Low Dyn Air and MAP at WOT

[jonnycatz]

2007 Chevy Avalanche with 5.3L, catback Magnaflow exhause is only mod. In my WOT runs, scanner shows from 0.56 to peak 0.64 g/cyl for Dyn Air and MAP will start off at around 92 kPa and then slowly drop to about 88 kPa at 5000+ RPM. These numbers seem low. Does anyone have a logged WOT scan on a Avalanche, Tahoe, or Suburban 2007-08ish that I could see

[realspeeddan]

What is your altitude?

g/cyl numbers don't seem all that low to me for a 5.3L truck engine.

[jonnycatz]

about 2500 ft

[jonnycatz]

Bump.. any1 have a WOT run scan with a 07+ Avy, Tahoe, or Suburban to view?

[Russ K]

This is a stock 2007 5.3 Sierra with just a cat back exhaust. Altitude is 1900 ft.

Russ Kemp

[jonnycatz]

Thanks Russ, I checked the scan you sent. My MAP values are virtually the same, but my dynamic air in g/cyl. never passes 0.65 where as this truck is hitting close to 0.75. I have recently installed a new high flow K&N intake system, hoping it would improve MAP and Dyn Air stats a little. It has made no difference at all, at least as far as I can see in a scan. The IAT temp on your run is about 65 degrees whereas I was at 85 degrees. Would that make that big a difference? Or is it the heads on my truck just perform like this?

[Russ K]

The higher IAT is part of the difference, but the real problem is because your commanded AFR is so rich, your Maf table is lower and this will lower the dynamic cyl air.

Russ Kemp

[jonnycatz]

The higher IAT is part of the difference, but the real problem is because your commanded AFR is so rich, your Maf table is lower and this will lower the dynamic cyl air.

Russ Kemp

I noticed in my scan versus his that my injector duty and mV was quite lower the entire pull rpm vs. rpm as well. Do you recommend I "increase" change the MAF output vs. airflow freq table? Is there a way to accurately calibrate the MAF sensor? My commanded AFR for that run should have been 1.188 EQ ratio or so. I have recently lowered it to 1.17 and to 1.18 from 4400 rpm up, because I always hit about 3-4 degrees of KR at exactly 4800 rpm with 25 degrees advance. I also lowered advance to 24 degrees in that rpm range. Thanks again.

[Gh0st]

You do have a wideband, right?

[jonnycatz]

Yes, it reports my commanded AFR as accuarate.