sydneyACE

OK tuning gurus,

I've got a 2001 C5 Vette that I put an LS3 and a T-Trim Vortech on.
I'm running a medium camshaft (BTR supercharger cam), LS3 style card MAF in a 4"tube and an LS9 3-bar MAP sensor.
After doing some more reading, I realized that I may have screwed up a little bit with the 3-bar sensor, since I'm only shooting for about 8lbs of boost... but the LS9 sensor fits the intake with no mods, and the LS9 is using it with low boost, so WTH?

I want to start flashing some tuning on this thing.
Should I be using the 3-bar upgrade option when I start?
The upgraded OS is free right?
Is it easy to switch between the OS options?
Is there any good reasons to tune out the MAF? (I've heard lots of mixed opinions about MAF vs SD and changing elevations/density altitudes etc.)

Thanks in advance!

tblu92

I have tune many many older cars that have retro fitted a LS3 engine into them Even with a supercharger----My experience has been--Tuning with a custom operating system or a 2-3 bar MAP is also troublesome--yeah some tuner will insist on a custom OS and 2-3 bar MAP---- Because they want you to pay $650 for a tune-----Fact being on a daily driver type car with street boost (5-8 PSI) the stock OS system and the stock 1 bar MAP will worl just fine and the dive ability pre boost will be far improved--
I haved tuned cars with 8 lbs of boost with no issues using the STOCK 1 bar OL/CL system----Using the stock MAF sensor------The key to knowing if this will work is done by data logging your MAF table being sure that under a full load that your engine does not exceed the end of the MAF table in your tune In older LS engines the MAF table ended at 11250 HZ ( about 500 crank HP)
then in about 2001 the MAF table ended at 12000 HZ (about 575 crank HP) BUT when GM went to the E38 ECM 2007+ the new MAF table ended at 15000 HZ--meaning the stock system can handle up to 700 HP + So the stock system OL/CL and MAF will work just fine and improve drive ability for a street car NOW if your car is a dedicated RACE cae YES you may gain some extra HP and TQ by going to a custom system but at the risk of dtive ability on the street---Plus the gain of a custom system are miminal----In racing yes 10 HP is huge--on the street not so when you have boost that can add 100 HP plus anyway----- My opinon on;y---- and I have tuned over 2500 GM LS engines including cams--turbos supercharged etc--- Plus when you go to s custom OS system which eliminates the MAF sensor and fuel trims---To be spot on the AFR ratio you would need to re tune the engine at every differnet location to get max HP depending on the air density and altitude correction

aaronc7

With your mods I'm going to guess you'll be maxing out the MAF pretty easily. Even using the LS3 style MAF in a large tube, which will keep your Hz in check, the gen3 PCMs have a limit of 512 grams per second of air when using MAF, which is about 67 lb/min or 670 crank hp.

There's a technique out there to scale a bunch of tables such that it thinks its a smaller engine running smaller injectors and thus you keep it below this 512 value..... but most at this point naturally just convert to speed density because its easier and some would even argue for SD on any FI build.

In my experience SD handles changes in elevation/temp etc fine, it is just more sensitive to changes in engine modifications, IE make sure you check the fueling after any hardware changes or mods. MAF since its directly measuring airflow, you put a better flowing part on, it can see that change and account for it 'automatically' to a certain extent.

On this car when I switched to SD I instantly noticed the car running smoother, less idle dips/fluctuations etc (I have a mildish cam on LS1)...which I was pleasantly surprised with. You can still run closed loop fueling of course,

3 vs 2 bar, you lose some 'resolution' but in this application doesn't really matter IMO. I have a 2 bar, but the efilive custom OS tables go up to 285 kPa, so there's a good chunk of the table my MAP will never be able to see anyways.

OS upgrade is free on both efi and hptuners now (I use efi but read that for hptuners).

switching between OS's is pretty easy on efilive at least, you have to do a full OS/calibration flash when going between OS's, which takes longer and resets the oil life monitor, but nothing cosmic about it.

Hope that answers some of your questions.