Safe Speed Forums

Fair enough, that's got me beat. I was under the impression cars lost power over the years, not gained it.



So the picture quality is ok from behind the glass?

I might look into it, admittedly it's been quite a few years since I looked, and apart from the price it was the memory space that stopped me (they had very little recording time).

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If you think everyone else around you is driving badly, perhaps it's time to examine your own driving.

Pretty common with these cars, the engines loosen up after 10-20K miles apparently. Of course one of my other cars is 55bhp down, but then the manufacturer was notorious for overestimating the output.





Providing you clean the inside occasionally, it also helps if you can mount it within the sweep of the wipers.

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Driving fast is for a particular time and place, I can do it I just only do it occasionally because I am a gentleman.
- James May

B4509 for the 0-60 test. B4058 (on a flat straight section) for 40-70.



It's going to be "close enough for the purposes of demonstration". It's fairly easy to anticipate when to press the stop button on the stopwatch, after all this is how VASCAR works (and that has Home Office type approval).



I have a speedometer and a stopwatch.

Drivers have been convicted of speeding based on the evidence of a police officer with a stopwatch and/or speedo (can't remember the exact reference but I'm sure someone on here will point it out).



It's a turbocharged diesel engine which has (from memory so figures are approximate) 170PS and 265lb/ft torque.

After remapping it produces approximately 210PS and 350lb/ft. I had it tested after remapping on a rolling road and it gave a figure of 208bhp (which roughly corresponds to the metric quoted power of 210PS).

Horsepower (whether imperial BHP or metric PS) gets you from 0-60. Torque gets you from 40-70. And this is a big torquey diesel, even before remapping.



The car has done 77,500 miles in 2 1/2 years. The engine however has done 18,000 miles since September last year when the engine was replaced under warranty following what can only be described as a "catastrophic failure". Although the car was still running it left a massive pool of oil and coolant on my driveway! Still not 100% sure what caused it... and it wasn't remapped then.

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Magistrates rule #1: "Never let justice get in the way of a conviction."

Having the video definitely helped, it removes the ability to use a cosy self supporting memory of the event to convince yourself you were perfect. I suppose you have to be willing to examine your own driving in the first place though.

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Driving fast is for a particular time and place, I can do it I just only do it occasionally because I am a gentleman.
- James May

No one will. The speedo has to be calibrated; no calibration certificate - no admissible evidence.
Like I said, you are likely to get caught out by speedo overread and speedo non-linearity (overreads by a greater multiplication factor at higher speeds).


That makes no sense. Power gives you acceleration regardless of speeds faster than stationary (torque on it's own doesn't); [edit: removed]

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign

Maybe all cars should be fitted with them for a week, say every three years, then we could have our driving assessed (just like an MOT) and anyone not up to scratch should be "retrained".

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My views do not represent Safespeed but those of a driver who has driven for 39 yrs, in all conditions, at all times of the day & night on every type of road and covered well over a million miles, so knows a bit about what makes for safety on the road,what is really dangerous and needs to be observed when driving and quite frankly, the speedo is way down on my list of things to observe to negotiate Britain's roads safely, but I don't expect some fool who sits behind a desk all day to appreciate that.

When you accelerate you increase the kinetic energy of your car (Joules) to do this requires power (Joules/second) to achieve, the power spare after over coming aero drag and rolling resistance etc. determines your acceleration.

Big, flat torque curves can help as you generally need less gear changes and ironically is better for the 0-60 dash as it is easier to get full clutch bite at a higher output than you would get with a high revving engine. Have a look at this site, though it is comparing V8s and high revving I4s rather than diesel/petrol I think you will find it interesting.

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Driving fast is for a particular time and place, I can do it I just only do it occasionally because I am a gentleman.
- James May

When I get a chance I shall time the 40-70 acceleration again. Unfortunately on the occasion I did it I only got the one attempt before coming up behind traffic crawling along at 50mph...

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Magistrates rule #1: "Never let justice get in the way of a conviction."

Interesting idea, except I would not trust a government not to make it permanent and a way of fining you for every minor infraction.

I think you would also have a problem with people trying to drive on best behaviour while at the same time feeling stressed and making mistakes due to exam conditions. Perhaps going out with an observer then reviewing the recording and discussing it together? I know you need an observer in the car and there is the resultant time cost, however who is going to sit and watch a weeks worth of driving? If it could be done, in whatever way, as a positive rather than punitive process then maybe it could work. As Ed_m points out the trick would be getting drivers to accept they are not already perfect.

