First, if you don't know what the MAF mod is, this is not the place to ask about it. Look in the how-to section, or on my CarDomain site for more info about it.

This information may allow you to get the MAF mod working properly on a 4.0 liter. But in my usual long-winded way, I'm going to give the background on it.

Doc came to me recently with his new acquisition: a stock 4.0 SOHC MAF unit. He wanted to do the MAF mod but was justifiably anxious about it, considering the warnings I give about problems doing it on the 4.0.

Well, we did his mod this past Sunday, and I tried something different. I only cut the bottom of the MAF, and not the back (again, see my MAF mod how-to for more info on what I'm talking about).

I put the scanner on and looked at the long term fuel trim (there is one for each bank of cylinders) and both were about maxed out. I should have revved it and checked them. They were at +21 to +22 and max is +25. I asked Doc to try it this way and see what happens.

Well, what happened is he asked me if it could aggravate his timing chain rattle. I said I didn't think so. But he wasn't hearing timing chain rattle, it was pinging and soon his CEL came on throwing codes P0171 (lean condition bank 1) and P0174 (lean condition bank 2).

He brought it to me and I cut the back of the MAF and the idle LTFT dropped a point or two. Not enough. When revved it peaked back up towards 25.

So, I began to fool with it. What I finally did was this. Use the photo below as a reference to what I'm saying. I did not photograph the final result.



Now what you are looking at is the MAF sensor, already cut. The cut surface facing you is the "bottom" of the sensor.

What I did, was sand that "floor" down to near paper thin. I put the MAF with that cut end down on sandpaper and rubbed it back and forth until it was a very thin "wing" between the arch shaped chamber above and the outside.

The result was an LTFT of 6 to 8 with plenty of room for adjustment. We'll see if the CEL comes back on, but I think not. He had no idle problems anyway, but time will tell. Revving it yielded brief excursions towards 25, but iit didn't stay there (which is typical when you suddenly add air anyway).

Doc drove it and there was no pinging anymore.

I'll let you all know (or Doc can post) if there are any further developments (such as a returning CEL). But those of you who have cut MAF's and had problems, or are itching to do this, perhaps this could help. No guarantees.

One other thing: Doc has the FIPK kit which aggravates MAF tuning for just about all MAF's to some extent. Sometimes so bad you have to get a special "cold air tuning" for them.

 

i did the maf mod on my 4.0 and have never had a problem with idle. I put on my FIPK and had to clean the MAF within a few weeks cause of the filter oil.

 

Cool. I know some haven't had problems, and some have. If lean operation ever becomes a problem, it's something you could try.

I really have no idea how applicable this is. I only have "one data point" to work on and I didn't have a scanner or monitor to watch things with back when I first started doing them (and did most of them).

 

i have the 75mm... And ordered a modified bridge.. And i thought that ment, cut shaft, but it wasnt cut, just overall bigger... And the MAF was calibrated different..

You think i could modify it too..? John...

Ill get a pic of you want me too..

 

I'm wondering if it's necessary or would do much for you. I haven't even had an up close look at the big aftermarket ones.

Special calibration and all, huh? I'd love to play with it, but it's risky. Do you think it's restricting your power output? 75mm is pretty big for a 4.0, I would think.

 

I dont think it is...I can tell a difference when its off...

It feels restricted when going back to stock... Especially arounf 2-4 grand.. Like theres a plug in it...And no air is getting too it...

Feels better with it on

 

Yeah, I would think since it's already "supersized", it might not be worth it to try playing with it. The MAF mod is primarily for coaxing a bit more out of a stock MAF -- but there's probably not much more to be had from one so large already.

 

WELL... So far so good. No codes and boy have I run the truck! The power increase is unbelievable!! The truck used to get up and go but know.. it just flies! Thanks John for your expertice.

 

My (old) 3.0l went from 11.28 to 10.69 in the eighth mile from doing the MAF mod alone. But I wonder what can be done with the "newer" MAF's in the flat retangular metal housing?

 

John cut mine on my old 4.0 and it was great. I even installed that one into my mothers Sport Trac and had John cut me another one, and that one was good to go as well. I sold the truck, ripped the MAF out of my Dad's Sport trac and traded with my cut one, and now he has no problems either. I like the mod.

 

You are risking catalytic converter damage. If it runs out of fuel trim and goes lean enough to throw codes it may already be too late. It only takes minutes to melt a cat if you are lean enough.

 

Not that lean, Dave. It was just bumping up against the +25 limit. It took it quite a while to finally generate a code. If the CAT was so damaged you'd face another CEL from the catalyst efficiency monitor.

 

Relying on a monitor that takes 330 seconds of the engine running before it starts, and 700 seconds of part throttle operation before it finishes, is not a good way to protect your truck while you test your modifications. It can take several drive cycles for the catalyst monitor to even run, and by then it would be too late.

