"Slightly off topic, but if all you do is lower the FD of a standard ratio box you've gained nothing much other than worse fuel economy on the motorway. The RPM distance between gears is what makes an impact on acceleration, albeit relatively small. The only time this isn't true is when you exactly hit the rev limiter when it's time to brake - in that sole case you'll have fully utilized the power band."
Robin I beg to differ on this one it does not matter what power the engine makes only what the tyres see and this is where the gearbox comes in
the gearbox is a trade off for either top speed ( relaxed cruising ) or acceleration now if we start on a hill in first gear it will get us up it due to the torque it produces try again in fifth less torque hence no movement note the engine is still making the same power, engine wise nothing at all has changed but gear wise the lower first has added more toque than 5th gear .
Try a std s1 box that I could describe as a four speed with overdrive as the std s1 will not pull in 5th but will cruise and give good relaxed mpg but fit a lower diff note same gear ratios so same engine rpm loss/ change point , top gear speed is now reduced but acceleration is improved , you will be doing 70 mph at more rpm( hence top speed reduced ) than the std box but you will see 70mph a bit quicker lets not forget the engine rpm loss between gears has not changed but the lower diff has traded top speed cruise for acceleration via toque but as all the gears fitted are now lower ( note not closer or wider ) . Therefore we have added torque across the full range of the box !
If we add gear ratios to all this by optimising the ratios to suit the engine torque band we can maximise the torque the engine produces where it counts At the wheels
But what may be classed as a c/r box on one car , fit it to another with different wheel sizes ( effects diff ratio ) and extended rpm ( widens the gear ratio ) it no longer becomes a close ratio or a low box hence the need for the ucr box on the vhpd
It all a trade off by how many gears you have , what the car is used for , and for track use sometimes its better to hang onto a gear or use slightly wider ratios ( if changing up just before a corner for instance ) but get the box right and its far cheaper to make the most of what the engine has than trying to make more from the engine
summary
a gear box is only a torque converter, a diff will lower or higher the top speed , gear ratios multiply the torque thats going in , and we trade torque for speed hence the need for more than 1 gear
gearbox options
gearbox options
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
Re: gearbox options
First off, there is no difference between doing the sums in terms of energy/power or doing the sums in terms of torque. You'll get the same acceleration in both cases with any gearbox, any ratios. So wherever the difference between the boxes lies it is not a torque vs. power discussion. I'm sure I've demonstrated this before - feel free to search to find it - if you cannot, I'll be happy to show why it's true.
Let's take an example to show why shortening the final drive isn't a guaranteed win:
If you shorten the final drive such that 2nd can do 55, 3rd 84 and 4th 110 compared to the longer FD with the same ratios where 2nd can do 62, 3rd 96 and 4th 125.
Let's start at 55mph and accelerate to 95mph (a pretty common pattern for an 1.8K on track - it never seems to get that much faster than that
).
The short FD box will start at the very bottom of 3rd at 4,500RPM. It'll climb speed/RPM all the way to 84mph, then drop RPM to 5350 and continue on to 6,045RPM when it hits 95mph.
The long FD box will start at the top of 2nd at 6,200RPM. Then it'll drop to 4,500RPM at 65mph and then climb speed/RPM all the way to the nearly the red line when it hits 95mph
Are you sure the short FD box is going to beat the long one? I'm not.
Cheers,
Robin
Let's take an example to show why shortening the final drive isn't a guaranteed win:
If you shorten the final drive such that 2nd can do 55, 3rd 84 and 4th 110 compared to the longer FD with the same ratios where 2nd can do 62, 3rd 96 and 4th 125.
Let's start at 55mph and accelerate to 95mph (a pretty common pattern for an 1.8K on track - it never seems to get that much faster than that
).The short FD box will start at the very bottom of 3rd at 4,500RPM. It'll climb speed/RPM all the way to 84mph, then drop RPM to 5350 and continue on to 6,045RPM when it hits 95mph.
The long FD box will start at the top of 2nd at 6,200RPM. Then it'll drop to 4,500RPM at 65mph and then climb speed/RPM all the way to the nearly the red line when it hits 95mph
Are you sure the short FD box is going to beat the long one? I'm not.
