Bear in mind that only 2.4% of cars sold in the US (at least at Carmax) are manual. The rest are automatic. Worldwide the share of manuals is 30 or 40%, much higher.
Small cars can’t safely tow boats or whatnot yet Hondas still have tachometers. Why? I find the purely aesthetic choice reason most compelling, but I’ll list other comments:
Dihards frequenting YouTube love the tachometer.
What else do you want to do with that space? One poster suggested installing a wine cooler, something I could get behind.
Some people used to drive a manual with a tachometer and they like the extra info
Some people like having a feel for the machinery, during an age when engineers have successfully reduced engine noise. They may even be able to achieve better fuel economy.
Ironically, my old car had a manual transmission but no tachometer. Now I have an automatic with a tachometer, and I’m not using it much.
The whole point to a transmission is to keep the engine within the healthy range of RPMs: less than the redline (i.e., the point where the engine is spinning so fast it damages itself), and above the point where the engine bogs down. Within this range, there are also separate points where the engine is most efficient and where it makes the most power.
If you want to accelerate as quickly as possible, you shift right at the redline. Less than that and you are not at maximum performance; more than that and you will damage the engine or the computer will cut the fuel flow.
If you want to drive more normally, and with better efficiency, you shift at a much lower point (generally less than half the redline).
At any rate, the tachometer helps with both these cases. Experienced drivers can generally shift by sound but they’ll still be more accurate with a tach.
So you are concerned about the red marker, not the number? You don’t have to learn that (for example) 2500 is good but 3000 is bad in situation x? You could have the same advantage by a display with just black and red lines with no numbers?
There are lots of good answers and I think @Francis_Vaughan gave a particularly good explanation for the reasons you might want to have a tach even with an automatic. The simple way I would put it is that it’s useful to have a tach for the same reason that it’s useful to have an engine temperature indicator: engine RPM is one of the absolutely critical performance parameters of an engine, and temperature is another.
The temperature gauge is important as an indicator of engine health (as opposed to a simple “idiot light”) while the tach tends to be more important as an indicator of performance and how the transmission is behaving. Furthermore, with modern automatics there are various ways to control shifting and RPM, including just the throttle. Even aside from that, I like glancing at the tach when at highway speeds to confirm that the overdrive has engaged and the engine is comfortably idling at a low RPM.
It’s true that the “need” for this kind of information is somewhat subjective and the person solely interested in getting from Point A to Point B may not need anything more than a speedometer, and perhaps not even that, but many of us find it very useful to have information about what’s actually happening under the hood.
Sorta, yes. The number is just so you can remember what works best. RPM is an arbitrary unit anyway; it could just as well have been radians per second or something else.
Different engines have different redlines. 5500, 6500, even as high as 9000 RPM. It depends on the design.
The “normal” shift point also depends on the engine, but your preferences as well. Maybe you want to drive a little more aggressively, or a little more efficiently. So your typical shift point will vary based on how you want to drive. I tended to shift my BMW at 3000 RPM, which is arguably a little high but had more oomph than shifting at 2500. On the other hand, there are some high-strung engines for which 3000 wouldn’t have been on the high side at all. It’s variable.
Take this with a grain of salt, but I’ve been told that modern ECUs don’t display accurate information on the temp gauge, because people will call in to service if it reads on the high or low side of normal. So instead the gauge only ever displays high, low, and dead center. Making it no more useful than an idiot light, since it’s been reduced to a binary (er, ternary) error condition.
I don’t care about quantitative accuracy, but I do care about relative temperature fluctuations. And on my car, at least, the fluctuations seem to correspond with reality in a useful way. If I’m stuck in heavy freeway traffic on a hot day with the A/C on, it will climb somewhat higher than normal, then drop again when I finally get moving. I find that information valuable, and important to know if the temperature is climbing to abnormal levels. The temp gauge also seems to accurately indicate the gradual warming of the engine from a cold start. So I’m a bit skeptical of your claim, though there may be some element of truth that is perhaps being exaggerated.
I’ve also been told that the outdoor temperature indicator is equally inaccurate, but it seems to work just fine on my car, and often reads exactly what the weather report just announced. I notice that it’s often higher on hot sunny days on big freeways, but I presume that’s from all the heat radiating from the wide black asphalt.
Formula 1 cars have electronically controlled gearboxes but are shifted via paddles by the driver. Drivers get indications as to when to shift via the on board computer systems. Most have shift lights on the steering wheel, but some drivers prefer sounds delivered into their earpieces. Lewis Hamilton for instance.
Interestingly these shift indicators are programmed by the engineering crew, and don’t just take into account the track being driven but also intrinsic human lag times, with the lag being tweaked to the driver’s preferences. If a particular corner is loading the driver with work, the shift indicator can be pushed a bit earlier to compensate. The margins of performance are silly tight.
All right, that’s different behavior than I ever saw. Aside from the initial warmup, I never saw my temp gauge budge from dead center, regardless of load or outside temperature. Either the thermostat was perfect, or the car was fudging the numbers. It’s possible the practice varies between makes.
I drive automatics and I find the tachometer useful in one situation: when you’re mired in snow.
See, if you pay attention to the tachometer when you’re stuck in snow, you know when you’re pushing the engine too hard - the needle shouldn’t be in that easy-to-see red section. And you don’t set the car on fire like my dad did. The fire department wasn’t impressed, and he had to pay out of pocket for his replacement car because that kind of idiocy wasn’t covered by his insurance policy.
