Can't Add Fuel

[Bill Putnam]

What should I look at as to why you command a richer fuel condition and it doesn't change or goes leaner? Making pulls with my car from 2500-3500 and no matter what meter we use the A/F stays in the 13.5-14 range. F/P is steady at 39.5-41 psi.

Bill

[NeverEnuff]

Get your MAF Xfer function correct. Base Fuel table doesn't know left from right unless that is correct.

[Bill Putnam]

That's the thing the MAF Xfer should be fine. First we tried with the VMP 100mm MAF/HPX sensor and it wouldn't respond. Then we figured we would rule out the MAF by putting the stock 90mm in because it's a factory meter and it was working perfectly before. Same problem.

[ONELOWF]

Originally Posted by NeverEnuff

Get your MAF Xfer function correct. Base Fuel table doesn't know left from right unless that is correct.

+1
I would: use the pmax, force open loop, adjust the xfer at all of the datapoints up to 4k rpms or use 250 rpm increments in steady state before trying any pulls....per Mr. Banish, "it's hard to hit a moving target".

[Gt]

Just like the others have stated. Make 100% sure the MAF xfer is correct.

The way I do it is:
Set to open loop
Turn off all adaptive functions
Make sure the Base fuel table is set to where I want it.
starting @ idle I go up each MAF data point and make sure a/f matches commanded all the way to 4500 rpms.
Then start working on the WOT runs.

If you want to send me the file to streetstang@gmail.com I can look it over just for the heck of it.

[Bill Putnam]

What would cause the MAF xfer to change though? That's what makes no sense the stock 90mm meter was in there before and was dead on with my Eaton. We put it back in, change the value files back to where it was and same problem.

[dave281sc]

MAF xfer is never fine out of the box on blower cars. 25% off isn't unusual.

First thing is make sure your LTFT's and STFT's are all below 5% during normal driving. If thet are not you need to adjust your MAF Transfer Functions before any more WOT pulls.

Check the following items:

Make sure "Aircharge WOT Multplier" Scalar should be 1.9

Make sure your all of your "Adaptive Fuel" tables are all positive numbers like 3 or 4. No negative numbers.

Make sure your "Base Fuel Table" has loads in the left column above 1.0.

Set your "Base Fuel Table" are .80 or smaller numbers at loads above .90.
Set all your "Fuel Base Table Cold" numbers all below .80 for now.

Set "Fuel Base Table Enleanment when Cold" to ALL 0's.

Open Loop A/F Multi BP Lugging Sea Level 0 multiplier no lower then 22 and 1 Multiplier no higher than 28.

Now tune the WOT MAF xfer.

[NeverEnuff]

Just like dave said.

You MAF Xfer function is the base of everything that the motor looks at. Hell I just put a 90mm LMAF on my car, loaded it in the tune, and it is cammanding a 12.57:1 AFR, but when I do my WOT pulls, it is in the 9.7-10.7:1 range. I had to pull out between 10-30% fuel to get it to the 12.5:1 I need.

If your car is commanding a 12.5:1 AFR and the car thinks 9.7:1 is 12.5:1, then there will be problems across the board. once you get the xfer function correct, then you can change the base fuel table and the corrections should take place with what you input. So if your Xfer function is correct, and you are commanding a .781 (11.43:1 AFR), and then you change the .781 in your base fuel table to .802 (11.75:1), it should respond accordingly...but only is the xfer function is dialed in.

Old saying...garbage in...garbage out.

[Bill Putnam]

I understand that it needs to be dialed in but what has me concerned is that (using rough numbers here) we are commanding 11.5:1 A/F and it's seeing 13.5:1 A/F. We then change it to 9.5:1 A/F and it still shows 13.5:1 A/F on the dyno. Even if the xfer is off we expected it to at least respond so we knew we were on the right track and that there wasn't another problem some where.

[dave281sc]

It sounds like your car is not going to open loop.

There are a lot of possible scenarios.

Here's one

If your MAF transfer is incorrect, your loads could therefore be incorrect & you could be staying in closed loop at WOT. If your adaptive Fuel Tables are not all positive numbers this could make the situation even worse be allowing learning at high loads from inaccuracies in cells at low RPM and low loads. Kind of like a dog chasing it's tail.