Cheers,
Robin
I is in your loomz nibblin ur wirez
#bemoretut
#bemoretut
Re: gearbox options
Robin, the engine produces torque this we can measure , power is calculated from torque x rpm
but in any car all that matters is what the tyres see !
my point is the gearbox is here to get the most from what the engine produces , it does this by producing torque at the tyres
the lower the gear the more torque the box can produce ( ie torque converter ) we know we accelerate quicker in the lower gears yet the engine has not changed therefore torque = acceleration however we trade torque for speed hence acceleration
down but speed up
now we decide what we want the car to do for motorway we dont require acceleration or any performance therefore if we gear the car to do 180 mph and cruise at 70 the engine is not producing the torque its capable off and we now have good mpg
on the other hand we now want a sports car that can make the most that the engine can produce therefore we want the engine to produce its best it can , as you pointed out it makes its best at a higher rpm.
we now gear the box to produce the best it can from what is going in ( from the engine ) this means for acceleration we need the best torque at the tyres and this is done via a lower ratio
hence if we are never going to do 180 mph then we can drop the diff to gain torque over speed
now if we add gears we also add torque, we can because we can now close the ratios ( same diff ) hence moving the change point further up where the engine is producing more torque / power ( your example )
Therefore a 5 speed box is going to be better if geared right than a 4 speed + overdrive
However your example is also right there are times when its better to use the best the engine can input into the box as the final result is by putting more in you can still get more at the tyre and thats the problem with gears you choose what you want and calculate the most suitable for its intended use
on a 0-100 sprint the lower box will win
but in any car all that matters is what the tyres see !
my point is the gearbox is here to get the most from what the engine produces , it does this by producing torque at the tyres
the lower the gear the more torque the box can produce ( ie torque converter ) we know we accelerate quicker in the lower gears yet the engine has not changed therefore torque = acceleration however we trade torque for speed hence acceleration
down but speed up
now we decide what we want the car to do for motorway we dont require acceleration or any performance therefore if we gear the car to do 180 mph and cruise at 70 the engine is not producing the torque its capable off and we now have good mpg
on the other hand we now want a sports car that can make the most that the engine can produce therefore we want the engine to produce its best it can , as you pointed out it makes its best at a higher rpm.
we now gear the box to produce the best it can from what is going in ( from the engine ) this means for acceleration we need the best torque at the tyres and this is done via a lower ratio
hence if we are never going to do 180 mph then we can drop the diff to gain torque over speed
now if we add gears we also add torque, we can because we can now close the ratios ( same diff ) hence moving the change point further up where the engine is producing more torque / power ( your example )
Therefore a 5 speed box is going to be better if geared right than a 4 speed + overdrive
However your example is also right there are times when its better to use the best the engine can input into the box as the final result is by putting more in you can still get more at the tyre and thats the problem with gears you choose what you want and calculate the most suitable for its intended use
on a 0-100 sprint the lower box will win
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
Re: gearbox options
It's simple really. You just need to look at the cascade curves for each of the boxes.
I will say though that the C4BP box is generally better than the C6BP and there is little benefit on all but the highest tuned engines in using a B4BP over a C4BP.
/2p
Dan
I will say though that the C4BP box is generally better than the C6BP and there is little benefit on all but the highest tuned engines in using a B4BP over a C4BP.
/2p
Dan
Re: gearbox options
Dan is right.
Bob, you're right in a way but a box with the wrong gaps between the gears will still be wrong when you shorten the FD. Indeed shortening the FD on such a box can actually make it worse on track. I gave a perfectly reasonable example of that. If you drop the FD so far that the top speed is very low then of course you'll have a faster car to that speed than the original box, but it might not actually be that much faster on track and it will definitely be much worse in terms of comfort and MPG on the motorway. I was warning the OP not to change the FD without proper consideration to all the facts and also some careful thought about how the car would be used. I did that on the basis of simple fisics but also experience - I've been through just about every type of box on my S2 and concluded that it really doesn't make very much difference at all on track so for someone who does the odd track day and needs to use the car for road driving I would advise strongly against just shortening the FD.
