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Old 08-02-2008, 10:52 AM   #1
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not using radio?

does anyone actually know how much using the radio affects your mpg? I'm starting to think it's not worth it...
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Old 08-02-2008, 10:57 AM   #2
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Unless you have a huge aftermarket system with a big amp and a back seat full of subs and you crank it really loud all the time, the amount of energy it uses is small.
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Old 08-02-2008, 11:17 AM   #3
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Originally Posted by collegekid01 View Post
does anyone actually know how much using the radio affects your mpg? I'm starting to think it's not worth it...
Radios mostly effect FE by using electricity, which usually has to be generated by alternator drag on the engine. So not running the radio can help FE a small amount, by lowering the total electrical power used, and therefore lowering the alternator drag on the engine.

However, (electrical) "power savings" from (not using) a radio are no more (or less) significant (to FE) than any other electrical power savings. And in general, I don't think the radio uses a large batch of power (especially compared to things like car lights and car fans), unless you are someone that has one of those stereo systems with big (power drawing) sound amplifiers (although how much power a radio uses does vary a lot with radio brand/model, with some using much more power than others). So if you like listening to the radio, I'd say "go for it" and just deal with the very minor FE hit. After all, you will probably get a better FE gain by other electrical savings in the car (such as switching your secondary car lights to energy efficient LED modules, not using the fans when not needed, etc), than you will by not listening to the radio.

Now, one thing that you can do (that seems to help), is to disable any "backlighting" features of the radio you don't need. For example, my stock CRX radio used to always "light up" whenever my car lights were on (even if/when the radio itself was "off"). Not only did this waste (electrical) power, but I actually found the additional cabin illumination (as a result of the radio's backlighting) slightly distracting when I was driving at night (i.e. I generally prefer a darker cabin at night, so that my eyesight is more easily focused on the road and the illuminated instrument panel). So what I did was test for (find) the specific wire (leading to the radio) that powers up only if/when I turn my lights on, and cut that one (radio harness) wire (while still leaving the other wires leading to the radio as-is). The result is that now my radio no longer has any "backlighting" (that comes on with my car lights), but the radio still works normally otherwise (including having its display light up when the radio is actually turned on). IMHO that (saved electricity from no lighting up of the radio with the car lights) probably saved more power overall (and therefore more FE), than any attempts to "not turn the radio on" if/when I was in the mood to listen to it. And the only thing I "lost" by that modification, is that my radio no longer lit up when the car lights are on but the radio itself is off. And IMHO that radio "backlighting" was really a "feature" I was more than happy to lose anyway!
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Old 08-02-2008, 11:25 AM   #4
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Think people!
A good sounding stereo consumes maybe 100W at maximum.
That's about 1/6 of a horsepower.
Average power draw will be much lower, unless you're trying to induce permanent hearing loss.

Enjoy the music and try not to obsess about the 0.05 MPG you are sacraficing!
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Old 08-02-2008, 11:26 AM   #5
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I feel the same way about the backlighting. That reminds me -- I need to remove that little light bulb inside my center storage area that activates when the door is open. Not a lot of power but still wasted (especially when the dash "door ajar" icon lights up or I can activate the ceiling door light).

But to the radio -- stock sound players shouldn't be a major hit on the FE (ie. too small to detect). It would take a lot of miles and gas before I would notice any difference on my puny Scion but then again I'm not taxing the system by blasting it at obscene levels either.
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Old 08-02-2008, 12:19 PM   #6
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Quote:
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A good sounding stereo consumes maybe 100W at maximum.
That's about 1/6 of a horsepower.
Actually the 700 watts is approximately 1 HP rule, is really only true for systems that are 100% efficient. And since car alternators, batteries, etc, are generally not even close to 100% efficient, you are probably looking at something closer to 300 watts (of usable power) in the car causing a 1 HP drag on the engine.

Also, keep in mind that most small (fuel efficient) cars use/need very few HP at highway cruising speed, so even a somewhat "small" HP drag from the alternator (due to the electrical power used) can (in some smaller cars) easily be enough of the total drag on the engine (at cruising speed) to make a quite noticeable (sometimes even a few MPG) difference in FE.

Quote:
Originally Posted by Geonerd View Post
Average power draw will be much lower, unless you're trying to induce permanent hearing loss.

Enjoy the music and try not to obsess about the 0.05 MPG you are sacraficing!
While I think the hit on FE is often greater than you are estimating, I do agree that the radio load is often not anywhere near your most significant electrical load on the engine, much less your most significant load on the engine from all sources. And driver comfort is worth something too IMHO.

So while we might disagree "on the numbers", we do agree that it's probably not worth it for someone to sacrifice the radio (assuming it makes their drive more pleasant), just to try to squeeze a little extra FE out of the car. Yes, technically the radio is fully "optional" (in that you don't "need" to run the radio when driving), but it none-the-less can add to driver/passenger comfort at only a small cost (to FE).

Besides which, if saving electricity (in order to get better FE) is the goal here, there are (as I mentioned in my other post) much more effective places (in many cars) to save power (than turning off the radio). For example, both car lights and car fans tend to be real energy hogs in most cars, so anything you can do to lower their power usage (not run them when not needed, switch some car lights to energy efficient LED modules, etc) can make a big difference (likely much more significant than the radio) in total electrical power used in a car.
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Old 08-02-2008, 12:41 PM   #7
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Stereo = 7 lbs. It's in a box.
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Old 08-02-2008, 01:46 PM   #8
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You'll never notice the difference. It's probably only drawing max power during a big bass boom. That's only a momentary transient. But...if you have one of those stereos that can be heard booming six blocks away, TURN IT DOWN! Why?

1. You are probably driving it into distortion, annoying the hell out of everyone.
2. It is vibrating parts of your car. You may not be able to hear that inside, but I can outside.
3. You are damaging your hearing, probably most pronounced in the female voice range. You were wondering why your wife/girlfriend keeps saying that you don't hear them?

Now, if you want some significant power draw, perhaps a tube-type, circa 1955 AM ham transmitter, about 100 watts or so, plus a tube type ham receiver, and a dynamotor to provide the high voltage might well add up to a couple horsepower...
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Old 08-02-2008, 02:57 PM   #9
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yea a stock radio draws less than an amp and when playing a cd its right around an amp at normal levels. so in the big scheme of things no, you wont see any fe improvement...

also i really dont think removing the dome/door lamps that liht when the door is open is really gonna do anything... i mean really in a week those lights are on what a total of 10 minutes?(prolly less, considering it takes about 10 seconds to get in a car and close the doors)
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Old 08-02-2008, 03:41 PM   #10
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yeah I didn't really think so.... thanks guys
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