If the problem was that he couldn’t make it up the hill at all, then downshifting would help, but that’s not what he said. He said he can’t maintain a speed of 65 MPH going up the hill, and downshifting won’t help with that. The maximum speed you can maintain going up a hill is purely a function of engine power.
Key word there, “little”. It takes more power to move a big mass uphill at speed than it does to move a small mass uphill at the same speed.
Well, I’m not a mechanic or a physicist or anything - but what about torque? Or keeping the engine at / near it’s peak power revs?
I’m sure there’s any number of people here that have more experience with the matter than me. But I know from my own experience that what “pulling power” my car has at 60 in 5th is very different to the “pulling power” at 60 in 3rd.
Personal experience tells me that while I may not be able to accelerate at a given speed in 5th, if I shift to a lower gear, higher revs I have more “power” to pull. Part of this is going to be of course the better gear ratio - part is also going to be that I put the car into a higher place on its power curve - bearing in mind that for most engines peak power is somewhere round the 5k RPM mark (give or take) and I would expect a “V10 Truck” to be turning over at what - 2k RPM at 65? Which may only be generating 50 - 60% of peak power.
And small is realtive - if the V10 Truck doesn’t have a better power to weight Ratio than my car, then either the designers are stuck in the 60s or I will toast my hat and eat it with strawberries and cream.
I don’t know, what about torque? What’s the question? And the peak power revs would work against downshifting, not for it: Going 65 MPH at anything other than your top gear would mean that your engine is running at well over its optimum rotations per second.
Your notion that your car has more “pulling power” in lower gear may be due to a misunderstanding of what power is. Your car can exert a greater force in low gear, but it also moves slower. Force is not power; power is the product of force times speed. Your car’s power is the same in any gear; it’s just a question of what the breakdown of force and speed is.
Optimum for what? 6th / Top gear is normally set at optimum for fuel economy.
I just checked a Dodge Viper SRT10* ('08 Model).
Maximum power is generated at 6,100 RPM. For a vehicle like this, at 65 is Top gear is not going to be anywhere near 6100 rpm. So be shifting to a lower gear, revs go up, the engine will be generating more power - so speed should be easier to maintain.
Take a look at the POrsche 911 GT3 power / torque graph Here I can see that at 2,000 RPM the car is generating abt 82hp, at 7,600 RPM it is 415hp.
So - more revs = more power. More power = higher speed on the gradient. How to get more power? Shift to a lower gear. (not that simple because lower gear also = lower drive ratio, but you get the point - I hope)
*OK - not exactly a truck, but it is the first US based V10 that occurs to me, the next would be a Lamborghini Gallardo, which has even less relevance
Sorry - wanted to specifically address this. The power generated by the engine is NOT the same in any gear (assuming speed is held constant) Why do you think manufacturers specifically tell you where in the rev range peak power is generated, why some cars tell you when the best time to shift is? Engines generated different amounts of power and torque and different revolutions. Moving down a gear moves you up the rev range, which generally means more power…
This may be true if you’re driving a Geo whose engine is screaming in top gear at 65 mph. In most cars, the engine will be turning pretty low RPMs at 65 mph, especially if top gear is overdrive. Like maybe 2000 or 2500, pretty far from peak horsepower and torque. They make it this way for fuel efficiency. Less RPMs means the cylinders are undergoing combustion less times per minute. You don’t need all that power to stay at 65 on a level road. Here is a dyno graph of a '05 GTO. This may help illustrate the idea of peak power. The lavender-ish color is torque and blue is horsepower.
This is all fine and dandy until you need to accelerate, or climb a hill. Now, you might not have enough power at that low of RPM to maintain 65. There are only two ways to get closer to the optimum RPM, either by accelerating in top gear until you reach it (not possible in this scenario) or downshift to a lower gear.
[anecdote] Recently I had to drive an older vehicle up and down some steep grades through part of West Virginia. The car had a V-6 that was pretty worn out and weak. On the uphill, the car couldn’t maintain the speed limit (either 65 or 70 mph i think) while it was in top gear. It would slow down to probably 50 or 55 by time it got to the top. That is unless I downshifted out of overdrive and into 3rd gear. Unfortunately, the car blew massive amounts of blue smoke out the tailpipe when I did this (due to the engine being extremely worn out)so that was out of the question. :eek: [/anecdote]
Honda can be seen on its website boasting about its transmission in the Prelude, which includes the Grade Logic Control System.(about halfway down the page)
In the case of the V-10 truck, if bengangmo’s assumption is right, and the truck is in top gear at 2000-2500 RPM at 65 mph and not able to maintain speed, a downshift would most likely help.
100%. I’m not suggesting fast cars not be available, but the current situation of fast cars (by this I mean cars capable of exceeding the speed limit quite generously) available employing technologies which can (have… will?) go awry and result in the car being at higher speeds than the driver wishes opens the door on a lot of legal issues.
What if a Toyota driver gets pulled over for speeding and insists he’d tried to brake but the car didn’t respond, in fact it accelerated? The government has allowed him to be sold a vehicle capable of exceeding the speed limit and now wants to punish him for speeding, although the driver didn’t wish to speed?
I have difficulty believing that modern automotive technology couldn’t design an engine/transmission system that is very economical, and quick to accelerate to legal speeds (or even say legal limit +20%) but not exceed them.
I think that you need to move away from this issue of “evil car accelerating when driving didn’t want it to” the number of cars that have done that is actually vanishingly small when compared to the number of cars on the road. Its a sideshow.
You real question needs to be - why are we enabling people to break the law (when it serves no pracitical purpose), then punishing them for breaking the law.
