Almost ! I was quite a sight there at the kitchen counter with the wife's reading glasses clipping out pieces of screen.

After all that, I'm not sure I'm even going to use it. I got this bug in my head after thinking about keeping some of the diffuser properties of the screen while opening it up to better air flow. Seeing the one LPE sells convinced me to at least try it.

 

OK OK I did it. SO NOW ITS STORMING HERE AND I CANT CHECK IT OUT. :nonod:

 

Better remove the air-box and have a good look at it. It can and will warp in the middle of the filter. Mine was like this when I first purchased it. Zip sells an upgraded unit, made of a more heat-resistant plastic. :cheers:

 

Maybe it should be wrapped in cheesecloth? :skep:

 

I took mine out over two years ago and have had no problems. I installed a K&N at the same time and noticed a small increase in power.

 

Still no posts either way on the effects to an LT1??????

-Rick

 

It's vacation season... I haven't seen him for a over a week. A quick phone call though and he confirmed what's already been posted. The maf in the LT1 requires a SMOOTH air flow for proper calibration. According to him even a dent or a chip in the honeycomb pattern will upset the values to the ECM. Also according to him DON'T modify the LT1 maf! It'll run but it will hurt performance; not help. Of course I don't have any experience with the LT1 but I can tell you that removing the screens on my L98 has made a huge difference in torque by the SOTP meter and I can rev into the red at will! I have yet to see what kind of top end I can muster...kinda affraid to! :seeya

 

I read somewhere that the screens are for strightning the air flow thing is for camaro TPIs not for vettes because camaro L-98`s has different type of air cleaner assambly !! Camaro air filter system consists of two small air cleaners , one on each side in front of the radiator that mates exactly in one pipe exact in front of the MAF sensor , that`s why !! but for vettes you don`t need them as the air filter is in front of the MAF sensor !!

 

This has been debated ad nauseum at http://www.thirdgen.org DIY prom board and ben the source of many arguments. According to what I have read there and also TPIS Handbook, Corvette Fuel Injection by Proebst and Modifying Chevrolet Fuel Injection, removing screens increases airflow but that increased airflow is not accounted for by the MAF because it is no longer calibrated. MAF determines airflow by the amount of voltage it takes to keep the the thin wire inside at a constant temperature. The more air, the higher the voltage. The ECM interprets that voltage baed on a set table that thas been calibrated to the the known airflow when the MAF is intact.

So basically, when you gut the MAF, the ECM is basically not accounting for the increased airflow thereby leaning out the mixture. Most people agree that these cars come from the factory on the rich side jsut to be safe.

I'm no expert, but I would say the gain your feeling is due to the leaning of the mixture which you could probably do with an adjustable fuel pressure regulator. On an unmodified car though, you're probably looking at less than 5 horsepower. There are other issues such as reversion that I won't go into because on a stock to bolt-on motor, the effect would be minimal.

By the way, on a near stock set up the effect of the ported sensor is ony felt at WOT (open loop) because during closed loop, the O2 sensor is making corrections to the injector PW to keep the AFR at 14.7 to 1.

Just my .02


[Modified by GlennS87, 1:04 PM 8/9/2003]


[Modified by GlennS87, 1:06 PM 8/9/2003]

 

Doesn't that make it calibrated? Unless you mean that air is getting through the MAF that has no effect on the wire and therefore not accounted for when increasing the voltage and using the table lookup. I thought the MAF would run out of calibration only at a very high volume of flow (high RPMs) because of limitations in the depth of the lookup table. As long as all the air passing through it is accounted for, it shouldn't matter whether the ECM is using the table from when the MAF was intact or not should it?

 

Actually the calibration refers to something else. The ECM is limited (due to its 8 bit processor) to read a max of 255 gm/s. That a whole other problem for people running highly modded motors.

By calibration I mean you take a MAF to a test bench and determine that for a given measured flow it takes a certain voltage to keep the wire heated. I've never done it myself but from what I've read, if you were flow 300 cfm air thru an opening that can max flow 590 cfm it will generate one level of voltage for that airflow. If you take 300 cfm of air and flow it thru a fully ported unit that flows aroun 750 cfm max it will take less voltage to keep the wire heated to the constant temp. I'm not sure of the terminolgy (maybe an engineer could chime in here, I'm a finance guy by trade) "density" of air will be different due to the increase in "area" the air travels thru the sensor.
For example on my 383 setup, the max value I get on the MAF at WOT is about 235-240 gm/s sec. When I use a Wells aftermarket unit that hasn't been tinkered with, I get up to the max of 255 gm/s.

You can "calibrate" a ported MAF but you would need to do extensive work on a test bench and then adjust the scalars in your prom to reflect the revised airflow. There are few companies that make products to adjust the calibrations for the newer GM MAF's LT1/4 and LS1/6. Unfortuantely no one that I have heard of does this with the L98 MAF's.

An example of a company that has products like this can be seen at http://www.pro-flow.com

There are others but I am unaware of their names. BTW I am not affiliated with any of these companies.


[Modified by GlennS87, 3:05 PM 8/9/2003]

 

OK, thats the part I don't get. Density should change based on temperature, humidty and altitude. I thought all else being equal the higher volume would translate into a higher voltage requirement and an accurate table lookup until as you say the max value represented by eight bits is reached. I had previously heard that since the straightening effects of the screens are not present that is where the inaccuracy comes in. I wonder if its more related to velocity now that the restrictions are removed. When you read 235-240 gm/s is that on a fully ported stock MAF?

Glad I modifed a spare one :D

Another thought. If true that a modified MAF "reads" less air than is actually flowing, couldn't that be accounted for in a new chip by changing the table values? I'd like to get to the bottom of this - I want to get a new chip done soon.


[Modified by 1MoorTym, 4:20 PM 8/9/2003]

 

When I fixed and openned up the front air filter box... I looked at my MAF sensor... somebody already took the screen out.

I guess the previous owner.

cool
:)

 

Good mod for an L98, bad mod for LT1/4 (if you have a MAF ;) ).

Nobody has ever shown an improvement on an LT1/4, except of course the butt-o-meter dyno. No strip/dyno results proving an improvement on an LT1/4, none, nada, zip.

:cheers:

Eric

 

If you do a search on MAF on thirdgen board, there are guys changing the MAF scalars which I believe is what you are looking to do. I am currenlty using my ported Bosch unit which is the one that seems to read a little low on airflow. The other one I have is a wells aftermarket unit. I choose not to use it because under one condition (1/3 throttle form about a 40 mph cruise) I sometimes get a code 33 which is telling me the ECM is seeing airflow beyond it's programmed parameter for a given throttel and engine rpm. If was into chip burning I could change it and eliminate the problem but I'm not. I spent way to much money on a custom chip tha twas tuned on a dyno tha tI'm thrilled with. I should probably get into burning but there seems to be a long learning curve to do it right and I don't have the time.