PREDATOR-Z

Hi,

Question: On an export open loop/MAF tune (NO O2s), does the PCM rely on VE table (same as SD) and then adjust with MAF?
How does it do that without any O2 feedback?

Could I assume that open loop/MAF tune has twin High/low octane tables? ie they are identical?

Thanks,
Mark

TSDuke

subscribing....

Billiumss

iTrader: (11)

I'm going to guess the PCM will use the OLFA table and VE table for fueling.

GuitsBoy

iTrader: (4)

Open loop works effectively the same either in maf or SD mode. Open loop by nature does not receive any o2 sensor feedback regardless of which mode youre in. The difference between SD and maf modes, is that SD calculates airflow based on VE table and a host of other sensors, while the MAF directly measures the air. In actuality, The MAF mode will still favor the calculated airmass at low rpms where reversion could skew data, or during transients while the manifold vacuum is filled, however not all air will enter the cylinders. During steady start operation (no throttle changes) the MAF is far more accurate and repeatable than SD calculations, assuming its dialed in properly.

Also, the octane tables should be the same MAF or SD, although the stock OS will revert to the low octane table on a MAF error.

RedHardSupra

iTrader: (1)

MAF mode is not a pure MAF mode really, it's a mixture of SD (based of VE and other sensors, calculated dynamically) based airflow, and lookups in the MAF table.
so the answer is really: it should (I never tried OL-MAF myself) be using both--that's just the code that's in the PCM.

not having trims doesn't mean it's not able to do SD calculations, it just means it doens't do any realtime corrections on the already existing VE table.

I'm not sure about timing, it's a good question, we know it goes to low oct table for SD, but does it behave the same for OL?

SmokingWS6

iTrader: (1)

OL maf fuctions the same as CL maf except it takes the fuel trim learning and swinging fuel mixture out of the equation. I have not noticed which timing table is referenced since I always copy the High Octane over to the low.

PREDATOR-Z

Well, I double checked an Hi/Lo are identical (Hi has more cells though)
so it follows SD method. Hmmmmm

SmokingWS6

iTrader: (1)

Are you talking about timing or fuel? Low octane has the same resolution as the High octane timing table.

ZL1Killa

iTrader: (17)

on open loop if you have a narrowband you will notice that it will swing to what your car AFR is VERY close to. the car monitors the voltage on the 02's still.

i was a dumbass and bought a narrowband and well what ya know,,, its actually good for something. lol

SmokingWS6

iTrader: (1)

Only if you are refering to STFT enable with open loop.

RedWS6 00

I have been running OL-MAF for some time now, not really has any problems. My Hi and Low octaine tables are different, it seems to be running from the hi-octain table. I have also disabled the fuel trim learn by extending the thresold temperature to something it shouldn't reach.

As for the VE table I only have one due to being the HP-1BAR-OS.

The reason I'm running in OL-MAF mode all the time is that I can run my own choice of AFR depending on MAP and temperature. So when under little load I'm at about 15.8 AFR, getting near on PE is 13.5 AFR, then PE will take over shooting for 12.5 to 13.1 depending on RPM.

I like running in this mode, getting more MPG on the highways, as once upto speed I guess I'm pretty much running 'lean criuse' mode without lean cruise being in the OS.

GuitsBoy

iTrader: (4)

I definately run from the high octane timing table in O/L-Maf mode. I truly feel that the MAF is a requirement in eliminating cam bucking (not surging). I have the best luck richening up in SD mode, then enabling the MAF and tuning that for 14.7. It richens up the transients when it reverts to the VE table then leans out to stoich for steady state.

PREDATOR-Z

I'm able to dial in fuel by just modifying open loop table. STFT and LTFT are dissabled since I do not have any O2 sensors except my wideband one.
WOT fuel is done via PE, took me a few tries but i'm at 12.8 from 3200> 4800 after which it goes 13 flat till 6400 where I richen it back to 28 till 6700 shift point.
seems to like that best.
25* advance tops (more just doesn't make any more HP)
And yes I was refering to timing tables, my Hi and Lo are identical.

I love this HPT, still newb at it but it works. (also I had some help as i'm modifying a Allen Nelson base tune)

PREDATOR-Z

Same thing here, only 1 VE table.
Cruising at 85 mph with 15.5, no KR, Wot is taken over by PE.

jimmyblue

iTrader: (11)

I would love to get ahold of a 2002 F-body export tune
file.

RedWS6 00

Is that becasue you want the true 'Lean Cruise' enabled?
I guess I'm running simulated lean cruise, mines just a regular trans-am. Keeps me happy.

2001 Pewter WS6

iTrader: (43)

So you have the MAF enabled and just have the trims turned off?? What does your table look like for commanded A/F?? Do you just use your Wideband and adjust VE from your A/F error amount?

RedWS6 00

I already had my VE dialed in before I went perment open loop. However you could adjust it from the A/F error amount, which I have done a couple of minor tweaks. The OL fueling table depends on temperature and MAP. All temperature ranges other than warmed up is left as stock, so around 170degrees I made it about 0.90 at the lower map, up to about 45 MAP where I have put in 1 (stoich), then above that fading to 1.1 to 100 MAP, PE would take over before 100 MAP which is about 1.14 depending on RPM.

I'll post a screen capture later, its on my laptop and I'm at work at the mo.

2001 Pewter WS6

iTrader: (43)

Thanks,,, that would be great. Do turn on lean cruise mode also??? My VE is pretty close. There are only a few cells I haven't been able to hit. My main issues are surging when coming to a stop and stalling when put into reverse. Not all the time but enough to make me crazy. It will run fine then two days later it will run weird. I want to see your OL fueling table and your PE table. My email address is metalam@upmc.edu

RedWS6 00

The reason I done the OL - MAF tune is becasue it wasn't possible for me to activate 'Lean Cruise' mode as its not in the US PCM's, only in the Australian PSM's, like Holden HSV etc..