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I'm not an expert racer or anything but I know a thing or two about it (who knew all that video game playing would actually pay off?). The point of racing is to keep momentum up in the car, and stay off the brakes. By apexing turns choosing the correct line you are reducing the work required by the car's engine. If you drive haphazardly, the car must make up for it by using more fuel. This has probably alreayd been covered here, but it just occured to me the other day.

I'm not an expert racer or anything but I know a thing or two about it (who knew all that video game playing would actually pay off?). The point of racing is to keep momentum up in the car, and stay off the brakes. By apexing turns choosing the correct line you are reducing the work required by the car's engine. If you drive haphazardly, the car must make up for it by using more fuel. This has probably alreayd been covered here, but it just occured to me the other day.

Also consider that the cars when bunched up are really bunched up - usually within a foot or two of each other--in effect, they're all drafting each other and only the car in front is destroying his gas mileage.

Also consider that the cars when bunched up are really bunched up - usually within a foot or two of each other--in effect, they're all drafting each other and only the car in front is destroying his gas mileage.

But 2 cars on the oval track can go faster than a lone car, so there's some aerodynamic help from behind.

cheers,
Bill

But 2 cars on the oval track can go faster than a lone car, so there's some aerodynamic help from behind.

cheers,
Bill


True, but the engine in the lead car works harder.

True, but the engine in the lead car works harder.

Agreed.

A little OT, but here's a thought experiment:

2 identical cars have to get from point A to point B (large distance, level ground)
traveling at almost constant 75MPH. (trying to eliminate hypermiling techniques...)

Is less fuel consumed overall if they do not draft, or if they draft and take
turns in front?

I do not know the answer, but I'm curious.

cheers,
Bill

Agreed.

A little OT, but here's a thought experiment:

2 identical cars have to get from point A to point B (large distance, level ground)
traveling at almost constant 75MPH. (trying to eliminate hypermiling techniques...)

Is less fuel consumed overall if they do not draft, or if they draft and take
turns in front?

I do not know the answer, but I'm curious.

cheers,
Bill

Drafting is far better.

What? You think professional bikers, racecar drivers, and umpteen millions of migratory birds haven't figured this out?

Also, the whole "lead car works harder" myth is only true if you're upsetting the aerodynamics around the side of the car- 2-5 feet max. Otherwise its free energy. Racing does this. Commuting shouldn't.

One problem w/ the racing to 'hypermiling' analogy is that the objective of (most) racing is to get around the track as fast as possible. FE is not the primary concern. (Okay okay, enduros and the like have tire/fuel efficiency concerns as well. But most motor-sports are about getting from one place to another as fast as possible.)

High FE commuting is all about saving energy and reducing fuel usage at all costs. Speed is definitely one of the first thing high FE advocates suggest parting w/.

There may be some parallels. But there are also some very opposing objectives.

The OP cited brake usage. Most auto racers I know are brutal on their brakes. The idea is to brake late and brake hard.. and to carry speed through a corner. High FE uses the carry speed part, but certainly not the brake hard part. If after high FE and you are braking hard/late then you were on the throttle way too long in the straight. No?

I also wonder if apexing is necessarily the most FE line. The inside of a corner is the shortest path. Racing tells us it is not the fastest though, not so good for keeping the speed up. Then hard cornering definitely rubs of speed, maybe gliding the outside of a corner is best for keeping the momentum up, but then that is unquestionably the longest way 'round. I dunno..

The best translation between racing and hi-miling is knowing how to handle/drive a car. Joe Schmo consumer usually doesn't really know how to handle a car. I'd think any pro racer would have an edge when it comes to hi-miling.

As a new member, I thought it would be a while before something came up on which I could speak intelligently. But, I have been an amateur sports car racer most of my life, have lots of experience, some championships, and some reading. A famous California Porsche racer named Alan Johnson wrote a book way back in the late 60's with some analysis. I think some of these techniques would go a long way toward conserving the momentum in a car that has already been bought with fuel.

Johnson classified turns into three types, I, II, and III, in priority order of their importance to lap times. Type I, the most important, are turns onto long straights. Type II turns are those at the end of long straights, and type III and all the slow or in-between turns which are only important in that are used to set up the next type I. Every racer soon learns that fast lap times are made on the straights, not in the turns. The idea is to get onto the long straights, i.e. throught the type I, with a line that gives the highest initial speed onto the straight. Then that baseline contibutes to a higher average speed on that straight. The line through the type II at the end of that straight is used to maintain that speed as long as possible.

