Petrol use and aircon. Page 1 / 2

thewomble1, Dec 31, 12:11pm
The friction of the belt turning the pulleys, inside the pump parts are still moving and will still use a very small amount of power even when aircon is turned off.

mopeds, Dec 31, 12:19pm
A mazda 2 ac unit would be a max of 0.54 kw, so given that your engine max load is good for 80 kw then your ac accounts for less than 1% of your cars performance. You wouldn't notice this in fuel consumption except under very strict conditions.

lugee, Dec 31, 1:10pm
Sounds like your air con is rubbish. My 97 Accord was out in the sun all day when it was 36 degrees recently, cabin would have been the best part of 50 degrees. I busted out the air con when I left work and I had cold air in about 10-15 seconds, and the whole cabin was down to the set temperature by the end of my commute (8 minutes).

If yours is taking that long there's something seriously wrong with it.

m16d, Dec 31, 6:33pm
The best way to save petrol,is to chuck the car into maori overdrive on the downhills.

elect70, Jan 1, 3:04am
It was so hot inside couldnt even hold the steering wheel initially & stop start driving for hour in full sun it hardly gets to full output . efficiency at idle is only around 30% Nothing wrong with the A/c

gammelvind, Jan 1, 4:07am
I'm figuring that you are joking but many of today's engines, especially autos, use less fuel rolling dowhill in gear than in neutral due to the computers.

lookoutas, Jan 1, 7:37am
You actually answered the question in the first post.
You got 420, so budget on that, and anything better will be a bonus.

intrade, Jan 1, 7:42am
yes i made a video on youtube proofing just that on my 95 corolla. injector turn off fuel on over-run

r.g.nixon, Jan 1, 8:01am
On really long hills, I used to turn the motor off. Watch out though, you have to really stand on the brakes to use them, and the steering is heavier. Then I'd crash start into 3rd or 4th gear (manual of course) when I got down to below 90 km/hr again.

m16d, Jan 1, 8:31am
And with a HQ, if you turned the key off one click too far, you'd lock the steering too.''
Then it got real exciting.

lugee, Jan 1, 2:13pm
Still sounds rubbish, I get ice cold air in 10 seconds even at (cold idle admittedly, but the engines usually cold when I start it) idle, and Christchurch is the hottest of the main centres by a mile. I can absolutely say there's something wrong if it takes an hour to get the cabin down to temp, what's the point in that? 95% of peoples commutes are over long before then.

marte, Jan 1, 4:44pm
There's a electric clutch, the only resistance is in the belt and the bearing.
Hardly any at all.
The compressor does not turn over if the aircons not used.

marte, Jan 1, 4:48pm
It should only take a few seconds to build up pressure, and vacuum on the other side.
From that, once it leaks from one side to the other, it produces heat, and the other end, gets cold.
Fridges only run for a short time, then stop.
Running it 100% of the time does not make it colder than freezing. -5degC.

marmar1, Jan 1, 6:19pm
I used to have a 1500cc mazada and when turning of the a/c the car would actually pick up speed,lol.

intrade, Jan 2, 12:17am
just wotching a ignition diagnostic training.
guy said no spark on a toyota . toyota have hvac module it has the ignition coil imput to the hvac module so it turns off the ac clutch when you come to a red traffic light full stop so engine dont stalls . Hvac module was shorted no tachometer rpm and no spark.
hvac module shorted caused no spark, go find that one with no wiring diagramm haha. hvac=aircondition. module= a computer , one of loads on modern cars.
might have a hvac code if your lucky or no counication to hvac module
but hey we have no spark change all plugs ane everything else and dont fix it lol

elect70, Jan 2, 2:00am
Must be some A/c 30 o drop in cabin temp in 15 minutes requires 7.5 Kw , plus there is also external heat . so more like 10 kw & car A/c sure dont put out that

datoofairy, Dec 30, 11:01pm
I'm trying to get an idea of how many K's I can get out of a full tank of petrol. I've only just bought the car so its only had a full tank once. When I filled it I set the trip counter. The fuel light has just come on, having done 420ks. However I have done 2 trips out of town, including quite a few long steep hills, during which I really pushed the car hard (I wanted to see what it could do). I've also had the aircon going almost the entire time.
The car is a Mazda 2, automatic.
Can I assume using the aircon and speeding up hills used more petrol and so in fact I should be able to get more k's on average? If so, approx how much more?
I'm trying to work out how much I need to budget for a trip from Dunedin to Nelson.
Thank you.

