MAF question?

[whackem04]

I want to see if my descreened MAF is accurate. If I take a stock one, put it in its place, log and then evaluate, will that tell me how to compensate for the lack of screenon mine? I have another one to borrow off my bros truck.

[Tordne]

You could try changing to the stock MAF and then see if you can work out a calculated "difference" factor to multiply the MAF table by.

As this is posted in the Gas section I assume it is for the 5.3? You could also consider doing the same as the AutoVE to get the MAF table accurate (requires WB02 which we'd recommend anyway).

[whackem04]

yes 5.3. i know about the wbo2. its about the money. and i think its close.
so its possible thanks.

[pullincrazy88]

if you actually look at the logs you create de-screening the MAF sensor makes the reading unstable and choppy making the vehicle run ruff

[whackem04]

i did notice this but it wasnt till later in the rpms.

[Redline Motorsports]

I wouldn't bother going thru the exercise. We make over 700 RWHP with stock MAF's with screens. Its there for a reason and should be left. Even though you can fix some of it with a MAF calibration its never going to be a clean signal.

Howard

[Gordy M]

I don't know if this still holds, but in late 2001 our Corvette Club had the engineer in charge of the Z06 engine development program give a presentation on the difference between the 01 and 02 engine. In describing the 20 hp increase they gained, he mentioned the decreened MAF accounted for 2.2 hp. When it was asked what changes it would make on a regular Corvette he said none, the changes were in the firmware of the PCM to account for the changes in the turbulance and a software change to the program to compensate for a very slight increase in airflow. His final comments were each cylinder in the engine can only accommodate so much volume and no matter how large an air meter you had, it is the density of the mixture that matters. The 02 MAF would outflow the TB and a Z06 405hp engine needed less than 600 cfm at 6500 rpm. FWIW

[Mr. P.]

I want to see if my descreened MAF is accurate. If I take a stock one, put it in its place, log and then evaluate, will that tell me how to compensate for the lack of screenon mine? I have another one to borrow off my bros truck.
No, this will not work for a couple reasons - when MAF sensors are made/calibrated at the factory the production tolerances are +- 5%, my point being that your brother's MAF is not a laboratory-grade device, you cannot compare to it as a benchmark. The suggested way to calibrate your modified MAF is to first dial in your VE using the AutoVE process and get it dead-on-balls-accurate, then use *that* as your comparison benchmark to measure/document your MAF's response curve (AutoMAF process).


I wouldn't bother going thru the exercise. We make over 700 RWHP with stock MAF's with screens. Its there for a reason and should be left. Even though you can fix some of it with a MAF calibration its never going to be a clean signal.

Howard
Agreed - especially on truck applications because the airflow path is not a straight shot from the air filter to the intake (as in the case of the Vette) you will hurt more than help if you remove the screen from the MAF, the signal will get really random and jitter a lot when air speeds through the intake tract are low (less than high-RPM WOT).


...His final comments were each cylinder in the engine can only accommodate so much volume and ... it is the density of the mixture that matters...
That is a GREAT little pearl of knowledge.

Mr. P. :)

[pullincrazy88]

is there really any advantage though over a MAF-less tune in a more mild cam vehicle? i know removing it will help with the flow but not to any mayor extent. is it really worth all the VE table inputs in the end i guess over running a MAF sensor with the same amout of auto VE inputs. kind of straying from the original subject but i think still is very useful info.

[macca_779]

is there really any advantage though over a MAF-less tune in a more mild cam vehicle? i know removing it will help with the flow but not to any mayor extent. is it really worth all the VE table inputs in the end i guess over running a MAF sensor with the same amout of auto VE inputs. kind of straying from the original subject but i think still is very useful info.

Plenty of workshops (mostly US based I might add) are of the opinion that the MAF isn't a large restriction. I never understood how they come to that conclusion because those of us in AUS have proved time and time again that there are noticable gains to be had with removing it. Certainly more so for the LS1's but even the GEN IV's show measurable gains.

Here we do have a stronger culture with doing it. That probably stemed from when HSV was removing MAF's from factory with the premium C4B (Callaway LS1) engines.

Howard mentioned that he has had cars make 700RWHP with a screened MAF. Thats great and all, but you could get more without it there at all.

As far as when to remove it goes. We remove MAF's on complete stockers and see gains. Add a cam to the mix and the difference gets wider.

[whackem04]

well since i descreened my maf and the values get erractic after 4000 rpm or so, if I change B0120 (os 12212156) to say 5500 I should get more power, Right?

[WeathermanShawn]

Whacked:

Its an admirable exercise you are carrying out, but I just do not believe that any tuning manipulation can compensate for a descreened MAF.

You can get into a lot of physics and engineering to debate the whys, but it is a futile exercise (IMO). I went the descreened MAF route originally (ignorance), and ended up just buying a stock MAF fairly cheap to properly tune it.

I will stay away from the SD vs MAF debate. It is always best to have each tables airflow 'estimates' match. From there, depends on your application.

While I do not think you can accomplish what you are trying to do..if I and others are wrong..just let us know how it works out. It is always good to learn something new..but in all honesty my advice would be to put in a stock MAF with a screen.

[mr.prick]

Your erratic values are more likely from improper filtering,
technique, inconsistent load/TPS% or all of the above.

The screens aren't a factor IMO.
Look at all the newer MAFs, even the C5 ZO6 had a screen-less MAF w/LS1 PCM.

[joecar]

well since i descreened my maf and the values get erractic after 4000 rpm or so, if I change B0120 (os 12212156) to say 5500 I should get more power, Right?I don't know about more power... (power is made by having the actual AFR and timing "dialed" in... there are an almost infinite number of ways to get there, but only a small number will also produce driveability... but, a for a drag car driveability is not important).


This is how B0120 works:
Above B0120: airmass is calculated from MAF exclusively.
Below B0120: airmass is calculated from MAF during steady state airflow/throttle, or from VE during transitioning airflow/throttle.

So if the MAF is enabled, it will be used.

[joecar]

The MAF is sensitive to the plumbing that connects it between air filter and intake manifold...

The aerodynamic effects come into play, and the matter is further complicated by wave tuning effects (reversion)... some de-screened MAF work good, others don't.

[whackem04]

i guess what i should have stated is that im only trying to dial the crap i have in the best i can with my mind more then tools cuz i lack some; WBO2 and $. As far as my intake tract, I have a S&B 5.3 truck intake rev.2 with the front of the box cut open. Will the erratic MAF, which according to my tune kicks in at 4000 rpm make me loose power when im there? No debates just questions to learn.

[WeathermanShawn]

You will not loose power as long as your Air fuel Ratio and Timing are optimal..and you are not getting KR.

Whacked, I know money is tight..but tuning at WOT without a wideband is like swimming in a deep lake without a life jacket. It is very risky.

Having said that, if you are still using your narrow-band O2's, you can monitor your LTrims, and attempt to make a 'guess' at your WOT AFR. It is not the MAF that will cause you to 'lose' power. It is inaccurate fueling that could cause power loss or engine detonation. Some of the guys that de-screen their MAF's sometimes report that it causes them to be a little leaner at WOT..maybe that is where the potential 2.2 HP gain comes from. But, too lean..bad!

[whackem04]

Yes. I get it leave it alone and wait for the WBO2, gotcha! Thanks
"Whacked" out