so as i was doing some reading while at Barnes and Nobles. I usually never read car mags but stumbled upon the july 2010 import tuner issue there was a blurb titled "Do aftermarket intakes cause a decrease in horsepower?".

they were saying that in some applications cone filters skew maf readings because they do one of two things.

A. cause the air to flow in a vortex hence increasing the air speed as it flows past the sensor causing the ecm over estimate air flow rate and in turn increases the fuel creating the engine to run rich.

or B. it causes the air to flow along the inside surfaces of the pipes hence tricking the ecm to thinking that the engine is getting less air then it really is making the engine run lean causing detonation and and knock..

then they came to conclude that this may be fixed by some thing as simple as a screen or other apparatus to diffuse the airflow within the pipe so as to create a more even flow and accurate reading


any input?

I am thinking something fabricated similar to this and inserted into the intake pipe with the cone point facing with the airflow will work.

 

Yep, if it's not to restrictive but you'll prob have to adjust the tune for it also. I doubt the airflow over the MAF with the stock airbox is perfect.

Even relocating the MAF sensor to the charge piping before the throttle body needed a 7% shift in the MAF freq table (same diameter as the stock placement) and some minor MAF correction table work to get it dead on.

 

well I currently have the hahn cool ram air intake, I run very rich evidence in carbon build up on spark plugs and within my exhaust system with frequent back fires. I am running the trifecta select a tune with stock down pipe with gutted cats and muffler delete. I throw no CELs so I am going to try and fabricate something to place after the filter in the intake pipe before the MAF. so, if I can get the back fires to lessen without tuning I know that it has done some improvement and to test if i can replicate the results i am going to test it on multiple ss/tc's

 

Trifecta ran a pretty rich A/F ratio for a long time, that and the untuned Hahn CAI would do it IMO.

 

my trifecta tune included tuning for the intake

 

It will do nothing...been there done that. Also tried a homemade velocity stack...choked it bad.

 

The GMofHouston "Skunkworks" tested a MAF screen about a month ago on an AEM intake with promising results.

 

Pretty sure this has been covered in a lot of detail in Terminator 2's intake sticky:

https://www.cobaltss.net/forums/2-0l-lnf-performance-tech-153/thoughts-all-intakes-currently-avaliable-ss-tc-206581/

Simply dropping in a screen without tuning for it probably won't help you like I am Broke said.

 

Yes, if placed directly near the MAF. But if placed where the intake connection is on the HAHN intake or at the filter, it is too far from the MAF to do anything.

 

Exactly. The MAF is approx 12-14" downstream from the inlet on the filter so a MAF screen is not going to help much unless you hacked the pipe apart and placed it right at the MAF. A venturi, screen, or blades placed close to the MAF will help straighten airflow. On the stock airbox the stock airfilter acts as an airflow straightner. That is why doing nothing other than a K&N drop in filter will skew the MAF 3-6%. Almost as much as some intakes.

 

I was thinking about a thin silk screen right, maybe an inch, before the MAF.

 

Short term yes...but long term....ehhh. On mine with a shortened snorkel and a K&N I stay at 0 to -1 LTFT. Maybe I am just lucky. With an intake I saw as high as -12.5 ltft.

 

I'm not sure if you're joking or not, but that will mosy certainly not work. They are refering to an air strainer type of screen. An air strainer is usually around 1" thick and looks kind of like a honey comb. This will "strain out" most if not all of the air turbulance over the MAF giving a much more consistant reading

 

I wasn't going to put just a silk screen and walk away something like you are referring to and this.

 

Yeah, in the case of the AEM filter with the screen, the MAF is close to the filter by where the screen was installed. On a factory setup, this wouldn't be of much use.

On setups with the MAF far away from any opening in the intake, I'm not sure what exactly could be done.

The screen we used was some stuff from Home Depot. Cubaniche was the one that had it on his car. I'll ask to see if he can post up a pic or description of what he used. I don't have a ruler around right now to give a good desciption myself. It was just some galvanized metal mesh. We saw no degrading of the metal either after it was removed.

The idea we went by was to have a mesh that was dense enough to straighten the airflow, without being so dense that it would restrict airflow a great deal.

 

Right, silk is not that restrictive, but not as strong. So it's only in brainstorming mode now.

 

Stamina is correct. On my AEM intake the maf is about an inch or two from the inlet and filter. We did an HPT log and found it to be -11% before the screen, -08% with the screen and -03% or lower when tuned for the intake with the screen. So there was a noticeable difference with a straightner.
Since then I got AEM to issue me a refund for the intake and I am now stock airbox and my trims are all over the place. After they issued the refund the tech informed me that the 'revised' intake with a venturi on it is almost ready but still not 'certified' for the 09 models year, which is total BS in my book. The silicone elbow remains unchanged.
My plan is to use the refund and get the hahn cai since it seems to be the one that has the least amount of issues and can be tuned for to fix maf skew. When vararam realeses its model, then I will most probably invest in it.

 

Also, it should be added that although there was still some skew in LTFTs, once it found it's place it was very consistant (STFTs calmed way down). That should make it much easier to tune for as it's no longer a moving target.

 

with out physically tuning the maf scaling per car, you will not get it set right. even stock cars have skewed maf readings. fuel trims are doing their jobs. this is the whole intention of them anyways. weather changes, and pressure changes. the trims comp for it.

fuel trims are a never ending battle to keep at zero. they will NEVER stay at perfect zero on ltft or stft regardless of what you do. you can get them damn close though. +/- .8 to .2 +/- speed variances, air flow, windspeed, all play a huge role in it. i went 2 weeks straight working my maf table on the 98 lb injectors, and got them down to .8 across the board at 70 mph. my average speed. i jump to 75 they sit at 0. jump to 80 the went -.8.

the weather changed 15 degree's and it **** the bed.