rem83's Forum Comments

Showing comments 1-30 of 48 by rem83.

High NO reading on Smog Test?

If you have a cone filter without a proper cold air box and snorkel, you'll have higher intake temperature and consequently higher nox readings while on a testing dyno. I had to buy a stock intake for my Miata when I moved to Texas, in order to pass emissions - it brought nox levels down by several hundred ppm over the k&n filter that came with the car.
posted by rem83 January 26 at 10:52 AM

Ethanol

If you are talking about E85 ethanol, then you should check your owners manual to see if your vehicle can use it.
posted by rem83 May 6, 2010 at 10:37 AM

ETHANOL

Ethanol has less energy per unit volume than regular gasoline, so you need to burn more of it to extract the same amount of energy (as in, you need more fuel to get up to speed or to go a given distance). It does have a higher octane rating, though, so if you designed an engine to run only on ethanol, you could probably increase your compression ratio which would allow for improved efficiency and might balance out the lower energy content. Diesel is a great mix of both, which is why diesels get such good fuel economy. Diesels run much higher compression ratios fuel AND have more energy per unit volume than gasoline.

I wonder - do the revised EPA tests use E10 or straight gasoline...
posted by rem83 May 6, 2010 at 10:36 AM

Performance and Economy?

In the US, the Corvette is king. In the US, the Lotus Elise - obviously not the base model you get in the UK (I'm assuming), is rated 21 City / 27 Highway (miles per US gallon) and capable of 0-60 in 4.9 seconds with 189 HP and a weight of 1984 lbs.

The Corvette, a car weighing 3208 lbs with 430 hp, is rated 16 City / 26 highway. It's not stellar, but it's really not bad for the level of performance you're getting.

Performance and economy certainly don't have to be mutually exclusive. There are certain technologies, like direct cylinder fuel injection, that create more efficient combustion and result in both power and economy gains. Other technologies like turbocharging allow you to increase maximum performance, but with minimal losses in fuel economy during relaxed driving.

I still think the best performance technology is 2 wheels, though. My carbureted motorcycle manages 0-60 times in the low 4 second range while achieving crusing economy in the low to mid 40s.
posted by rem83 May 6, 2010 at 10:31 AM

fuel economy question

I'm not too sure about diesels, but certainly with gasoline engines, you require a richer fuel mixture before the engine gets up to operating temperature. Since, when it's cold, the engine takes significantly longer to reach operating temperature, you're running a richer fuel mixture and burning more fuel.

Also, just keep in mind in general that coolant temperature is not the same as oil temperature. My Miata is an excellent example, where the coolant temperature rises really very quickly, but oil temperature (and I am using the oil PRESSURE gauge to make inferences about oil temperature, assuming that higher idle oil pressure is due to higher viscosity and therefore colder oil) takes many more miles to get to operating temperature / pressure. I would not start flogging your car just because the coolant gauge has reached a normal operating point.
posted by rem83 February 8, 2010 at 1:17 PM

Garage size

Heh, I had this problem too, but I think accounts were capped to 5 then. I wanted to include my g/f's car in my profile, since I'm the one who enters all of her data anyway, but ended up having to make a separate account for her. It's pretty easy to exceed 6 vehicles if you have a few bikes and a few extra cars lying around...
posted by rem83 January 15, 2010 at 7:12 AM

Broken Odometer

get the gear kit from http://www.odometergears.com/bmw.html. you'll have to check to see if you have a vdo or motometer instruments, and it might help if you pull your instruments and the tach to verify that you're ordering the correct gears.

i've been through this on both BMWs that I've bought - the gears WILL break. even if you somehow find instruments with working original gears, they won't last long, and it'll throw off your car's odometer reading. buying new gears is the only reasonable way to go, even if it's a bit pricey.
posted by rem83 December 15, 2009 at 1:18 PM

Topping it off screws my MPG

Yup, just suck it up and understand that there is going to be variation between your fillups anyway - the pumps won't always shut off at exactly the same point. Your average fuel economy over time will still be correct, which is why it would be nice if fuelly would incorporate the ability to plot running averages with user specified # of points to be incorporated into each average. It's essentially the same thing as if you just did a partial fuel-up. The two fuel-ups affected will be dramatically off (one high, one low) but they will cancel each other out when it comes to average mpg.
posted by rem83 March 4, 2009 at 1:32 PM

Pulse and Glide?

