Hello, Gary! Yes, I remember you're older, lol. Thanks for jumping in there with a cool headed assessment. You've got me nailed, for good or for ill.

I think I got the nickname after someone got a little jiggy with one of the young ladies on the site, and I intervened. I believe she gave me the nickname then, and it was affectionate.

Nice to see you over here. I have buttons that are too large, to my regret. I apologize to everyone who has had to watch me go over the top. I have to confess, Dave pushes my buttons like few other people -- even Colin can't do it quite as well, lol. I'm not sure why that is.

New members please note: I'm a cranky, middle aged guy and do not represent the overall tone of this site.

Thanks folks for the supportive PM's, and in general not turning this into a free-for-all.

Anyway, I'm done regardless. Do or don't do this mod, it's all the same to me. I've given you what I know and will continue to do so as I uncover more information.

 

He does it to us all! See some of my photo related posts..

 

You, push things, Colin? Unthinkable!

Hey, I'm trying to clean up the mess a bit -- don't run behind me dropping more trash!

 

Not sure if you mistook my last post!?! I edited it down.. Whatever.. disregard me and carry on!

 

Thanks for sharing the info on the MAF mod with all of us. I believe that many of us on this site enjoy reading about and perhaps trying some of the ideas that you come up with. I pulled my MAF out today and took a look at it and I agree with you that increased contamination is probably a non-issue.

I still believe that there would be some increase in flow over the sensor elements after the mod. With the backside cut away, the flow would be straight through and not have to change direction twice like it does in the factory configuration. At low flow rates, this shouldn't make much of a change in the measured flow rates but should show a greater increase as the overall flow through the MAF increases.

This may, in fact, be what prevents the mod from pushing the mixture too far lean. Increased flow over the sensor elements would increase the measured flow rate at the same time the actual flow rate increases while bypassing the sensor.

As far as WOT mixture goes, I believe that you will find that there is no determination of fuel trim during open loop operation. The LTFT is developed during closed loop adaptive mode based on the what is learned from the oxygen sensor operation. The fact that the LTFT says that you are not near the fuel clips in closed loop feedback says nothing about where the mixture is during open loop operation.

If you are seeing a power increase, though, it is pretty clear that the OL mixture is not running much if any richer than stock. Ford calibrations (and many others) are deliberately run richer than ideal during open loop operation for cat temperature protection. That's why it's so easy for aftermarket chip manufacturers to make more power, even on 87 octane fuel. Having no concerns about catalytic converter temperatures or the emissions performance warranty, they just lean out Ford's calibration until it matches the ideal power mixture (about 12.5:1).

It is possible that this is another way that the MAF mod returns more power. In addition to the probable flow rate increase, the net mixture change may make it slightly leaner than the overly rich factory calibration.

 

Ah, that explains a lot, thanks.

Well, the only saving grace here is that open loop operation, barring O2 sensor failure, is a mercifully short time. The engine has operating modes based on engine temperature, but as soon as the O2 sensors get hot, closed loop operation starts. Since the sensors are heated, that doesn't take too long.

Are we fully "open loop" on WOT, or is there still and adaptive mechanism for that mode? Guess I"ll look that up, or if you have the answer let me know.

I'm not sure HOW long though. I need to find that info or figure it out because you've made me curious.

 

Well, this is from the service manual (my italics for emphasis) on fuel trim:

Long Term Fuel Trim (Long Term FT) (displayed as LONGFT1 and LONGFT2 on the scan tool) is the other parameter that indicates long-term fuel adjustments. Long Term FT is also referred to as Fuel Trim. Long Term FT is calculated by the PCM using information from the Short Term FT to maintain a 14.7:1 air/fuel ratio during closed loop operation. The Fuel Trim strategy is expressed in percentages. The range of authority for Long Term FT is from -35% to +35%. The ideal value is near 0% but variations of ±20% are acceptable. Information gathered at different speed load points are stored in fuel trim cells in the fuel trim tables, which can be used in the fuel calculation.