It's a pass/fail monitor, it won't tell you anything until it's already failed. I suppose you can watch the HO2S's cycle and calculate the index ratio between the two front and one rear in your head and watch the potential damage as it happens in real time if you want.

The PCM is too dumb to know the actual catalyst temperature anyway. It takes a guess at it and creates an inferred catalyst temperature value, but it will not light the MIL until the misfire rate and temperature have already exceeded the damage temperature.

 

Well, we'll see. I take heart from the fact that you are excessively pessimistic as a matter of course and that this is a very unlikely outcome.

 

I am merely supplying you with facts to help you out, you can choose to give them whatever emoitional quality you like.

 

he he! C'mon, you know you love it!

 

There's no risk of overtemping the cats during closed loop operation at +22 LTFT because the 02 sensors are still in control. Even if you go very lean in the closed loop region, there shouldn't be a problem. It is a misconception to believe that a leaner than stoich mixture will cause increased cat temperature. Catalytic converter temperatures will drop for a mixture that either goes lean and stays lean or goes rich and stays rich.

During open loop operation, the cats, especially the light-off cats, need an artificially rich mixture (richer than power enrichment would dictate) to protect them from temperatures that could affect service life (1700F+). Here, a MAF error that causes a leaner than desired (but still richer than stoichiometric) condition could increase cat temperatures. The mixture doesn't create this problem by increasing exothermic chemical activity in the cat - it is still richer than stoich and richness alone would reduce chemical activity and the temperature. But it does increase the upstream Exhaust Gas Temperature and that is a threat to the cats, especially the light-offs. Could the temperature get all the way to substrate melt-down (2200F+)? Possibly but the MAF error would need to be fairly significant. If the MAF error could push the mixture toward stoich at WOT, the cats would die a quick and ugly death.

Dave is right that the cat monitor won't do any good here. It takes forever to complete, even when all of the entry conditions have been met. Many vehicles will never have it complete. If and when it does, it just tells you whether the switching ratio has dropped low enough to imply that the cat efficiency is too low to do its job, nothing more.

 

I don't think it is a good idea to even mess with the MAF unless you have calibration data for the PCM and the MAF itself. The goal is not to change the calibration but to increase flow through it. You need to the PCM data to prove it can use the increased flow, MAF calibration data to know the MAF calibration has not changed and a flow bench to prove increased flow even exists. (A dyno to prove there was a gain wouldn't hurt either.) Only then can you remove the risk from the other components.

Experimenting with expensive sensors at the risk of expensive exhaust system components just doesn't seem worth a couple of possible horsepower.

I'm surprised at you John, I thought you were an engineer.

 

FWIW: I would tend to agree w/ Dave. How much gain are we really looking at here anyhow? Has anyone, even w/ a 3.0 (which seems to have the most to gain) even done any real measurements, ie back to back dyno runs w/ and w/o this 'mod'?

Personally my truck is powerful and fast enough as it is.. All I ask is that it run reliably every day!

 

Aw, Dave, that really hurt...

First of all, if you understand that no MAF is "right" to begin with, they you understand why the PCM has such a wide range of fuel trim.

As long as the fuel trim stays within range, THE PCM IS MAINTAINING PROPER FUEL MIXTURE AND THERE ARE NO PROBLEMS.

In fact a perfect MAF is not possible to make. So all we have to do is stay within the adjustment range. As an engineer, Dave, I understand enough about the process to understand this. YOU might want to actually think about it, instead of just using "spin" to try to prove an unsupportable point.

And why is it unsupportable? Because measured results have proved that it does make a difference. If you read some of the posts you'll see that track times prove it, and we've done before/after 0-60 runs with trucks before that bear it out as well. I'd LOVE it if someone would dyno it, but no one has and there is plenty of substantive evidence (measurements, not "butt dyno" stuff which has bit me also) to support this. You just don't WANT to accept it for some reason. I'll leave speculation as to WHY to others.

As usual, when you can't win, you resort to personal attacks -- that's one predictable thing about you. It used to get me mad, but now I just pity you -- I hope you grow out of it.

 

Colin, my response to Dave covers the measurement issue.

Secondly, there are "tweakers" and those that are satisfied with an "appliance" approach. The appliance approach says, "it was built this way, and that's fine."

The tweaker experiments to find ways to push the limits. Some of us try to find inexpensive ways to get gains. Some work, and some fail. FWIW, this one works. All the "churn" on this issue doesn't explain the measured gains that people have reported, above and beyond the "feels better" stuff.

If you're an appliance user, fine. You're not really the kind of person who mods. Dave, for one, is an appliance user masquerading as a mod expert. You are just someone who is generally satisfied with the level of performance engineered into your product, and so you apparently have not much desire to make changes. Fair enough.

However, just because you don't get it, and I'm speaking to Dave here, you don't have to attack peoples ideas, particularly personally, all the time.

The list of mods Dave has done and documented is long (sarcasm noted?) and so his expertise and bona fides in modifying processes are well established. So I guess it's just a "difference of opinion".

