I know its a kind of funny gearbox, some like it, some dont. Just looking for more info.
Whats the max speed at the limiter in each gear?? (what is the limiter of the vvc in the S2??)
Also, what kind of revs does it drop to when you change up?
Thanks folks
Neil
S2 111S gearbox??
use the gearboxman, gear calculator thats on his site its very good and yet simple to use
i quite liked the mgtf box for a road based car having a 5th between the std and c/r box but thats with approx 175 bhp
best way for track use is to have the gears drop right into your highest torque curve imo and make use off all five
the set rpm limmit has a huge effect
the wheel size also make a differance and i have read of s2 cars using s1 size wheels for track , again the calculator will show if its worth it
i quite liked the mgtf box for a road based car having a 5th between the std and c/r box but thats with approx 175 bhp
best way for track use is to have the gears drop right into your highest torque curve imo and make use off all five
the set rpm limmit has a huge effect
the wheel size also make a differance and i have read of s2 cars using s1 size wheels for track , again the calculator will show if its worth it
bob
Light travels faster than sound. This is why some people appear bright until you hear them speak
Light travels faster than sound. This is why some people appear bright until you hear them speak
Code: Select all
Gear Ratio Speed @ limiter RPM Start
1 3.250 41
2 1.895 70 4198
3 1.308 101 4970
4 1.033 128 5686
5 0.848 156 5911
Final Drive 3.94
Rolling Circ 1935
Limiter 7200
Same for the S2 standard CR box:
Code: Select all
Gear Ratio Speed @ limiter RPM Start
1 2.92 41
2 1.75 69 4191
3 1.31 92 5232
4 1.03 117 5528
5 0.85 143 5746
Final Drive 4.2
Rolling Circ 1935
Limiter 7000
Robin
Last edited by robin on Sat Jan 26, 2008 10:13 pm, edited 1 time in total.
I is in your loomz nibblin ur wirez
#bemoretut
#bemoretut
neil you realy do need a r/r graph
a stock vvc wont rev to 7200
http://www.dyno-plot.co.uk/dyno/dynoplo ... -Elise.htm
ratios on above should be calculated at 6500 max bhp limmit with a shift light fitted as its loosing power afterwards ,then diff altered to suit
a stock vvc wont rev to 7200
http://www.dyno-plot.co.uk/dyno/dynoplo ... -Elise.htm
ratios on above should be calculated at 6500 max bhp limmit with a shift light fitted as its loosing power afterwards ,then diff altered to suit
bob
Light travels faster than sound. This is why some people appear bright until you hear them speak
Light travels faster than sound. This is why some people appear bright until you hear them speak
I'm pretty sure my standard vvc goes to 7200. S1 though...not S2.hiscot wrote:neil you realy do need a r/r graph
a stock vvc wont rev to 7200
http://www.dyno-plot.co.uk/dyno/dynoplo ... -Elise.htm
ratios on above should be calculated at 6500 max bhp limmit with a shift light fitted as its loosing power afterwards ,then diff altered to suit
will check tomorrow
Baggy
Silver S1 111s
The Deen
Silver S1 111s
The Deen
Why do you think it won't rev to 7,200 - every one I have ever driven will rev that far and recently we had one on the hub-mounted torque measuring rolling road and it went to 7,200 also (albeit this one was a bit fettled). There is something very wrong with that plot - I suspect the operator lifted as soon as the power had peaked.hiscot wrote:neil you realy do need a r/r graph
a stock vvc wont rev to 7200
http://www.dyno-plot.co.uk/dyno/dynoplo ... -Elise.htm
ratios on above should be calculated at 6500 max bhp limmit with a shift light fitted as its loosing power afterwards ,then diff altered to suit
Surely to get the most acceleration possible you must change up when the revs in the next gear give you more power than you're making at current engine speed in current gear. For every elise except the weezy 118BHP engine that turns out to be at the rev limiter, simply because power rises all the way to the rev limiter, or tails off only marginally in the last few 100 RPM.
The S2 111S and S2 111R gearboxes actually reinforce this brutally - change up too soon and it's like you're walking ...
