348 MAF settings

Cant easily measure the AF, the exhaust is shared across banks. Typically need to remove cats and put in test pipes with bungs. An alternative is to measure voltage with the 02 sensors unplugged. Typically though you would have to tune on a dyno as closed loop is above a certain rpm to about 6000 rpm if I recall, on either end it is table driven if I recall? In any event your readings seem very lean, probably done to pass emissions. I'd put them back to 383 even though the car was likely a few ohms on either side from the factory they certainly were now what you have now. "If" I recall higher ohms is leaner not richer so its odd that the higher number was cooler. My 2 cents. Probably need to adjust the air screws as well back to normal vacuum with gauges as well.

 

Practically all write-ups I have found on the Ferrari MAF CO screw adjustment state that higher ohms (turning clockwise) result in leaner mixture and vice versa. However, this seems to be incorrect (perhaps due to somewhat strange translation from Italian to English), i.e. the effect of the CO screw on mixture should be the other way around - higher ohms, richer; lower ohms, leaner. Reading the info in the Workshop Manual, the following can be concluded.

First: turning the screw clockwise = higher ohms; counterclockwise = lower ohms.

The Workshop Manual (Page C36) states what happens with the mixture when the CO screw is turned clockwise, i.e. to higher ohms as follows.

1. "clockwise adjustment thickens the air-fuel mixture" - not really a very good translation but I would understand that "thickens" means "makes richer"

2. "ruotando in senso orario si ingrassa la miscela aria-benzina" - Google: "turning clockwise greases (fattens) the air-fuel mixture" - "fattens" should mean "makes richer"

3. "etournant dans le sens des aiguilles d'une mantra on enrichit le melange air-essence" - Google: "by turning in the direction of the needles of a mantra (= clockwise) one enriches the air-gasoline mixture" - "enrichit" in French clearly means "makes richer"

4. "durch Drehen im Uhrzeigersinn wird Luft/Benzingemisch fetter" - Google: "turning it clockwise makes the air / gasoline mixture richer"

So, I am sure that we can conclude that the description in the Workshop Manual means that turning the CO screw to higher ohms (clockwise) will make the mixture richer.

In the case of similar MAFs used on certain Saabs, the info I found on saabnet.com states that turning the CO screw clockwise (higher ohms) results in richer mixture and counterclockwise (lower ohms) results in leaner mixture.

Finally, I have an Italian friend (neighbour) who's big interest are cars and motorbikes. When I next see him, I will show him the Italian text describing the function of the CO screw and ask him to translate/explain the correct meaning of "ingrassa".

Also, the Italian members (who read this thread) here can provide explanation of the actual meaning of "ruotando in senso orario si ingrassa la miscela aria-benzina".

 

See how quickly I forget, I remember we found that when was doing AF mixture and found that in the manual, Somewhere around on page 3.
https://www.ferrarichat.com/forum/threads/maf-adjustment-and-open-loop.626174/page-3.

Of course there is lots of is translation issues, perhaps that was one. I did see AF changes at 5000 rpm but I not forget what direction. One thing for sure, changing those CO screws did nothing at idle for me so changing that for emictions as often does it fruitless and I checked with a wide band. Once you get over 2500 rpm you could see effects. I not forget which was was richer or leaner. In the end I went back to 383 and balanced intakes, idles great now.

 

It is easy to remember: Lower (ohm)-Leaner.

In one of the rather old write-ups or forums (~2005) I have saved on the Ferrari CO screw operation, the info in the Workshop Manual was interpreted as follows (not quoting just describing):

The manual states that turning of the CO screw clockwise thickens the air-fuel mixture. Because it thickens the air - fuel mixture, it means the result is more air in the mixture (as if putting thicker air in the mixture) i.e. the mixture becomes leaner. Since clockwise increases the pot resistance, it means higher resistance = leaner mixture. Interesting interpretation/conclusion. From there, it seems that a number of others just followed.

 

Which us odd as thicken clearly indicates air density or adding liquid to thicken the density. Everyone has breathed humid air and said "boy the air is thick".

 

The way I see it is more fuel means less air
Like setting up a motor for elevation vs sea level

But I'm a pollack

 

Just met my Italian friend. He confirmed that "ingrassa la miscela" simply means "makes the mixture richer". In Italian, they use the word "grassa" when talking about "rich" fuel mixture. Literally translated, ingrassa means "fatten" or "make greasier" but it seems that, during translation, the word "thicken" was found as more appropriate when it should have been "makes richer".

It is much simpler when talking about lean mixture as the Italian term for it is "miscela magra" which is translated as "lean mixture".