I have a hypermiling application for my tach.
If my car is above 1200 RPM with no throttle, fuel injection ceases, which saves me gas.
If I’m decelerating, I’ll downshift just above 1200 RPM to keep my fuel injectors shut off when I don’t need to maintain speed or accelerate.
I don’t really see downshifting during deceleration to move the car from 1300 RPM to 1800 RPM as hurting the engine or tranny, and it can substantially improve my gas mileage if I’m driving certain routes.
That’s a nice application, but optional. My first manual tranny car just had marks at the redline for each gear on the tach. I just shifted at half the redline speed for a given gear and was fine.
Without the lines, I could have just learned by feel and sound.
My Mazda RX-8 redlines at 9k…I kind of like thinking of that as “astronomical.” 
Agreed. I learned how to drive on a manual, and I don’t remember ever “absolutely needing” to look at the tach. I’m frankly not sure my mom knew what it was (or if that car even had one), and it definitely never came up in my department store driver’s ed class. I learned how to shift purely by ear/feel.
Rotary engines are a little different. It’s still crazy high (and very cool), but they don’t tend to blow themselves up like piston engines when you rev them to high heaven. The same 9k RPMs is a little more impressive (from an engineering standpoint) in the S2000 since it’s a piston engine.
People rev race-prepped rotary engines to something like 14 or 15,000 RPM…they are nuts. As long as you can flow enough air, you can make power that high with a rotary. It’s those apex seals you have to watch.
Buzzkill. 
Ok SpeedWay, let me apologize first for going over the top. You seemed to me to be taking a confrontational tone, but I could have just avoided escalation. Your last post explains your point of view, which is quite reasonable. I didn’t pick that up from your earlier posts, and I have an unfortunate tendency towards hot-headedness.
Yes, for those who know what they are doing, the tach can be useful. And I use it myself for evaluating my gas mileage. I only have one car with a stick now, and only put a couple of thousand miles a year on it, in the summertime only (ragtop), so at the beginning of the season I’ll keep an eye on the tach to make sure I’m shifting at the right speeds, looking for clutch slippage, and checking for poor mileage. So yes, there are useful functions for a tachometer, for me, for you, and for an additional smalll percentage of all the people who have a tach. The original intent of my statements was that the vast majority of tachs are unused, or used for dumbass stuff, like teenagers power braking cars with an auto. I suppose it would have been easier to clarify that than arguing with you and escalating a misunderstanding into an argument.
"Wombat": my apologies to you too, for making your job harder.
No worries man…I apologize as well, for coming off as confrontational from the get-go. I guess when you get a couple of us hotheads together, it’s bound to happen occasionally. I’m new here, so hopefully I can figure out the tone of this board and fit in and discuss fun stuff without things escalating into this type of thing. I totally agree that while a tachometer is important to you and I and some others like us, most of them probably don’t really get used, especially on a car with a “slushbox” 
What kind of convertible do you drive?
Misnomer: don’t take that as a buzzill – the RX-8 (and its predecessor, the RX-7) is a cool car, and the rotary engine is a really cool piece of mechanical technology…I’m glad there’s still a rotary-powered car available today. The whole reason that 9k is slightly less impressive on a rotary is that rotaries ARE so rev-happy and well-engineered!
My baby is an '85 Celica GTS. One of only 2000 made. I’ve kept it mint condition until recently. Now little plastic pieces are breaking of their own accord, and it needs a few touch-ups to the paint (painter did a fabulous job though, Viper-Red, he relined the doors and the hood, and put a thick sputter coat on the lower half of the body).
I need a new timing belt, valve adjustment, and power steering unit, so I’m considering a full engine rebuild. There’s a big shop in the Northwest that specializes in 22R engines, so now that its off the road for winter, I might send it out. They can bore it out, but I’ve kept everything so close to stock so far, so I don’t think I’ll do that.
I just moved out a Corolla with a Mazda rotary engine, so with only two other cars around to drive, I’m starting to feel needy. I’ve lost out on two recent attempts to pick up muscle cars, a '71 Chevelle with a 327 had a title dispute, and a '68 Charger Hemi, but the guy left town before we could settle. I keep running across old Mustangs, but they are in such sad shape I’ll never find the time to get them running, and they are always overpriced.
How bout yourself?
Right now, I’ve got a mildly modified 1997 BMW M3 (K&N filter, exhaust, suspension mods, etc) and a 1970 Chevy C10 pickup with a decently built 350 that could use some rust repair and a paint job. I’m a fan of 80’s Japanese steel too – I’ve owned 3 Honda CRXs (a second-gen Si and DX, both with Japanese-market VTEC engine swaps, and a first-gen Si with the stock engine). My first vehicle was an 88 Ford Ranger with a 289 V8 pulled from a '66 Ford Fairlane with lots of go-fast parts. I’ve also owned a turbocharged AWD Eagle Talon (Mitsubishi Eclipse sister car) with the boost cranked up and lots of goodies. My uncle has an early 90’s Toyota 4x4 pickup with absurdly low miles on it that he bought new, and I’ve already got dibs on it when he finally decides to buy another daily driver (he’s got a C6 Corvette as his fun car, so he’s not terribly motivated to upgrade his truck).
I’m strongly considering a convertible for my next car – a Honda S2000. I’d probably try to get a factory hardtop for it, though. Classic Mustangs have always been some of my favorite cars, I’d love to get one and drop in a fuel-injected 5.0 from a Fox-body Mustang – the block is the same as the old small block V8s, so they bolt right in. An LSX-powered S10 always sounds fun, too. Heck, I’ve got a list a mile long of cars I’d like to own.
A timing belt and valve adjustment are pretty quick and easy maintenance jobs…do you really need an engine rebuild, or are you just thinking it might be a good idea? If it’s still running well, I’d do that work and see how long it keeps running. Heck, if you were around here, I’d tell you to bring it by some weekend and we’d knock that stuff out.
If you do go the rebuild route, though, you might as well have it bored out…even to a purist, an overbored engine is still considered pretty darn stock – after all, we’re only talking thirty thousands of an inch or so.
A Corolla with a Mazda rotary! Now that’s not your run-of-the-mill swap!
My first was a 67 Buick Skylark with 400ci and four barrel. Kind of ugly, but it beat the pants off all those pretty cars with smaller engines.
There’s driving, and then there’s driving with the top down. Whole different world.
I’ve got a list like that too, but it changes almost daily. Usually with something I spot added to the top of the list. The El Camino never gets far from the top though. I had a 84 Toyota long bed, great truck. Got a lot back selling it. F150 now. Always need something to haul stuff with.
Well its starting to burn oil too, and yes, I’d get it bored, but only enough to get good seals. I don’t want to add a lot of horse to something I drive so carefully now, and it’s never lacked for power at it’s light weight. It’s also an aluminum block, and I’d worry how long it could stand up over time with a big bore. It’s always run a little hot, a side effect of fuel injection I think.
A long story how it ended up that way, multiple engines, a dragster, and lots of comedy and tragedy. But it’s not that hard to drop the Mazda in a lot of cars. It’s not too big, or too heavy, and it wasn’t that hard to match the housing to the transmission. It did seem kind of strange when it was all done though.