The correct way to enter a long straight, or a downhill glide, is to use a late apex so that the acceleration can come on as early as possible. That makes the straight or glide section faster and longer. Treat the end of the straight, or the downhill glide as a type II, using an early apex, again making the average speed higher and length longer.

As nhbubba says, the objectives are totally different, but I think some of the techniques used along the way are similar. Interesting discussion:)

I also wonder if apexing is necessarily the most FE line. The inside of a corner is the shortest path. Racing tells us it is not the fastest though, not so good for keeping the speed up. Then hard cornering definitely rubs of speed, maybe gliding the outside of a corner is best for keeping the momentum up, but then that is unquestionably the longest way 'round. I dunno..

I think that apexing is sometimes very important. After all, using all the available road, both on the outside and inside of a turn, makes the turn straighter, allowing for higher speeds - if speed becomes the issue. If speed in a particular turn is not the issue, then perhaps it doesn't matter much.

As a new member, I'm still learning, but it seems to me that much of the hypermiling is done during repeated commutes over the same roads. In this case, the hypermiler has a good opportunity to evaluate all his turns, deciding which ones have a speed issue :)

Apexing reduces tire slide = less loss of momentum.

One problem w/ the racing to 'hypermiling' analogy is that the objective of (most) racing is to get around the track as fast as possible. FE is not the primary concern. (Okay okay, enduros and the like have tire/fuel efficiency concerns as well. But most motor-sports are about getting from one place to another as fast as possible.)

High FE commuting is all about saving energy and reducing fuel usage at all costs. Speed is definitely one of the first thing high FE advocates suggest parting w/.

There may be some parallels. But there are also some very opposing objectives.

The OP cited brake usage. Most auto racers I know are brutal on their brakes. The idea is to brake late and brake hard.. and to carry speed through a corner. High FE uses the carry speed part, but certainly not the brake hard part. If after high FE and you are braking hard/late then you were on the throttle way too long in the straight. No?

I also wonder if apexing is necessarily the most FE line. The inside of a corner is the shortest path. Racing tells us it is not the fastest though, not so good for keeping the speed up. Then hard cornering definitely rubs of speed, maybe gliding the outside of a corner is best for keeping the momentum up, but then that is unquestionably the longest way 'round. I dunno..

Imagine that you are coasting. You want to keep your speed up as much as possible in that instance. The theory or maintaining momentum in racing is the same. I think the shortest path is not always the most fuel efficient if it cause you to lose momentum in the process.

The correct way to enter a long straight, or a downhill glide, is to use a late apex so that the acceleration can come on as early as possible. That makes the straight or glide section faster and longer. Treat the end of the straight, or the downhill glide as a type II, using an early apex, again making the average speed higher and length longer.


Excellent post, jimepting. I agree that apexing properly and carrying as much as speed through the corner is probably close to the optimal FE strategy.

However, I think in most cases late or early apex may not use the least fuel overall. For example, in everyday driving, a straight is usually after a turn, and it's analogous to the Type I turn. In racing, we want to maximize the exit speed of the turn, so we should apex late and get back to accelerating early. In FE driving, we probably want to minimize the energy wasted (due to braking or coasting) in entering and getting through the turn. The intuitive thing to do is to maximize the minimum speed during the turn to minimize the energy required to accelerate the car back to cruising speed. If we decide that we are going to use at most x% of the available traction in the corner, because of the variable radius of the late-apex line, its minimum speed in the turn is less than the speed of a line with a neutral apex (is that the correct term?) with a constant radius. In the picture, if we take the late-apex cyan line, we may have to slow down to 32mph in the corner before we get back on the throttle because of the smaller radius before the apex, yet the neutral-apex green line only requires us to slow down to 35mph and maintain a constant speed in the turn. This means the late-apex line costs us 3 extra mph of energy to get back to cruising speed after the turn. So, although the late-apex line gets you back to cruising speed sooner, the neutral-apex line probably saves more gas.

Of course this simple comparison between lines is done without an accurate FE model of the vehicle which at least takes into account the efficiency of the drive train during different load conditions. It probably is of little use in real world, where the narrow lanes and high curbs probably make the difference between the lines insignificant. On the other hand, using more of the available traction (with a healthy reserve for the unexpected, of course) and carrying more speed during a turn probably should the the first thing to look into for FE driving.

http://upload.wikimedia.org/wikipedia/commons/thumb/b/b7/Racing_line.svg/600px-Racing_line.svg.png

Why don't some of you with SGs do some comparisons on turns on your daily commutes?

Hi 93Hatch:

___Because an SG-II or OEM instrumentation is not going to show the difference between the three. There are other factors at work and fortunately, the scrub losses can be reduced because we are generally not running high speed. Second item is there is no lane markers although I run the light green without consideration for lane markers when conditions allow.