Cheers,
Robin
I is in your loomz nibblin ur wirez
#bemoretut
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Robin
some more graphs one by dva and emerald r/road
http://www.dyno-plot.co.uk/dyno/dynoplo ... /index.htm
S2 vvc elises may be differant ?
the c4bp box is well suited to a 7000-7200 rpm limmit imo but as you can see here std these S1 vvc elises make max bhp approx at 6500rpm and peak bhp is the best time to change as you want max engine power dropping into maxium torque , thats why its called a shift light not rpm limmit
on a std s1 its max is approx 5800 yet my own car would rev to its ecu limmit but if its loosing power after 5800 then theres no point holding onto the gear
however mine as std may off been making power beyound 5800 thats why a r/r graph is handy
But for track use gearbox wise the 7000 rpm one is better suited as a track box on the above std graphs imo
quote from S Earland
No the VVC engine does NOT have a 7200rpm rev limit, it has a 7200 "intermittent" rev limit , as Rover dubbed it
Essentially, after ignition, the ecu will allow you to rev to 7200 in 1st , 2nd, and 3rd , ONCE in order for the journalists to get a good 0-60 time.
weather the above is right i dont know it would require data logging to see
any aftermarket ecu will allow any max rpm you like , and as we both know its not hard to get a k series fettled to give good power and produce power beyound 7200
mine is still climbing at its 7000 imposed safty limmit therefore its shift light is at 6900 with a soft cut at 7200 hard at 7400
my point is unless you know its power curve the 7200 box may be wrong
some more graphs one by dva and emerald r/road
http://www.dyno-plot.co.uk/dyno/dynoplo ... /index.htm
S2 vvc elises may be differant ?
the c4bp box is well suited to a 7000-7200 rpm limmit imo but as you can see here std these S1 vvc elises make max bhp approx at 6500rpm and peak bhp is the best time to change as you want max engine power dropping into maxium torque , thats why its called a shift light not rpm limmit
on a std s1 its max is approx 5800 yet my own car would rev to its ecu limmit but if its loosing power after 5800 then theres no point holding onto the gear
however mine as std may off been making power beyound 5800 thats why a r/r graph is handy
But for track use gearbox wise the 7000 rpm one is better suited as a track box on the above std graphs imo
quote from S Earland
No the VVC engine does NOT have a 7200rpm rev limit, it has a 7200 "intermittent" rev limit , as Rover dubbed it
Essentially, after ignition, the ecu will allow you to rev to 7200 in 1st , 2nd, and 3rd , ONCE in order for the journalists to get a good 0-60 time.
weather the above is right i dont know it would require data logging to see
any aftermarket ecu will allow any max rpm you like , and as we both know its not hard to get a k series fettled to give good power and produce power beyound 7200
mine is still climbing at its 7000 imposed safty limmit therefore its shift light is at 6900 with a soft cut at 7200 hard at 7400
my point is unless you know its power curve the 7200 box may be wrong
bob
Light travels faster than sound. This is why some people appear bright until you hear them speak
Light travels faster than sound. This is why some people appear bright until you hear them speak
I am very skeptical of the 7,200 RPM limit is for the journalists story.
Firstly the VVC ECU has no gearbox input so doesn't know what gear you are in.
Secondly, at the recent rolling road session we did several runs without switching the engine off and the recorded RPM was always 7,200.
Thirdly you only need to change gear once to get 0-60 so it only needs to allow hitting the rev limiter once.
Finally the only source for that story is Simon E. and he is often found saying the exact opposite of the rest of the world ...
BUT, one nugget of truth shines out from it - revving to the limiter gives faster acceleration on these particular engine/gearbox combos.
The peak-power to peak-torque thing has to be a red herring - power and torque are the same thing (the engine only produces torque) - power is just torque * engine speed - an engine could produce peak torque at very low RPM (long stroke engines do this) - you really wouldn't want to be shifting all the way down there (try shifting 1st to 4th
).
Power is what matters - more power for longer is better.
vvc example
This graph allows me to illustrate the point nicely.
Say you're in 2nd gear and shifting to 3rd - no matter where you change gear, assuming the S2 VVC box and no loss in vehicle speed you'll drop to 1.308/1.895 of the revs when you shift (in truth you will lose speed and so the drop will be higher, but this would only serve to make my point better, so I don't care).
If you shift at 7,200 that's taking you to 4,970.
If you shift at 6,600 that's taking you to 4,555.
