2008 Silverado timing question

[Stroked250r]

Hey guys, been reading the forums for a while and just purchased a copy of EFI live for myself. This site has tons of great info!

Heres a short rundown of what I have: 2008 Silverado 5.3L with an aftermarket converter and has been tuned with EFI Live by someone other than me.

Maybe it's just in my head, but it seems like my truck just doesn't pull like it did with the factory converter. I do have heavy 33" tires so I know what is hurting me but it just seems like the tuning I received after the converter installation doesn't have the same power.

I've logged a WOT run and noticed that from 4000-5200 rpm my timing stays static at 21.5 then progressively climbs to 28 before the shift into 3rd gear, then falls back to 24ish.

Just curious if this is normal and why does the timing start advancing when rpm > 5200?

Thanks,
Keith

[joecar]

It seems to me to be too lean at WOT (can't really go by the HO2Sx1 voltages, but they range 860-880mV which I would consider too lean).

Spark timing reaching 28° seems too much advance to me.

Use scantool->tunetool cursor highlighting to see what cells in your spark table is commanding spark.

Has MAF been modified...?

What cam do you have...?

What axle gear ratio...?

I think the large tire diameter may be hurting.

[Stroked250r]

Joe, thanks for the response. Please see my comments below.

One of my big questions is does EFI Live have a fix for the 4L60E truck OS that unlocks the converter when APP=0? This is pretty annoying when in traffic on the interstate with a higher stall converter.

I think I also figured out why my timing starts to advance after 5200 rpm, table B5112 adjusts timing based on EQR, so when COTP kicks in, the timing advances to offset the rich condition, correct?

It seems to me to be too lean at WOT (can't really go by the HO2Sx1 voltages, but they range 860-880mV which I would consider too lean).

It's actually pig rich judging by my black rear bumper LOL and my wideband shows as low as 11:1 at WOT. Wouldn't 850mV indicate a rich condition? I'm thinking COTP is causing this. I guess I need to adjust my MAF calibration right?

Spark timing reaching 28° seems too much advance to me.

Use scantool->tunetool cursor highlighting to see what cells in your spark table is commanding spark.

Didn't realize that, thanks for the tip!

Has MAF been modified...?

No it's all stock, waiting for the TVS 1900 to get bolted on

What cam do you have...?

Stock cam

What axle gear ratio...?

3.73

I think the large tire diameter may be hurting.

Yeah the tires alone weigh 75lbs/tire

[joecar]

Yes, that seems feasible, COTP kicks in causing EQR timing change.

I would have expected to see something like 900-920mV, but this is what we can't rely on (as your case indicates).

[Shupe]

One of my big questions is does EFI Live have a fix for the 4L60E truck OS that unlocks the converter when APP=0? This is pretty annoying when in traffic on the interstate with a higher stall converter.

We might be making headway on the TCC unlock issue. I've been watching / waiting for resolution for some time.

http://forum.efilive.com/showthread....l=1#post185219