The two times my temperature gauge didn’t just rise up and sit in the middle were when the thermostat failed and when the radiator leaked.
Useful gauge.
C programmers will understand the old joke about the poor error messages in the early C compiler.
Brian Kernighan’s car: its only instrument is a big question mark on the dashboard, which lights when something goes wrong.
“The experienced driver,” Dr Kernighan is quoted as saying, “will know what’s wrong.”
Not really useful as a gauge, though, since it only gave you pass/fail information. That’s in contrast to speedometers and tachs (not to mention gas gauges), where the range of values they provide are actually useful.
The tachometer in my automatic can be very useful when I am driving downhill, and using the engine as a braking device. In paddle shift mode, I can easily figure out whether to shift up or down depending on the slope angle, my present speed and rpm. The manual shift mode has set gear ratios, so it functions like a manual shift transmission. Under most conditions, my Constantly Variable Transmission is in auto mode, but I can select manual shift, and must do so in order to do what I’ve described above.
I’ve noticed this as well. On cold days in the winter, it can take much longer for the little bars to build up to the centre than when I’m driving in the summer.
Heck, on really cold days (Wolfpup knows what I’m talking about ), I’ve been able to drive to the grocery store or my office ( between 3 to 5 km) without any little bars ever showing.
Certainly looks to me like the thermomètre is a real one.
If you’re the kind of person who never saw any reason for automatic transmissions to have positions other than park, reverse, neutral, and drive, you won’t see any reason for a tach.
If, on the other hand, you’ve been known to drop it into S (or 2) to let the engine compression restrain your downhill speed instead of riding the brakes; or you throw it into L (aka 1) to merge into the highway from the short little entrance ramp, or into either of those ranges when stuck in the kind of bumper to bumper traffic that goes from 40 mph to a dead stop to 4 mph to 20 mph etc etc… then a tach can be useful. Yes, you can hear when your engine is revving and close to the top of its range; but when your engine is going more slowly and you’re contemplating dropping it into a lower setting, it’s nice to glance at the RPM as it stands now and using that as a guide to which slot to shift to – 1st, 2nd, or whatever.
Actually it was as a gauge it was useful. A failed thermostat is indicated by the temperature only very slowly rising from cold. The thermostat stops coolant flowing through the radiator when the engine is cold to encourage reaching of operating temperature. A failed thermostat means even when cold the cooling system is trying to cool the engine.
I had manuals my entire life until my current car, and these are precisely the reasons I finally got fed up with them: shifting all the time in stop and go traffic, shifting down to accelerate or go up a hill, and so on. My automatic transmission does all that perfectly well without my having to worry about it. If I need to kick it into low gear to accelerate in a short lane, I just hit the gas hard enough to effect the change. If I wanted to drive like you are describing I would still have a manual. I predict this is sacrilege in your eyes, but it’s eminently practical to me.
And while I have great respect for folks like @Francis_Vaughan and their knowledge of cars and driving, all that sounds like way more work and attention than I want to spend on my car. I am a careful driver in the sense of paying attention to other drivers and surroundings and traffic conditions and things like that. I am not particularly careful of my car, and I don’t regard driving as anything but a very utilitarian activity. As it happens, my Subaru Impreza doesn’t have a tachometer. In its place, it has a dial that gives me an estimate of how my current driving is affecting my mileage. Reasonably useful, when I pay attention to it.
The automatic versus manual thing is another of those US-Europe gaps. In Europe, cars have traditionally been overwhelmingly manual, to the point of many Europeans being unable to drive an automatic without at least a little introduction e.g. at the rental company. In recent years this is changing, but I observe that the change happens at different paces in different countries. In Germany, new cars (electric ones aside, of course) are now about half automatic, half manual; in many other European countries, automatic are still a tiny minority. Germany has also recently abolished the old rule that if you take your driving test on an automatic, then your licence will include a note limiting you to automatics.
In my experience, those European drivers who drive manual don’t, usually, watch the Tachometer very closely. Usually, shifting gears is done by listening to the sound from the engine. That tells you when the RPM reach the point where it’s advisable to shift (or thereabouts). The thing about wringing the last bit of performance out of a car by watching the tach is possible, but (at least in my experience, and I’m a manual driver myself) is not what people do in everyday life.
Last week was the hottest day of the year and we took a trip up to the Mogollon Rim to escape; at 7,000 feet it’s cooler. We took the ‘back way’, the Desert to Tall Pines highway. In the lower part there some grades of 7 or 8% so between that and the heat the temp gauge would climb quite a bit. When it got close to the redline I’d shut the a/c off which would hold the temp where it was. At least I didn’t have to do the ‘turn on the heater’ trick.
Back in the 90s, when I went back to driving heavy trucks, I found the tacho an essential tool. Over here we laugh at old fashioned American trucks with a set of dials and gauges that would not look out of place on a WW2 bomber, while we go for the minimalist look.
Trucks then had speedo, tacho, temp and fuel, plus some assorted glyphs to tell you when something unusual was happening. The tacho had a small green area, maybe a couple of hundred rpm, which was the “sweet spot”. The ideal was to change down at the bottom of the green and up at the top.
More recently all trucks have been auto’s, so the tacho has become irrelevant. The gear change paddle is mainly used to force a downshift when slowing for a junction, otherwise, the computer-controlled gearbox makes pretty good decisions by itself.
), I’ve been able to drive to the grocery store or my office ( between 3 to 5 km) without any little bars ever showing.