I added 47 lb injectors and a BAP, and increased my nitrous shot from 125 to 150(wet kit) my newest tune revision shows a drastic drop in MAF flow from 46-47 to 39-39 lb/min. Would there be a reason for this with my recent changes? No codes of any kind, and no leaks vacuum or otherwise.

 

Without having any actual experience on the matter, it could maybe be the liquid nitrous displacing air and slowing down the overall airflow? Could be as simple as MAF scaling too. But, like i said, i have no actual experience on the matter lol. Maybe woot692 will see this and chime in

 

So the MAF reading is low even if I log with no nitrous at all. Seems to be in the tune. I'm just trying to figure out why?

 

I assumed that was with nitrous. Probably a scaling/frequency thing. I’ve seen mustang guys talk about how they can make the stock car show 80lb of flow by just messing with the scaling/frequency

 

nitrous is displacing air, as someone else said.

Since you're using a wet kit it's not pre maf. IF you were spraying before the maf it would show true flow, which would probably be something like 6x lb/min.

In all my experiences all my wet kit mustangs read low despite not actually being low on power. It causes you to have to beef up how the transmission shifts at lower torque or else it will bust the transmissions ***.

couldn't tell ya "in the tune" anything that would make your maf read low except MAYBE timing pulled for the nitrous.

 

So with the wet kit the nitrous comes in at the throttle body after the MAF. Also, the maf readings are the same if I spray or if I just make a run with no nitrous on the nitrous tune. Maf frequency appears to be identical, but absolute load is way down.

Oddly enough this tune is running more timing for the 150 shot on e85(25ish at wot), than my tune for 125 on e85 (22ish at wot) ??♂

I really just need to put some numbers down at the track and dyno and that will paint a better picture.

 

If your absolute load is reading lower, MAF lb/min is reading lower, and you're running more timing with a tune that made for more nitrous you have a potentially dangerous situation going on. My guess is that you have a faulty/dirty MAF, or at some point while you were upgrading things an air leak was created after the MAF. What do your fuel trims looks like, any data logs without the nitrous?

Absolute load is calculated from the MAF readings, so lower MAF readings will create a lower absolute load which in turn means the PCM will command extra ignition timing due to the "low load". If the route cause of your lower MAF readings is an unmetered air leak or faulty/dirty MAF, this would mean that you're running extra ignition timing while running lean on one or more cylinders. I wouldn't run the nitrous or go WOT for long until I had this figured out.

 

Great insight. So where I get lost is the first version of the tune sent did not have this happening. It was the revision and 2nd revision where load and MAF flow are low. If I load the original tune, I still see load at .9x, maf flow of around 44-45.

I can attach a SCT log or message to you if you care to look it over. I do see the long term trims a bit lean at 1.08-1.09

 

That's really bizarre if you can go back and forth and it's really in the tune, I would bring this up with your tuner. It's possible something got changed accidentally or corrupted when the tune was sent to you although in that case I typically wouldn't expect the truck to run well if at all. It's also possible that some changes were made to the camshaft timing for the larger shot and those changes are negatively impacting airflow, but again I wouldn't really expect this to be the case fro the jump from 125 to 150. A 15% decrease in reported air mass is pretty big, but not so big that your fuel trims can't compensate, still I'd avoid the nitrous until you at the very least get the all clear from your tuner. The last thing you want is to run lean while spraying.

 

So I have noticed the cam timing is indeed different. I haven't checked if it's different between the first installment of this tune and the revisions though.