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Driving fast is for a particular time and place, I can do it I just only do it occasionally because I am a gentleman.
- James May

How about setting up a video camera, not hand held of course, and timing the speed change off the recording. I use a camera to time clear laps on track days like this.
As Steve mentions getting true readings off a speedo is tricky, apart from the steady speed misreading errors the reading can lag or lead the true value during acceleration. The only way to do really is with some proper instruments, you can get the cheaper end of this kit from http://www.racelogic.co.uk/ or http://www.racetechnology.co.uk

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Driving fast is for a particular time and place, I can do it I just only do it occasionally because I am a gentleman.
- James May

Yep, dangerous. Unless you are not watching the speedo, which makes the test even more pointless, then your attention is not on the road at all. Sorry but the image of someone watching a speedo holding a stopwatch in one hand while trying to get an (in)accurate time test is not safe even on a straight.

You can even google link the exact stretch you did and I can tell you why it was dangerous.

I notice you said you had to slow down for traffic, so it's not like you were the only one on the road.

What if the cars ahead had stopped for some reason while you were watching the speedo/stopwatch?



What, the driver uses the stopwatch?



But, those times are simply not possible in your car.



Why? It's another flawed test. The driver having to start and stop the stopwatch while concentraiting on driving, and a speedo that's not calibrated. You also think that it's quicker to get from 30 -60 than it is 0 -30, when pretty much every car spec sheet says otherwise (and real world tests), so perhaps you would benefit from reading up a bit, and to why torque doesn't suddenly come into effect on higher speeds.

Does it *really* matter what your car can do? Surely it can wait until you can do a track day? I think we are all old enough to be past the 'My car is faster than yours' saying

It's only the young girls that hang around McDonalds that are impressed with people hooning about and how fast 'My motah is'. Safe and sensible driving is way more impressive, as is considerate driving.

Which would you give the more respect, the guy that's hooning up the road taking corners fast, or the one that let you out of a bad visability junction?

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If you think everyone else around you is driving badly, perhaps it's time to examine your own driving.

DAMN! THAT'S where I've been going wrong!!!

What an odd thing to say! So an engine with no torque will have a good 0-60 time and an engine with no power will have a good 40-70? Surely this is a gross over simplification?!

Power and torque are odd concepts to get one's head round because people always try to think of them in terms of what they do for the car's performance. They're inextricably linked to each other. One of the nicest examples I heard was the weightlifter and the sprinter. They are both given a job to do - move a pile of bricks 100 yards. The weightlifter has a lot of "torque". He picks up the whole pile of bricks and struggles the hundred yards with them all in one go. The sprinter runs like hell and makes several trips with a few bricks on each trip. He has a lot of "power". They both complete the task at the same time. The trouble with the "bar banter" is that the figures people always brag about are the "peak" figures (power or torque) and what's important is how much of either there is elsewhere in the car's rev range (given that it can't always sit at one engine speed). it's the "area under the graph" that's makes all the difference.

Speaking of graphs, that one you posted the link to seems odd. I've not read it properly but it starts off with two completely unrealistic power curves, so I'm not quite sure what it's setting out to prove, other than the higher the car revs, the harder it is to find one convenient gear. The same happens with alternators and aircon pumps. On car that revs to 8k, it's quite hard to make the alternator and aircon pump (and power steering pump and water pump for that matter!) work well at idle if they're not to "grenade" themselves at the redline. It's a lot easier to do on a car that only revs to (say) 5k - but so what? I can't relate that to the power debate!

yes mole the average punter at the National Trust properties and dainty tea rooms you hang out at are much harder to impress.

Well they probably wouldn't notice the noise at least

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If you think everyone else around you is driving badly, perhaps it's time to examine your own driving.

I am assuming the first two paragraphs are a reply to Squirrel's post as the first, at least, agrees with mine. The wording of the third paragraph makes this uncertain, however I will continue and reply to that section. I think we would find we basically agree about the torque/power thing, it is likely that it was the brief way I replied to Squirrel's point that caused confusion.

The sites owner is obviously a fan of big V8 engines and is probably trying to prove a point, he is also failing to mention that the lower reving car has much higher torque. This page goes into more detail and uses more realistic power/torque curves to make his point, you will note that he raises the importance of the area under the curve particularly when gearing is taken into account. I was hoping Squirrel would be interested enough to have look further into the site from the first link I posted rather than us exchanging posts.

The point you make about getting the pumps to match the engine is not dissimilar to my point about how a lower revving engine allows you to get full clutch bite at a point in the torque curve giving you higher available power, at least I think it is as similar. As an aside I have recently done a bit of research on the various types of supercharger and how they compare with turbochargers, I mention this as it appears this is another case that is easier to implement over a lower rev range.