At 7,200 you're making 145. At 4,970 you're making 120.
At 6,600 you're making 150. At 4,555 you're making 110.
So if two such cars are travelling at 6,600 in 2nd gear, one shifts, the other doesn't. For the next 600 RPM the one that shifted gets an average of about 115BHP while the one that didn't shift gets an average of about 147BHP.
No prizes for guessing which one will reach the end of this 600RPM band quicker.
In fact, even if both engines were making the same power, the gear differences means that the shifter would cover 433RPM while the non-shifter covers the last 600. But, seeing as how the shifter dropped to about 3/4 power he will in fact only cover 325RPM in that same time (and so he'll be about 100 revolutions of 3rd gear behind).
Now the non-shifter runs out of revs and has to shift - she drops back to 4,970. Meanwhile the early shifter is at 4,555+325 = 4,880. They're both in the same gear. The one with higher revs is going faster, is about 100 revolutions ahead on the tarmac and is going to continue to pull away from the one with lower revs.
What am I missing?
Cheers,
Robin
Firstly the VVC ECU has no gearbox input so doesn't know what gear you are in.
Secondly, at the recent rolling road session we did several runs without switching the engine off and the recorded RPM was always 7,200.
Thirdly you only need to change gear once to get 0-60 so it only needs to allow hitting the rev limiter once.
Finally the only source for that story is Simon E. and he is often found saying the exact opposite of the rest of the world ...
BUT, one nugget of truth shines out from it - revving to the limiter gives faster acceleration on these particular engine/gearbox combos.
The peak-power to peak-torque thing has to be a red herring - power and torque are the same thing (the engine only produces torque) - power is just torque * engine speed - an engine could produce peak torque at very low RPM (long stroke engines do this) - you really wouldn't want to be shifting all the way down there (try shifting 1st to 4th
).Power is what matters - more power for longer is better.
vvc example
This graph allows me to illustrate the point nicely.
Say you're in 2nd gear and shifting to 3rd - no matter where you change gear, assuming the S2 VVC box and no loss in vehicle speed you'll drop to 1.308/1.895 of the revs when you shift (in truth you will lose speed and so the drop will be higher, but this would only serve to make my point better, so I don't care
).If you shift at 7,200 that's taking you to 4,970.
If you shift at 6,600 that's taking you to 4,555.
At 7,200 you're making 145. At 4,970 you're making 120.
At 6,600 you're making 150. At 4,555 you're making 110.
So if two such cars are travelling at 6,600 in 2nd gear, one shifts, the other doesn't. For the next 600 RPM the one that shifted gets an average of about 115BHP while the one that didn't shift gets an average of about 147BHP.
No prizes for guessing which one will reach the end of this 600RPM band quicker.
In fact, even if both engines were making the same power, the gear differences means that the shifter would cover 433RPM while the non-shifter covers the last 600. But, seeing as how the shifter dropped to about 3/4 power he will in fact only cover 325RPM in that same time (and so he'll be about 100 revolutions of 3rd gear behind).
Now the non-shifter runs out of revs and has to shift - she drops back to 4,970. Meanwhile the early shifter is at 4,555+325 = 4,880. They're both in the same gear. The one with higher revs is going faster, is about 100 revolutions ahead on the tarmac and is going to continue to pull away from the one with lower revs.
What am I missing?