Cheers,
Robin
Bob, you're right in a way but a box with the wrong gaps between the gears will still be wrong when you shorten the FD. Indeed shortening the FD on such a box can actually make it worse on track. I gave a perfectly reasonable example of that. If you drop the FD so far that the top speed is very low then of course you'll have a faster car to that speed than the original box, but it might not actually be that much faster on track and it will definitely be much worse in terms of comfort and MPG on the motorway. I was warning the OP not to change the FD without proper consideration to all the facts and also some careful thought about how the car would be used. I did that on the basis of simple fisics but also experience - I've been through just about every type of box on my S2 and concluded that it really doesn't make very much difference at all on track so for someone who does the odd track day and needs to use the car for road driving I would advise strongly against just shortening the FD.
Cheers,
Robin
I is in your loomz nibblin ur wirez
#bemoretut
#bemoretut
Re: gearbox options
Obviously I'm missing the context of this discussion. Where's the thread this originated from?
Dan
Dan
Re: gearbox options
It was a post woody made on this thread:
http://www.scottishelises.com/phpbb/vie ... 15#p404920
He describes, I believe, using a lower FD on an otherwise standard S1 gearbox on a sport 160 (which is peaky as these engines go).
My reaction to this was that it might not be such a good idea as the lower FD won't change the fact that the ratios are not matched the engine's power band AND it will make it worse in other respects.
I think I'm right, obviously
Cheers,
Robin
http://www.scottishelises.com/phpbb/vie ... 15#p404920
He describes, I believe, using a lower FD on an otherwise standard S1 gearbox on a sport 160 (which is peaky as these engines go).
My reaction to this was that it might not be such a good idea as the lower FD won't change the fact that the ratios are not matched the engine's power band AND it will make it worse in other respects.
I think I'm right, obviously
Cheers,
Robin
I is in your loomz nibblin ur wirez
#bemoretut
#bemoretut
Re: gearbox options
Having read the original context. I agree with Robin, mainly.
On a 160 engine I can't see any major advantage of a C4BP over a C6BP.
It's worth saying though for track use, all the standard Rover offerings are far to tall overall.
I was running a C4BP in my race car and with my new 8600rpm rev limit it was geared for 186mph in 5th.
I have just swapped to the Quaife UCR ratios with a 4.2 FD and it's now geared for 136mph in 5th. However, these ratios are no good for road use IMO. It will do 57mph in 1st and at 60mph in 5th it is at nearly 3800rpm.
So, as Robin says, the differences in ratios and FDs offered from the Rover gearsets are so small they make virtually no difference to performance on track but make a big difference to the usability/comfort/economy of the car on the road.
/2p
Dan
On a 160 engine I can't see any major advantage of a C4BP over a C6BP.
It's worth saying though for track use, all the standard Rover offerings are far to tall overall.
I was running a C4BP in my race car and with my new 8600rpm rev limit it was geared for 186mph in 5th.
I have just swapped to the Quaife UCR ratios with a 4.2 FD and it's now geared for 136mph in 5th. However, these ratios are no good for road use IMO. It will do 57mph in 1st and at 60mph in 5th it is at nearly 3800rpm.
So, as Robin says, the differences in ratios and FDs offered from the Rover gearsets are so small they make virtually no difference to performance on track but make a big difference to the usability/comfort/economy of the car on the road.
/2p
Dan
Re: gearbox options
I have the C6BP from the 160 and the C4BP from the TF 160 available. Based on a pm between Dan and me a while ago, I thought I may as well give the TF box a go.
Back in my peugeot days, everyone wanted to fit a 1.6 gearbox to their 1.9 GTI. The 1.6 had a 10% lower FD so felt faster, but had gear ratios that were far poorer spaced. Bizzarley, I had a 1.6 (albeit far from standard) with a 1.9 box. The FD was far too tall at Kames and especially on gravel (not an Elise consideration
) & I bought an Mi16 box with the lowest FD of the lot to fix to my 1.9 box.
So with that in mind, Dan's pm and having long found 3rd too tall for my local roads, I decided to fit the TF box.
I'm still open to using either. The TF box is probably worth a few pounds, where I wouldn't sell the 160 box if it wasnt fitted.