gsimpson, Dec 30, 11:07pm
If you run with AC off you will have to open window or cook. This is likely to increase fuel consumption due to air drag. Affects airflow over car. My car showed little difference in fuel consumption with AC on (has instantaneous fuel consumption on computer)

intrade, Dec 30, 11:30pm
air drag becomes a factor at above 80kph see mythbusters .
however aircon has to be used or it can fail premature id compressor is never on . i tend to use aircon only downhills or on long trips . other then that aircon is on for short times only longer if stuck in traffic in auckland as opening the windo when you dont move wont do much .
Never have window open and aircon on. aircon dont puts cold air in the room
aircon removes heat from a room, so by opening the windo you try and cool the whole planet with your aircon.

morrisman1, Dec 30, 11:30pm
Modern air con is pretty efficient. Old air con you could feel slow the car when you pressed the button. Racing up the hills wont make a huge difference as its only a short period in the big scheme of things but it would still have some effect.

The tank will be pretty small, what you shoudl do is fill it up again, record how many KM you did on that tank, then divide litres by km then x100 will give you L/100km. Id expect it to be around 7L/100km in that car.

socram, Dec 30, 11:35pm
Going uphill is the biggest fuel user - by a country mile. How much is debatable. Generally, you have to press the accelerator pedal to maintain speed and some modern automatics will drop down a gear or three, particularly on a long hill where you may well be doing a lot less than 100kph.

Trundling around here and driving carefully, computer shows an average speed of just 33kph since the last fill. If on any open road, still with a light right foot, the average speed would be much higher - and the fuel consumption at least 50% better. If you think the a/c saps too much power, just switch it on going downhill and put it on 'recirculating'.

intrade, Dec 30, 11:36pm
actuarly your incorrect aircon is aircon modern or old nothing has changed magically its not the aircon whom got more efficient
its the engine managment whom manages aircon that has beome more efficient-->there is where you went wrong right there.

intrade, Dec 30, 11:52pm
did you guys read the thread from budgel i dont know he never posted in there again i dont mind explaining things if he dont understands what the guy said in the video, if he did actuarly whatch it all . one has to whatch and try to understand things before i am willing to talk about aircon and hvac .
So that we are on the same page to talk.
often people want a quick fix.
there is no quick rich seems that work and there is no magig quick fix in most things in live , that is for dop-heads whom have scitsofrenic paranoya from the crap they smoke , when they think the world ends or you could drive your car on water. etc
i dont say you cant drive it on water you acturaly can but not the way these morons dream it to work.

vtecintegra, Dec 30, 11:55pm
It's both - modern compressors are definitely more efficient than older ones

intrade, Dec 31, 12:03am
there was 1 guy whom "seemd to know hvac on one of my threads. i know mr olivas from La trade tec scool is a pro. i compair what somone posts with if it maches what a real pro talks about , if it dont i ask more questions and if the answers start going in to kuku land then i get my red marker out and mark-them as moron down.
i dont know the full hvac i have not even read the book i got for free but i know the basic phisical principle that apply to any hvac aircon refridgeration you name it .
if some guy now tells me its not like this My red marker comes out of my pocket instantly

Most important thing is heat is removed there is no such thing as pumping in cold air. hvac is removal of heat= you feel colder and thats NOT clear unless you learn the basic phisical process correctly.
i know about 10 to 20% of what is to know now.
so if somone knows less and calls him self a professional
then my red marker is out in a flash.

Share this thread

Buy me a coffee :)Buy me a coffee :)