Lean Tune

[Steve1972]

I'm helping a friend with a L33 5.3 he is putting in a '63 Buick. Currently we have the engine on a run stand with a short exhaust and mufflers. He mail ordered a ECU and they sent him a stock 5.3 tune with the VATs removed. Since the L33 has a different cam and a little more compression I copied the differences from a stock L33 file I found in the repository. He also had to swap to a LS1 intake and injectors for hood clearance so I copied the injector tables from a 2000 f-body. It runs really well and we aren't getting any codes.

We have a LM2 wideband with Innovates tailpipe clamp in the exhaust and the AFR is between 23 and 25. I can't believe it runs so well if it was really so lean. I would question the meter but I hooked up the clamp to my 2001 tahoe and it reads 14.7.

I configured a Lambda error PID to check the MAF calibration table (we are running a K&N filter) and it showed it was off by 1.477 in almost every cell. So I adjusted the MAF table up by 1.477 and the AFR immediatly dropped to 14.5. After it idled a few minutes it began to increase until the AFR was right back to 25.

I took another swing at it and increased the entire VE table by 10%. Again it started with a good AFR and it jumped right back up to 25.

I went into the VCM controls and adjusted the AFR control down to about 12 and the AFR gradually dropped to 14.

What ever is causing it to run lean it's fairly consistant. Here is a copy of my tune and log of it running. Could that fact that there isn't any load on the motor be affecting anything?
Hopefully I uploaded the tune correctly

Thanks
Steve




Buick 5-6.hpl
Kevins Buick with L33 changes & 2000 f-body injector data.hpt

[Steve1972]

Can anybody give me a direction to start looking?

[DrLoch]

Well by looking at the log the NB's are switching and your fuel trims aren't going totally crazy so I would suspect the WB or placement or transfer function of the WB.

[Steve1972]

Thanks for the reply.
That's where I'm confused, I can't believe it would run so well with an AFR of 25. I've never used a wide band with a tailpipe clamp before, so I suspected it, but when hooked the clamp to two stock vehicles it worked correctly. Maybe it's the short exhaust pipe on the run stand that's throwing it off. The Display on the LM2 and the Hptuners read the same. Hopefully the motor will be installed in the car in the next few weeks so I can test it with full exhaust.

[planethax]

You could be getting some scavenging with short pipe.
I would install engine with full exhaust then weld a bung in the header for WB

[DrLoch]

You could be getting some scavenging with short pipe.
I would install engine with full exhaust then weld a bung in the header for WB

I agree