It's the drag, man... - Fuelly Forums

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Old 11-11-2006, 06:24 PM   #1
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It's the drag, man...

Before coming to this site, I reasoned that the best way to get real FE gains, while avoiding the BS, was to go based upon sound engineering principals. And so the next question I asked myself, is what general areas are there, that engineering says we could (at least in theory) help FE with. Here is the list I came up with:

1) Efficiently turning the fuel into "work". In theory, if you could burn the fuel more completely, or fail to "waste" energy (say out the tail pipe), you could get better FE.

However, I also realized that most changes in this area were beyond what I was likely to be able to effectively tinker with. You can effectively tinker a little bit (for example, by indexing your spark plugs, or carefully using a small amount of gas additives), but it's just a little around the edges. IMHO this isn't an areas that a small user can easily get big gains from (but every little bit helps).

2) Avoiding "losses" in the systems involved. For example, if you have a belt that is "slipping", you are wasting energy. As I see it, the main things that a normal user can do about this, is to just keep things running in good repair.

3) "Double-dipping" from the energy used. i.e. getting two (or more) "useful" things done from the SAME energy input. One of the more "extreme" examples of this is co-generation power plants, where the fuel not only produces power but also gives off "waste heat" that is used by a nearby factory or greenhouse (thereby getting two uses out of the same fuel). This one is a real "coup" when you can do it, as the 2nd/3rd/etc uses of the power are essentially "free" (as you have already paid the power price for the first use). However, the places were you can effectively do this in an automobile are limited. You might (for example) be able to use the "waste heat" (or "waste" exhaust gasses) of an engine to do useful work, after the engine is done doing its useful work (from the exact same fuel), but that's probably about as far as you can take "double-dipping" in a car...

Which brings us to 4) "Drag".
Given that objects in motion tend to stay in motion unless acted upon by an external force, science tells us that it should take virtually no gas/energy to maintain a constant speed if there wasn't "external forces" acting on the car. And most of those "external forces" go by the general term of "drag". So it follows that as you lower "drag", you should get closer and closer to the ideal of just setting a speed and continuing to coast without using up any additional fuel. As you will never fully get rid of drag (there will always be some "wind resistance" for example), it's impossible to fully get to the ideal. But I reasoned that there was a lot of potential in lowering drag, and that this was the one area that a normal person could usefully tinker with! And this theory seems to be supported by this forum, as many of the techniques this forum found to work, are really just different ways of lowering the various types of "drag" we encounter (be that drag from friction, rolling resistance, aerodynamic drag, or...).

But if you look at it from a "lowering drag" standpoint, IMHO it helps to let you see "the big picture". Because at that point, you are looking for ANYTHING that accomplishes the general principal of "lowering drag", and not limiting your mind to just the areas that someone has already thought of. This allows you more freedom to "think creatively", and still be working in a useful direction.

For example, it was that general principal/reasoning that first got me thinking about car lighting as a source of improvement. I already knew from general electromechanical principals, that the more electricity you actually use from a generator, the more "fuel" (mechanical resistance to turning the generator) you will need. So it stood to reason that lowering car electrical use would lower "drag" (from the alternator) and therefore (slightly) help FE (and tests on this forum, have since confirmed that theory). Which is why car LEDs (i.e. "energy efficient lighting") actually helps FE, even though that seems to be a major secret to most everyone else (ironically, even the companies that sell LEDs for cars, don't mention their FE benefit).

Likewise, it was the principal of "lowering drag" (in this case friction resistance) that caused me to want to do an extra good job of lubing up my wheel bearings. Because the more free the wheels spin, the less you slow down when just coasting. Again, the idea is to lower "drag", in this case friction inside the wheels slowing you down. And this really makes sense to anyone who has ever worked on a bicycle, as the more the bicycle wheels turn freely, the more you can coast, and the less work it is to move when you do have to pedal. Likewise, lowering drag in auto wheels, should greatly help FE even when not coasting (and indeed it does seem to help).

And it was even the principal of lowering "drag" that caused me to switch to high quality synthetic motor oil and transmission fluids. Because the more lubricated that the engine (and transmission) are, the less effort is being wasted going into friction. And that in turn means that more of your effort is being put towards useful work (i.e. greater FE). And I'm far from the first person to notice that better quality oil (or transmission fluid) can help FE a small amount all by itself!

And those are just examples of things that previously occurred to me. There are many other examples from this forum, that also prove the point (but for which I initially didn't think about). For example, all of the talk about "aerodynamic mods", is pretty much talk about lowering aerodynamic drag. And when you do such things right, they can be amazingly effective (just look at how effective "grill blocks" can be, for example).

Which brings me back to the general principal of lowering drag. Lowering drag just seems to be the "glue" that ties so many of these FE techniques/tricks together. And I will go further, and speculate that "lowering drag" should almost always be useful (for FE) unless it has some higher "cost" to it. For example, a solar cell can produce electricity, and thereby lower the alternator drag on the car. But when looking at FE, you have to weigh this against the extra weight of the PVC array, and any lowering of car aerodynamics that your mounting position might entail (as you don't want to trade one gain, for an even bigger loss).

