In the early '60s, my father and many of his co-workers went on a British sports car kick. Some had 4 cyls, some 6es. Someone was talking about how he wished his car was available with a six, cuz his four was so anemic. One of the guys took him for a ride and surprised the heck out of the owner at the performance available from that "anemic four." I remember a comment that "if you're going to run a four cylinder below
3000 rpm, you should be pulled over and stopped."
I don't know what your driving style is, but if you're seeing 1000 rpm at any time your car's moving in a gear other than 1st (and then only when moving at very low speed), I'd suggest your "expert" friend is right--watch that rev counter and keep it wound up (forget whatever that
6 cyl auto Camry does, too! I've got one myself, and it's a whole different animal from my 4 cyl, 5 spd Subie.) With a little practice, maybe some tips from your friend, you can learn rev-matching techniques that allow you to shift up and down smoothly without losing RPMs (I saw an automotive writer once liken using the throttle to "using a dimmer switch, NOT an on/off switch.") That will help "outsmart" the computer that's cutting your fuel flow and make your driving much smoother (as well as taking a lot of load off the drivetrain every time you let it jerk.) Computers are great, for computing! But IMO the programmers are more concerned with fuel economy and emissions than anything else, so the computers try to do things that aren't exactly "right" with respect to getting the most out of your engine.
I was talking to a lady who also owned a 2.5l Outback. She was complaining about the lack of power going over the Sierra Mountains. I asked her if she downshifted and wound it out. "No, it makes too much noise and it sounds like it's hard on the car...."
thanx for the reply oh yeah, I noticed that too..... when RPM below 2000, the torque seemed aint too well to push the car forward, and the engine makes sorta humming noise.... is this common in H4? never driven a 4 cyl before...
Err, yes. That's called "lugging the engine", and is completely normal in a manual shift car. You have allowed the revs to drop too far, and that's how a manual transmission reacts.
Automatics are entirely different, the fluid drive of the torque converter eliminates that "jerking".
I'm guessing you've never driven a stick before. Like the old joke says, "Doctor, it hurts when I do this." "Well, stop doing that." Don't let your revs drop that far, there's almost no reason to do so, and if you really need to creep along like that, feather the clutch.
Pulling away in second is no big deal, either. It's a good thing to learn to do, to prevent tire slippage on slick surfaces, though with a Subaru that's less likely.
(Try having your shifter jam in 4th some time (not in a Subaru), and finding out at a stop sign at the top of a hill. That was fun.)
Can't say I'm an expert on what range to run you car in, but I've learned a coupla things in the first million or so miles I've put on smaller (under 2 liter) 4 cyl engines that might help... at least I can say they "work for me!"
First thing I look for is the specs on the engine: I want torque and horsepower peaks. I don't know where the numbers fall on the 2.5l, but let's use my 1.8l for an example. Torque peak is in the neighborhood of
3200 rpm. Horsepower is around 5000 or so. This is similar to most other fours I've owned, so it serves well enough for discussion.
Others can describe better than I what the differences between torque and horsepower are, but let's oversimplify things (these are generalizations, no need to nitpick any slight errors right here) and say torque gives the ability to keep the load moving, horsepower gives the ability to make it move faster. Once torque reaches its peak number, it generally stays fairly flat over a wide range of engine speeds before dropping, while horsepower continuously climbs until its peak, then usually stays at that level only for a short time before starting to drop off, sometimes dramatically. So while my engine redlines at 6500 rpm, it may actually be making less power at that point than it does at
5500.
Now, what's this mean for driving? Basically, for most purposes, I find I get the best OVERALL performance (combining acceleration, passing ability, fuel economy, engine life) by keeping my driving within the rpm range defined at the lower end by the torque peak and the upper end by the horsepower peak. So, for my engine, that's saying I should keep it between 3000 and 5000 rpm.
Below the torque peak, the engine will work harder to do the same job, down to the point you're lugging the engine, which CAN do harm. With a four, you're less likely to harm it by winding it up than by lugging it down (assuming you're NOT lead footing it. You'll get better lubrication keeping oil flow up, better cooling by keeping coolant flow up, better fuel economy by letting the engine breathe properly, etc.)
Above the horsepower peak, you're probably not gaining much (there ARE reasons to hit redline, but IME most people don't REALLY know what they are or use them properly.)
Now we look at shifting points. As a general rule, manual transmissions on the cars I drive are set up with a span of somewhere around 1000 rpm between gears (some are wider, some closer, but let's stick with this number for now.) I want to keep at or above the torque peak in each gear, so a beginning shift point is relatively easy to figure: take where you want to be in the next gear, and add 1000 (watch your rev counter to learn the actual shiftpoints to use in your car.) In other words, I want to start in 1st, and still be at 3000 rpm after the shift to 2nd, so I take 1st out to 4000, then shift. I continue that thru the gears. For downshifting, if I'm starting to lose rpms below my target of
3000 rpm in whatever gear, I'll downshift. So if the car's not pulling well (as in I have to do more than just cruising) at 3000 in 5th, I'll drop to 4th, etc. For example, if I'm cruising along on flat ground in
5th at 3000, then start up a grade, when I feel the engine starts to take more and more throttle to hold that engine speed, I'll downshift. One should NEVER let the revs drop to where the engine starts to buck.
