MAF relocation?

[sprinto7]

I had HUGE problem with my last GM 1.4 Turbo engine stand alone swap. The MAF was kept in the same general location, that is it was just after the air cleaner, and before the turbo inlet. It was mounted in a 2.75" tube as recommended by some experts. It always read way high. I took someones suggestion and zeroed out the MAF settings and ran the engine in Speed Density mode. It runs quite satisfactorily, and the customer was satisfied.

Now I'm about to do another stand alone swap and will try an experiment to keep the MAF reading correctly.
This time I'm getting the air cleaner box as part of the "lift out" package. (2014 Trax).The plan is the attach my Shop Vac to the tube that would normally attach to the Turbo inlet. run the Shop Vac and record the MAF reading.
Then after the swap is complete verify the MAF has the same reading as original. This may require changing tube size, but I'm guessing the reading needs to be the same as OEM.

Any one tried this?
How wrong could it be?

Sprinto7

[cobaltssoverbooster]

larger the tube the lower the maf hz reads.
smaller tube has higher velocity which causes the sensor to read differently (usually higher hz rate)

[Flyer]

Stick with the same size tube.

[sprinto7]

larger the tube the lower the maf hz reads.
smaller tube has higher velocity which causes the sensor to read differently (usually higher hz rate)

My problem seemed to be my larger than stock tube gave higher readings than the stock one was supposed to give. Until now, I never had the stock tube. I picked up the Trax engine yesterday. The stock air box has a smaller tube than I was using.
I think you are the person who suggested disabling the MAF and running SD. THANK YOU VERY MUCH. It worked great. It was much easier than than it sounded like it would be.

[cobaltssoverbooster]

Stock size would be recommended but if the rest of the intake is more efficient than stock then that same size tube will still skew the results. To achieve same flow you have the right idea. TEST it in stock intake with fixed source...then test diameter to get close with same fixed source.

[sprinto7]

Thanks. As soon as I get the harness back, I'l test it out.

[mbray01]

In my experience, if the maf reads higher in a larger sized tube, its usually because it is close to a bend. When its too close to a bend, it will typically read either too high or too low, do to air movement not being uniform through the bend. (air is going to try to go straight) and therefore will load one side of the bend more than another. Much like water running through a river bend, its deeper to the outside of the bend, as its trying to go straight so it loads the outside of the bend. I see most people suggest the maf at least 4" from a bend, however I usually like to see 8"+ to ensure a clean reading. If your dialing in the maf and the line is not smooth its usually an indication of a dirty signal

[sprinto7]

I tried several different locations. All read the same. I'll spend more time on the next one. If I can make the new setup work, I'll replicate it on the old one.
This is all difficult on a non road car, and no dyno time. (Too cheap)
I'm also challenged by needing to run a 33 mm restrictor in the air inlet. Plus it was in an 80" wheel base car so VERY limited space to get any straight sections of tubing.

[sprinto7]

Deleted

[sprinto7]

I have been give an explanation for this situation by someone I consider an expert with the 1.4 turbo engine.
This vehicle is an Autocross only vehicle, so it is only run in 1st and 2nd gear. He says the larger turbo and the fast acceleration will throw the MAF reading WAY off.
That makes sense, so I'll just run it in SD mode and stop worrying about the MAF reading.
I've noticed the "Absolute Load" percentages are way off also. I don't know for sure how that is calculated but I wouldn't be surprised if the MAF is involved.
The tune runs fine. More power than I've gotten out of any of the others. Lambda seems to state reasonable from idle to wide open, so I'll just leave it alone for now.
I have NOT touched VVE. Not that I have a clue what to do with it. :-)

[KLUG'S SS]

I've been wanting to try a pure SD tune on my Cruze. I think I will give it try this weekend. Just for shits and giggles!

[KLUG'S SS]

I know the way that GM has the tune setup in the OEM calibration for the Cruze/Sonic it would "appear" that the cars are running in speed density right as they leave the assembly line. But through some of my own testing I would have to say at this point that the tune is still referencing and using the maf.

[cobaltssoverbooster]

have you tested the theory by unplugging your maf signal wire from the harness and leaving the other maf wires still plugged into the maf sensor?

the maf signal feed is coded per factory to limit the use of mass air sensor calculations until x rpm.....(i believe around 7k) therefore it has low authority which may cause the trims to wander a tad more than usual (a few %) when disconnected. If you unplug the maf harness completely you bypass the iat sensor in the maf and cause major error swings as the iat has strong bias in the VVE system. The only true test would be to record a ve histogram and record error of trims. then record the same histogram with just the maf signal wire removed. they should be within 5% of each other. if it swings more than that then the maf settings don't allow maf bias disable like the old ones do. this test will only be accurate if you let the ecu throw a maf code which guarantees the ecu ignores said circuit completely. I would perform this test if i had access to this style ecu but i do not. instead ive been waiting patiently for someone to run the maf test and generously post the data online.

[KLUG'S SS]

No I have not yet pulled the maf signal wire yet sir. Some of my preliminary tests have suggested it (the maf) appears again the word I used in my other post "appear" to have some say in it BUT I am not one of those guys that is going to sit here and swear up and down that it does without further testing ie pulling the maf signal wire out. I've been tuning for over a decade now and I have a very good understanding of the various operating systems so seeing the airmass settings set to 7000 and 6900 I believe (don't have my tune file open in front of me) that immediately tells me that "should" be in speed density mode ignoring the maf.

My tuning roots starting out was all LS based stuff so as sure as the sky is blue when tuning the VE table of course fail the maf by setting the high frequency to 0 hz and then raise up those numbers from the stock 4000/3900 numbers to something high. Basically to make a long story short I agree with you 100% on all your points. I am busy a lot but I am going to find a few minutes very very soon to pull the signal wire and then do some more testing to really truly get to the bottom of it! I will absolutely report my findings back in this thread or maybe start another one.