___Good Luck

___Wayne

Of course this simple comparison between lines is done without an accurate FE model of the vehicle which at least takes into account the efficiency of the drive train during different load conditions. It probably is of little use in real world, where the narrow lanes and high curbs probably make the difference between the lines insignificant. On the other hand, using more of the available traction (with a healthy reserve for the unexpected, of course) and carrying more speed during a turn probably should the the first thing to look into for FE driving.

http://upload.wikimedia.org/wikipedia/commons/thumb/b/b7/Racing_line.svg/600px-Racing_line.svg.png

Excellent analysis spacepilot. Racing I know - hypermiling, not so much:) After reading your post carefull, I tend to think that you have it right. I suppose the real answer would lie in experimentation, as someone else suggested, or in an extremely elaborate computer simulation.

I learned when I was practicing various racing techniques (heel&toe, cornering, etc.) on the public roads, at safe speed of course, that many traffic lanes are about twice the width of a small car. So, there were some opportunities to put at least "mental" picture together.

Loved the graphic. Lets see what others have to say:)

Another thing to think about is that if you're coasting through a turn and pushing the limit, you will have less available traction through that turn than if you have the transmission engaged and are pushing through. ie - I maintain more of my available momentum if I use a little juice through a turn as opposed coasting alone, because my front wheels (FWD) are maintaining traction by appying force in the new direction - correcting the vehicle's direction. Savy?

Imagine that you are coasting. You want to keep your speed up as much as possible in that instance. The theory or maintaining momentum in racing is the same. I think the shortest path is not always the most fuel efficient if it cause you to lose momentum in the process.Perhaps. But only if the shortest route means you loose momentum. Is that always the case? Not for me.

Given two routes where the driver and machine can maintain the exact same FE, the shortest will use the least amount of fuel every time all the time. Therefore if you can maintain the same momentum, the inside line (no apex) would be best for minimizing fuel usage.. which after all, is what we are all after, no? However this would not be reflected in your FE calcs; it would be reflected in less overall usage instead. (And we can't compare that! ;))

Don't get me wrong folks, I'll keep hitting those apexes as w/o them my life just isn't the same! :D

Hi Maxx:

___If you are applying any kind of power to keep the front end hooked up in a DWB turn, you are coming in way to hot and you are not saving anything in the way of fuel while doing so. Cart racing is pretty cool up to about .4 - .5G’s but anymore on public streets and you will eventually end up sliding your ride into somebody’s front lawn or worse yet, maybe even into their house :rolleyes: This is not a race to see who is first around the corner but who saves the most fuel. They do not necessarily go hand in hand although it can be a little fun when and where they cross paths ;)

___Good Luck

___Wayne

BTW, the term I've seen used for the line that is neither an early nor a late apex line is "geometric apex".

Turning the steering wheel at all increases RR --in racing terms, it "scrubs speed", which means friction, which means more resistance. So the less turning you can do, the better. But you wind up trading off how hard you turn the wheel for how long you are turning the wheel. There must be some sort of minimum for overall friction, and I think (without analytical proof) that the geometric apex line is the line that does that.

I find myself going into corners "hotter" than I otherwise would because I know I have a long glide coming up. The two main examples on my commute are pulling into the parking lot at work, and turning onto my street at home. I am certainly scrubbing off speed, and therefore throwing away kinetic energy, by going around those corners relatively quickly. But my choices are to do that, or to accelerate after the turn.

I'm starting to think that my approach may not be correct, here... Perhaps I should enter the corner at a slower speed, so that I am scrubbing less. I will have to accelerate a little after the turn, but that will be at a lower speed and will likely use less fuel than I use getting to the higher speed before the corner. Hmmm....

Anyway, there are certainly parallels between racing and hypermiling. Especially when you race a "momentum" car, rather than a "point and squirt" car. But the object certainly is different, so even the similarities would be approached with a different mindset.

I'm not sure you needed my two cents' worth, but there it is! ;)

-soD

I think that like racing, hypermiling requires your full attention and focus. You pay attention to things that casual drivers are completely unaware of. Maybe that's why hypermiling is so addictive.
I used to race sailboats a lot and I still occasionally do the friday night "beer can" series at the Austin Yacht Club. Winning at this sport demands total focus on what is going on around you.

Excellent analysis spacepilot. Racing I know - hypermiling, not so much:) After reading your post carefull, I tend to think that you have it right. I suppose the real answer would lie in experimentation, as someone else suggested, or in an extremely elaborate computer simulation.