About now the "higher rpms mean lower gas mileage" folks start to wave their hands in the air. This is where the guys who program the automatics get to put their two cents in, and they usually screw it up IMO. I'll agree, there's no sense in running excessive engine speeds, but there's a range where the engine works best, and many automatics are programmed to run below that range more than is good. Which they can do smoothly, since there's slippage in the system as others have described. But your manual has already told you what's not good when it started jerking.
Last point for now is when do we wind the engine up further? Using my engine, normal shift points when I'm not trying to get somewhere in a hurry are around 4000 rpm, which keeps me at 3000 or so in each successive gear. That's fine for normal use. But there are times I need more: passing, merging onto the freeway, driving up in the mountains. This is where experience and "feel" for a particular car, engine and gearbox come in, but I'll sacrifice a tiny bit of fuel economy for the control of knowing exactly what the car's gonna do next in these situations. For example, when merging into 70 mph freeway traffic, I know the car CAN go 70 in either 3rd, 4th or 5th. But in 5th, I'm down around 3000 and the engine isn't coming up on power, so I can cruise, but not accelerate easily. At 4000 in 4th, I've got power coming on, and can continue to accelerate when that guy yakking on his cell phone in the big SUV is coming up on me a bit fast and doesn't seem to notice I'm in front of him. So I'll plan my upshifts to keep the engine up on the power band with some reserve until I'm in a position to upshift safely--which moves my 3rd-4th shift to 5000 and so forth. This is where that "extra" range between the horsepower peak and redline can be properly utilized once in a while.
There's WAY more to all this than what I've explained, and I apologize if I haven't done a good job, but I think you can see what we're trying to achieve. For a REALLY graphic demo of the "theory" see if you can hitch a ride with a big rig driver and watch how he uses those 10 or more gears for a while. BTW, once you've gotten your engine broken in, you'll probably find you will actually get better fuel economy using "my" method than by simply trying to keep rpms as low as possible! And you'll probably also be amazed at how much your engine can do without ever even seeing WOT (wide open throttle!)
Sorry, Ed, I'm half asleep here: is that range the point below which you'd downshift (like the 3000 rpm point on my engine), or the upshift point (like the 4000 rpm point on mine?)
I think that is a very succint explanation of how to handle a 4 banger. Wish I had known that when I first got my 1.8L VW GTI. Now that I'm driving a '03 WRX Wgn lessons learned with my first 4 banger are helpfull, just have to learn how to use the turbo better.
I'd just like to point out, for the record, that following this advice on a WRX STi will give you extremely bad gas mileage, will be obnoxiously loud and piss off your neighbours, and will generally make the car more difficult to control.
The HP/torque peaks in the STi are 300 ft-lb @ 4000, and 300 HP @ 6000. If you keep your STi between those numbers, you're going to be wasting a lot of money on gas.
The STi has, in my experience, the best gas mileage at that sweet spot right around 2100 - 2900 RPM. The engine doesn't labour up hills, and the overpowered turbo hasn't fully kicked-in to eat up all that extra gas.
Shifting is easier, rev-matching is easier.. it feels like you're gently rocking the car to sleep at that RPM.
"Sleep, my friend, we're not racing to work this morning."
No argument--remember my post was prefaced to address "under 2 liter" engines, few of which are "overpowered" in street trim, and further went on to mention "experience" with a particular car...
Now, it's no surprise if what I described as a driving style won't work wonders on an STi on the street. Why not? Let's face it, the STi is probably closer to being a street legal race car than a reasonable daily "driver", kinda like a return to the concept of some of the late '60s-early '70s muscle cars (of course it handles, stops and does all that stuff those cars didn't do!) Not to say that type of machine can't be a fun car to drive, but it's too much for many drivers. Your comment on "more difficult to control" suggests that problem may surface here. OTOH, an STi on the track in the hands of a driver experienced with such cars is probably a joy to behold!
But... people will buy what's offered, so cars like the STi have a built in market! And I'm glad they do--the almost total econobox mentality of the mid-'70s to mid-'80s or so was pretty boring. Still, I think I'd be hesitant to want a car I had to almost lug around to keep from going broke at the gas pump or wrapping around a tree when it got away. Guess I was in on building too many of those 40 years ago... some things don't change much!
I'm still trying to decide whether you're playing around, or whether you're serious--no, there's not point now in trying to tell me one way or the other. :)
Anyway, even the 2.0L WRX was similar in its power delivery band not being an appropriate cruising RPM. Your advice just doesn't apply to any modern Subaru vehicle in N.A., and it certainly doesn't apply to the topic of discussion in this thread: the guy has an 06 Impreza Wagon. :)
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