Back in my peugeot days, everyone wanted to fit a 1.6 gearbox to their 1.9 GTI. The 1.6 had a 10% lower FD so felt faster, but had gear ratios that were far poorer spaced. Bizzarley, I had a 1.6 (albeit far from standard) with a 1.9 box. The FD was far too tall at Kames and especially on gravel (not an Elise consideration
) & I bought an Mi16 box with the lowest FD of the lot to fix to my 1.9 box. So with that in mind, Dan's pm and having long found 3rd too tall for my local roads, I decided to fit the TF box.
I'm still open to using either. The TF box is probably worth a few pounds, where I wouldn't sell the 160 box if it wasnt fitted.
Re: gearbox options
A 160 VVC engine is a very different proposition to a Sport 160 engine.
The C4BP box will work well with the VVC engine, as long as you can live with the lower gearing in top for motorway cruising.
Probably wouldn't get much for the C4BP if you wanted to sell it Woody. I buy them on a regular basis for £10 a pop.
Dan
The C4BP box will work well with the VVC engine, as long as you can live with the lower gearing in top for motorway cruising.
Probably wouldn't get much for the C4BP if you wanted to sell it Woody. I buy them on a regular basis for £10 a pop.
Dan
Re: gearbox options
roadboy wrote:A 160 VVC engine is a very different proposition to a Sport 160 engine.
The C4BP box will work well with the VVC engine, as long as you can live with the lower gearing in top for motorway cruising.
Probably wouldn't get much for the C4BP if you wanted to sell it Woody. I buy them on a regular basis for £10 a pop.
Dan
I plan to put the 160 head and cams on the TF bottom end, so it will effectively be a sport 160 engine. I had thought the relative lack of mid range torque the sport160 has Vs the TF 160 would have made the shorter FD desirable.
I do Ayrshire to Glasgow on the motorway fairly often, but it's only 25 minutes each way, so not particularly bothered.
In the context of the other thread, I'm not sure the CR box would survive a cost/benefit weigh up for my car.
Re: gearbox options
Not into all the technicalities, but I do know that in order, the biggest enhancements to my two S1's were suspension, C/R gearbox, tyres.
You may lose out on M/W cruising, but a standard S1 in 5th has virtually no acceleration above 90, the C/R is much more fun.
tut
You may lose out on M/W cruising, but a standard S1 in 5th has virtually no acceleration above 90, the C/R is much more fun.
tut
Re: gearbox options
In terms of cost effective easily available solutions, what about an S1 CR box in your S160 Woody?
How would the ratios compare against your pikey (;-)) lowered final drive approach?
Presumably if you build a table showing rpm in each gear at the limiter, and the rpm you arrive at when changing up 1 gear, you can get a great feel for the options? On paper at least...
How would the ratios compare against your pikey (;-)) lowered final drive approach?
Presumably if you build a table showing rpm in each gear at the limiter, and the rpm you arrive at when changing up 1 gear, you can get a great feel for the options? On paper at least...
http://www.rathmhor.com | Coaching, training, consultancy
Re: gearbox options
Dan here is the post I replied to
quote "He describes, I believe, using a lower FD on an otherwise standard S1 gearbox on a sport 160 (which is peaky as these engines go).No I replied to the above post "Slightly off topic " however the diff does not alter the ratios
note 2 robin is explaining the diff makes NO impact on performance except fuel ecom
robin is stating using 4 gears for performance is as good as 5 by using his diff that gives him around 180 mph max in 5th and I agree for motorway perfect for performance he is loosing torque across the full range of the box ie acceleration something folk spend thousands seeking I understand his comment about the track but my first post states choose what you want from the car fit the diff to suit then if you can then alter the ratios to suit even better Cascades will give an idea but for track a lap sim may even be better
note 3 robin is saying the gear ratios only make a relatively small impact on acceleration
again if we can tune the ratios to either the power output or for track factor in the change points to the layout, we can make the most of what we have , on a peaky 160 its even more important
note 4 robin is stating what difference he felt on his own S2 with 17" wheels not a s160
now lets not forget robin now has a higher diff ratio than a s1 due to the s2 wheels no matter what box , and with the pg1 we are lucky we have options we could use, for example a cr box with a higher 5th for that motorway slog
but my post is trying to explain the impact a gearbox with a choice of diff and then choice of ratios can have
the audi conversion makes more power and torque than a n/a honda conversion , Steve b showed how through gear choice and amount the honda is the quicker car ( cascade curves )
robin is stating above that he thinks the diff adds no performance , the ratios only a relatively small impact ,and is using a four speed box and overdrive
I also think I'm right, obviously
tune for torque , use the gearing for getting the most from it = Engine Basics
note 1 "slightly off topic" ie we are talking gearbox in general not 160robin wrote:Slightly off topic, but if all you do is lower the FD of a standard ratio box you've gained nothing much other than worse fuel economy on the motorway. The RPM distance between gears is what makes an impact on acceleration, albeit relatively small. The only time this isn't true is when you exactly hit the rev limiter when it's time to brake - in that sole case you'll have fully utilized the power band.