I learned when I was practicing various racing techniques (heel&toe, cornering, etc.) on the public roads, at safe speed of course, that many traffic lanes are about twice the width of a small car. So, there were some opportunities to put at least "mental" picture together.

Loved the graphic. Lets see what others have to say:)

Lol. Racing and hypermiling, I don'g know much about either. But I'd like to learn more about both. That's why I lurk around the CleanMPG forums. And I just picked up my first book about racing, Skip Barber Racing School's "Going Fast", in the hope that I can be at least a better spectator, and one day I may take some racing lessons and drive on the race track. If I have some questions about racing, do you mind if I drop you a message and ask?

I knew that the average lane width in the US is about 12ft, and a small car is about 70" wide, but it never dawned on me that a lane is as much as two times wider than a car. I guess racing does change how one thinks about driving. :) Well I'm a chicken on the road, and I surely don't have your ability to control the car, I think I'll try to stay in the middle and not use the full width of the lane for now.

As much as I want to, I cannot take the credit for the figure. I found it on wikipedia. For the overall FE, I think that efficient deceleration before and acceleration after the corner, which I have little knowledge of, is as important as the line taken in the corner. And I don't know how the energy lost due to cornering relates to the G-load, as some_other_dave has mentioned. I'll keep an eye on this thread, and see what others has to say. :)

Hi Maxx:
___If you are applying any kind of power to keep the front end hooked up in a DWB turn, you are coming in way to hot and you are not saving anything in the way of fuel while doing so.

There's one turn I play with on my way into work. It's a REALLY hairy hairpin right with an immediate left after. It's also on an approx. 30 degree decline, coming at speed (30-40mpg) immediately after a big bridge. Practically turns underneith it.

It's pretty hairy, but fun. Very easy to lose grip on.

There's one turn I play with on my way into work. It's a REALLY hairy hairpin right with an immediate left after. It's also on an approx. 30 degree decline, coming at speed (30-40mpg) immediately after a big bridge. Practically turns underneith it.

It's pretty hairy, but fun. Very easy to lose grip on.

It sounds fun. Do you have a google maps link for it? :)

Hi Maxx:

___Nice little chicane you described there ;)

___The training center I used to enter was a sharp and small width entry off a 55 mph country road. I would start my glide from about half mile back and by the time I approached the entry, I was under 30. Hard right into the facility but instead of taking the hard left into the tight parking area, I would go straight towards the much larger parking lot in the back of the building and make a long loop back up towards the front and park where I would normally but without using brakes and without risking that tight parking lot at those kinds of speeds. I hope you can figure out something similar.

___As for needing power on, if you did need to add a blip, look at it as a P&G opportunity rather than keeping hooked up. Parking areas are a bit to tight to be messing around with the higher speed stuff.

___Good Luck and I hope that helped?

___Wayne

Google Maps:

http://maps.google.com/maps?f=d&hl=en&geocode=&saddr=arrigoni+bridge+portland+ct+&daddr=wolcott+ave+portland+ct&sll=37.0625,-95.677068&sspn=41.089062,62.314453&ie=UTF8&z=17

Also, I come in coasting (albiet hot) and give a little juice through the middle of the turn, where the wheels want to give the most.

Hi Maxx:

___Nice entry …

___Another thought … I assume you are coasting down the bridge to the off-ramp. I hope it’s a 4-lane and if so, right turn signals way early to clear the proctologists (reverse passing comes to mind before even arriving at the bridge let alone the climb and fall) and glide all the way down and around the corner. I would not refire until on Walcott if this is any of that is even possible and only to get enough to make it into the work parking lot. Expand the control volume a bit and you will find out what works for you with higher overall FE than running the ICE for grip as it is so wasteful :(

___Good Luck

___Wayne

one day I may take some racing lessons and drive on the race track.Look into autocrossing through the SCCA.

http://www.scca.org/hub.aspx?hub=3

I have a game called Gran Turismo III for playstation 2. In order to get one of the licenses to advance in the game you must race an underpowered car through a course (I forget the name of the car or course) and the name of the game is keeping your momentum up by taking the runs just right. That is a great game! And by the way, the first car I ever really got good at racing in it was a Dihautsu of some sort. This is a good simulator to safely learn how to race or learn how taking corners can help you maintain momentum in a car.