I remembered (incorrectly) the ranger of authority being +/- 25%. However, it says the +/- 20% is "acceptable" so I would presume being less then -20 or greater than 20 percent would eventually trigger the CEL. Since Doc's truck was at 22 when I first cut it, and went UP from there, that would be consistent with that.

No doubt his trim table is pretty well updated by now.

 

There is a complete base open loop table based on RPM vs Load that is used as the default fueling for the calibration. It has multiplicative and additive modifiers based on inputs like temperature and inferred barometric pressure. When closed loop operation entry conditions have been met, the calibration switches over to a closed loop using fuel trim and the O2 sensors. There are certain RPM/load cells that are always open loop. The trend is the higher you move in RPM or load, the more likely you are to be in the open loop only region of the tables.

WOT at all RPMs is open loop.

High RPMs cells are usually open loop at all loads.

There is no adaptive learning or feedback operation in open loop. There may, however, be an Open Loop Fuel Modifier that is uses the LTFT to attempt to correct open loop fueling based on what was learned in closed loop.

 

Hey John, do not forget about the dementia also.... LOL
I am glad to see we are bacjk on topic... I always thought this site was against bashing, I guess the moderators have gone away... oh well.

Answer to the question: What kind of milage data you looking for? I normally got 150 miles per tank w/ stock intake. Went to 160 w/ K&N. I have yet to refill with the maf mod so I do not know that milage.
-Doc

 

oh ok, 160 isnt good!

 

well I have 33's so my milage sucks.. never wasany good to begin with!

 

Is that with or WITHOUT compensating for those monster tires?

 

i get about 240 a tank....and i think thats horrible....

 

I have never seen any where near that.. unless I forget to reset the trip meter when I fuel!!

 

Thanks, D. Your information got lost in the brou-ha-ha....ha ha.

10:1 is leaner. Target A/F from Ford is about 13.5 to 1 (or about that, I forget the exact number off the top of my head).

Yes, I was surprised by the lean condition as well. I would have thought flow through the MAF sensing tube would increase with the flow through the whole MAF on a 4.0, but it did not.

I think the reason why is laminar flow. The uncut 4.0 MAF sticks slightly over halfway across the MAF body (tube) inner diameter. At the sides of the tube, flow is more chaotic and of somewhat less effective velocity. When we cut the MAF, we are no longer measuring between the side (inlet) and the center (outlet) -- but between the side and the side.

So in fact, cutting the MAF in a 4.0 reduces flow through the MAF as measured by the fact that the predicted required fuel is not adequate -- reflected by the high LTFT number. So the engine THINKS there is less air, puts in the fuel for that, and then tries to add more when the O2 sensor feedback reports lean.

On my 3.0 the sensing tube goes the full diameter of the MAF body. It measures from one side of the body to the other side of the body. Cutting it means we're measuring just across one side, but still both inlet and outlet are on sides of the tube. That could be why 3.0's are less affected in terms of calibration by the change.

Thanks for the data, D.

 

I remember anytime you offered to do the MAF mod, you always gave a warning beforehand and asked if the person still wanted to proceed!

 

Yes, we "informational pedophiles" are very considerate of our victims that way...even when the victims are over 30 years old...

 

Chemically correct mixture for gasoline is about 14.7:1. The oxygen sensors switch the mixture slightly above and below 14.7:1 at closed loop idle and cruise.

Maximum power enrichment for WOT would be about 12.5:1

Excess enrichment for cat temperature protection is often about 11~11.5:1

10:1 is so rich that it can cause cylinder wall washing and is not commanded when the engine is at operating temperature.

 

Oh, yeah, you know I COMPLETELY inverted that, lol! Sorry about that. DOH! [hits self roundly on forehead]

I really don't know what I was thinking. I guess somehow because Doc's was running lean. Oh well.