Fixed MAF in spare time and an airbox observation...

[ScottJackson]

So after reading another post about a Q running rich at times and being able to relate with my own experience of MAF failure, I decided to dig into the two "dud" MAFs that came with the car before I put my spare one on it (was on my parts car). I tested one of the bad ones once again and the car started but idled very low and rough. It was also putting out dark smoke from the exhaust and then it died. So I took the top off of the MAF and found where pin "B" connects inside didn't look like a good connection. Busted out the soldering iron and resoldered all three pin connections. Put the square cap back on and tested it again. The MAF now works great. So yes, it would seem that a bad connection at terminal B inside the MAF causes a very rich condition.

As for the airbox, I never thought it was a restriction to the engine. However, I stuck my hand down in the inlet (under the filter toward the front) and found that it's only about a 2.5" opening for the air to come into the filter. I'm not talking about the oval tube that connects directly to the air box where the air filter is, but sticking my hand through that tube and forward underneath where the headlight is. The MAF inside diameter is close to 3.2". So that's around 82mm for the MAF and I think the throttle body is 90mm. The area of a 2.5" circle is 4.90 square inches. The area of a 3.2" circle is 8.04 square inches. I'm no expert, but aren't cars supposed to generally have a larger intake tube/opening than exhaust by a sizeable amount? Unless I'm missing something, it seems a 2.5" opening to feed a 4.5L engine (especially one that likes to rev) is a restriction. Please tell me I'm missing something obvious. Doing the horseshoes and hand grenades math, I find at 100% VE a 4.5L 4 stroke engine will consume 495cfm at 6000rpm. A 2.5" pipe flows around 485cfm at 28" of water. Seems like a restriction to me.
Modified by ScottJackson at 9:55 PM 9/13/2007

[ScottJackson]

This just in! I am an idiot. The 2.5" hole is a "junk outlet" hole in the piping. It just took me a little more digging to see where the main inlet pipe goes.

[qsiguy]

I don't remember a 2.5" restriction but I do believe there is at least some restriction there. Contrary to what a few are likely to interject here, no automaker makes their intake soley for performance on a car like this. They have to consider noise, protection from the elements, etc. Whenever someone brings up a CAI for the Q there's a few people that still believe the Q's intake system is gods gift to the automotive world.

I'm still keeping my home made CAI....until my turbo is done that is. Then again, with the turbo I still have my own custom intake,
Modified by qsiguy at 3:18 PM 9/13/2007

[ScottJackson]

Yeah, those high rpm spinning fan intakes are the best!

[Q45tech]

Now that you have successfully followed instructions to repair MAF.

Mr Phleps your assignment is:

Measure the restrictions at various points in the air passage as I've been suggesting for about 7 years because your eyes, mind, and a ruler can deceive you.

A series of restrictions are not algebraically additive plus the air flows in, is in sinewave shaped gulps 460 @6900 rpm per second.Luckily you know that the system is being supercharged by earth to 14.7 psi [barometric correction required].

Air speed thru the opening is more important.http://www.pipingnews.com/online.htm

The answer is <1/4 of a psi [<7.0" H2O] from atmosphere to MAF inputA K&N cone filter will have 2-2.5" H2O from atmosphere to MAF

How much is 4" H2O worth..................4/27.7=0.1444 x 6.8%= 1% at the best case but you give up addition tuning of system to boost highway cruise MPG.

[brymax]

Uhm-uh, Huh?

[pbedrosi]

I'm having some bucking issues on my car.....how about loaning me that fiexed MAF for trial

[ScottJackson]

yeah, I probably shoulda just put that part about the B terminal failure causing overly rich dark exhaust in the other post where the guy was having issues. And the air box observation turned out to be more of a glance than a real observation as I foud the folly of my ways with a little more prodding. I'm gonna agree with Qtech about air speed being important. I don't have a flow bench but I know that a lot of the guys who build all-out racing big block fords will just close their eyes and listen to the air as it flows through the head. They (guys like Jon Kaase and such) can hear a good port vs. a bad one and it doesn't matter all that much what the flow number is when they're fine tuning a set of heads.

[ScottJackson]

I'm not on this forum all that often, but if you're a stand-up guy who'll actually send it back to me (I would really like to keep a spare on hand) then I could loan it out. I'm gonna run it this evening just to make sure it's good to go first.
Modified by ScottJackson at 11:24 PM 9/13/2007

[qsiguy]

Maybe you could snap a photo of what you did inside of your MAF to inspire others to give it a shot. It's not that difficult to do and resoldering an already bad one won't make it worse...

[ScottJackson]

pin furthest to the right is pin B in the photo

[qsiguy]

Now that's what I call fast service! Thanks for the photo.

Quick question just popped up. Do you, or anyone else, know if the MAF is pressurized, can the air easily escape through the MAF connector holes? How air tight is it? Referring to a blow through boost configuration by the way....

[Q45tech]

That location is a rare problem source the main ones are inside under the copper shield............................be careful.

[Q45dude]

Qsiguy,

any pics or possible instructions on how to build a home made CAI?

[qsiguy]

Sure, here's the thread I made about it. I have a few more of the flanges for them so I can make 2-3 more with the parts I have if you are interested.

It does require a little cutting and complete removal of the OEM airbox & plumbing. Also, it will not work on an active model as there are active components where the new airfilter will be located.

My original prototype one is for sale since I have my new one made with the BOV now. Was asking $125 for it but email me if you are interested and we will discuss...

zerothread?id=246554

[ScottJackson]

yeah, my other dud MAF I melted the solder for the copper shield and pulled it off there. I re-melted most of the connections although nothing looked bad. I also re-did the three connectors in that pic. It still didn't seem to work right when I hooked it back up to the car. Maybe I'll dig into it again. With the MAF in the pic, I saw the suspect connection before I even got to taking off the copper cover. Still, I bent it up enough that I could see underneath it and I didn't see any burn marks and all *looked* well. It works as is so I didn't mess with it further. Yes, the tube can be pressurized and it shouldn't leak. The pole that goes down into the housing has a rubber O-ring on it and it seals tight inside the housing.

[Q45tech]

Make sure you carefully resolder the solder pads where the "pole" actual sensor connect to pc board.

So inside MAF the would be [4+3...under copper]+3 resolders to cover most bases.

[pbedrosi]

Scott....no worries....bought a few things from PopPop and Drew in ATL. I'll send it back insured too. Just email me, my NICO id plus yahoo.

Can't tell you what i do but work for a company located near the town listed in my profile. It would be very bad for me to rip you off.

[Q45tech]

Now [Tn member] if you could just acquire a schematic for the electronic design inside MAF..........................and FPCU.............and....and......and et naseum.

[pbedrosi]

in my previous position it would have been no problem. Let me ask a few contacts on the island.