cars at higher altitudes

Jarago · Post by **Jarago** » December 26th, 2005, 3:49 pm

quick question for ya's...at higher altitudes cars are not as fast I believe right? If that is true, do cars actually burn more fuel at higher altitudes in any way? I was thinking about it, and was wondering if this would be true.

Thanks guys

stereoking15 · Post by **stereoking15** » December 26th, 2005, 10:03 pm

yes cars do burn more fuel, it is a combination of the map sensor and other inputs because the air is much thinner at altitude more fuel is added to compensate for the lack of air

hgallegos915 · Post by **hgallegos915** » December 27th, 2005, 7:37 pm

I tought cars burned better at sea level? more concentrated ait than higher altitudes....or im wrong? air expands with altitude...bleh im dumb

projectmx · Post by **projectmx** » December 31st, 2005, 11:51 am

that makes no sense if cars burn more fuel when there is less air why do they burn more fuel during the winter when the air is more dense and they get more air? istn' it impossible to for the car to burn more fuel both when the air is thicker and thinner?

Nd4SpdSe · Post by **Nd4SpdSe** » December 31st, 2005, 4:44 pm

actually, it depends on the sensors. Thereare probably more designs, but i know these two because of the MX-3:

VAF - Volume Air Flow. It measure the volume of air coming in, but will not vary on the air density. I'm not expert on this thing, so i'll do my best. But say you have a a 1L container filled with air, when air gets colder, the molecules start to get closer together. So the colder is gets, the more air molecules will fill that 1L container. The hotter, the less molecules. Fuel mixed with hotter air will make the mixture more rich, mix it with colder air, the mixture becomes lean

MAF - Mass Air Flow - It measure the weight of the air coming in. Now i don't need to re-explain what air molecules do when the temperature changed. Say you have that same 1L container. Because there would be more molecules when it's colder, that container will weight more, and weight less when it gets hotter. Because MAF can sense the changes in the weight of the air, it can more accurately adjust the air/fuel ratio and have it much more consistant and efficient.

ktmrider · Post by **ktmrider** » January 12th, 2006, 8:55 pm

Higher altitude = less air AND oxygen, thus less fuel is required to achieve the desired 14.7:1 air/fuel ratio.
Being from a carburated past and 5300ft - 1600m altitude, I always go smaller on the jets.
The previous post explaining flow vs density is right on. There is also another factor, lower atmospheric air pressure. The vacuum of the piston going down in the cylinder is one way to ingest air, the other is the atmospheric pressure "pushing" air into the cylinder. The higher the altitude, the lower the ambient air pressure is and less air being pushed into the engine.
The simple definition for a internal combustion engine is "air pump", with the term air being a big variable. More air in AND out = more power. This is why forced induction is so cool for us high altitude folks.