Cheers,
Robin
I is in your loomz nibblin ur wirez
#bemoretut
#bemoretut
robin
agreed ecu has no g box imput but can be limmited by elotronics ie hit 7200 three times it changes to 6900 but as i said data logging required its also not relevent
power is what matters only as long as its not falling
peak torque to peak power is very revelent
note on graph peak torque is produced lower than peak bhp
hence at max bhp 150 @6600 torque = 120
change gear and it goes into max torque 127
torque = acceration more you have at wheels faster you accerate
your max bhp = 145 @7200 your torque is a poor 105 so you have wasted time to get a lower bhp and torque plus when you do change your torque is still lower and falling mine is still delievering
max bhp and max torque is always a winner
now this is about matching the right box here goes
the box converts power to torque at wheels try climbing a hill in fifth then try in third note you still have the same bhp
but more torque in 3rd = faster acceration
the lower the box the more torque at the wheels and 156 mph on track is usless if he cannot pull in 5th
so we want to be in max torque at engine and also at the g box
them hondas have as much torque at wheels as the audi conversions due to right ratios
two 170 bhp engines can have two differant torque figures its all in the head tunning you can increase torque even move it around yet still have the same bhp
what your missing
is that torque and bhp are two differant forms of power
i will try to explain
if we push a heavy jcb at 10 mph (mph=rpm ) into a stone wall it bursts throu lets call the jcb torque
if we push the lighter austin metro into the wall also at 10 mph it bounces back lets call the metro bhp
if we push the metro harder to say 40 mph its inertia bursts it throu the wall
now at 40 mph the bhp is matching the torque (jcb ) for power however we can push the heavy jcb to a max 50 its gained inertia also gives it more power hence peak torque
but for the metro to gain the same power its going to require to be pushed faster ( rpm ) being lighter we can push it to 60 and now its making more power than the torque can
a vvc or 111r lacks torque power so requires more rpm to get the same or better power
a heavy car requires the stronger torque to push it along a lighter car benifits from higher rpm hence f1 cars rev to silly figures to make their power but a turbo car will give shed loads of torque but at lower rpm
a high rpm gives more inertia = power
a g box is a torque converter hence 1st ratio =
engine # x #####
2 nd = #x####
3 rd = #x###
4th = #x## ect
on a box 1-2nd will give a 3000rpm drop
2-3rd a 2500 drop
4-5 a 2000 drop as you see as the g box torque lessens the rpm power rises to componsate
a vhpd makes its power at 7800 more rpm = more power
but if limmited to say 7000 with stock pistons then we cannot raise the rpm to gain power but we can raise the wheel torque through better engine torque or better still better g box ratios
their is a cross point where rpm is making more power than torque
sorry robin i was doing a edit as you posted
but i think we will beg to differ
agreed ecu has no g box imput but can be limmited by elotronics ie hit 7200 three times it changes to 6900 but as i said data logging required its also not relevent
power is what matters only as long as its not falling
peak torque to peak power is very revelent
note on graph peak torque is produced lower than peak bhp
hence at max bhp 150 @6600 torque = 120
change gear and it goes into max torque 127
torque = acceration more you have at wheels faster you accerate
your max bhp = 145 @7200 your torque is a poor 105 so you have wasted time to get a lower bhp and torque plus when you do change your torque is still lower and falling mine is still delievering
max bhp and max torque is always a winner
now this is about matching the right box here goes
the box converts power to torque at wheels try climbing a hill in fifth then try in third note you still have the same bhp
but more torque in 3rd = faster acceration
the lower the box the more torque at the wheels and 156 mph on track is usless if he cannot pull in 5th
so we want to be in max torque at engine and also at the g box
them hondas have as much torque at wheels as the audi conversions due to right ratios
two 170 bhp engines can have two differant torque figures its all in the head tunning you can increase torque even move it around yet still have the same bhp
what your missing
is that torque and bhp are two differant forms of power
i will try to explain
if we push a heavy jcb at 10 mph (mph=rpm ) into a stone wall it bursts throu lets call the jcb torque
if we push the lighter austin metro into the wall also at 10 mph it bounces back lets call the metro bhp
if we push the metro harder to say 40 mph its inertia bursts it throu the wall
now at 40 mph the bhp is matching the torque (jcb ) for power however we can push the heavy jcb to a max 50 its gained inertia also gives it more power hence peak torque
but for the metro to gain the same power its going to require to be pushed faster ( rpm ) being lighter we can push it to 60 and now its making more power than the torque can
a vvc or 111r lacks torque power so requires more rpm to get the same or better power
a heavy car requires the stronger torque to push it along a lighter car benifits from higher rpm hence f1 cars rev to silly figures to make their power but a turbo car will give shed loads of torque but at lower rpm
a high rpm gives more inertia = power
a g box is a torque converter hence 1st ratio =
engine # x #####
2 nd = #x####
3 rd = #x###
4th = #x## ect
on a box 1-2nd will give a 3000rpm drop
2-3rd a 2500 drop
4-5 a 2000 drop as you see as the g box torque lessens the rpm power rises to componsate
a vhpd makes its power at 7800 more rpm = more power
but if limmited to say 7000 with stock pistons then we cannot raise the rpm to gain power but we can raise the wheel torque through better engine torque or better still better g box ratios
their is a cross point where rpm is making more power than torque
sorry robin i was doing a edit as you posted
but i think we will beg to differ
Last edited by hiscot on Tue Jan 29, 2008 9:52 am, edited 2 times in total.
bob
Light travels faster than sound. This is why some people appear bright until you hear them speak
Light travels faster than sound. This is why some people appear bright until you hear them speak
Torque at wheels is a long winded way of working it out, but here goes.
