Air / Fuel Tuning

[OneSlowGTP]

If you have a “perfect” Injector flow rate calibration
And a “perfect” MAF calibration

What would you adjust to make your car run richer or leaner?

I imagine variables such as cam overlap will affect the actual amount of air that makes it into your cylinder resulting in less actual air then metered by your MAF. What tables compensate for this? (I would expect the VE table, however that table is apparently only used during MAF failure)

hmmm

[ssms5411]

I use PE add vs. rpm, works well for me.

[OneSlowGTP]

That's only for "Power Enrichment" though... I'm talking for general driving.

[never0101]

contrary to what the table says, it works full time. thats why the table goes down to 0% throttle .


*edit*

i mean the PE vs TPS table, not PE vs RPM vs Time table..

[OneSlowGTP]

Well that would be interesting because 0 to 35% throttle, +2.3 is commanded.

That would convert a target A/F of 14.7 to 16.9 (lean) and require more fuel to bring it back in check.

(my car seems to run quite lean at lower Throttle)

wonder why GM didn't have this table start at 0 and work into negative numbers instead of set it up to have the trim catch it.

here's the table for all those curious:

TPS begins at 0 and increases by increments of 5 to 100
2.3 2.3 2.3 2.3 2.3 2.3 2.3 2.3 2.02 0.72 0.45 0.26 0.1 0.01 0 0 0 0 0 0 0
???

I'll give this a try and verify the results with everyone.

[Bill@HPTuners]

what exactly is the problem that you need to change your PT fueling? Part throttle fueling would pretty much be controlled by the stoich a/f and then the maf & o2's would adjust the rest from what i know in our cars...are you running terribly rich/lean at part throttle that you need to change something?

[OneSlowGTP]

Well, I was able to verify that NO the PE table does not make trim adjustments unless the car enters PE mode.

I was hoping to get my trims dialed in for a few reasons. One to see if there was any effect on my driver information center's accuracy, and also to increase the accuracy of fueling when outside of the mapped “trim” area.

I think I'm just going to unplug my MAF sensor, and try tuning the VE table, then just re-connecting the MAF there-after.

[FastFieros]

I think I'm just going to unplug my MAF sensor, and try tuning the VE table, then just re-connecting the MAF there-after.

Good luck, when I unplug mine, it dies... or wont start with it unplugged.

I have had a few V6 3800SC cars that seem to run with the MAF unplugged, just not run very well at all.

Loyde

[OneSlowGTP]

I actually had the opposite problem before: My MAF had failed, (which I did not know) and the car wouldn't start. I thought something was really wrong. I cut open my oil filter and poured out the contents looking for signs of a spun rod-bearing. Oil was clean. I ended up hooking up my AutoTap and discovering my MAF freq. was reading 0, then 11,500 then 0...... Unhooked the MAF and the car started like nothing was wrong... I have since replaced the MAF, and used my old one as an experiment (cutting off the sensor and using it solely to cover the hole.) Car seemed faster without the added restriction of the sensor. This was about a year ago. Recently I switched over to an LS6 MAF and re-installed my hacked off sensor to fill the hole.

I’ll perform the MAF-less tuning sometime soon and report back. Your 04 that won’t run well without the MAF, what does your VE table look like?

-A

[jk99gtp]

I have done a MAF-less tune on my GTP, but only from 0-100kpa. However I have since demodded some items and will need to re-do my tune, but by judging how much time it took me to dial in the VE table the first time I think I am just going to cheat with the IFR table until I get something like a hot cam which will then require me to tweak the VE table.

Before you start your VE tune, remember a couple of pre-steps:

- Copy the high octane table to the low octane table
- Keep PE enabled, you wouldn't want to go into boost with just the VE tables. I have never tried it, but all I hear are bad things about what could happen if you did so...

I used the histogram to help my tune go a bit quicker, took the average then took half that value and added/subtracted in the VE table. If the table looked bad overall I would just use the smoothing feature to smooth out the table abit. After tuning with the car for a couple of days I was able to get the LTFT's to 0% - -7% at idle and cruise cells and I called it a day. I then plugged the MAF back in , and my LTFT's moved to very negative numbers (about -11% - -14%), so I had to rescale some areas in my MAF table abit to get them back to normal. Just to give you an idea on where I had to start from, my LTFT's were +25% at idle, and +15% - +20% at cruise when I first unplugged the MAF to start my VE tune, with the MAF plugged in the LTFT's were around -2% - -3%. I had a stock cam, but I did have 1.9RR rockers, 3" pulley, Intercooler, downpipe, cold air kit, etc.

However, like FastFieros stated, just be careful when you do a MAF-less tune on these cars, my car died three times while just driving normally for absolutely no reason, which would have been pretty dangerous if I would have been in traffic.

Good luck and let us know how it goes for you!

[OneSlowGTP]

A few strange things to note about the car's behavior with the MAF disconnected...

I have 3.69 gears so I hit 4th gear at 35mph.

at 60 my RPM during lockup is rather high.

with the MAF attached. If I were to be driving say 60mph, and let off the gas... my RPM would stay at a rate corresponding to my speed.

with the MAF disconnected. my RPM will drop to ~550 when I let off the gas.

odd.....

As far as tuning went, it would appear that low RPM / low load required quite a bit of reduction in VE values, higher RPM / higher load required increased VE values. All in all my table looks much steeper now then it did before.

[louvered97gtp]

Before you start your VE tune, remember a couple of pre-steps:

- Copy the high octane table to the low octane table
- Keep PE enabled, you wouldn't want to go into boost with just the VE tables. I have never tried it, but all I hear are bad things about what could happen if you did so...

Hey guys, was searching the forums and found this interesting. In regards to the above mentioned, is this still accurate to follow if one decides to tune the V6 VE tables? if so, can someone explain why do we keep PE enabled during VE tuning? I'd just like to understand what's happening.
And lastly, I assume staying in PE is just PE Enable TPS > set to 0?

Thanks