph
21.09mph x 3000rpm = 63.27mph
21.09mph x 4000rpm = 84.36mph
21.09mph x 5000rpm = 105.45mph
21.09mph x 6000rpm = 126.54mph
21.09mph x 7000rpm = 147.63mph
Fresh underwear please at those speeds in a mini!Is gingerwizard a copper trying to suss out if any mini owners have been speeding, if so 70mph is strictly the fastest a mini will do on an appropriate motorway.
Your max speed obviously depends on what the engine will rev to, that in turn be limited by the power the engine has to overcome the wind resistance. A bog standard 1275 with 3.1fd with only enough power to pull to 5500 in top is topping out under 100mph.
Many many years ago I used to have a highly tuned 998 that rev'd like mad but had a really tall final drive, 2.7 possibly. Its max speed was 90mph in 3rd but in 4th it just wouldn't go any faster.
I reckon 120mph is achievable from a decent tuned motor of approaching 100bhp, on a 3.1fd pulling to 6500rpm. A race motor might achieve a similar maximum speed but maybe at 8000rpm with lower gearing and greater acceleration to boot. Getting more speed than that from a flying brick is limited by the greater power needed to overcome the wind resistance, for the mathematicians isnt there something about the inverse square law that says you have to double the power to get a small increase in speed?
Your max speed obviously depends on what the engine will rev to, that in turn be limited by the power the engine has to overcome the wind resistance. A bog standard 1275 with 3.1fd with only enough power to pull to 5500 in top is topping out under 100mph.
Many many years ago I used to have a highly tuned 998 that rev'd like mad but had a really tall final drive, 2.7 possibly. Its max speed was 90mph in 3rd but in 4th it just wouldn't go any faster.
I reckon 120mph is achievable from a decent tuned motor of approaching 100bhp, on a 3.1fd pulling to 6500rpm. A race motor might achieve a similar maximum speed but maybe at 8000rpm with lower gearing and greater acceleration to boot. Getting more speed than that from a flying brick is limited by the greater power needed to overcome the wind resistance, for the mathematicians isnt there something about the inverse square law that says you have to double the power to get a small increase in speed?
You are right. wind resistance grows exponential with speed increase.
In reality something around 100mph is the max. But a mini at that speed becomes realy unsafe. The whole suspension/drivtrain meets its edge. And anywhere except a racetrack it becom far too hasardous.
By the way, we all did our speed-tests on racetracks
.
In reality something around 100mph is the max. But a mini at that speed becomes realy unsafe. The whole suspension/drivtrain meets its edge. And anywhere except a racetrack it becom far too hasardous.
By the way, we all did our speed-tests on racetracks
.Edited by camelotr on Thursday 8th July 13:16
I took my 1330 up to 6.5k when leaving Vmax at Bruntingthorpe a couple of months ago. Using the calculator that equate to 108mph.
Mechanical sympathy meant that I let off to about 5.5k - It had reached 6.5k after about 1 mile of the runway and there was still over half a mile to go before the timing beams.
Went through the beams at 93mph.
Doubt it would go much faster with a taller diff - last time it was on a rolling road max hp was at 6,300rpm.
The Clubman front end, webasto roof and wheels sticking out past the arches don't exactly make it streamlined either...
Mechanical sympathy meant that I let off to about 5.5k - It had reached 6.5k after about 1 mile of the runway and there was still over half a mile to go before the timing beams.
Went through the beams at 93mph.
Doubt it would go much faster with a taller diff - last time it was on a rolling road max hp was at 6,300rpm.
The Clubman front end, webasto roof and wheels sticking out past the arches don't exactly make it streamlined either...
Edited by JimexPL on Thursday 8th July 14:37
A huge Thank you all for your input, some very very good answers above.
I was just really trying to gauge what rpms would be turning at 70-85mph. I've been looking at various diff/wheel diameter combinations to try and decide if i am going to fork out £1500 on a Jacknight 5 speed or not.
Without writing a huge post, all my questions have been answered. One of my old minis had a 3.44 diff 4 speed 1293cc engine and would pull cleanly up to 100mph on the flat. But as everyone mentioned its bloody dangerous/scary i went "through" the mass vibration about 90mph and then it all went very quiet apart from the engine as i approached the magical ton....
Does anyone have any direct expirence with the jacknight 5 speed box? I was speaking to Bill Richards about a month ago and he said 5-speeds are weak as are all A series Boxes, but that depends on the application and the manner in which they are used. We left the conversation there as we where talking about cylinder heads and i had many questions.......
oh and i am not a copper.......
2nd person this week to ask that!
cheers all, really very helpful stuff,
Gwiz
I was just really trying to gauge what rpms would be turning at 70-85mph. I've been looking at various diff/wheel diameter combinations to try and decide if i am going to fork out £1500 on a Jacknight 5 speed or not.
Without writing a huge post, all my questions have been answered. One of my old minis had a 3.44 diff 4 speed 1293cc engine and would pull cleanly up to 100mph on the flat. But as everyone mentioned its bloody dangerous/scary i went "through" the mass vibration about 90mph and then it all went very quiet apart from the engine as i approached the magical ton....
Does anyone have any direct expirence with the jacknight 5 speed box? I was speaking to Bill Richards about a month ago and he said 5-speeds are weak as are all A series Boxes, but that depends on the application and the manner in which they are used. We left the conversation there as we where talking about cylinder heads and i had many questions.......
oh and i am not a copper.......
2nd person this week to ask that!
cheers all, really very helpful stuff,
Gwiz
GingerWizard said:
Does anyone have any direct expirence with the jacknight 5 speed box?
i cant comment on the jk boxes (bar jk are very very diffcult to get spares / new stuff from and their gearboxes tend to use odd sixed (read hard to find and expensive) bearings),but i know of a mini spares five speed that did 80000miles under a 1380 used as an every day car.
after 80 thou the engine was pulled to refresh the rings, at the same time the box was stripped and needed only a few bulk rings and bearings - none of the five speed parts needed any attention - obviously this was driven with some care as its rare for a normal 4 speed to attain those sort of milages - but just shows that it can be done.
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