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Driving fast is for a particular time and place, I can do it I just only do it occasionally because I am a gentleman.
- James May

My phone has a stopwatch facility - and it's small enough that it can be held against the wheel and the start/stop button pressed with the index finger on my right hand.

(Disclaimer - my spare phone with the SIM removed, so it can't be classed as a "communications device.)

Get to biting point, press button as car starts to roll, accelerate as fast as possible, press button again when speedo needle passes 60mph. Allow a small degree of over-read (I happen to know from GPS that with new tyres the speedo overreads by <2mph on that car).



There was nothing in front of me at the time I carried out the 0-60 test. I wasn't able to carry out the 40-70 test at that time as there was traffic ahead.



Ask that question (removing the stopwatch reference) in relation to speed cameras and you'll see the whole point of the SafeSpeed campaign.



With VASCAR this is entirely possible. The first speeding ticket I ever got was one copper with a VASCAR unit in an unmarked Vectra. Had I had the insider knowledge I have now I could probably have got away with it as he was on his own.



I haven't ever tested the 0-30 time on my car. I was comparing the 0-60 time against the 40-70 time, which in real-world driving is comparing "burning off" some little chav at the lights against the mid-range acceleration that comes in so useful when, eg, overtaking a 44 ton truck on a single carriageway.



Don't get started on the impressionable teenagers! No, really... just... don't.

She said she was 18, Your Honour...



Neither. The guy that manages to drive from one end of the Cockadilly road to the other (B4058 Horsley turning to B4066 Frocester Hill crossroads) faster than me in a lesser car. (Where 'lesser' means lower powered, skinny tyres, front wheel drive etc.)

If you can take a 1 litre Saxo with rubber bands for tyres down that road quicker than I can in my A4 then you may have earned a small amount of respect. But I don't see that happening any time soon.

Right, I'm off to do some donuts in McD's car park and see if I can pick up a couple of teenage slappers...

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Magistrates rule #1: "Never let justice get in the way of a conviction."

Did you not spot the tone dripping with sarcasm?

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Magistrates rule #1: "Never let justice get in the way of a conviction."

When coming around EVERY corner that is 'blind' with NO prior knowledge of what can be around it, (no treeline or posts to indicate road layout) , no through hedge glimpses, no view or other roads about to join, no signs indicating a junction and road joining, in other words you have no concept as to just what maybe around the bend:
You should be travelling so that you can stop safely on your side of the road, (to use the FULL phrase here), in the distance that you can see to be clear in. If as you suggest that the car pulled out after you saw it with little vision of it's prior existence, could you have stopped 'properly' as above phrase suggests? No by your account.
So what went wrong, your entry speed to the bend was likely too high, giving you less time to assess the junction. Did you miss a sign or was it covered over ? (Tell the Council if it is.)
Let's say for a minute that you saw the car, and sped up believing it to be 'safe' well that can be an error. IF room, on the road layout I would have moved to the center, of the road, or even mostly to the opposite lane, giving the widest possible space between me and the possible 'leap out of junction car', as MUCH room as is safely possible to do so, given the unknown intentions of the waiting car. This allows for such a possibility and gives you extra space and so more control for this or any other sudden possibilities. Slowing a LOT and going past at a sedate, but steady rate, but not too much to look confusing and possibly, SO slow that they then think you are letting them go, needs to be judged at the time.
When looking at an unknown car's intentions: we can view the driver and look for eye contact and or the front wheels to look for movement. Never rely on passengers in your car or other cars.
By saying that you felt the need to gesture and comment, implies that you are not in control and enabled others to encroach into your space around you car, enough to give you fear and concern.
Good driving should enable you to have enough experience and ability to pre-control these possibilities, and make them always safe for you, as well as for the others who make the mistakes.
Whether you saw the L plate, should not really make *that* much difference, to what you could do here in this scenario.
Good driving often requires you, to use your ability to control your vehicle, and use your ability to risk manage & judgment to ensure that you do not get into these incidents, in the first place. If you do find yourself like this again, I would hope that your positioning and anticipation can help you be, in the right place, and out of any danger area when they occur, so the other person 'leaps out' but your anticipation has you in a safe place.
Then instead of gesturing and braking hard, you can smile to yourself, pat yourself on the back and either stop gently and let them out, or be away from any danger, and with a little throttle drive away distance yourself from their movements toward your car, and increase your space safety 'bubble'.
Think about it like this :
Never position your car into any 'CLOSING GAP' scenario.

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Safe Speed for Intelligent Road Safety through proper research, experience & guidance.