Tuner said my cylinder airmass too high

[Jason B]

Being right in front of a bend and being right behind the filter is far from ideal. It also looks like the tube is also maybe oversized which will cause a weak maf signal at lower throttle. Add in what looks like a diameter change in the same area and you have the recipe for a bad maf reading.

Well I got rid of the bend since I posted that picture, haven't driven it yet rrrrrrrrrrrrrrr deleted

So is 4 inch too big?

[Fast4.7]

Being right in front of a bend and being right behind the filter is far from ideal. It also looks like the tube is also maybe oversized which will cause a weak maf signal at lower throttle. Add in what looks like a diameter change in the same area and you have the recipe for a bad maf reading.

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.

[Fast4.7]

Well I got rid of the bend since I posted that picture, haven't driven it yet https://ibb.co/5LJ9B4x

So is 4 inch too big?

4" is not too big, I ran a LS3/Spectre 4" MAF on my near stock L31 for 3 years.

[gtstorey]

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.

[Jason B]

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.

[Jason B]

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.

file deleted

[gtstorey]

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.

Sorry, I didn't zoom in enough on the picture to see that you weren't using a card style, although I should have since I don't know were you you find a card style mount that puts the air filter that close.

[Fast4.7]

Sorry, I didn't zoom in enough on the picture to see that you weren't using a card style, although I should have since I don't know were you you find a card style mount that puts the air filter that close.

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

[gtstorey]

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.

[Pekka_Perkeles]

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.

Factory design did take care of that. Of course they do test the system so that MAF values are stable in all conditions.

Diameter of the tube does not change the maf signal...

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.

[Pekka_Perkeles]

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.

Indeed and air is quite different from water.

[gtstorey]

Indeed and air is quite different from water.

But there are also a lot of similarities also so not sure what your point is.

[Pekka_Perkeles]

But there are also a lot of similarities also so not sure what your point is.

Water does not compress (not sure is this is correct english term) as air does. But anyway, maybe not that relevant in this thread. :-)

[Pekka_Perkeles]

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.

Here's an example of turbulent MAF:

https://forum.hptuners.com/showthrea...=turbulent+MAf

[gtstorey]

Water does not compress (not sure is this is correct english term) as air does. But anyway, maybe not that relevant in this thread. :-)

This makes me think that the issues with turbulence and bypassing sensors to be a bigger problem with air, but that’s just an educated guess. And definitely getting way off topic.