You claim that the the short shifter will accelerate faster because by switching at 6,600 they get back to steady 127lb.ft in 3rd while the other driver gets 120lb.ft in 2nd and falling to 105 at the limiter, so assume an average of 112 over the remaining 600RPM.
But that's at the flywheel, so you must apply all of the gear ratios to it to compute torque at the wheels (which in the torque-oriented world governs acceleration). Ignoring the things that will be the same (final drive, wheel diameter), the difference in our gearbox is 1.895 in 2nd vs. 1.308 in 3rd.
Remember that the gearbox is a torque multiplier (more torque at output shaft compare to input shaft, fewer RPM at output shaft compared to input shaft).
So the short-shifter's 127lb.ft in 3rd equates to wheel torque of 127*1.308 = 166 lbft at output shaft.
Meanwhile the other driver's 112 in 2nd equates to 112*1.895 = 212 lbft at output shaft.
All that remains to beat this to death is to convert from output shaft torque to actual acceleration (I hope you're sitting comfortably):
Apply final drive of 3.94 (another torque multiplier):
shorty 166lbft output shaft -> 654lbft at drive shaft
revver 212lbft output shaft -> 835lbft at drive shaft
Convert from lbft (yuck) to Nm (lbft to Nm = multiply by 1.356)
shorty 654lbft at drive shaft -> 887Nm at drive shaft
revver 835lbft at drive shaft -> 1,132Nm at drive shaft
Factor in actual wheel radius to convert torque at drive shaft to force at wheel contact patch - (divide by the radius of the wheel in meters = 0.317).
shorty 887Nm at drive shaft -> 2,798N at contact patch
revver 1,132Nm at drive shaft -> 3,571N at contact patch
Remember F = m.a; assuming a mass of 800kg we can compute a as F/800:
shorty 2,798N -> 3.498 m/s/s
revver 3,571N -> 4.464 m/s/s
Now if you are still not convinced I'll demonstrate that the power-oriented computation produces essentially the same result:
Shorty's average power post shift into 3rd was 115BHP.
Revver's average power for the rest of 2nd gear was 147BHP.
Converting from BHP to Watts is generally accepted to be multiply by 745.
shorty 115BHP -> 85.675 kW
revver 147BHP -> 109.515 kW
Kinetic energy = 0.5 m v^2 (half time mass times square of velocity in m/s).
At the point of shift, each car had velocity of 64mph = 28.5 m/s, assuming same 800kg mass each car has an initial kinetic energy of:
0.5 * 800 * 28.5^2 = 324.9kJ (kilo joules)
So after one second at each of the average power outputs, the additional kinetic energy would be:
shorty 85.675kW * 1s = 85.675kJ
revver 109.515W * 1s = 109.515kJ.
If you add that to the initial kinetic energy you get:
shorty: 324.9kJ + 85.675kJ = 410.575kJ.
revver: 324.9kJ + 109.515kJ = 434.415kJ.
Converting back to speed in m/s at the end of the one second burn (v = squareroot(2ke/m)):
shorty: 410.575kJ -> 32.038 m/s
revver: 434.415kJ -> 32.955 m/s
Bearing in mind the initial speed was 28.5m/s for both cars the acceleration over that one second was:
shorty: 32.038 - 28.5 = 3.538 m/s/s
revver: 32.987 - 28.5 = 4.487 m/s/s
Now what are the chances of coming up with the same answers using two different calculations (on torque based, one power based) and both of them be wrong? Pretty slim! Chances are that both methods produced the same result because both methods are correct; given that both methods give the win to the revver, I hope you will consider this reasonable proof that maximising average power is all that matters and however much torque your engine may or may not be producing is not an issue to worry about while choosing which gear to be in.
Or am I still missing something?
