***Prof. MAF Tune vs Mystery SD Tune***

[valdeztke]

LS3 427ci motor
CNC'ed L92 heads, (360cfm intake and 280 cfm exhaust)
40lb injectors
Comp cam 232/234/595/598/112LSA

Org MAF tune is attached along.
The owner had the car retuned SD by a different tuner.

Attached are the two tunes.

Edit see latest post below for progress.

[HNK]

I thought I would start a new thread based on the most recent turn of events in my vehicle family tree.

The car was built and tuned by Charlie at RPM Motorsports (CA) and installed by A&A.

I purchased it 25,000 miles later from the original owner.

It appears after the car was delivered the owner removed the MAF and forced the car into SD and possibly had someone retune it.

Attached are two tunes that claim to be for the exact same motor - one pulled from my car and the other from the engine builder.

Here is a list of the car specs:

LS3 427ci motor
CNC'ed L92 heads, (360cfm intake and 280 cfm exhaust)
Patriot gold duel springs
stainless valves
titanium retainers
Scat 4.100 forged crank
Scat rods
ARP bolts
Diamond forged pistons
ARP head studs
L76 manifold
40lb injectors
Comp lifters
Hardend pushrods
Comp cam 232/234/595/598/112LSA
MSD wires

Given the quick run down I'd like the professionals (and noobies) to compare the two files and share with me your thoughts.

Off the bat - why would they change the cylinder size? Please feel free to expand. I'm trying to get to the bottom of who did what and why.


Again when the car left Charlie's place it was flashed with the attached MAF tune. When I picked up the car from the seller he didn't say anything about a tune or MAF. Just said the idle isn't great, but that's a stroker motor for ya.

Great exhaust flow numbers, did you get those with pipe or headers?

[RWTD]

On the MAF tune, that equals a PE Raping tune! The PE table is all jacked up. If you look at the MAF table, I don't believe there was any actual error % correction on the entire table. Sigh! When will so called "pros" stop doing this shit?!

What injectors are you running, as well? Like exact brand and part #. The injector calibration was raped.

[RWTD]

If you were in my neck of the words, that would NEVER happen. So many places sell great parts and do great work mechanically, but they know jack when it comes to professional based tuning. You have to get out and start asking questions, and seeing who actually understands MAF and VE tuning. Even then, when they claim they do, they'll still take shortcuts to tuning your vehicle. Case in point, a guy in the Gen3 section had this happen to his CTS the other day. The guy knew how to do it right, but didn't. He just wanted to save time and get paid.

[RWTD]

Wait, just looked at your file, you talking about the low airmass areas. That's perfectly normal to have more spark there. Less airmass requires more spark to ignite and complete the combustion process properly.

[valdeztke]

We need a Tshirt that says - "My PE was raped by (Fill in tuning shop)"

[5_Liter_Eater]

Yes, the MAF tune was tuned via PE. Common among pro shops. The second tuner who switched it to SD did more than inflate some numbers. There are a lot of tables touched and they are not just bumped up by x%.

- Cylinder size is different but that parameter is irrelevant in gen 4 PCM's.
- Final airflow min was increased but not just by a straight percentage across the board. Maye he had a canned RAF table for strokers and just applied it.
- Startup airflow is drastically higher. Rule of thumb is to start out ~4 grams/sec higher than normal idle running airflow and quickly taper down to normal idle airflow.
- Idle RPM lowered to 650.
- The effective area min and min fail are different although I can't say I know what effect this would have.
- MAF tables are slightly different. Kind of irrelevant
- VE is different as would be expected. The first tune probably did not have the VE touched if it was PE tuned.
- PE Delay RPM is raised a lot but that parameter is ignored by your vehicle
- PE table is different. Raped on the MAF tune and set at 13:1 in the SD tune.
- Lots of differences in spark, idle spark and adaptive idle spark.
- Knock sensors: decay rate is more aggressive and attack is less aggressive. Odd. Burst knock is less aggressive.

Those are the main differences. Not sure what you can take away from it.

[HNK]

Headers - Kooks 1 7/8

Those are what is on the car, but what was used when the heads where flowed? 280 cfm on the exhaust with kooks is way more than almost all ported LS7 heads. Such figures usually are achieved not with street headers like we have.

[RWTD]

We need a Tshirt that says - "My PE was raped by (Fill in tuning shop)"

LMFAO, you're giving me evil ideas! I should market this stuff!

[valdeztke]

just wanted to update this thread a bit -

Here is the lasted tune along with a short scan I performed tonight.

I'm still chasing down some surging in the 1500-1000 range- mainly in gears 4-5 and at lower speed (under 45mph). I'm sure this is something I'm going to have to workout in the Final Air Flow table. The adaptive idle didn't have to get too involved, which is good.



Bill - What exactly is Table 12 showing me? Is that actual airflow at those RPM

thoughts comments or input?

[5_Liter_Eater]

Whats table 12?

[valdeztke]

Whats table 12?

Sorry Bill, I misread that. Table 10 in the Histo.

IDLE AIRFLOW, VE AIRFLOW

Trying to determine how these numbers apply to my base idle airflow table.

[5_Liter_Eater]

If you're using my idle tuning config then histo 10 plots the airflow as determined by your VE table against the final airflow minimum table. It's for step 1 of the two step idle tuning procedure.

[valdeztke]

Thanks Bill.


I've gotten to where the car is very drivable but I still get a little bucking from in the lower RPM range under light throttle.

I thought I read that a few people changed the high spark table to match the idle spark and saw improvements.

[5_Liter_Eater]

Idle tuning is not going to fix light throttle bucking. You have some decent duration and tight LSA on that cam. I'd venture to say it's going to buck <1500. I think it is DSTeck that has done quite a bit of work getting big block large cammed cars to buck less.

[valdeztke]

Thats exactly what I wanted to hear. This is my first cam'd car (the rest were all stock + boost applications) so I'm new to what a cam car drives like.

Welcome to the world of overlap I guess!

I'm fine with it - just wanted to make sure it was typical.

When cold I still get just a bit of idle dip when disengaging the clutch, but only when the engine is below 140 temp.

[valdeztke]

Frost - might need to set a date with you to just start over from scratch on this