Optimum Shift Points

Factual Questions
1

I did something both insanely impulsive and extremely sensible this weekend.

A little background. I’ve wanted a Mini Cooper for over 30 years, ever since I went to England at the age of 17. When they were finally released in the US a few years ago, I couldn’t bring myself to spend $20K+ for a car (I generally go with basic transportation). But I never stopped wanting one.

I am planning a sale of a property this summer that should net me enough that I figured with trade-in, I’d either be able to buy one outright or only have to finance about $5K or so. So I figured $20K wasn’t too much to pay for a thirty year dream, and I decided this summer I’d finally get my Mini.

Then I got on Consumer Reports and saw the reliability predictions. Not good. I also wasn’t happy with the gas mileage - isn’t that one of the points of a tiny little car?

So yesterday I bought a Scion XB. Manual transmission (the only thing I’ll drive) and bright yellow ( (I figured the visibility factor would be excellent). It’s way cool. Weirdest looking thing you’ve ever seen, storage space out the wazoo, and a very small footprint, good safety features, great standard equipment, very good gas mileage and very high reliability. Not to mention over $5K less than the Mini I would have gotten.

All of this by way of getting to the point. The dealer told me that I was shifting at too low RPM. I’ve been driving standard all my driving life, and I’ve always shifted by sound, usually around 3K RPM. He said that not only did this diminish my pick-up (which of course I knew), but could lead to the spark plugs clogging more readily - that it actually was a strain on the engine, which I’d always figured I was sparing my engine by shifting so low. Hell, my old Saturn always told me to shift *sooner * than I did.

So what’s the straight dope here? The engine is the same as the one in the Toyota Echo, but the dimensions of the car itself are very different - 155" vs the Echo’s 165 " length, 67" wide vs. Echo 65", 98" wheelbase vs. 93", and the biggie - 65" height for pretty much the full length of the car (figure not available for the Echo). The weight is 2450 lbs vs. the Echo’s 2150 (the Mini is 2,560 - whoda thunk it!), which along with the less aerodynamic shape, I’m sure, accounts for the considerably lower mileage (the Echo gets 34/41 vs. the Scion XB’s 31/35 - still quite a bit better than the Mini S’s 25/32). Oh, and the car (a Limited Edition - how silly!) includes among other features a spoiler and a special, lower resistance muffler (it’s noisier, although not offensively so). I have no idea which if any of these points is salient, so I figured I’d give you everything I knew or could find out.

The dealer said I’d get a feel for the comfortable shift point, but the fact is, I’ve always done it by sound. This car sounds like a jet getting ready for take-off at 4500-5000 RPM, but he said that’s where I really should be shifting. The thing is, he knew I had initial reservations about adequate pick-up, so he may have been bullshitting me. Well, it’s too late now - I bought the car (and I quite love it), but I’d really like to know - at what point should I REALLY be shifting for it to be best for the car. I’m clueless - I did a GOOGLE on shift points and got nothing of value. Can anyone help me?

Sorry for the long lead-in, but I thought you guys might like to hear my little saga for fun. It’s not every day I buy a new car, and surrender a 30 year dream at that!

2

According to the Car Talk guys:

3

Do you know, I never thought of going to the Car Talk website! I thought of trying to call the show, but I never know when it’s actually on and you can call. It broadcasts at a different time everywhere, so how do people know?

Thank you, Dr. Lao!

If anyone has any more specific information, I’d still appreciate it. Are there things other than the sound that I should be looking or feeling for? I mean, I know when I’ve undershifted - you can’t have driven standard for thirty years without knowing that hesitation! But how can I tell what makes the car happiest and will get the best combination of pick-up, gas mileage, and engine wear? I’m willing to sacrifice a little gas mileage for adequate pick-up, but running it up to 4500-5000 every time? That’s what the dealer seemed to think I should do! Can that be right?

Suddenly something I’ve been doing forever seems so complicated! It’s reassuring to know that Click and Clack don’t think I’m doing any real harm either way though. Thanks again.

4

Wouldn’t the boxy design of the Scion have an effect of its mileage?

5

:smack:

Or ON its mileage?

6

It’s probably worth noting that some dealers know nothing about cars other than how to sell them.