Cheers,
Robin
You claim that the the short shifter will accelerate faster because by switching at 6,600 they get back to steady 127lb.ft in 3rd while the other driver gets 120lb.ft in 2nd and falling to 105 at the limiter, so assume an average of 112 over the remaining 600RPM.
But that's at the flywheel, so you must apply all of the gear ratios to it to compute torque at the wheels (which in the torque-oriented world governs acceleration). Ignoring the things that will be the same (final drive, wheel diameter), the difference in our gearbox is 1.895 in 2nd vs. 1.308 in 3rd.
Remember that the gearbox is a torque multiplier (more torque at output shaft compare to input shaft, fewer RPM at output shaft compared to input shaft).
So the short-shifter's 127lb.ft in 3rd equates to wheel torque of 127*1.308 = 166 lbft at output shaft.
Meanwhile the other driver's 112 in 2nd equates to 112*1.895 = 212 lbft at output shaft.
All that remains to beat this to death is to convert from output shaft torque to actual acceleration (I hope you're sitting comfortably):
Apply final drive of 3.94 (another torque multiplier):
shorty 166lbft output shaft -> 654lbft at drive shaft
revver 212lbft output shaft -> 835lbft at drive shaft
Convert from lbft (yuck) to Nm (lbft to Nm = multiply by 1.356)
shorty 654lbft at drive shaft -> 887Nm at drive shaft
revver 835lbft at drive shaft -> 1,132Nm at drive shaft
Factor in actual wheel radius to convert torque at drive shaft to force at wheel contact patch - (divide by the radius of the wheel in meters = 0.317).
shorty 887Nm at drive shaft -> 2,798N at contact patch
revver 1,132Nm at drive shaft -> 3,571N at contact patch
Remember F = m.a; assuming a mass of 800kg we can compute a as F/800:
shorty 2,798N -> 3.498 m/s/s
revver 3,571N -> 4.464 m/s/s
Now if you are still not convinced I'll demonstrate that the power-oriented computation produces essentially the same result:
Shorty's average power post shift into 3rd was 115BHP.
Revver's average power for the rest of 2nd gear was 147BHP.
Converting from BHP to Watts is generally accepted to be multiply by 745.
shorty 115BHP -> 85.675 kW
revver 147BHP -> 109.515 kW
Kinetic energy = 0.5 m v^2 (half time mass times square of velocity in m/s).
At the point of shift, each car had velocity of 64mph = 28.5 m/s, assuming same 800kg mass each car has an initial kinetic energy of:
0.5 * 800 * 28.5^2 = 324.9kJ (kilo joules)
So after one second at each of the average power outputs, the additional kinetic energy would be:
shorty 85.675kW * 1s = 85.675kJ
revver 109.515W * 1s = 109.515kJ.
If you add that to the initial kinetic energy you get:
shorty: 324.9kJ + 85.675kJ = 410.575kJ.
revver: 324.9kJ + 109.515kJ = 434.415kJ.
Converting back to speed in m/s at the end of the one second burn (v = squareroot(2ke/m)):
shorty: 410.575kJ -> 32.038 m/s
revver: 434.415kJ -> 32.955 m/s
Bearing in mind the initial speed was 28.5m/s for both cars the acceleration over that one second was:
shorty: 32.038 - 28.5 = 3.538 m/s/s
revver: 32.987 - 28.5 = 4.487 m/s/s
They are the almost same. The reason they aren't quite the same is that the torque equation computes instantaneous acceleration while the power equation averages out over 1s but the acceleration is non-linear so an average is not entirely appropriate. If you computed it over a 0.001s period instead of a 1s period you would get closer to the right result.my own calculation from half way up the page wrote: shorty 2,798N -> 3.498 m/s/s
revver 3,571N -> 4.464 m/s/s
Now what are the chances of coming up with the same answers using two different calculations (on torque based, one power based) and both of them be wrong? Pretty slim! Chances are that both methods produced the same result because both methods are correct; given that both methods give the win to the revver, I hope you will consider this reasonable proof that maximising average power is all that matters and however much torque your engine may or may not be producing is not an issue to worry about while choosing which gear to be in.
Or am I still missing something?
Cheers,
Robin
I is in your loomz nibblin ur wirez
#bemoretut
#bemoretut