V8er

iTrader: (2)

Can anyone comment on how large altitude and/or temperature changes affect SD-tuned cars? It is my understanding that MAF equipped cars are more capable of dealing with large changes in alt. and temp. whereas SD cars don't have the same range of adaptability, which is why most auto mfg's use the MAFs. Any truth to this?

My driving patterns regularly take me from sea-level to 4500ft+ and from 20F to 90F so I don't want to convert to a MAF-less SD tune if it will hurt my driveability in any of these situations.

Thoughts and advice?

Thanks

ringram

Plenty in the search man.

<lights touch paper>

Basically no difference. Other than the MAF being a relatively slow sensor restricting airflow as stock.
MAF only requires about 85 values to be close to work properly. Where as SD needs 380 values to be close to work properly.
Also as long as you dont alter the MAF unit itself it will stay pretty accurate independent of engine mods. SD will require all 380 values to be recalculated after each mod in order to remain accurate.
Thats the real reason manufacturers use it. Its cheap and easy.
Altitude and temp are irrelevant.
IAT sensor measures intake temp, MAP and Barometric sensors read altitude/pressure and are used in both calculations.

SD is more responsive and doesn't cause a restriction in flow. Sure you can get a larger MAF sensor to reduce restriction, but why bother wasting the money? Spend it on a nice exhaust, or intake instead of a chunk of crap used by lazy manufacturers.

</lights touch paper>

24v

Can you elaborate on this a little further?

foff667

iTrader: (2)

primary VE table is like 20 cells by 19 cells of 3d resolution=380, whereas maf is only like 85 cells of 2d resolution

24v

Ok, next question. I am running just over 14 psi right now. If I go to SD, I need 3 bar, correct? Is a 3bar sensor available for an ls1?

foff667

iTrader: (2)

you could go 2 bar but you'd be pushing it, unfortunatly I don't know if hptuners offers a 3 bar for your particular 04 OS if you indeed have the 04 GTO in your sig.

24v

I do have an 04 GTO. So, do I just use 2 bar, and sacrifice a little of the upper resolution?

foff667

iTrader: (2)

you won't loose any resolution...2 bar is good to ~15psi...you'll just be damn near the last cell basically.

RedHardSupra

iTrader: (1)

that's correct, but theoretical, it would be much more realistic if you actually counted how many cells do you hit in most driving conditions, most cars dont do past 6800rpm, or high pressure/low rpm, or high rpm/low pressure, cammed cars dont get <50kPa, stalled cars dont really do 3000-5000rpm, etc... you get the idea. i'd like to actually see a comparison how many cells are actually used--it's an interesting little tidbit

ringram

True, Im sure not all MAF cells would get hit either. But likely a lot higher percentage than the VE for sure. However you would be surprised what cells you do hit in ve. Especially on startup and stop. Way in the corners.

foff667

iTrader: (2)

under normal driving probably 1/3 of the ve table would be used from idle, part throttle, wot so probably still more then maf, but not much more.

foff667

iTrader: (2)

maf would probably only hit about 1/2 of the total cells in most applications...kinda depends on the application though, many wouldnt touch hz below 2000 or above 10000 and then in between theres alot of cells that generally wont get hit unless you like cruising part throttle at 4500 rpms lol

ringram

Cool. I never used the MAF. First thing I did was to pull it off and sell it