7

Your salesman was giving you a line of crap. On a small four like that 3000 is about right for normal driving and good fuel economy. I think he was afraid you’d think the car was underpowered, so he wanted you to run up into the power band before shifting. I’ve been driving stick for over 20 years and have always shifted around 3000 (except when I wanted a little more acceleration). I’ve never had fouled spark plugs.

Congrats on your new car. I’ve been intrigued by the xB – we have quite a few of them in CA.

8

Yes, the boxy shape definitely has some impact on its mileage - that’s why the same engine in an Echo gets 34/41 vs. the Scion XB’s 31/35. Particularly at high speeds you lose some efficiency. On the plus side, it’s got enormous cargo capacity for its size - comparable to most SUVs, and since I don’t go all that far to work each day, it seemed a worthwhile exchange for the occasional convenience of being able to cart stuff around when necessary. Plus, it’s cool, or at least I think so.

It’s true that many dealers don’t know anything about cars except how to sell them. However, this was an older guy (probably 60 or so) who’d been driving standard all his life, and whose business is cars, these cars in particular. It’s certainly not a given that he knows what he’s talking about, but it’s by no means out of the realm of possibility.

I’ve bought the car, and I’m content with that - it’s described in every review I’ve seen as a highly practical, sensible car at an extremely good price for its features and quality. The issue isn’t whether the guy is trying to sell me - that ship has sailed, for good or ill. The question is simply whether or not he was right about the shift points, and what’s the best way to drive it. I’m convinced that it’s not disastrous to drive it either way, but if any one has some actual knowledge of either the specifics of this car or how to judge what is best in general, I’d appreciate the input.

9

I have a '94 Escort Wagon. It has a 5 speed and one of those annoying “upshift indicator” lights on the dash. It doesn’t have a tach, so I don’t know what the engine speed when the light comes on. The shift points are marked on the speedometer, though. It doesn’t seem that the engine is revving too highly when the light comes on.

10

Nope. 3000 RPM is nowhere near high enough for a 1500cc engine to push a big box through the air efficiently. Shift to keep the engine speed between the torque and power peaks (between 4000 and 6000) while accelerating, and cruise at around 3500-4000 RPM. Little engines are built to turn fast, and friction losses are pretty small.

11

Thanks, zagloba. I wondered if that was the case. Oddly, I didn’t find it significantly underpowered even when I shifted at my normal 3000, although it certainly gets better with the higher RPMs. You should go to a dealer and test drive one, even if you’re not in the market. They’re fun!

Mr. Blue Sky. I had the same experience with my Saturn, although that was a little larger, more powerful engine than this. As I mentioned, it often told me to shift before I was willing to, so I think those shift indicators are geared towards maximum fuel efficiency rather than performance.

chaparralv8, I was about to post this and saw yours. This was the impression I got from the dealer - he sounded like he wanted me to change my shifting habits with ANY small car, not just his (he was also very straightforward about this not being a performance car - sensible on his part as he knew I would figure that out anyway). And I had gotten the impression somewhere or other over the years that the newer small engines really were designed to rev considerably higher than the larger ones.

How do you know when the torque peaks are?

12

Check reviews of the car. The automotive press tends to publish that kind of thing in reviews read by the driving enthusiast type.

The 2004 Scion xB has a peak torque of 105 feet-lb @ 4,200 RPM <1>. Peak horsepower is 108 @ 6,000 RPM.

It’s been 4 years since my daily driver was a stick, but you should be safe following your instincts with when to shift.
The more you need to accelerate quickly the further you want to take your car towards the redline before shifting.
With a car like the Scion, you don’t have gobs of low-end torque, so I’d probably choose to shift between 2400 and 4200 RPM 99% of the time. The other 1% of the time I’d be operating it full throttle in order to get out of a bad situation, and might choose to shift right at 6,000 RPM.
For comparison, I have a car with very similar peak RPMs, a modern 24-Valve V6 and a 4-speed auto. It chooses shifts anywhere between 1800 and 3400 RPM for me unless I have the gas floored, in which case it chooses 6000 RPM.