So what do people think? Should we be putting on "our thinking hats", and trying to find "out of the box" ways to lower drag? Or is that really what we have been doing all along, and I'm just finally putting a name to it.
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Old 11-11-2006, 08:12 PM   #2
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I like this topic, there's nothing like an open-ended question to spark the imagination.

There are many ways of lowering drag, it's just a matter of putting in the time and effort to attain those improvements. Then there's the question of value; how much time and/or money does it take to get X ammount of improvement?

About your comment about greasing wheel bearings really well, adding more grease will increase a bearings viscous drag because the grease is constantly being pushed around as the wheel turns. I happen to work in the bicycle industry, and the fastest bearings are ceramic ball bearings which use no grease. Second best is a typical sealed cartridge ball bearing with the seals removed, grease flushed out, and a light oil used as a lubricant- these get dirty quickly and need to be replaced. Obviously this is not practical for cars, but the point is to use light weight synthetic grease, and use it sparingly. Make sure the seals are making light contact, and lube the lip on the seal.

Engine and tranny oils have been covered in other threads, and the conclusion seems to be to use light weight synthetic oils, and to slightly underfill it.

How about shaving the sides of tires? There are two benefits for this one, to smooth the sidewalls for less air drag, and to reduce rolling resistance. There might be a tradeoff of reduced durability if it's taken too far.

How about cutting a larger central channel in the tread of the tire to mimic a trucks dual tire? It might also give air a place to flow through instead of being pushed around to the sides of the tire.

ECU program tailored to each individuals preferences. I wish everyone had a programmable ECU like I do. I've found about two dozen areas that have the potential to improve FE to various degrees. There are portions of the timing and fuel maps that seem to be set up to make the car easy to drive at the expense of FE. I have a feeling the engineers were more concerned with making the car easy to drive for the worst drivers so that customer satisfaction is highest. That's an area I (and I'm sure others) would gladly sacrifice to meet their own individual needs, habits and driving style.
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Old 11-11-2006, 11:51 PM   #3
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So how do you like your Laser? I had the exact same thing about 2 years ago, funnest car Ive ever owned by far. When I saw you are doing 37 mpg I instantly thought you had the 1.8, but the 4g63 getting that mileage is incredible. Especially since that tiny turbo would hit full boost by -+ 2100 depending on which gear. I had to get rid of mine because it lived up to the DSM reputation

Your car probably runs low 13s and gets 40 mpg, cant ask for more than that
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Old 11-12-2006, 02:13 AM   #4
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Adressing aero drag is where the largest overall fuel economy gains can be made, assuming about an even mixture of city and highway driving. Going from a .32 to .16 drag coefficient in today's cars would increase combined mileage by about 40%, with no other changes. This is the ticket to 30-35 mpg V8 musclecars and 35-40 mpg V6 sedans that use no weight reduction, no hybrid drives, no diesel engines, no LRR tires, or any other mods. With LRR tires, synthetic gear oil, weight reduction of 300-400 pounds by removing all sorts of useless interior filler, and other mods on top of extreme aerodynamic efficiency, 35-40 mpg combined V8 musclecars and 50+ mpg combined V6 family sedans become possible, which would incur no cost penalty, no horsepower or engine displacement reduction, no size reduction, no comfort reduction, and in most cases, an increase in cargo capacity. Going from a gasoline to a diesel engine or to a gasoline-electric hybrid drive would improve fuel economy by about 30% given horsepower remains similar. Going to a diesel-electic hybrid drive would improve economy about 50% over gasoline given that horsepower remains similar. This is how cars like the GM Precept got 80 mpg, while still being the same overall size as a Ford Taurus, and still managing 0-60 mph in 11 seconds: extreme aerodynamic efficiency, weight reduction, and diesel-hybrid drive.

Read the following article:

http://www.evworld.com/blogs/index.c...d=87&archive=0

Yes, the methodology is a little flawed given that it is an estimation, and the flaw is particularly egregious that it is a linear estimation, among other noticable flaws. I'm working on an updated article that uses a larger sample size, uses a nonlinear approxomation by finding a paraboloid of best fit, and factors in peak motor horsepower as well, to estimate the effects of having a more powerful engine on fuel efficiency. So far, I've played with what numbers I've derived with my current sample size of over 80 cars, and that's how I arrived at the possibility of 35-40 mpg combined V8 musclecars with 350-400 horsepower.

Extreme cases like the Opel Eco Speedster sports car get 94 mpg. It has a .20 drag coefficient, ~15 square foot frontal area, and weighs ~1,500 pounds. It's engine is a 112 horsepower inline 4-cylinder turbodiesel. It tops out at 160 mph, and would go faster if the governor were removed.

High performance and high fuel economy can coexist, while still remaining affordable. But the auto industry refuses to go that route. It would rather push onto us high-maintenance gasguzzlers with high profit margins.
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Old 11-12-2006, 09:20 AM   #5
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Quote:
Originally Posted by DRW
About your comment about greasing wheel bearings really well, adding more grease will increase a bearings viscous drag because the grease is constantly being pushed around as the wheel turns.
I was aware of that, but it is worth repeating.