And in answer, I don’t think the days are too far away when you will see every car fitted with GPS, and then will come speed limiters linked to GPS… (as in, GPS will know speed limit of your location)…so speeding will basically become impossible.
This is what I was getting at.
From there, it’s probably not far to “self-driving cars”. You can bet we still won’t have flying cars or lunar holidays by then, either. 
Well self driving cars aren’t so very far away either. I think Singapore would be the perfect test bed - their vehicle laws and small size make it a perfect test bed.
I think the biggest hurdle is “knowledge of precise placement” on the roads - and for Singapore this is easy to overcome.
I don’t think you’ve framed your OP well because restricting top speed by restricting engine power is never going to work: people are always reasonably going to want power to cope with load and hills and to gain acceleration. ISTM what you should be asking is why speed limiters aren’t compulsory. With GPS a system that controlled top speed depending on where you might be is hardly technologically infeasible, so most of the jurisdictional or geographical objections could be overcome if the will was there.
Really, the difficulties aren’t technical, they are a matter of philosophy and politics. Philosophically many would regard it as overly nannying and big brotherish.
As to politics, IME everyone speeds. Everywhere I’ve driven with the possible exception of Norway, driving at the limit on a road where traffic permits you to go faster will hold up a long line of cars. Almost everyone goes a certain margin above the limit, and they like doing so.
Safety studies show that speed kills, and most people would tut tut at speeding if asked their views in public, but then they also like to go fast for fun and convenience too.
This means the subject is a political hot potato. Activities like speeding, drink driving, viewing porn (where illegal) and taking soft drugs are or were at one time in the same sort of limbo. People like to indulge secretly or not so secretly in these activities but at the same time feel they shouldn’t or shouldn’t be seen to. The common political compromise is to make them illegal but not enforce too effectively, thus allowing politicians to both claim the high ground when necessary while not upsetting a large body of voters too much.
How about we just stop with the thinking that we need big government to legislate every minute detail of our lives. Enough already…
GREAT thread, RD…terrific question.
I loved the Eden analogy. (Just did a thread of my own on that subject!)
Apropos of the question, I often wonder why manufactures are allowed to have television ads that show cars obviously speeding and doing things that would never be allowed on open roads…often with disclaimers! And showing automobiles as “big dicks” with speed, muscle, and maneuverability at high speeds being highlighted…really make piss-poor sense considering the carnage occurring on our highways each day.
In any case, I have fewer problems with higher speeds on some of the highways and turnpikes than I do with the streets normally designated 25 MPH roads. The idiots who speed down small streets where kids often play or animals walk are the ones who bug the shit our of me.
I live on a street with a school at one end…and where parking is allowed on both sides of the street. 25 MPH is too fast for the road…but that is what it is posted. I do not know of anyone other than myself who actually honors that…and the majority seem to think 40 or more is reasonable.
WTF is it with people so anxious to get where they are going that they do not care that animals and kids often dart out into the street without looking or thinking…and a “I didn’t mean to do it” does not change the condition of someone or something smashed to pulp in the middle of a road.
Speed governors seem to be in order…or devices like in the **Tapioca Dextrin ** link should be required…and the fines for going over the limits our to be increased significantly.
Government does just fine in many areas!
I suppose some people would just as soon do away with all those pesky traffic lights and stop signs also…but there are more of us who see the need.
This isn’t really relevant to the thread except possibly to show that maximum speed limits change by state and over the years, but I don’t think there is a single state that still has a 55MPH maximum speed limit. Speed limits in the United States - Wikipedia
I recently wrote an article for a magazine.
At 50km/h, if someone steps into your lane 30m in front of the car, you can stop
At 80km/h, in the same situation you will hit the person **before you can even react.
**
So it’s not a matter of hitting a few km faster, that 30 km/h is the difference between stopping and hitting someone at 80.
Yeah, I speed, and yeah - this scared me on hell of a lot
Ford 3/4-ton pickup, long bed, crew cab, V10.
I always turn off overdrive coming up to that particular grade. If I leave it in drive, it will slowly lose speed. If I downshift to 2nd, I can almost hold 65mph to the crest of the hill. The truck simply isn’t designed to go that fast in 1st, so I’m not trying that experiment.
Yes, it’s a seriously steep grade. I’ll have to go check the sign, but I think it’s 12%. The primary issue, though, is that it’s long and has a turn at the base of the steepest part, so if the road is at all wet, icy, or otherwise slippery, you’re starting the worst part of the grade at below the speed limit.
I’m certainly not saying the truck can’t climb that hill. I’ve climbed it towing 10,000 pounds, albeit at 30mph. But I can’t (quite) maintain the speed limit all the way up when the truck is empty.
I remember in the 1950’s there was talk about cars in the near future being self driving. Just get in put in your destination and the car will drive you there.
You can already get self parking cars. My car has adaptive cruise control. Self driving is getting closer.
Because it’s the governments place to set laws that are reasonable.
Saying that there’s never a situation in which a person could exceed the speed limit, under reasonable circumstances, is ridiculous.
In my short life of 19 years, I know of three situations where it was necessary or prudent to exceed the speed limit. Once, an at home birth went terribly wrong, with the mother and babies lives being put in danger, there wasn’t time to wait for an ambulance (both the mother and baby are healthy, though they thought the baby might have been brain damaged – she’s not), once when someone cut off their hand (I guess they might have been able to wait for an ambulance) and once when someone was very ill – although strictly speaking that last one was only necessary because they lived so very, very far away from anything resembling civilization.
