just a quick question, by adding things in like amps and subs, can it cause an increase in petrol. beside weighing the car down more, can the extra power needed to run them make, lead to the engines power supply (alternator) having to work harder and increase petrol

No chance m8

Not enough for you to notice it I wouldn't think.

I'm not sure if its the weight or the electrical draw but i can guarantee you i get less km out of a tank when my stereo is in the car

I'm not sure if its the weight or the electrical draw but i can guarantee you i get less km out of a tank when my stereo is in the car

thats cause ur sub weighs as much as M4DDOG alone man! :bowrofl: i wont even mention yhour amp!! i have a lead foot and as a consequence bad fuel consumption so i wouldnt know if the stereo made a diff to my car...

thats cause ur sub weighs as much as M4DDOG alone man! :bowrofl: i wont even mention yhour amp!! i have a lead foot and as a consequence bad fuel consumption so i wouldnt know if the stereo made a diff to my car...
Damn that's a big sub!

Yeh there's no denying that stereo gear will make your car slower and less fuel efficient. If your stereo was presenting a load where your sparkies weren't operating to what they should be you would know, your engine would start missing/struggling.

all current draw is from the battery.
the alternator floats the battery during operation
anytime a big bass note is hit.. the surge is taken directly out of the battery.
No the alternator will not work harder... (you don't need much power for a spark)
the largest draw (besides your stereo) is the starter which averages at about 120 cold crank AMP draw.
the weight of the stereo can cause fuel consumption to rise but only marginly..
have you changed your driving style with the stereo on? ie... faster off the traffic lights... revving higher before a shift.. all this can lead to increased fuel consumption.

a LARGE stereo would weight about half of a person, or like driving around really fat... so no real difference i wouldn't think

Electrical draw would be as good as nil.


Weight would be like having the spare tyre or not, unless you have a very elaborate system, in which case its like having 2 spare tyres or not. I couldn't see this making much difference.


As soon as I head the second symphony though, I can't help but drive like the stig, which in turn increases fuel consumption. This is probably also true in your case but with missy higgins :P

I don't notice it so much now with the 3.5L TJ, but in my TR 2.6 auto i was amazed at the difference in the car when i took out all the stereo gear (as i was about to sell it soon).
My gear would have easily weighed 100kg, possibly abit more. Without the stereo it accelerated quicker and fuel consumption dropped approx. 1L/100km.
Same driving style too.

I heard an amusing story about a DIY installer who thought his stereo had mucked up his fuel consumption and when a shop looked at it they discovered he had drilled into his fuel lines!

i just noticed since i got my car audio i cant get under 11.4 ltr per 100. all i do well bout 85% of what i do is highway kms. iv gotten 10.8 before

Mine weighs heaps - random guess of around 150kg. So a couple of passengers

2 big dual sub boxes, 3 big amps, 3 boxes of sound deadener, subs, speakers, mdf. heaps of runs of speaker, rca and 0 gauge wire.

Guessing around 30km less per tank.

No complaints

a LARGE stereo would weight about half of a person, or like driving around really fat... so no real difference i wouldn't think

Half a person? whats your idea of large? My sub box is 70kg with the subs and amps, and add speakers. Thats 1 average passenger.

Not enough for you to notice it I wouldn't think.

Correct

i havent notice any lose in economy or sluggishness in my car
i have a big *** sub box in the back with 2 amps on panels
the only time the car feels abit sluggish is when i have just filled up my fuel tank
i can actually feel the rear being heavier, but it soon goes away after a few minutes driving ;)

If you point your sub correctly you might actually see a rise in acceleration during bass notes...

i agree with the op

my car is laggy when the stereo is on flat out!!

the current draw must take away from the processig power of the invecsII trans ecu, and it seems to be more sluggish in response and kickdown...

my headlights were also dimming pretty bad whilst ideling at the lights (when system is going)

i have since changed the battery terminals and stuffed about with the wiring and the dimming issue isnt anymore... the trans seems a tad better too :) but it's hard to tell in my car due to the inconsistant performance at the moment

i just noticed since i got my car audio i cant get under 11.4 ltr per 100. all i do well bout 85% of what i do is highway kms. iv gotten 10.8 before

far out.. either way your car has issues dude :\ ive got a 3.0 manual, and by no means do i drive it lightly.. about 30% highway driving, and half of that in heavy traffic, and i average about 9.5L/100km now.. that is with about 50% air con usage and stereo constantly cranked.

if i granny it, 100% highway driving, and no air con, strangely it only drops down to about 8.0L/100 :\

all current draw is from the battery.
the alternator floats the battery during operation
anytime a big bass note is hit.. the surge is taken directly out of the battery.


I think you will find that the alternator powers the electrical system when the car is running,it also replenishes the battery at the same time,the battery is just a dirty big storage device,hence when you are drawing more current then your alternator can provide,you will then begin to flatten the battery,the battery used to start the car,then the alternator can take over and any slack is then taken up by the afore mentioned alternator.

far out.. either way your car has issues dude :\ ive got a 3.0 manual, and by no means do i drive it lightly.. about 30% highway driving, and half of that in heavy traffic, and i average about 9.5L/100km now.. that is with about 50% air con usage and stereo constantly cranked.

if i granny it, 100% highway driving, and no air con, strangely it only drops down to about 8.0L/100 :\

well i dont have any stereo stuff at all but as a point of information i rarely get below 13L/100K out of my 3.5 TJ. I am reasonable heavy on the right foot. Bout 15% highway driving

what about the grouding kit, isnt that surposed to reduce the resistance to the battery and increase power, allowing a better spark, im not saying if this is true or not, but wouldnt having a powerfull system cranking do the opposite? so i guess there is some grounds for thinking along these lines

http://www.aussiemagna.com/forums/showthread.php?t=47786 look as this thread too

If you point your sub correctly you might actually see a rise in acceleration during bass notes...


Extend the port out of the boot..

Drop some Bass mekaniks and yeah.. its a possibility! :bowrofl: :badgrin:

There are two occasions where the battery is used to supply electrical current. During starting before the alternator is up to excitation RPM, and during peaks where the alternators capacity is exceeded. At any other time all the battery is really doing is helping to stabilize the system voltage.

An alternator being called on to put out 120A continuously is likely going to be drawing almost 3HP from the engine, the 3.0L V6 I believe is around 160-170HP at the top of the power curve, so not likely to be noticed. What will be notice is the headlights dimming as the alternator struggles to maintain voltage (Ohms law, the alternator windings have a finite resistance, and therefore a finite current capacity at 13.8V), likewise with the battery. Even though a multimeter can show 13.8V from the battery when the alternator isn't running, a multimeter has a very high resistance, and therefore no load. Keep the meter on while cranking where the battery has a 500A load on it, and you'll see the voltage go down to 8-10V!

The noticeable difference in fuel consumption is the physical weight of the stereo. Aftermarket speakers can be a couple kg's heavier than factory, subs vary between 5 and 50kgs each, MDF (assuming you're not building boxes out of 3mm!) stacks up very quickly, there could easily be a few kg's in cable, sound deadner, amps, etc etc all adding up. 150kg all told would have been about right for the system I had in a past car, it certainly made a difference to the back end when it was removed before selling the car!