Railguy

iTrader: (4)

Hi all as you know by now im new too this

i live at 7000 foot altitude ,,, town is at 5300 foot average and the track is at about 5800 foot

so im guessing its all gonna be closed loop for me IE no forced open..

will the computer compensate for this change in closed loop or should i expect too tune at different altitudes

i ask because i dont know and i cant afford too lean out and crown

thanks rail

PS obviously the stock computer does make the change fine i just dont want too smoke it then get 33 replies saying oh ya dude you didnt know when ya edit these it disables...........

okfoz

I am not a Great programmer, but I have done my share...

A brief overview of how i understand how the MAF system works... Basically a MAf has a heated wire... As Air rushes accross the wire the computer measures the resistance, as the temp drops it indicates more air coming in as the wire cools. The ECM with that data in turn relates the temperature of the air in the Plenum to calculate the amount of air coming in, and the O2 sensor indicates a lean/rich condition and the ECM from that information calculates the amount of fuel to add in relationship to the Throttle posistion...

With all that said the systems compensate for the altitude changes. In OPEN loop you may have some issues, BUT I suspect it would be minimal... Now that would not mean that altitude/barametric pressure/Humidity etc will not change the performance of your car, as it does, but you should not need to have a special program for 7000' vs 300'... Of course I have noticed that serious racers have weather stations that they take with them to the track to dial in their car... How this changes everything I cannot tell you BUt it has to have some sort of effect otherwise people would not have the weatherstations...

Of course thats how I understand how it SHOULD work...

On further thought I would think the purpose of the MAF is to compensate for the changes in weather, altitude etc. If it was a perfect world the use of a MAF or later MAP sensors would not be necessary as it should be possible to program the ECM based on throttle, O2 and RPM. .. BUT we do not live in a perfect world so the MAF is to compensate for changes in the Weather...

Someone please correct me if I am wrong... Its late and i am tired

John

jwscab

MAF is a MASS air flow sensor, therefore, it measures air MASS, which has different volumes for different altitudes, but it measures the same, Mass is mass. So by design, the sensor removes altitude from the measurement.

one thing that does alter the heated element MAF is humidity, less humidity will register a more accurate air mass.

Railguy

iTrader: (4)

thanks excellent ,,,

our average humidity is below the 20% my weather station will measure at lowest

i knew its function in stock form but you know one question which may seem stupid too you guys could save me much grief

i answer the same questions over and over,,, i sell ham radio antennas, mostly at trade shows,,,so a few thousand people walk by in a day,,,,but even though its the same question over and over if i get aggravated i think back too the day i started, and how important that stupid question was too me !!!

i appreciate all the input i get here,, rail

okfoz

I can understand how this might be true, but I would think that when the system was calebrated it was calebrated at an unknown humidity. When running your car at the humidity the car was programmed at I would imagine it would run the best... I do I get slightly better fuel milage when the air is dryer, what exact humidity I could not tell you is ideal...

Just a thought...

jwscab

I'm sure it was definitely designed to provide a specific transfer function (airflow/volts) at a specific pressure, temp and RH (relative humidity). Pretty much anything engineering wise and sold in the US using safety standards is usually tested with STP criteria (standard temp and press), and it's pretty much good engineering practice. there are environmental chambers that allow engineers to vary all of that stuff (temp, press, RH) for just this purpose.

this is just a guess, but if the effect of humidity was linear, they probably designed it to have it's target transferfunction at 50% humidity, this way, it will stay somewhat accurate over the entire range. it may only be 1 or 2% change anyway, I don't know for sure.