V-10 Killer

iTrader: (22)

I've seen so much talk about this stuff the last few months that I can't help but wonder when would be the best situation to use either of these tuning methods. And what would the advantages/disadvantages of each be?

Let me be more clear:
Open Loop
or
Tuning VE and MAF, then returning to normal open/closed loop combination tune

tici

iTrader: (1)

I'm happy with the second tuning method:
adjust the IFR according to the injectors and to the fuel pressure (and not for LTFT)
adjust VE disconnecting he MAF
reconnect the MAF and adjust the MAF curve for negative LTFT
tune PE
tune timing

I don't like only SD: in my case (big temperature difference between summer - winter) it's always a mess. Every day a little different. Car runs a little better but I prefer a solution that holds in each condition.

Just MY opinion, for MY car for MY goals...

jimmyblue

iTrader: (11)

They sort of pertain to different aspects of operation and
my opinion is, you want all 3 (OL, SD, MAF) right.

Open Loop is the fundamental operation. It has to do with
how accurate your models of airflow, fuel delivery and
target mixture are.

SD is the MAP*RPM-based model of airflow. The VE table is your
handle on this. SD rules the low end and transient-throttle
operation. If you go MAFless then this -has- to be tuned in at
the mid-high RPM end where the MAF covered it up before.

You would like the SD and MAF airflow calcs to return the same
and accurate values so that when you flip between them the
engine runs the same, and at its best. For example when you
mash the pedal and the car seems to stumble and then get
better a couple tenths of a second later, that's probably the
SD tune being too lean for the mods and the MAF dropping out
(unsteady-MAP) and coming back on line again, with the mixture
jerking around in the meantime. If you see "lean holes" on tip-in
it means the SD tune is needing to be richened up at that
(start of tip-in) MAP*RPM cell and the others you traverse.

Having a clean open loop tune requires that the airflow (SD
and MAF, if you keep the MAF) be right. The fuel side too.
If your open loop tune is tight then there is very little trimming
required.

Things like O2 sensor problems can take a perfect open loop
tune, and trim it into ****. Open loop would be pretty nice for
a car with true offroad exhaust, no O2s. You might tolerate a
little bit of idle stank for getting rid of header-induced O2 trim
errors (thermal).

txhorns281

iTrader: (12)

Open loop requires constant user correction since you don't use any of your sensors as correction factors. This would be ideally a method for people who's cams distort sensor operation or just have race cars. This requires alot of effort on the tuner's part to maintain since you basically become "god."

Closed Loop w/ all your sensors is more friendly and adaptive to a variety of road/weather conditions but like these guys said, you must have confidence in your sensors. If the MAF is not calibrated correctly, that could cause problems. If your O2s are not calibrated correctly thaty coudl cause bigger problems. By running SD, that takes away one of your encompassing correction factors (MAF) and places more weight on the VE, which you as the user must manage and tune into good standing operation.

Computers are only as dumb as we tell them to be!