I recently switched back to my original S1 standard ratio gearbox in EGOR and on track at Oulton Park it made no noticeable difference - made a big difference on the motorway though!
Cheers,
Robin
quote "He describes, I believe, using a lower FD on an otherwise standard S1 gearbox on a sport 160 (which is peaky as these engines go).No I replied to the above post "Slightly off topic " however the diff does not alter the ratios
note 2 robin is explaining the diff makes NO impact on performance except fuel ecom
robin is stating using 4 gears for performance is as good as 5 by using his diff that gives him around 180 mph max in 5th and I agree for motorway perfect for performance he is loosing torque across the full range of the box ie acceleration something folk spend thousands seeking I understand his comment about the track but my first post states choose what you want from the car fit the diff to suit then if you can then alter the ratios to suit even better Cascades will give an idea but for track a lap sim may even be better
note 3 robin is saying the gear ratios only make a relatively small impact on acceleration
again if we can tune the ratios to either the power output or for track factor in the change points to the layout, we can make the most of what we have , on a peaky 160 its even more important
note 4 robin is stating what difference he felt on his own S2 with 17" wheels not a s160
now lets not forget robin now has a higher diff ratio than a s1 due to the s2 wheels no matter what box , and with the pg1 we are lucky we have options we could use, for example a cr box with a higher 5th for that motorway slog
but my post is trying to explain the impact a gearbox with a choice of diff and then choice of ratios can have
the audi conversion makes more power and torque than a n/a honda conversion , Steve b showed how through gear choice and amount the honda is the quicker car ( cascade curves )
robin is stating above that he thinks the diff adds no performance , the ratios only a relatively small impact ,and is using a four speed box and overdrive
I also think I'm right, obviously
tune for torque , use the gearing for getting the most from it = Engine Basics
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
Re: gearbox options
campbell wrote:In terms of cost effective easily available solutions, what about an S1 CR box in your S160 Woody?
How would the ratios compare against your pikey (;-)) lowered final drive approach?
Presumably if you build a table showing rpm in each gear at the limiter, and the rpm you arrive at when changing up 1 gear, you can get a great feel for the options? On paper at least...
The ratios are undoubtedly closer and more evenly spread, but IMHO, at what a CR box sells for (I have the other two already) it's not worth it.
The Seloc techwiki has the ratios
Gearbox Code 1 2 3 4 5 Final Drive Used In
G6BP 3.250 1.895 1.308 1.033 0.848 3.938 S2 111S (WR "long" box)
C4BP 3.167 1.842 1.308 1.033 0.765 4.200 MGF VVC (as standard but final drive 4.2)
C6BP 3.167 1.842 1.308 1.033 0.765 3.938 Elise S1 standard and MGF
B4BP 2.923 1.750 1.308 1.033 0.848 4.200 S1 111S & S1 Sports 135 & S2 135R & S2 standard (CR Box)
B4BPU 2.923 1.750 1.308 1.033 0.848 4.200 Exige S1 uprated (CR Box)
B4BPQ 2.923 1.750 1.308 1.033 0.848 4.200 Exige S1 with LSD (CR Box)
B6BST 2.923 1.750 1.308 1.033 0.848 3.938 Rover "BRM" 200 - CR box with std final drive & torsen LSD
340R UCR 3.0 1.937 1.556 1.273 1.043 3.92 340R LOTAC05255 Conversion
NA 3.167 1.842 1.410 1.100 0.909 3.938 Eliseparts
http://wiki.seloc.org/a/Rover_PG1_gearbox