 

This is really interesting. As sort an experiment I decided to actually make what I would consider a light personal attack, hence the wink. I think you would be hard pressed to find examples of me personally attacking anyone, even you. You personally attack me regularly, and more than once in this post. Anyway, as usual I've tried to give you assistance and you took offense to it because I present a view contrary to yours. Then repeatedly try and tell me I am an idiot in a roundabout way by quizzing me on your vast diagnostic, engine control and OBDII systems knowledge.

I know you are an engineer, but you are missing a lot of the purpose of the long term fuel trim, deterioration of the MAF is only a small part of it. Engines also have ignition systems, mechanical systems, electical systems and fuel delivery systems that wear over time and need to be compensated for.

 

People have done back to back 0-60 tests? Really? Where's the results? In hovering around these forums for nearly a year and a half I don't remember seeing any charts or comparisons. If you have emperical evidence to back this stuff up please share! My comments originate from a position where I just havne't seen any.. Particularly any evidence that this is as much of a substantial improvment as some people think it is. If I recall, your 'butt' dyno told you the resistor mod was the best thing since sliced bread too, didn't it?!

And yes, to some degree I am an 'appliance' user of my truck. I think it's somewhat foolish to risk costly and permanant damage to a $15-20k vehicle by trying to squeeze an extra couple HP out of it. But yeah, that's me..

In the software field we have an expression: "You can have it done well, done quickly, or done cheaply; pick any two!" I think this applies to some degree to the Ranger as well. This isn't a GT level sports car. Certian design comprimises were no doubt made to deliver a product in a timely maner and within a certian budget. My conversations w/ Bob while in PA last fall certianly reinforced this opinion! To expect to be able to tweak one single part and get a sizable improvement w/o effecting something else (ie reliability maybe!?) seems foolish to this engineer. Let's face it, the Ford Ranger and it's engine and components are designed to be affordable and reliable, not performance oriented. I find it HIGHLY believable that modifying a component of the system to improve performance, especially w/o effecting affordability will result in deterioration of reliability. ..Otherwise why wouldn't the factory have done this years ago?!

Now having said that, I fully recognize that our friend Dave here has a certian lack of.. well, tact about the way he brings things like this up in these forums. His advocacy against the torsion bar crank is certianly evidence of this. But that doesn't mean he isn't right! There HAS to be a downside to this mod.. And w/o evidence of a substantial upside, I really don't think it's for me. And I personally would suggest that there are better ways of improving the performance of the vehicle than hacking up the MAF sensor!

..But like I said in the first post, that's just me personally! I'm just posting my opinion for whatever it is worth..

You've certianly got a way of polarizing things John!

 

I must say I am not against people playing with the torsion bars, I just want them to have an understanding of what they are doing to the suspension when they adjust them. It's all give and take, like you said.

 

Colin, I posted it EXTENSIVELY years ago on GenEdge, including 0-60 trials. If it's still there, great. If not, I don't know what to tell you. I probably have them kicking around somewhere. But they only apply to my truck.

Jeez, you guys act like I've never said there is a downside to this mod. Did you ever READ my how-to? I think not. I warn people EXTENSIVELY that there may be consequences that make it unusable. To act like I never said there was a downside, is plain obfuscation or lack of knowledge.

Your software example is excellent. But sometimes the "quick and dirty" solution is all that is required. This is not a product, this is a user "installed" mod that they are warned may not be useful.

Never-the-less: it gets results. What about the track time results that were posted? Do you accept them? Dyno results would be very nice to have -- but they would only prove the results on a dyno. You would still need "real world" evaluations, and those are being done. For the most part, people don't do them.

This is a low-cost mod that gets you much of the result of an aftermarket MAF. I've been doing these for YEARS and talked about it in detail in the past, whether you guys were around for it or not.

And Dave, you do get personal a lot. Your lack of ability to perceive it is perhaps your greatest weakness in that regard, if in fact you don't see it.

Polarizing, yes indeed! ALL THREE OF US do that, not just me. We have strong opinions and they are by nature going to create polarity.

But I point out again: I do mods, document them, and test them and if I'm wrong I post it. I'm not wrong on this one and I've never had to go back on it. It works and is useable if you do it right. And now I have the tools to check the impact better and even tune the flow through the sample tube a little to make sure it continues to work and does NOT adversely influence the truck.

Ford did it this way because it's "right" -- or because it's mass manufacturable? Think about that one. Lots of things are done for EXPEDIENCY and not individually tuned for performance. I do not believe the Ranger is performance tuned on the intake and exhaust and the experts have agreed on that for years and years.

For all your opinions, you guys generally are not doing that or even really testing what I do. You are being "talking heads" which is fine, but I think you should realize the limitations of it. I'm not wrong on this one and I've never had to go back on it. It works and is useable if you do it right. And now I have the tools to check the impact better and even tune the flow through the sample tube a little to make sure it continues to work.