Top speed vs improved acceleration
Discussion
I daresay this has been done a multitude of times before, so forgive me. Off the back of another thread/discussion, and it's something I've pondered a few times, what are the driving reasons (no pun intended) behind chasing top speed for cars, is it just a function of usable gear ratios?
Now, before people jump down my throat as is their wont on GG, I'm not necessarily advocating lower top speeds, I'm just asking if there are any mechanical reasons to not reduce top speeds while improving "punch" for want of a better word, throughout the resulting smaller speed range.
Personally I'd happily trade top end on pretty much any car that was to be used solely for road use beyond, say, 100mph, for better response/economy depending on application.
What would be the sort of "improvement" in acceleration by gearing a Golf GTi to max out at, let's be generous, 120mph?
Is it marketing that prevents it? Are people not interested in it? Is there a mechanically tricky balance to hit (regarding drivable gear ratios, I realise it's not difficult per se)
Or have I simply got completely the wrong end of the stick on this?
Now, before people jump down my throat as is their wont on GG, I'm not necessarily advocating lower top speeds, I'm just asking if there are any mechanical reasons to not reduce top speeds while improving "punch" for want of a better word, throughout the resulting smaller speed range.
Personally I'd happily trade top end on pretty much any car that was to be used solely for road use beyond, say, 100mph, for better response/economy depending on application.
What would be the sort of "improvement" in acceleration by gearing a Golf GTi to max out at, let's be generous, 120mph?
Is it marketing that prevents it? Are people not interested in it? Is there a mechanically tricky balance to hit (regarding drivable gear ratios, I realise it's not difficult per se)
Or have I simply got completely the wrong end of the stick on this?
A lot of it comes down to power delivery. If a car has a very peaky power band then close, shorter gears allow you to keep in that band from one gear to the next.
As cars become more torquier, with flatter power curves, then gears can be wider spaced and the performance benefits of close ratios are diminished.
On the standard gearbox, my 106 Rallye would max out at 125mph but was at 4,000rpm at 70mph. I've now fitted a slightly longer final drive, increasing the top speed to around 135mph and reducing the revs at 70 to around 3,600rpm. The effect on performance is minimal but it's much easier to live with.
As cars become more torquier, with flatter power curves, then gears can be wider spaced and the performance benefits of close ratios are diminished.
On the standard gearbox, my 106 Rallye would max out at 125mph but was at 4,000rpm at 70mph. I've now fitted a slightly longer final drive, increasing the top speed to around 135mph and reducing the revs at 70 to around 3,600rpm. The effect on performance is minimal but it's much easier to live with.
Edited by busta on Friday 24th February 23:58
If a car has enough power to have good acceleration, with decent aerodynamics and sensible gearing for economy, it will have a high top speed as a side effect.
Weight doesn't really affect top speed, but it does affect the amount of power you need for a given amount of acceleration. In other words, if you make a car heavier, to keep the acceleration the same you will need to give it more power. This will increase the top speed. All other things being equal (all other things being essentially frontal area and drag coefficient) if you have a heavy car and a light car that both do sixty in seven seconds, the heavy car will have a higher top speed - increasing top speed is also a side effect of making a car heavier while maintaining performance.
Weight doesn't really affect top speed, but it does affect the amount of power you need for a given amount of acceleration. In other words, if you make a car heavier, to keep the acceleration the same you will need to give it more power. This will increase the top speed. All other things being equal (all other things being essentially frontal area and drag coefficient) if you have a heavy car and a light car that both do sixty in seven seconds, the heavy car will have a higher top speed - increasing top speed is also a side effect of making a car heavier while maintaining performance.
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