My Express van was worse from the factory and they run fine. It actually has a hard tight 90* on the outlet of the MAF, a diameter change and a round filter on the inlet. Diameter of the tube does not change the maf signal, but it can slightly delay it in relation to throttle opening, however larger tubing also tends to kill off reversion from messing with the fueling.
From my limited experience and the reading I’ve done on maf placement (my set up is far from perfect) when the maf is in a turbulent area, an oversized tube means that the air is moving more slowly, so the air that may be bypassing the sensor can be a much larger proportion of the total air. We run into this on flow meters on water piping and often have to reduce that section to keep the velocity up at lower flows.
It looked to me like the tube might have been larger than 4”, hard to judge the scale in a picture.
I'm pretty sure thats for a card type maf, thats all I can find info on.
That filter was designed to fit on the end of the maf. Not that it makes it correct but thats what Spectre says.
I have experience in airflow also and learned that using a screen, as you probably know, cancels out the turbulence. Thats why I left the screen on my maf.
Well I changed the air intake pipe to the last picture posted. I did a MAF error run and corrected it by percent half. Still didn't hand smooth it, or the VE table.
Seems like it runs more on the lean side now.
My wideband math is adjusted to read correctly.
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Last edited by Jason B; 04-08-2023 at 08:07 AM.
GM makes a card style attached directly to a filter. The filter literally slides directly on a small flange inside the air box.
https://www.coulterautoparts.com/oem...SABEgIsy_D_BwE
I wonder how much tube is inside the box? Although with filter housing completely and symmetrically surrounding the filter, it probably pretty much eliminates turbulence. I know there are things that can be done to make less than optimum conditions work, it's just when people start modifying the intakes, it can cause additional "noise" in the measurement/calculation.
Factory design did take care of that. Of course they do test the system so that MAF values are stable in all conditions.
Agree, but the amount of airflow does change when diameter changes. Hence the error in airflow model and thus wrong cylinder airmass.
Quite often in LS retrofits in classic muscle cars this is the main problem. Either fueling is wrong or there are bucking/surging -related problems. Getting rid of MAF with (turbulent flow) and going with VE only fixes that.
Here's an example of turbulent MAF:
https://forum.hptuners.com/showthrea...=turbulent+MAf