Question for EFI gurus out there

[AlanCasida]

Will the aftermarket EFI systems effectively compensate for altitude changes(at the track or different tracks on difference days) automatically or do you have to make adjustments via lap top? There were a lot of atmospheric changes from track to track on RMRW is why I am asking.

[PaulProe]

Depending on your system, some adjust automatically when you start the motor and others adjust 'on-the-fly' compensating for pressure changes as you are moving, ie, changing altitude. Performance Electronics 8400 does either depending on the way you configure it.

Paul

[jayb]

All the systems I know about compensate in real time.  The MAP (Manifold Absolute Pressure) sensor reads the pressure in the intake continuously, so if you are driving from someplace at sea level to Denver, you will have a different MAP reading at the different altitudes assuming other conditions are the same (throttle opening, RPM, etc.).  The EFI's VE table will fuel the engine based on RPM and MAP readings, so changes in altitude are automatically compensated for.

[Cyclone03]

I may be the voice of dissension here.....
I have FASTez2.0.

If you have run through most of the thousands of tuning cells you should be ok,but if you have some load points you haven’t run through you might feel some choppy ness .

I had a problem with a MAP sensor and I had to reset to base tune. It would not take WOT and I needed it (lol).

I autocross and was at an event. I luckily could take it off site and power through some tuning loops. Second gear from 1500 to the point of choppy ness,back off,then lean into it and repeat. Shut engine off,wait for it to write,then repeat it took about 8 cycles to make it usable

Mine is still not 100% tuned after even 6 years. Every once in a while I will hit a temp/pressure/rpm point that is not tuned and it will act up but I know what it feels like and just crowd it a bit and it finds its way.

If you have drag raced it and it is tuned it should have enough cells filled to be fine,if not make another pass or two. 

[Barry_R]

I may be the voice of dissension here.....
I have FASTez2.0.

If you have run through most of the thousands of tuning cells you should be ok,but if you have some load points you haven’t run through you might feel some choppy ness .

I had a problem with a MAP sensor and I had to reset to base tune. It would not take WOT and I needed it (lol).

I autocross and was at an event. I luckily could take it off site and power through some tuning loops. Second gear from 1500 to the point of choppy ness,back off,then lean into it and repeat. Shut engine off,wait for it to write,then repeat it took about 8 cycles to make it usable

Mine is still not 100% tuned after even 6 years. Every once in a while I will hit a temp/pressure/rpm point that is not tuned and it will act up but I know what it feels like and just crowd it a bit and it finds its way.

If you have drag raced it and it is tuned it should have enough cells filled to be fine,if not make another pass or two.

Thats one of the bad points on the more O2 sensor reliant self learning systems - they will adjust themselves based on bad data and make a minor problem into a big one.  The more user tuned type of system (xFI FAST, Big Stuff 3, MS,etc) will allow you to build a reasonably close base map - whether through a learning function or manually on dyno/street use - and then you can lock that map down.  You disable the learning ability, and set limits on A/F correction so that a bad connection or a misfire does not wreck your tuning table.  You can always datalog and see where the O2 sensor is pushing against your set limits on correction and manually adjust the base to bring those cells into target ranges.