C_Rules

iTrader: (7)

Okay so I have been running in SD mode for the longest in my NA LT1. I started using the MAF and now I have to tune it since at WOT I'm not getting my commanded a/f as I was in SD mode. How do I go by tuning the tables when in tunercats they are broken down by Hz and gm/sec. Lets say at WOT i was moving 214 gm/sec how do i know which Hz range to modify and by how much?

In SD mode you know what VE cell to modify based on your current fuel trims for a given rpm and the map. In MAF all I have to go by is my afgs and Hz. However the datalogger does not tell me what hertz I'm at for each given value of the gm/sec. If I don't know what Hz I'm at how would I know which cell to modify?

LS1-450

iTrader: (33)

Am not sure about LT1 & tunercats, but think that this will work, if you can log STFT's. Start by increasing the whole MAF table 5 to 10% at a time while idling until your STFT's are between 0 & -3%. This should get the scaling close. Then confirm it by driving & going WOT.

Another thing to try is that if you know the stock scaling g/s to Hz, then you can look on the stock table & find the g/s that you have recorded. This will tell you how many Hz is currently registering the known g/s. You'll already know that the scaling is off, but, this will give you an idea off how far off. For example: 8K Hz may be registering 100g/s when it should be 180g/s ish. Your WOT g/s will likely be above any of the current MAF table settings.

Hope this helps

C_Rules

iTrader: (7)

So if at WOT i was around 214 gm/sec and registering according to my wideband low 10s a/f I would then need to find my the gm/sec that is 214 and then modify it so that it is leaner. I don't need to worry about the Hz only the gm/sec?

LS1-450

iTrader: (33)

Yes, this is one way to get closer to calibrating your MAF table. However, logging STFT's is a better method, if your OS has this capability. In an LS operating system the MAF is used mainly for normal driving & then the PE table is used mainly for WOT. I don't know your operating system. In any case, I would expect your g/s to be over 400g/s during WOT, beginning @ 5400 or 5600 roughly. This would explain a 10:1 A/F ratio.

So, does your operating system use the MAF table during WOT or does it default to a PE table say @ 70 MAP & above 50% or so throttle position?

MEAN LT1

iTrader: (2)

You got it and this is the way I tune as well. You take what ever your seeing in your log at wot. Take what the maf is giving in you in gm/sec at what ever rpm and and scale it by say 1.05 if you want to add say 5% OR .95 if you want to take away 5% fuel.

C_Rules

iTrader: (7)

I believe it defaults to PE mode according to the %Throttle for WOT vs RPM table. If I understand correctly the MAF is not used while in WOT. But if that is the case I don't know why my a/f was so rich. At WOT my STFTs are steady at 128. At the beginning of PE I was moving about 175 gm/sec and the number increased to about 390 as the rpms went up.

If the MAF table has no effect at WOT what could have caused me to go so rich? I'm going to have to put the car back in SD mode to see if I'm reading my commanded a/f at WOT.

LS1-450

iTrader: (33)

What??? You said your max g/s was 214 g/s. If it's 390 g/s then your MAF is not far off.

I said the PE is used "mainly" during WOT, not completely. The MAF table is used as a secondary reference. Also, if there's a fault somewhere, your engine protection fueling will be used, which will make the car run rich. If your STFT's are 128 & I'm interpreting that number correctly, then I'd expect the fueling to be pig rich.

Looking to see if you're PCM is reading, or where it's reading from during WOT fueling is a good idea, as you've suggested.

BlackScreaminMachine

iTrader: (17)

The one thing I do know about LT1 tuning is that when you are 100% WOT, the MAF readings do not matter

C_Rules

iTrader: (7)

I did say 214 but that was based on a real quick throttle push. I didn't give the MAF the time to shoot up. I went to a log where I was WOT for a lot longer and got the 390 max which I stated above. Sorry for that should've looked at the better data before I said that.

Damn MAF I should've stayed SD but I like to have everything in working order. Looks like I'm going to have to scale down my MAF tables to lean me out at the 400 and below range.

Quick question how were you able to determine the gm/sec i was running is that of a low 10 a/f ratio. do you have some type of conversion chart you'd be willing to share

LS1-450

iTrader: (33)

-Agreed, once you lean her out, it should be OK.



-I looked @ your signature & estimated based on where mine is. I don't have a conversion chart. Even 390 g/s may be low (no way for me to know for sure on an LT1). Just keep leaning her out 'till she reaches 12.5-12.8:1 during WOT.

-15.5 to 16.5:1 during normal driving should produce good gas mileage & should be a safe A/F ratio under normal driving conditions.

After you lean everything out, run a knock log to be sure there's no pre-detonation.