h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

This is a very well written entry and looks as it it's written using a lot of background knowledge, i do however have one, or two, criticisms with the advice regarding gears.

maybe I've been driving an old Mondeo for too long, but who in their right mind would cruise at say 60-70mph and change from fifth to third, i've used fourth many a time for overtaking, but third seem too extreme. surely any car that needs to go down two gears to accelerate at a good rate wouldn't be able to easily put up with running at 60mph in third gear.

also, relating to another point, driving in forth gear does nothing for fuel economy regardless of a bit more acceleration/braking performance.

Andy

You can run the revs a lot higher than most people think without any harm to the engine. It improves the performance immensely.

i doubt it does anything for the engines longevity, parts would need replacing more frequently, the car can make an awful racket, i never take my dads car over 4,000, and he only takes it to 3,000, there's enough stuff going wrong with it without taking it to the red line.

Yes, but most people rarely get above 2000.

2,000, you've got to be jokin, no wonder some people take so long to overtake. though i suppose it might be different for diesels.

i'm pretty sure my mate wasn't keeping to 2,000 when he decided to try and foolishly undertake me, and then he has a go at me cos he reckons i cut him up. i try to drive safely but still, as a teen, would get hit by massive insurance prices, if i wasn't on my dads insurance as a named driver that is, because people like him drive like idiots.

(bashes head against desk)

Andy, I too can not imagine any circumstances when a gear change from 5th to second to 'whizz' past a hazard would be either appropriate or safe!
As a advanced Police driving Instructor qualified to both A.C.P.O. and A.C.P.O.(S) I would be concerned if any responsible driver driving at a speed that required 5th gear, considered it correct to carry out such a change.
That said there maybe times that a down shift is required in order to create more power. I have driven and instructed in Ford Mondeos for a number of years now and would agree that a shift from 5th to 4th is all that is required for the extra power at the speeds described. If you did indeed select 3rd at 6o mph, your mondeo would be almost at the top of it's rev range which would and could easily cause problems when you proceeded to over take say a slower moving vehicle as your vehicle will very quickly reach it's rev limiter. This will then require you to carryout a quick, and I would suggest a rushed gear change while you are in the middle of the overtake, possibly alongside the vehicle you are overtaking, therefore requiring you to remove a hand from the steering wheel just at a point when full control is required.

i don't think i would find it too easy to change from fifth to third anyway, not without a liberal amount of force.

Every body seems to be missing the point about changing down to 3rd gear from 5th, I do it quite often to overtake a slower car as my focus can quite happily drive at 40mph in 5th, and therefore the change is not so violent, and of course there is absolutley no power in 5th at this speed

Quite right. I've done it occasionally myself.

I see, I thought you meant cruising at like 60mph.

on ther contrary...it is, for MOST modern cars, incredibly easy.

It's all down to the 'bias' of the gearlever..ie, the position the gearlever returns to, in neutral, when pushed from side to side.

On most modern cars, this position is aligned directly with 3rd and 4th gears [this assumes a 'dogleg 5th' gear selector position...there are oddball gearboxes out there].

therefore, a shift from 5th to 3rd gear is simply a gentle pull of the lever, then a brief 'let go' of lever, followed by a 'push forwards'.

A gear lever should never be 'gripped' tightly..such action being referred to in the trade as 'stirring the pudding stick'....and is responsible for most incorrect gear selections, or 'false neutrals' a driver is likely to make.

The gear lever should be either 'pushed' with the palm of the hand, or pulled using a cupped hand attitude, ie using the fingers rather than 'gripping'.....with the angle of the hand being either flat, for straight, [forwards or backwards] gear selection, or towards or away from oneself, for the appropriate sideways movements of the gearlever.

So, a 5 to 3 gearchange in the above circumstances would be with a cupped hand, flat....simply a 'pull', pause, then 'push'...without even angling one's hand.

whichever gear is used to increase the engine's output, thereby increasing acceleration rates, is entirely dependant on the speed ranges of each ratio.

[and the power characteristics, ie bhp and torque curves, for one's engine....a read of the owner's handbook will give one an idea of what the maker recommends]

At one's given speed, [for example, when planning an overtake] one must consider how much useable rev range one will have in a certain gear.

