Need help interpeting AFR data.

[Priesty]

Hi guys, hoping one of you carb gurus can help me out. 

I have been trying to dial out a persistent flat spot in my Holley avenger for a while with no success. I installed an AFR gauge & data logger to aid with diagnosing lean/rich conditions at WOT throttle in the hope this would allow me to get it sorted. Basically if I knew what a healthy WOT trace looked like I could try & emulate that. The seat of the pants tells me the bog is still there, but it has changed to a less violent event, albeit with slower subsequent acceleration. Any thoughts on the attached log details would be appreciated, note that there is no RPM data unfortunately so WOT is marked with a marker.

cheers...

[GoodysGotaCuda]

Do you have a .csv file or some other form that I could read? The .doc isn't the easy to see and view the values. If your data logger will take any 5v inputs, rigging up a TPS or MAP sensor will really help your ability to read a log.

In short, looking at a generic AFR table may help you understand what should be going on.

To level set, Generally Accepted AFR Basics:

• Max Power AFR: ~12.5 (~10.5 on boost)
• Max Torque AFR: ~13.5 [lower rpm, near peak tq
• Idle: 12.5-14.0, depending on what the engine wants
• Light Cruise: ~15.0
• Too lean: >15.2
• Too rich: <12.0 - dipping below 12 for a split second when the accel pump shoots isn't uncommon

The attached AFR table (mine), may help you understand what you're looking for. As I go down the road, this table is burned into my head and I can nearly tell which cells I'm running in at any given time.

• WOT = 100kPa (atmospheric pressure), you can see I want 12.6 AFR across the board
• Cruise = ~40-45kPa
• The 13s are transition cells and also rolling into torque when driving around town or on the highway.

Looking at your log, you should never be at 18.1 AFR, period. That's pretty much a misfire, likely a lean misfire/bog. I'd like to see the raw data before getting into too much detail, if you can highlight what you're doing within the log, that'd help. Such as "i was cruising for a second, floored it, then let off completely".

One more bit of information would help your log a bunch, TPS or MAP [vacuum]. The log below is from my 'Cuda: TPS, AFR, AFR Targert and RPM are shown.

[Priesty]

Thanks for your input Goody.
At cruise 14.5-15, Idle 13.6-14.3 I think I'm pretty close to OK. Just the initial second or two of WOT where it spikes lean & then rich is where I need tweaking. I did re-adjust the acc. pump arm spring to take out some slack after the last run which has taken the edge off the lean spike. I wish I'd spent more on a better AFR logger now that I can see how confusing the data is. The only accurate way to know when the car was at full throttle is to sit my wife in the passenger seat & tell her to mark the graph on the laptop when I hit it & again after I let off.
I tried exporting an CSV file, it just appeared as a series of numbers in an excel spreadsheet, don't know how helpful that is. (Sorry I'm no computer guru by any means 
Will try & upload as attach tomorrow. I ordered a smaller squirter nozzle to try for next weekend. I'll take a break till then.

BTW I'm lovin your facebook page too. 

[GoodysGotaCuda]

Uploaded a csv is helpful, it's a comma separated value file. Excel will take that and turn every comma into its own cell quickly.

I would look for a accel pump that shoots more sooner and can trail off. If that's available.

Thanks for the feedback on the FB page. I don't have too many projects on the car these days, however! I guess that's a good thing.


Sent from my iPhone using Tapatalk