Speed Density vs Mass Air Tunes

[DrWooWooWoo]

Whats the difference, im new to this EFI game

[Sleaper]

Doesn't really have anything to do with EFI as much as it does FI (forced induction). Instead of your pcm using the mass airflow sensor to adjust for fuel, you use a 2 bar map sensor (or 3 bar) that adjusts fuel based on boost and atmosphere conditions. The reason this is helpful is because your MAF will max out at a certain point and while you can still tune for it, it is an educated guess to add fuel for the amount of air going through. Where tuning using the MAP sensor is more accurate and smooth. You would have to relocate your IAT (intake air temperature) sensor if you go SD since it is within the MAF.

Overall, it's not somthing that has to be done since great tuners like Nelson can still tune using the MAF but some will argue that an SD tune is much smoother.

[Chevy366]

Not much really as far as power goes , a good NA SD tune and a good NA MAF tune make close to the same power on a Dyno .
One runs in CL (closed loop) and uses your O2 sensors and MAF for fueling and correction , the other , SD , just use the MAP and fuel tables for fueling (simplified) .
But a good Custom OS SD (1, 2, or 3 bar) can be nice for tuning boosting devices , "What does that do ?" , "It sucks !"

[85mudblazin]

open loop and closed loop are totally different then MAF and SD, you can have a SD open loop tune and a SD closed loop tune, the same with the MAF. Just depends on if you want the computer to adjust a little bit for you or if you want to have the greatest control over what your truck is doing then a SD open loop tune is the best. I currently have a SD open loop tune loaded on my truck and I love it, I tell the computer what to do and it does it.

[DrWooWooWoo]

k well i have a bone stock motor in the truck now, after this weekend im going to install a speedtek f1 cam and ditch the powershot noids for some bigger ones, still staying on a wet shot. I just didnt know when i get it tuned if i should get a SD or MAF tune

[Chevy366]

open loop and closed loop are totally different then MAF and SD, you can have a SD open loop tune and a SD closed loop tune, the same with the MAF. Just depends on if you want the computer to adjust a little bit for you or if you want to have the greatest control over what your truck is doing then a SD open loop tune is the best. I currently have a SD open loop tune loaded on my truck and I love it, I tell the computer what to do and it does it.

Yeah , I forget , I run OLSD (been running for over 2 years now), CLSD is kind of silly seeing after 4000 (WOT) your are in OL anyways .
VE has to be pretty close in SD to get correct AFRs in OL , so you need a wide-band and tune the VE to BEN of 1.00 .
With a custom OS you can gain a Delta Fueling table that enhances the tune even more , great for boost and for temperature changes a IAT and ECT fueling modifier .