Billiumss

iTrader: (11)

....butt it is to get it right.

I'm trying to tune a 98 Formula with the following:

Auto, 3200 Stall
02 LS6 Cam
Mac Mids headers
Delphi 50lb injectors
Stock MAF with screen
ATI Pro Charger running 8-10lbs of boost
160 Stat
Custom duals

It is so hard to try to get the Ltrims to go negative.

I tried adjusting the IFR table, added 20% to the Main VE table and no luck, they still are from +6 - +20 all the time when driving around. But the good news is, when you go WOT, they lock at 0.

I have the MAF table to stock. I know I could tweak that, but that is a big no-no...

Where do I start to get them negative all the time.

Another_User

You need a new MAP sensor and a mafless tune and your car should run great.

2000 ws6

iTrader: (10)

Actually on a supercharged vehichle or any forced induction vehichle I would rather have the ltrms slightly positive +5-10 area at part throttle so at full throttle the computer will compensate and add extra fueling at WOT. You wouldn't have to modify the PE table as much if you tuned it this way.

This is more true for turbo cars because slightly leaner at part throttle will allow the turbo to create more heat and spool up faster.

DarkFormula

iTrader: (80)

This is my PITA car he's tuning. All part of the learning curve

Another_User, you think I need a new MAP sensor and ditch the MAF? I'm personally not ready for that yet and would like to keep things the way they are, within reason.

Plus, we're still fighting with a mystery #8 misfire according to the PCM, but physically not manifesting itself. We have hurricane leftovers coming, so that'll give me a few days to go through and check everything again, and give Bill a few days to do some more tweaking.

jimmyblue

iTrader: (11)

MAP sensor is another component of the SD tune and if
you're "over the top" on the manifold pressure you may
not be able to fix it just with table adjusts?

However at idle and cruise you will not be above atmospheric
and this should not be an issue.Though I do not know how
the stock MAP sensor responds to overpressure; seem to
recall something about the diaphragm maybe getting messed
up or distorted? Wonder about whether the sensor may be
"bent"; it might be worth a swap-out?

Being as you are boosted I think you may want to mess around
the FTC boundaries like I did, only revised for your pressure
and idle load situation - lowest MAP boundary to be just above
highest idle MAP, lowest RPM boundary to be just above max
idle RPM, upper RPM boundary at the 4000 MAF cutover, upper
MAP boundary about where you are deterministically into PE.
Middle boundaries, split the difference arithmetic or geometric
as you see fit (I went by octaves in RPM and linear in MAP).

Believe w/ the boosted condition that the manifold pressure
will be generally higher and the pressure across the injectors
less; I guess the PCM might try and account for it but may
not do so well? With the dual pumps, is there a new fuel
pressure regulator setup? Is the rail pressure consistent
with GM nominal, or is there perhaps a baseline error there
that the PCM doesn't know about?

Another_User

I think it might be a good thing to try. I wouldn't want to depend on a sensor that won't be able to read all my boost. I am not a supercharger guy, but if you go beyond what the map can see before the MAF takes over I imagine it would be bad.

P Mack

iTrader: (6)

I could see that being a problem with the MAP maxing out before the pcm switches totally to the MAF, but it's probably less of a problem on a supercharged car cause it builds boost with rpm. I don't know why you think tweaking the maf table is a big no-no, it might be the answer to your problems. Also Jimmyblue has a good point about the ifr tables only going to 0 vacuum so they won't work for boost.

Another_User

I think tweaking the MAF table would be awesome. If we could find a way to do it the correct way. Or find a GM one that works right. Making the correct calculations and modifying the MAF table is far more complicated than tuning VE. And I only suggested this because fueling is far more important for a supercharged car. If it goes too lean it could go kaboom.

P Mack

iTrader: (6)

Whoops, that was directed toward Billiumss in his first post.