P&G may be a relatively main-stream technique (compared to some of the other stuff that hyper-milers do), but I think a lot of the hyper-milers aren't in it to save money, they just want to see how efficient they can be (kind of like people who race just want to see how fast they can go, not how much time they can save). I doubt those folks have stopped just because gas prices have dropped off. While this seems pretty dangerous, stuff like removing your external mirrors, taping up body gaps and intake holes and removing excess weight from the vehicle, etc... is also quite risky.
posted by rem83 January 28, 2009 at 6:36 AM
I know that on my manuals (I guess the bike's dont count because they use carbs) the engine starts to sputter and stall if I let the revs get below idle while coasting.
posted by rem83 January 16, 2009 at 7:06 PM
Are you positive that on a car with computer controlled fuel injection, the computer doesn't turn off the injectors while the car is coasting in gear? It's not actually necessary to have fuel in the cylinder during the power stroke if the engine is kept spinning by the rest of the drive-train (using the car's kinetic energy). With a carb, you're definitely still letting fuel into the engine through the idle circuit.
posted by rem83 January 15, 2009 at 9:59 AM
usually cars have 2 off positions - there's a kill switch position (just turn the key a little) and a full off position, which is when the steering locks. i discovered this the hard way on my e30 - the accelerator got stuck on the floor mats when i was on the highway and i put the car into full off, the steering locked, i lost power brakes, and i eventually went into the guard rail on a gentle bend, although i was only going about 20 at the time.
posted by rem83 January 14, 2009 at 1:38 PM
Pete - pulse and glide is generally considered a dangerous technique that probably shouldn't be used under normal driving conditions. i think odds are pretty good that you would reduce fuel consumption just by shifting into neutral and coasting, since you're getting rid of the majority of engine drag by keeping the revs low like that. i think, on older cars anyway, if you're moving, you can actually restart the engine by putting it into gear, but that's probably even worse for your clutch and transmission than using the starter is on your starter / alternator / electrical system. I guess the best solution would be to get a mild hybrid which is actually designed to cut off fuel / ignition during those low demand situations.
posted by rem83 January 14, 2009 at 6:30 AM

Fuelly for Maintenance?

I kind of think a lot of maintenance intervals need to be adjusted for driving conditions. Following the standard manufacturer suggested interval is better than nothing, but if you subject your vehicle to harder than normal use you really should decrease your intervals.
posted by rem83 December 5, 2008 at 6:44 AM

100,000 fuel-ups!

I think the problem with ethanol is that there is less chemical energy per unit volume. From what I understand, ethanol actually burns very well, it just doesn't have the same chemical energy. I kind of hate to run even 10% ethanol in my older cars / bikes though, I can just picture all of the fuel system seals dissolving...
posted by rem83 December 4, 2008 at 8:10 AM

Warm Up or No?

Just wanted to add real fast, while this advice is good for cars, do not treat a motorcycle this way. Particularly on air cooled bikes, you should let them sit and idle until they get reasonably warm. Clearances inside the engine are more of a big deal on a bike engine, and it's pretty much impossible, and a bad idea anyway, to drive most bikes (v-twin cruisers excluded) at low-ish rpms while cold.
posted by rem83 December 4, 2008 at 8:07 AM

Mileage trends with amount remaining in tank

I'm guessing on a boat, packaging is less of an issue than on a car. I think most fuel gauges still use a float, although I'm not sure about that, so they're actually measuring fuel height in the tank, not fuel. If you've ever seen a gas tank (here's a pretty extreme example: http://www.ineospolyolefins.com/Images/SM%20-%20Car%20Fuel%20Tank.jpg), you can imagine that fuel level really does not track fuel volume very closely.
posted by rem83 December 2, 2008 at 8:18 AM

100,000 fuel-ups!

