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Auto blips and rev-matching - how does your car engine work?

An increasingly common feature of sporty petrol and diesel cars, but how does auto blip software - aka auto rev-matching - work? We delve into the details

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There’s an awful lot of jargon associated with cars, so it’s not surprising that it leaves many of us confused. Often, the principles behind the words and phrases are pretty simple when they’re explained.

Auto blips and rev-matching are both cases in point, and once you’ve read all about them, you’ll be an expert on both.

How your engine works

To understand rev-matching, first, you need to understand what’s happening under the bonnet when you’re driving a petrol or diesel car.

The engine's internal components are turning at a certain speed, which the gears then convert into a different speed for the drive wheels.

In a low gear like first or second, the speeds of the engine and drive wheels are more closely matched to each other.

As you gain speed and switch up through the gears, the engine can make the wheels spin much faster at comparatively lower revs.

When you’re moving up through the gears, this can be done relatively smoothly as you have the speed and momentum to make the transition.

It’s different when you’re changing down in gears though. In this case, when you put in the clutch and lift your foot off the accelerator the engine speed drops suddenly.

Then, as you lift the clutch to engage the lower gear there may well be a sudden lurch as the speed of the spinning wheels no longer matches the speed of the engine. The engine revs will then rise suddenly.

This is bad for several reasons: it puts strain on the engine, gearbox and drive shaft, it can unbalance the car and, in extreme cases, it can sometimes even make the wheels lock.

What’s rev-matching?

Now we’ve explained the mechanics, let’s get on to rev-matching.

Put very simply, this is a driving technique in which you touch on the accelerator when you’re changing down a gear and just before you re-engage the clutch.

This raises the engine speed to match the speed of the wheels, making gear changes silky-smooth.

It's a technique that needs quite a bit of practice to master, but it’s well worth putting in the time.

It will make driving more enjoyable, put you more in control, for example when you’re slowing down into a bend, and will ease the strain on many components in your car.

It’s also especially useful when you find yourself driving along roads that undulate up and down steep hills.

It can be easy to lose momentum as you suddenly hit a steep section, leading to a struggling engine that may be in too high a gear.

By thinking ahead and making downshifts smooth, you should be able to maintain a steady speed, however extreme the incline.

An even more advanced method of rev-matching is called 'heel-and-toe'. This also brings the brakes into play as you apply them using your toes while 'blipping' the throttle with your heel.

This is considerably trickier to perform than simple rev-matching, so it’s generally only used by drivers wanting to squeeze every last drop of performance on track days or in race situations.

Turning to the auto blip

Because not all of us have the time, skill or application to perfect even the more basic rev counting, some cars will do it for us.

Nissan was the carmaker that first developed the technology for use in its 370Z sports car and other makes including some Minis.

Used BMWs and the more sporty versions of certain used Fords use the auto blip. As you might have guessed, this is a piece of tech that rev matches automatically when changing down a gear.

The way it works is by using a combination of sensors in the clutch mechanism, gear lever and transmission that are all connected by the car’s engine management system.

When it senses that there is a downward gear change that’s about to be made, a separate automatic throttle kicks in to raise the revs to the required speed.

The only sign the driver has that this is happening is when they see the rev counter go up momentarily.

Plus, because not everyone wants to have their blipping done automatically, it’s a system that can be turned off by the driver.

To blip or not to blip?

The overall conclusion has to be that rev-matching is well worth doing, whether it’s using your own skill or the car’s in-built technology.

It will make driving more satisfying and could even prolong the life of your car.

Plus, with automatics gradually becoming more popular and electric cars not having any gears at all, this could be one of your last chances to master a dying skill.

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