[SamPBronkowitz]

For the last week or so, my car has run like crap - poor idle, hard to start, lost steam at anything above 5000 rpms, etc. I couldn't figure out what was the problem, so I took it to a VW dealer to have it checked out (the dealer where I live is pretty reputable). They "adjusted the MAF, made the car run a little leaner (I have an AMS chip), and also adjusted the air/fuel ratio and idle."
Anyway, the car run better than it ever has before - it idles smoothly, starts quickly, and the engine just pulls from any rpm. It now runs better than it ever has.
What exactly is the MAF and how/what did they do to my car?

 

[fat biker]

Re: MAF - what does it do? + a few other ??'s (SamPBronkowitz)

MAF = Mass Air Flow
The mass air flow sensor measures how much air so that the injection knows how much fuel to deliver.
fat biker

 

[kickster]

Re: MAF - what does it do? + a few other ??'s (fat biker)

ok Good topic, I know that a Mass Air Flow sensor measures the amount of Air. But how does it do it?
As far as I know the flap that opens produces an electrical signal, thus, the more open the flap the stronger the signal.
I still dont know what makes that flap open? Does it open by vacuum generated as air pulled in? Does the computer opens it?
Now lets say we make a ram air. Since the amount of air entering is different would the car run much leaner?

 

[zoinks208]

Re: MAF - what does it do? + a few other ??'s (kickster)

quote:[HR][/HR]I still dont know what makes that flap open? Does it open by vacuum generated as air pulled in? Does the computer opens it?
Now lets say we make a ram air. Since the amount of air entering is different would the car run much leaner?
[HR][/HR]​

First off, its a sensor, the computer cant control the position of the sensor directly.
Yes a vacuum opens it.
With ram air, hummm.... Pressure = Force x area... for reasons i dont want to explane,,, i dont think compressed air would change the flow readings.
Area is constant
Pressure and force are increased... so there should be more force applyed to the MAF flap.
Dont know if I'm even right now lol
Anyway if your running a digifant, I STRONGLY recomend loessening the Air Flow Meter spring off. It will get rid of the hisitation off the line, for more info go here (not as scarry as it sounds) http://members.tripod.com/~fuelie/performance.htm

 

[VeeDubClub82]

Re: MAF - what does it do? + a few other ??'s (zoinks208)

uh I played around with my MAF and now my car doesn't work. It just shuts off right away. Can anyone help me? Please.

 

[zoinks208]

Re: MAF - what does it do? + a few other ??'s (VeeDubClub82)

Played around, like as with the spring tenssion? or wiring?

 

[VeeDubClub82]

Re: MAF - what does it do? + a few other ??'s (zoinks208)

I played around with the spring tension

 

[zoinks208]

Re: MAF - what does it do? + a few other ??'s (VeeDubClub82)

EEK,,, well I am cheap... here is what i would do, since a new AFS isnt cheap, see what the wreckers what first.
Im assuming a worse case senaro here i.e. the spring is totaly unwound.
If the wreckers want to much....
Crack one open in the yard, and count how meny turns to unwinde the spring, go home and make yours the same. Might give you a chance.

 

[VeeDubClub82]

Re: MAF - what does it do? + a few other ??'s (zoinks208)

I replaced it with one out of a buddys parts car. and it still doesn't work. Could there have been any damage done to anything else?

 

[SamPBronkowitz]

Re: MAF - what does it do? + a few other ??'s (VeeDubClub82)

I love this forum - 30 views and 9 replies. That's a sweet ratio. Keep 'em comin'

 

[kickster]

Re: MAF - what does it do? + a few other ??'s (SamPBronkowitz)

Ok Back to the topic. When you say vacuum opens the flap do you mean there is a vacuum hose or the vacuum generated as engine is pulling in the air?
How does the MAF measures the air flow? Under normal conditions the amount of air will be equal to amount of air pulled in by Vauum generated as pistons go down. Under a ram air situation the air is pushed in so the computer doesnt know how much air is being pushed in!!
For example if I add a electric turbo then the air pushed in will be much more than what MAF is reporting to ECU thus the engine should run very lean.
Another issue that I wanted to bring up is the function of O2 sensor in a Digi car.
Thanks in advance

 

[zoinks208]

Re: MAF - what does it do? + a few other ??'s (kickster)

I love trying to explane all this, when I'm not an mechainic.
Vacuum is created by the pistons.
Well it measures flow. The ram air simply increases the flow.
You can only shove so much air in to the engine. This is limited to the valves being open and port sizes and such.
On Digi cars, there is a flap that is pushed/pulled open by the flow of air. newer cars use a hotwire sensor (look on the web theres lots of info on hotwire sensors)
Pressure on the flap of the sensor = Force (thats the flow) x Area of the flap.
The o2 is there so the car can run most efficient, and make up for sensor errors, with a proper working o2 your car will try to keep the right mixture, except when the car is at wide open throttle, thats when the digifant system ignors the o2 because it dumps in more fuel then is nessary.
If you want to do some research go to this site... has all the VW repair info for digifant http://www.loam.org/vw/Vanagon/VanagonProTraining/DigiFant/