Some of you guys need to get an SCCA competition license:D

Some of you guys need to get an SCCA competition license:DHi Jimmy:

___If I even touched an SCCA license, it would probably melt my fingers off my body or something :D

___Good Luck

___Wayne

This is some very cool stuff. Question I have is this: Especially on front wheel cars, handling improves and the maximum cornering speed increases when pulling the car through with the engine (on my car light acceleration seems to work the best). However this uses gas, but speed can be saved. Obviously it varies for each given corner to maximize FE, but can someone describe (or well theorize) how to decide when to use gas in order to corner faster, with maximum FE in mind?

Well, I'm the novice but I still have one opinion/viewpoint ;) Seems to me that if your turn if followed by a relatively straight section long enough that you glide down to your next pulse, then you will gain FE by adding a bit of power in the turn to maintain speed. If you have to brake shortly after the turn, before running out of momentum, then adding power will probably hurt the FE. That would probably be the two extreems of the question. I'm a pretty experienced race driver, so it's kinda hard to think in terms of FE. But I'm working on it:D

I have a couple of turns near home that I apex in a pretty extreme
way only when *nobody's* around. Any traffic visible, I don't
try any funny stuff. But when the opportunity presents itself
to more than double the turn radius and avoid scrubbing sideways,
it's a lot of fun to tear through the turn and continue the
nice glide much farther on the other side before having to
shovel coal.
.
It must look like a weird disparity to an observer -- someone
hypermiling is drifting along relatively slow and mellow by
comparison with "normal" traffic, and then yanks this hard
screaming turn within an inch or two of the bordering curbs,
and then right back to poking along. But it really helps, especially
if I've come into the vicinity a little too hot.
.
_H*

Hi All:

___Hobbit will like (or remember ;)) this one.

A Strange Thing Happened on My Way Home Last Night. (http://www.cleanmpg.com/forums/showthread.php?t=3599)

___Good Luck

___Wayne

Hi All,

Doing a good apex and using all the road between the curbing is a good way to put 50 yards on a tailgating SUV. And save gas at the same time. I mean, who needs to slow down below 30 mph, if the sightlines are good, and there is nothing around the turn?

The Prius has a cold weather mode it gets in, and if you touch the brakes, you need to get over 35 mph to be able to glide again. So, doing a lift-throttle decelleration and glide around a curve one can sometimes avoid this.

P.S. Do not try this in a stock Prius if the road is a little damp. Gets some good tires, an alignment and a stiffener plate first.

P.P.S. 93hatch, that is interesting abotu GrandTurismo video game - its great for somebody who has never driven before. But the key do being able to safely do this stuff on the public streets is reading the road surface. This takes a few years of experience driving allot in all weathers. That game teaches one to look at the curves. Experienced drivers can glance at a roads curves and its in the memory, its just so automatic after a while. What is not automatic is what the road is like this time through. I keep the eyes peeled on the road surfaces, steering into the most favorable surfaces. On public roads, this can only be done in a few places, as there are other cars, and hazards to also be aware of. If one cannot closely focus on the road surface, as saftey requires keeping an eye on something else, well, then one just has to go slow. And that is it. Otherwise, its not driving, its gambling.

P.S. Do not try this in a stock Prius if the road is a little damp. Gets some good tires, an alignment and a stiffener plate first.

Pssssst... I don't think you should tell this to Wayne... ;)

Some of you guys need to get an SCCA competition license:D

Costs too much... I actually qualified for one last year, but it's not worthwhile for me. Too many other venues for me to get my track fix. ;)

-soD

Driving my FSP (AKA the race car) on an errand today, I realized that there are some very important, even crucial, skills that are used almost the same ways in both activities.

1--Concentration. You have to maintain your concentration almost 100% of the time when racing, because if you get distracted by something else you are likely to either go off-line and lose time, or lose traction and spin or slide off-track. When hypermiling, you need to concentrate most of the time in order to properly time lights, pulses, glides, FASes, and so on.

2--The most crucial thing we instruct racers-in-training is "look ahead". In fact, at the track I will often keep telling myself (out loud!) "lookahead lookahead lookahead lookahead..." When you Hypermile, you also need to look ahead. You need to see when stoplights are changing (and when they are likely to change), what drivers around you are doing, what the road surface conditions are, and so on.

There are definitely some similarities.

-soD

spacepilot, yes you may certainly email me directly if you want to talk racing, or ask questions. Sorry I missed your question earlier.

As nhbubba indicated, autocrossing is available at a much lower cost. Autocrossing, which is sometimes at quite high speed, is an excellent way to learn car control. I autocrossed a couple of years before I even went to my first racing school. When my daughter wanted to race, I insisted she autocross for a year first. Won the Washington, D.C. Novice championship her first year. Got into daddy's wallet right away.

Many fine responses so I'll try to refrain from repeating any of it :-)