<1>http://www.automedia.com/autoReviews/rts20031001xb/rts20031001xb.asp?affid=

13

Thank you, Mr. Chance!

14

The Car Talk guys’ response disturbs me a little bit. How can that lady’s husband be shifting at 1800 rpm and not lugging the engine? Makes me cringe just thinking about it.
Then again, I’m not one to take advice from. I always delay my shifts until about 5,000 rpm when accelerating. After a couple upshift, when I’m not trying to pick up speed as fast, I may shift into 4th or 5th at about 3000-4000. Part of this may be to make up for not enough power. =) I do find that a lot of people seem to have a fear of running their engines high on the tach. I, on the other hand, believe that the red line is where it is for a reason. If the manufacturer thought it was a bad idea to hit 5500 rpm, they wouldn’t have put the red line at 6500.

By shifting early like you do, you’re probably doing yourself a favor in the way of fuel economy. But for performance, you have to climb the tach a little more. Just do what’s appropriate for your situation.

15

1800 RPM isn’t generally enough to lug an engine. The only engine I personally know of that doesn’t like anything under 2K is the WRX (before the Turbo kicks in the compression is really low and HP is horrible). I can shift from above 1500 RPM in my Matrix (1.8L I4 high compression) without lugging.

OY!, just follow your manual. It should give you speed ranges for shift points. Mine recommends (it’s a 6 speed) a typical 3000 rpm shift point for normal operation as well as max speeds for each gear.

16

You have a Mini? What other cars are available in six gears?
Thanks for the further input, guys!

17

No, I have a Toyota Matrix XRS. The Mini is too small and expensive for my tastes :smiley:

18

[QUOTE]

Whenever you call you will get a recorded message telling you to describe your problem. If it interests them they will get in touch with you. They make it seem as if they are answering these questions cold but in reality they have weeks to research the answers.

19

It’s been my expereince that you want to shift right about at the torque curve peak for best acceleration and about 2/3 of that for best overall driving. Since the torque peak is at 4200 rpms then it would seem that 2800 rpms would be the most comfortable shifting point.
Side note;
You don’t always get the best acceleration by shifting at or near the red-line. if the torque and hp curves aren’t still climbing at that point then it makes no sense to race the engine to red-line just because you can. You would need to see the graphs for the HP and Torque curves to identify the optimum shifting for racing and the best shift point for economy driving.
Article on your Scion.
**With output rated at 108 horsepower at 6,000 rpm and 105 pound-feet of torque at 4,200 rpm, our test car posted a
0-to-60-mph time of 9 seconds flat. Some folks thought the engine refined all the way up to 6,300-rpm redline,
while others felt the car couldn’t be pushed past 4,000 rpm without trembling.
Hardly enough oomph to excite the intended consumer — the young urban male — but what did you expect with only 108 hp?

But even though it lacks the peppy throttle of a 145-horsepower Suzuki Aerio SX or 160-hp Element, the xB has ample
power for passing and merging on the freeway. Still, we couldn’t help but daydream about what a supercharger would do.
Our test car did come with a cold air intake kit which, according to Toyota, added about 10 more ponies under the hood. **
(as mentioned in the other thread, 10 horses might go unnoticed.)

20

Shifting at max engine torque is not the fastest way to accelerate. The fastest acceleration is had by maximizing the area “swept” under the power/rpm curve for each gear. This requires a knowledge of each gear’s ratio and the power curve of the engine. The trick is to shift from one gear into the next at a point that allows both gears to maximize the area under the power curve.

Max torque has little to do with it, because it’s not engine output torque that’s important. It’s transmission output torque (at the wheels). The tranny is a torque multiplier, and the amount of multiplication is given by the gear ratio (along with the final drive ratio). For most street cars, the torque at the wheels in any gear near redline is higher than at any RPM in the next higher gear.

So the goal is to maximize the total amount of power under the HP curve, as well the amount of torque delivered to the wheels. Doing both requires the same strategy: namely, shift late. Not necessarily as late as possible, but late. The best shift points are going to be determined by the characteristics of the car in question.

What all this means is that for most cars, you’ll hold a gear a little past peak horsepower, into the range where it actually starts dropping. That way, when you shift into the next gear, you’re not too far down on the tach.