Data sources:
flat 1/2 mile section of a North Dallas toll road
rolling start to 25 mph
WOT in third gear 1500 rpm to 6200 rpm (about 25 mph to 110 mph)
All accessories and A/C OFF
65 degrees F
Data devices:
data acquisition hardware, video w stopwatch overlay, I Phone app decibel meter, Laptimer app g-force
Car:
09 Stock LS3/MT w CAI and Loudmouth axle backs (GS bodywork)
Rationale:
I do track days around DFW once a month and autoX 4 or 5 times a year. Third gear efficacy is very important on race course-I might catch 2nd once a lap but will hammer it in 3rd 90% of the time. Pro racers who have driven my car report the same usefulness w 3rd gear at the local tracks. (AutoX's are run in 2nd gear.)
Results:
Post-recall I am 2 seconds slower. Data are consistent that this occurs below 3500 rpm. Comparisons from 3500 to 6200 RPM show pre post similarity. Above 3420, g-forces are same, and stopwatch timing is the same 4500 to 6200. 3 decibels quieter (with "4 dbl" being significant to the human ear) AND coolant temp runs 7 degrees cooler. NOTE: receipt from dealer says that I received the "latest ECM recalibration for this recall". Have they varied?
Final thoughts:
Everyone wants to see dyno results, but I need gear efficacy for my type of spirited, enthusiastic driving, and 3rd gear covers 85 MPH on the speedo. So...Low end grunt or pull (g force) is reduced. Also, I stall when a traffic light changes to green because the car needs more throttle to move from a stand-still. A long, high toll road overpass (fly over) now requires a downshift to 5 th or else I reduce speed--6th gear now for flat highways only; inclines require downshift.
The issues I'm having are in the lower range of RPMs

 

No way I was going to do this recall. No benefit.

 

I'd take it back to the dealer.

 

Besides adding cats, GM leans the motor way out to pass Ca. emissions.

Granted that in CA, you can not get your plates until the recall is done, but in any other state that is not requiring the recall be done to get plates, why in earth would you have the recall done to start with??

Truth is, even in Ca, if you have to have the recall down to get the plates, nothing stopping you from having the car tuned after the fact to rich it back up again.

So the added cats will cost you a few HP's, but it the GM re-flash that leans the car way out, and the real HP lose instead.

 

Just what I did.

But at additional cost, $300 for a retune.

Biggest seat of the pants is the lower rpm throttle response, which is just what the OP's complaint is about.

 

I'll take GM's gift of a new $1300 4-cat high flow exhaust system. It will only cost me what I pay for a re-tune to restore "liveliness" below 3000 RPM. Truly an awesome deal.
I'll post actual rear-wheel dyno results of the current ECM recalibration issued by GM for this recall [before] AND a dyno sheet of results for bringing a bit of life back into the car [after]. That will provide everyone with an analysis of the "before-OEM", the "recall recalibration", and the "after re-tune". All have used/will use my "3rd gear efficacy" test.
This is fun. Many have commented with frustrations. I'm living in the fun of analysis.
I appreciate LG Motorsports (vender on this forum and local to me) for their help throughout this.
Merry Christmas
Paul
Dallas

 

Has anyone compared the oem vs recall tune and looked at the differences in the tune? I compared my 08 manual, NPP factory tune to the catylitic recall tune.

Here are the differences:

Airflow = none
Power enrichment (PE) = none
Torque management = none
Spark tables = none
Idle = none
Retard = none
Knock sensors = none

Then what has changed?

02 sensor changes - voltage thresholds

In summary, the new catalytic recall tune should have no effect on the performance at WOT. Now we can stop speculating on the tune.

Does adding two smaller catalytic converters cause a loss of HP? I let you guys speculate, since I do not have before and after dyno runs.

One thing I have noticed is the sound is coming back!

 

Not true! My 2008 oem tune commands A/F ratio of 11.25 to 11.75 at WOT. With COTS (catalytic protect) the A/F ratio will drop into the 10's. If anything GM will error on the richer side to protect the engine from leaning out and cooling the catalytic converters. Emissions are more of a concern when in closed loop (at cruise) with the 02 sensors active maintaining 14.7 A/F ratio.

The new recall tune changes nothing with PE or A/F ratio tables at WOT.

Yes, it is true in CA, no recall = no registration.

 

That's what I was about to ask.. It sounds like there is next to nothing changed tune wise based on your post.

The O2 voltage thresholds barely matter. I've moved them large amounts and it never made more than a 1-2% difference in fueling.

On gen 3's those values seemed to matter quite a bit.. but for whatever reason they don't on get 4's

 

UPDATE: No "1-to-4 skip shift mode" in GM recall calibration. Hard to believe, they took away the command mandating a shift from first gear to fourth gear.

 

Maybe that was an emissions cheating device?

 

Interesting, tune file shows no changes from the oem 2008 manual tune vs new recall tune that was installed in my car:

Disable TPS - 13%
Min. coolant - 171*F
Enable speed - 16 mph
Disable speed - 19 mph

Was the coolant temp at or above 171*?

 

Were you on factory original tune prior to the update?

 

My skip shift was tuned out prior to the recall and it stayed tuned out after the recall involving the reflash.

 

I wonder if the new recall tune only wrote the new calibration changes and not the entire tune file?

 

That sounds correct. I've seen a few people say it didn't mess with their skip shift settings

Would be interested to compare OS #'s before and after though.

 

PM sent.

 

2009 Auto.

Same OS before and after on mine. Most of the changes were in the transmission area.

DJ

 

Ah well.. I guess GM can do whatever they want