JohnnyHess86

Good afternoon,

I am in the end stages of turbo prep for my '99. Right now my focus is getting used to the MS2PNP tuning, while the car is still N/A. I'm running an AEM wideband (X series), stock injectors (for now), and almost nothing else apart from pollution control deletes.

My big question right now is about the MAT density table and how it actually works. I have my VE table pretty well nailed down, and the car runs great after playing with idle. Both open and closed loop idle are smooth at this point, with solid AFRs throughout driving range. Of course, once the car gets hot...or rather when the IAT rises enough after letting the car sit hot while I grocery shop, I see my AFRs rising. I've read a lot and now believe I need to dial in the MAT correction table. My question is about how this table works, and how it should be adjusted for conditions.

If I am understanding right, as the air temp rises (in relation to my 100% point) , the engine needs MORE fuel. Is this correct? Also, is the correction % an addition to the fuel calculation? For example, if I tell the table to go to 102% at 120*F IAT, it is adding 2% fuel to the calculation, right? Furthermore, does the inverse apply in colder temps? Does the engine need a little less fuel in colder conditions. Cold of course is only a wish list item for me, as I live in Central Texas and temps here rarely dip below 60*F, but throughout summer they are 99+ for months on end.

Thanks in advance for all advice and information.

18psi

iTrader: (76)

With MAT, you need less fuel when hot and more when cold.
In addition to MAT density table, you need to also account for fuel/injector heat soak.
Two different things, often people confuse them but they are not at all the same.

SpartanSV

You're backwards. Add fuel for cooler temps. Remove fuel for hotter temps.

If your VE table is correct at a certain MAT take note of that temp. Using the MAT correction table add fuel below that temp and remove fuel above that temp.

DNMakinson

iTrader: (3)

Turn MAT to all zeros (or 100%) until you actually begin to see REAL air temperatures above and below your typical tuning ambient of around 70F (depending on where you live).

Then use Add and Remove as SpartanSV discusses above, to keep the fueling correct when running about 100 kPa and 3K RPM. That area of the table.

Don't use MAT correction to fix a heat soaked sensor, or heat soaked injectors, or other such transient conditions.

In fact that should be a general Pro-Tip.... Separate Steady State conditions from Transient conditions, and tune each appropriately.
DNM

JohnnyHess86

Thank you all for your replies.
The MAT table that loads by default in the base map seems quite wide in it's range. I've read through some older threads where people had theirs dialed in to around 105-110 on the low end, and around 95 on the high end.
In your experiences, is this closer to where it should be? Seems like it's pulling a bit too much fuel when temps rise.

18psi

iTrader: (76)

yes that's correct