A couple of factors that could contribute to poorer winter fuel economy:

longer warmup times, potentially long idle times while waiting for the car to warm

reduced traction

winter gasoline formulation (although actually i think this helps, but not sure)

use of snow tires (i'd assume they would have higher rolling resistance) and potentially studs

increased traffic due to poor weather

that's all i can think of off the top of my head
posted by rem83 December 2, 2008 at 8:15 AM

Warm Up or No?

I would suggest that generally your car doesn't need much time to warm up. I live in Houston, so my winter temps are probably even higher than yours, but even in winter I generally only allow about 10 seconds to warm up. Back when I lived up north, I'd give it maybe 30 seconds to a minute, but nothing major.

HOWEVER - Until your temperature needle comes up a significant amount, drive your car gently. I generally try to keep the tach under 2k rpm, or 3k in my Miata. While 10-30 seconds of warmup time were more than enough to get oil flowing everywhere, things like camshafts and other parts of the drive-train have not reached operating temperature and clearances are not at the operating spec (thermal expansion causes clearances to change). While it is ok to drive like this, there is increased load on some parts, so you want to drive gently. Usually after about 5 minutes of driving gently, you can get a bit more aggressive, but again this will be dependent on your specific car and driving conditions. Do not be one of those assholes who just turns there car on and immediately revs it to 5k rpm (of course since you're on fuelly, you're probably not going to be doing that anyway).
posted by rem83 December 1, 2008 at 7:07 AM

Estimated Hwy MPG

yeah, I really think it's too difficult to differentiate between city and highway driving - particularly if you're in an area like Houston where you do a lot of city driving on the highway... the best you could do would assign a "feel" to your driving.
posted by rem83 November 26, 2008 at 10:15 AM

Performance mods for economy

Just remember guys, performance modifications that create more power and more torque do this almost exclusively by moving more air and more fuel into your cylinders, not by making your combustion more efficient. You may be opening the throttle slightly less to accelerate the same amount, but that doesn't mean that you're using less gas to accelerate the same amount. The only way to make your car more efficient is by reducing parasitic losses like driveline friction and aerodynamic drag, or by making your combustion more efficient. A performance intake and exhaust might (but probably wont) reduce engine pumping losses by a very small amount, but if it actually shows up as a fuel economy difference, I'm sure it would never pay for the cost of the mods.
posted by rem83 November 20, 2008 at 1:14 PM

Estimated Hwy MPG

Hrmm, I suppose you could try to estimate highway and city fuel economy by looking at the variance of your data?
posted by rem83 November 20, 2008 at 7:00 AM

Synthetic motor oils and MPG

@bates: I wouldn't use straight weight oil in most normal use vehicles. Even if you run high weights in summer and low weights in winter, you have too much engine temperature variation from a cold start to sitting in traffic. Synthetic oil already has pretty good breakdown protection, and modern, EPA restricted engines don't see the kind of stresses that cause breakdown. For drag racing or really high performance applications, your advice seems great, but for an '09 Sonata, I think he's a lot better off with Mobil 1 or Syntec.
posted by rem83 November 14, 2008 at 9:10 AM

How about retiring a car without deleting it?

