Maf placement and tube size.......

I have been running my car MAF only for a long time, and it has run great like that. I was running a 3 1/2 inch pipe with the maf in a pretty standard spot ( see pic below) and all was good. For reasons that are not important, I had to make a new IC to TB pipe. I decided to go from 3 1/2 to 4 inch and to move the maf to a different spot, (picture below) thinking maybe it would be smoother than it was before.
The new design is basically not tunable to my satisfaction. The car runs great, but has a small hesitation (lean spot) off idle and light surging at cruise.
I tuned the VE to perfection and when in VE only, the issues are not there. I would consider going SD except I have never found a clear answer on the relation of maf and/or VE to torque reporting. My car is a 6L80 and I don't want to take a chance of a change to SD screwing with the trans.

The real question I have is..... would the issue be due more from the different maf placement, the larger pipe, or a combination of both. I can change one, or both back to what they were before if needed, but would like to know which is really the culprit.

Thanks....

New setup....
Attachment 53265


Old setup....
Attachment 53266

Always best to have the MAF in a straight length of piping imo, less turbulence. Common practice in primary elements in instrumentation is to place the element 10 diameters from an elbow. Not possible in most vehicle applications, but the straighter the better. Midpoint between bends is the best you can do.

Increasing the diameter changes the immersion distance of the MAF in your case. While 1/2" doesn't seem like a lot, the flow is different farther away from the center of the tube. Could be the underlying issue since you were near a bend in both cases.

Spraying upstream of the MAF will def cause erratic readings as the droplets hit the sensor. Not sure if that is what the tubing/fitting in the 3.5" pic was or not.

You answered your own question. Placing the MAF right on a bend is not ideal either. Placing the MAF in a bigger tube increases the range but also kills signal quality.

Quote:

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Originally Posted by Iam Broke

Always best to have the MAF in a straight length of piping imo, less turbulence. Common practice in primary elements in instrumentation is to place the element 10 diameters from an elbow. Not possible in most vehicle applications, but the straighter the better. Midpoint between bends is the best you can do.

Increasing the diameter changes the immersion distance of the MAF in your case. While 1/2" doesn't seem like a lot, the flow is different farther away from the center of the tube. Could be the underlying issue since you were near a bend in both cases.

Spraying upstream of the MAF will def cause erratic readings as the droplets hit the sensor. Not sure if that is what the tubing/fitting in the 3.5" pic was or not.

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Quote:

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Originally Posted by BNA

You answered your own question. Placing the MAF right on a bend is not ideal either. Placing the MAF in a bigger tube increases the range but also kills signal quality.

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I realize the best thing is to have the maf in a straight section. I thought having it before the bend would be better than after, but I think the lower section of pipe may just be too short to put it there.
As for spraying.... the meth is spraying after the maf in both pipes.

I may try moving the maf to the top section, on the 4 inch pipe. If that is not better, I guess its back to a 3 1/2 inch again.

Have you tried running mixed mode? Not sure it'd be any better but figured I'd ask

I'm afraid if you put it up by the throttle body you will see a lot of turbulence at part throttle from that big blade in there. Keep us posted.

Quote:

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Originally Posted by schpenxel

Have you tried running mixed mode? Not sure it'd be any better but figured I'd ask

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I did try it and its the same issue as maf only.

Quote:

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Originally Posted by Iam Broke

I'm afraid if you put it up by the throttle body you will see a lot of turbulence at part throttle from that big blade in there. Keep us posted.

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It was good the way I originally had it set up. I will probably try the maf in that location on the 4 inch pipe, and if that's not better will go back to like the original.

Quote:

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Originally Posted by realcanuk

I did try it and its the same issue as maf only.

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Gotcha. Had a feeling it wouldn't but thought it was worth a shot.

I had the same thing and found that a honeycomb prior to the MAF helped a good bit on mine. I have some screenshots around here somewhere of the MAF signal before/after and it was a definite difference. Mine was damn near bucking prior to installing that.

I never could get MAF only to be smooth enough though so I ended up just staying SD. The honeycomb made it livable, but SD was still quite a bit smoother so I just stuck with that.

Hopefully you have better luck

Quote:

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Originally Posted by schpenxel

Gotcha. Had a feeling it wouldn't but thought it was worth a shot.

I had the same thing and found that a honeycomb prior to the MAF helped a good bit on mine. I have some screenshots around here somewhere of the MAF signal before/after and it was a definite difference. Mine was damn near bucking prior to installing that.

I never could get MAF only to be smooth enough though so I ended up just staying SD. The honeycomb made it livable, but SD was still quite a bit smoother so I just stuck with that.

Hopefully you have better luck

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Mine was fine with previous setup... probably end up going back to that.

Yeah.. not like you need more power :)

Quote:

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Originally Posted by schpenxel

Yeah.. not like you need more power :)

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LOL... no, I don't. It wasn't done for that reason. I needed to make a new pipe because at the time of the build, I didn't have the right bend in aluminum, so just made a steel pipe. At the time I knew it was temporary.... my mistake was instead of just duplicating it now, I decided to go bigger.... dummy I am.