A rev counter will help..as to an inexperienced ear, listening to the engine can be misleading.

Also remember, higher engine revs MAY NOT produce more power....there will be a point in the rev range where the power output levels off.

As an example, I once owned an Alfa Romeo 33 16v.....1.7 litre, flat-four engine.

The rev limit, ie red line, on the rev counter was around 8K rpm....so at 60 mph, I would still have around 1-1.5k rpm left, to the red line, in SECOND gear!

If I chose to blatantly flout the law, I usually could do so making whatever amount of noise I wanted to.

In a Nissan Micra, I'd likley only be able to use 4th gear to accelerate if doing the same thing.

In a 4 speed Reiant Robin/Rialto, at 60 I wouldn't be able to use much 3rd gear, so it would be a top gear overtake!

As to the wearing out of engine parts, modern engines are built to such close tolerances, compared to those of old,[computerised machining equipment...marvellous]...that actually ,frequently making use of high revs wont harm them...unless the driver hasn't checked the engine oil level recently?

no, see, when i meant it would be difficult, i mean old gearboxes don't mesh like they used to. so i would have to use a lot of force

I understand your problem, however, 'force' isn't what should be applied.....if it is, then it's use suggests something wrong with the driver's selection method, or, timing of the gearchange.


Many drivers 'assume' that changing gear consists of shifting the gear lever from one gear to teh next...[with appropriate clutch and gas pedal movements.]

In reality [apart from certain exceptions, such as Bristol double decker buses]...the process involves shifting from one gear, into neutral....then from neutral, into another gear.
This really should be reflected in the way the gearlever is moved.

The older, or more worn, a gearbox is, the more 'deliberate' the gear shift should be.

The two main mistakes drivers make when shifting gears [apart from the obvious, of going backwards instead of forwards]...is, selecting too low a gear at too high a road speed...and selecting too high a gear at too low a road speed.

If trouble is found, when trying to block shift from 5 to 3 on a worn gearbox, then the vehicle's speed may be a tad too high for that 3rd gear......there may also be an issue with worn synchromesh....or, [if shifting too quickly] with 'beating ' the synchromesh.

So one must adjust/acquire improved, driving techniques to get the best out of that worn component....I suggest trying a blip of the throttle once the clutch is depressed, just raising the revs a bit...this might ease the gear selection process?

Also, don't keep that clutch depressed too long, otherwise the 'take-up' of drive will be rough.

ok i'm going to get rid of any confusion that could have been caused here .

I said that changing to third whilst cruising at 60mph would be a bad idea, and that i wouldn't do it, and even if i wanted to change into third at 60mph i wouldn't be able to, because my cars gearbox wouldn't mesh, unless i double-declutched (which i've never done).

Don't worry about my method of changing gear, though i don't like to blow my own trumpet, i think i'm quite good, and aside from an embarrasing crunch after overtaking another car changing from 4th to 5th, my record is clean of gear change errors.

Having conducted a non-scientific poll of various car gearboxes..I reckon 3rd gear is roughly 1000 rpm's different to top gear [5th]...

On all my cars, strangely...5th gear, at 60mph, corresponds to roughly 2100-2300rpm.

At that speed, 3rd gear gives approx 31-3500 rpm.
On both a 2 litre, and a 1.3 litre engine, the red line on the rev counter is around 5500-6000rpm....so...even allowing a 5000 rpm peak power output, 3rd gear still allows more than 1500 rpm to use.


However, your figures bring into question the type of road you are driving on?

On a motorway/dual carriageway, with overtaking lanes, is there a need for rapid acceleration to pass?

On single carriageway roads, you speed limit would at best be 60mph anyway....so the question of using 3rd gear at 60mph shouldn't arise, if you intend to drive within the law??

Look at the torque curve of your engine. For example, my Citroën C5 1.6HDi produces maximum torque (177lb.ft) at 1700rpm. I can accelerate very quickly in 5th gear above 40mph. The thing pulls like a steam engine. Peugeot-Citroën Diesels sound a bit tractor-like but they do the business. It runs quite happily at 1100rpm although the turbocharger seems to start to produce worthwhile boost at slightly higher revs.

It's the most drivable car I have ever owned and 54mpg is not bad for a largish car. It certainly feels like it has more cubic capacity than 1560cc.