Thanks, it works now and I really appreciate it!
posted by rem83 November 12, 2008 at 7:39 AM
When I go into the edit car screen, all I'm seeing is remove car (no retire button). Was the change applied across all existing cars as well as new vehicles?
posted by rem83 November 12, 2008 at 7:09 AM

Synthetic motor oils and MPG

I don't think they do provide better fuel economy, if they do the effect is negligible. However, I ALWAYS use synthetic. They provide much better resistance to break down, and have better lower viscosity at low temperatures and higher viscosity at high temperatures. If your engine is in good condition, synthetic oils will pretty much keep it that way (barring any unforseen issues, such as overheating or improper maintenance). Synthetic will also allow you to extend your oil change interval, but I do not recommend doing this. If you plan to keep your car for a while, use synthetic! The extra cost is worth it.
posted by rem83 November 10, 2008 at 9:07 AM

Need help.

@naughtybeaver - You should keep your tire pressure at the correct setting regardless of whether you think it will improve your gas mileage or not. If you are running the incorrect pressure, your tires will wear pre-maturely and you are more prone to blowouts.

As far as economy goes, low tire pressure increases something called the rolling resistance of the tire. This force is pretty much independent of speed, so you won't see it's effects very much at higher speeds where drag dominates. Also, I'm not certain how much tire pressure changes rolling resistance, but rolling resistance itself is not a negligible component of the losses which result in fuel consumption. Unfortunately, there isn't a whole lot you can do to reduce rolling resistance - it's an unavoidable result of having a tire contact patch, and that's pretty much necessary to be able to accelerate, brake and turn.
posted by rem83 October 27, 2008 at 7:51 AM
I generally wouldn't run my tire pressure at more than 2-4 psi above the vehicle manufacturer rated pressure. Just because a tire can take 44 psi doesn't mean that's the best pressure to run at - it can adversely affect wear as well as traction (and ride quality).

Also, please make sure it is alright to rotate your tires before you go ahead and rotate them. I have an '85 BMW 3-series - it says in the owners manual "Do not rotate tires." I did not check this, and rotated the tires right after I got the car. I ended up spinning it into a guard rail on a highway exit ramp because there was essentially no traction on the rear wheels (caused by different wear patterns on the front and rear).

Your factory owners manual / shop manual / door panel sticker has the best information for your specific vehicle. If you don't have access to any of these, you can also try calling your dealer, although sometimes they'll blow smoke up your ass just to get you off the phone.
posted by rem83 October 23, 2008 at 9:29 AM

Hydrogen or H2O Systems

Sorry, just read www.iuseH20.com, which claims that their system works by improving your combustion efficiency (not by actually extracting energy from the water vapor, as many others of these scammers claim). This would theoretically work, except that modern engines already have extremely high combustion efficiency if they are working properly. I don't think this would have any effect, and you would still lose energy on the electrolysis side of things.
posted by rem83 October 7, 2008 at 10:37 AM
These things are a complete rip-off. Basically, this is how they work:
You have a container of water. The system uses electricity generated by your alternator to electrolyze the water into Oxygen and Hydrogen, which they call HHO gas. The hydrogen and oxygen gases then are introduced into your intake and sucked into the engine where they combust, releasing energy and adding water vapor to your exhaust. Sounds great, right? Well, the part people forget about is that your alternator puts drag on the engine to generate electricity, thus consuming more fuel. The other important thing to remember is that energy is conserved. So you start with water in it's base energy state, you add energy to it via electricity (which you used gas to generate), resulting in a gas that has chemical potential energy, you combust it thereby releasing that chemical potential energy, and about 15-20% (depending on your engine's efficiency) of that potential energy is recaptured by the engine and used for moving the vehicle. You are left with hot water vapor that actually has more energy than you started with since you wasted about 80% of the combustion energy as heat. Anyway, the point is that this will reduce your gas mileage since you're only reclaiming about 20% of the energy you used to make the "HHO" gas.

Sorry that's kind of a convoluted explanation, but the short version is: you start with water, you end with water that has either the same or more energy than the water you began with. You cannot make energy from nothing, even if they claim there is a magic catalyst involved. Good luck getting your money back - the way scams usually work is they don't honor their guarantee.
posted by rem83 October 7, 2008 at 10:30 AM
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