Focus high petrol usage

Jesus.

Your progress must be glacial, at best.

The pedal on the right goes all the way to the floor, you know.

And the needle on the dash won't explode if it hits 5k rpm.

Fangio!

In message , Nige writes

Even my handbook says "Do not change up at less than 2000 revs", so I don't. I don't know why they put 5 gears in cars, I often rev enough in 3rd to skip 4th.

I wonder what revs were used in the 1950s F1 cars? Anyone care to speculate?

I don't think changing at 5k is great for the engine. Plus I'm driving to sainburys not brands hatch.

I've been driving in 4th at 40 and seems less sluggish than 5th at 40. At

40mph in 4th it sits at 2k rpm which seems fine. At 40mph in 5th it sits at 1.2k rpm which is probably where I went wrong a bit and laboured it. I've put a full tank of shell regular today to see what kind of returns I'll get.

Details towards the bottom of the page.

To get back to the OP's problem, he'd need to know about and understand the Specific fuel consumption of his engine. For instance, the 2 litre Ford Zetec petrol is most efficient between 1500 and 3000 rpm, while developing 120 - 140 Newton-metres of torque (About 75% of maximum torque) at the flywheel. Other engines have different characteristics, so google for your engine type. He needs to keep the engine speed within these bounds as much as possible, but efficiency and torque are better at 4500 than at 1200, so late changing will give better fuel economy and performance than letting it labour.

To make it easy while you're driving, put a green mark on the rev. counter in the best range, and yellow above and below it.

I now don't touch 5th till 45/50mph. At 30 3rd seems happy at 2k rpm. It looks like its my gearing was a bit off.

I'm used to a mk4 golf 1.6 01 manual and used to drive 30 in 4th and

35/40mph upwards in 5th can't remember the exact rpm but way worked best. I got a personal best of 440 miles out of a full tank to petrol light on. At average 420 miles, so I guess that was good.

Granted I drive rather slowly compared to what some of you sound light you drive but thats just me, I prefer to save my money rather than blast it out of my right foot ;)

In message , Pete writes

Much of my driving is done in 30mph areas, and I don't find a problem with cruising along at about 1200 revs in the 1.8 Mondeo, because I also drive for fuel economy, and have a sensitive right foot. I avoid driving in thick soled shoes as far as possible.

To me, the term "labouring" an engine means accelerating hard from low revs, which was a cardinal sin when Dad was teaching me to drive. I often find it more comfortable using 4th around town, because it is more flexible. When the road opens up, I just drop a gear to get the acceleration.

I don't have my gaze on the rev counter, because I learned car sympathy by listening to the sound of the engine, long before rev counters were fitted to "ordinary" cars. Just another gadget we don't really need, but I missed the oil pressure gauge and ammeter when they were taken out. :)

On the contrary, 5k rpm is actually very good for the engine - you'll be clogging it up with all sorts of s**te that needs blowing out with a good revving.

You'll probably also find that peak torque, which is more than likely the most efficient speed at which to run the engine, is a lot higher than 2k rpm - closer to 5k, in fact.

2k rpm.

That's barely ticking over. Give it some beans, man.

Just the 5.

I have 7.

Mind you, I also have a supercharger.

And turbocharger.

I stand corrected :)

I've always been under the assumption that the lower the revs the better for the engine as in less engine wear and less petrol use. Seems I was wrong.

Interesting post.

Do you have an instantaneous fuel read out?

If so, try running on a flat 40mph road in a selection of gears, and you'll be able to see how engine speed affects throttle inputs and fuel consumption.

It's possible to be running on a much larger throttle input in a higher gear as the engine is working harder to keep itself spinning.

[...]

Yep, modern engines are designed to operate efficiently at higher revs than those of old. They don't perform well, and may suffer longer term,if driven like an old lady might. (And modern diesels can suffer harm quite quickly if used thus.)

Also remember that it's much more fuel efficient to accelerate up to your intended cruising speed fairly briskly; not red-lining it, but certainly not changing up at 2K.

Chris

5th @ 1.2k rpm is definately too slow / labouring - have you not noticed the 1.8's mapping causes it to fight against the car at low engine speeds? Dipping the clutch the revs will shoot up to 1800-2000rpm do they not?

Tim..

Definately not as a rule for 16v 4 cyl petrols. Often torque output falls away dramatically as revs drop from the peak figure. If say you use 5th gear at too few rpms, the engine may not be able to sustain that speed without a much wider throttle opening than it would in 4th gear at higher revs. More throttle uses more fuel than higher rpms and less throttle at certain speeds. This is especially the case where you may have vastly overdriven 5th or 6th gear. The 1.8 doesnt suffer from this quite as noticably as the 1.6.

Tim.

Indeed- best mpg is to accelerate using brief periods of about 2/3 throttle, changing gear at, or just over peak torque rpm (3800 in the case of the 1.8) then feather the throttle immediately you reach desired speed to *just* maintain that speed. You'll find there is quite abit of 'travel' in the throttle pedal that just maintains speed and still no acceloration.- well there was with mine!

Tim..

known as 'putting it on the step' in aircraft circles (so I understand)

Vanwall 1957 GP Engine: 4-Cylinder DOHC Bore X Stroke: 96 X 86 mm Capacity: 2,490 cc Power: 285 bhp at 7,300 rpm

six years later the supercharged 1500cc BRM was doing 11000rpm but not for very long!

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Doh.. earlier not later!

Fangio said about it It was the most fantastic car I ever drove - an incredible challenge in every way.

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I remember that screamer! I used to cycle the 30 miles or so to Oulton Park to watch in the G.O.D. when they still ran F1 there, the favourite event being the Gold Cup meeting.