De-screening the MAF....safe???

[WAGONBEAST57]

Hey dudes,

Just had the car (VX LS1) serviced by a very reputable workshop (they have a big reputation among the LS1 and LS2 crew) at which point they undertook some minor intake mods for me (2 hole etc).

One of the mods mentioned was 'removing the honeycomb/screen from the maf'. They said they do this to all of their customer's cars (LS1's and LS2's) and they run better like this.

After doing some searching I found that this is a very popular mod for LS1 drivers in the states. No results from Australia though...other than it is 'bad' for your auto and may make the engine run lean (no proof though). So is this safe?? Car seems to run exactly the same as it did before...better induction roar though What do you guys reckon?

BTW : The quality of the work, service, price etc and their reputation all seemed to be top notch which puts me at ease a bit more

[QldKev]

I did the same search with mine. I do not recommend it from what I have read. The idea of the honeycomb is ti distribute the air evenly across the hotwire in the MAF. Without it you can get irregular readings; resulting in incorrect fuel/air ratios. You would be way better off going for a mafless tune. Also the 2 hole mod doesn't really help that much when you compare it to an OTRCAI.

OTRCAI + Mafless = FTW.

QldKev

[V8Silverfox]

This may help from another thread ...

You'll be closer, but never on par with MAFless. If you are convinced that you want to stay MAFless though you are going the right way about it.

I noticed mentioned above MAF porting. Please don't do this as the mesh is in a MAF for a reason. If you remove the mesh you distrupt the flow, so it will need to be rescaled as a change. Not worth the effort. There have also been issues with automatic transmissions failing after a MAF screen has been removed. Don't ask me how this is related because I honestly have no idea, but I've discussed it with a few automatic transmission workshops and they've all confirmed it as a problem.

[WAGONBEAST57]

Thanks guys, that's what I thought - gunna save up and probably get it mafless tuned. Is it worth getting it mafless with the current set-up?I just want to keep it looking original. In the meantime should I just go easy on the car?? It seems fine -exactly the same as before actually.

[bricat]

Have had the screen removed for many years now and do not have any problems with automatic. Still original and unopened with shift points altered and mafless tuned. From memory the screen was more to do with the colder climate. ie snow but I am getting old now so memory is not what it should be Cheers Brian

[V8Silverfox]

Have had the screen removed for many years now and do not have any problems with automatic. Still original and unopened with shift points altered and mafless tuned. From memory the screen was more to do with the colder climate. ie snow but I am getting old now so memory is not what it should be Cheers Brian

The issue is not with running mafless, but rather removing the mesh from (and still using) your maf.

[mi04se1]

Removed the screen on my old car and threw 2 lean codes at WOT.

[WAGONBEAST57]

Removed the screen on my old car and threw 2 lean codes at WOT.

I heard that at WOT the MAF is effectively disengaged and the PCM runs off a completely different table or something. The MAF is basically not doing anything at WOT. That's my understanding anyway.

[mi04se1]

At normal speeds, the 02 sensors are in closed loop and the ecm can read the fuel trims. At WOT, the o2s are out of the picture and the ecm depends on the maf to calibrate the proper a/f. Without a screen, your getting to much airflow and the ecm cant rely on it thats why it was lean.....the a/f was off.Now maybe you can get a tune for it.

[WAGONBEAST57]

At normal speeds, the 02 sensors are in closed loop and the ecm can read the fuel trims. At WOT, the o2s are out of the picture and the ecm depends on the maf to calibrate the proper a/f. Without a screen, your getting to much airflow and the ecm cant rely on it thats why it was lean.....the a/f was off.Now maybe you can get a tune for it.

Thanks mate, so your saying if i get it MAF tuned as it is (no screen) it should be corrected and then running pretty much spot on? I dont wanna go mafless cos Im not chasing every last HP and I want to keep the motor stock looking. Ill try to go easy on the car in the mean time...

[vt1538]

Basically the maf is only used exclusively for the airmass calculation after 4000rpm.(in a standard calibration) Before that the engine runs off the VE table (mafless) with a sanity check from the maf.
The auto side of the tune however still uses the maf for torque calculations. A descreened maf if reading low, will give a lower torque estimation to the pcm. This will keep the trans pressures lower than normal & could cause premature wear. Retuning for the descreened maf will help, but personally I would either leave the screen alone, or go a full mafless tune.(this still needs some tweaking of the trans tables)