OTOH you have to work with what you have. For example, my mechanic could "easily" drill a small hole in the rear wheels to put in a grease fitting to add grease, but removing the old grease junk would have been a lot harder. So we "made do" with squirting a little new synthetic grease in there without removing the old/junk. Even though this situation wasn't ideal (it would have been better to get the old junk out, and only use a little new grease exactly where needed), it still made a HUGE difference in how freely the wheels turned.

Quote:
Originally Posted by DRW
I happen to work in the bicycle industry, and the fastest bearings are ceramic ball bearings which use no grease. Second best is a typical sealed cartridge ball bearing with the seals removed, grease flushed out, and a light oil used as a lubricant- these get dirty quickly and need to be replaced. Obviously this is not practical for cars,
I'm not so sure the concept wouldn't work. For example, has anyone tried plating all the moving surfaces (including each individual bearing) with Moly (a very good high-pressure dry lubricant)? I probably won't try it (due to the hassles of tearing the wheels fully apart), but it sounds (at least at first glance) like that could result in very freely turning wheels.

And if Moly isn't "high tech" enough, just consider some of the dry "Nano-Lubes" that some companies are working on. If you could work out a cost-effective way to "nano-lube" up the wheels, you may end up with easy turning wheels that stay lubricated.

Of course, neither of these approaches prevents you from also using good synthetic grease. And depending upon their lubrication properties, it might even be useful to do so (i.e. combine Moly plated metal parts with small amounts of synthetic grease). But the point is, there are dry lubricants (some of which, such as Moly, which can be "plated" to moving metal surfaces), that could be usefully used in a car...

Quote:
Originally Posted by DRW
but the point is to use light weight synthetic grease, and use it sparingly.
FWIW: This is the stuff I used in my car, and so far I really like the results.

https://www.amsoil.com/storefront/grg.aspx

Quote:
Originally Posted by DRW
Make sure the seals are making light contact, and lube the lip on the seal.
Good to know when you have a choice in the matter. But in our case, just getting the grease in any way we could (when the bearing unit was designed to not be greaseable at all) was our (mine, and the independent mechanic I use) first concern. Because even if we couldn't get the ideal greasing situation, just getting some good synthetic grease in there (after 15 years of nothing being done) was going to help a lot more than it hurt...

Quote:
Originally Posted by DRW
ECU program tailored to each individuals preferences. I wish everyone had a programmable ECU like I do.
Cost? Difficulty in installing? Which cars is it for?

I would be happy to consider a programmable ECU for my 1991 CRX. However, last I checked it would run me several hundred dollars for one, and even more for the EPROM programmer. And I just am not yet ready to fork over that much money to upgrade the computer in my car...
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Old 11-12-2006, 01:07 PM   #6
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Quote:
Originally Posted by DracoFelis

Cost? Difficulty in installing? Which cars is it for?

I would be happy to consider a programmable ECU for my 1991 CRX. However, last I checked it would run me several hundred dollars for one, and even more for the EPROM programmer. And I just am not yet ready to fork over that much money to upgrade the computer in my car...
If your comfortable with a soldering iron, you can run one of the free programs out there, and buy a cheap ($10-25) ECU chipping kits. Then all you need is a chip burner, or a chip emulator. I have aMoates.net Ostrich, GREAT service there too! I'd highly recommend it to any one. If you have a lap top (with USB port), you can buy the HULOG and datalog too!

I'm considering getting the FordEmu too, so I'll have to fully programable cars haha.
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Old 11-12-2006, 09:57 PM   #7
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Small world, I change the program on my ecu with a Moates Flash-N-Burn (aka burn1). It cost $85. I'd love to have the convenience of an Ostrich, but then I'd also have to get a laptop, and the cost doesn't justify the benefit at this point.

I guess I'm lucky that Mitsubishi made a small percentage of the DSM ecu's with eprom chips. From what I've heard there has been plenty of work done to figure out the ecu code on various GM, Ford, and Honda cars, too. Perhaps a visit to the popular tuner/hot rod forums might turn up more info.

The mention of Moly reminded me of CV joint rebuild kits. They come with a packet of moly grease, which has a lighter consistency. I wonder if this might work better in wheel bearings? Or would it be so thin that it oozes out of the seals and gets flung onto the brakes? I might look into it if I have the bearings apart.

Quote:
Originally Posted by BEN EJ8
So how do you like your Laser? I had the exact same thing about 2 years ago, funnest car Ive ever owned by far. When I saw you are doing 37 mpg I instantly thought you had the 1.8, but the 4g63 getting that mileage is incredible. Especially since that tiny turbo would hit full boost by -+ 2100 depending on which gear. I had to get rid of mine because it lived up to the DSM reputation

Your car probably runs low 13s and gets 40 mpg, cant ask for more than that
I love the Laser! I've had it since 1994. Sorry to hear yours didn't hold up so well. I've done quite a bit of work on mine, mostly to keep it running, some to upgrade it. My best mpg is 41.6, and my best time at the track with a little 100 octane was 13.1 @112mph last spring. Yeah, it's fun.
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