http://evoecu.logic.net/mirror/merli...UIDE-V1.7a.pdf get to reading. Or throw some money at your local tuner / etuner, they gotta eat too.

 

Most people neglect to mention with switching to SD ,it is a bad idea if you change elevation much. MAF can account for elevation, SD doesn't.

In majority of cases SD is better. But I wanted it and realized with trips I do it changes too much elevation to be safe without multiple tunes.

 

Is this true? I've moved quite a few times, from Miami to VA, and travel back and forth a bit between. This is something I wasn't aware of.

 

I am not an expert.
However SD uses a MAP sensor that requires a formula in your ecu to correctly determine what it is out putting in pressure because it has to account for elevations base pressure. part of that formula is a number that represents your atmospheres pressure at your given elevation. that number is a fixed number that doesn't change unless manually updated in the ECU. So if you change elevations (several 1,000s ft or more) then your MAP sensor is becoming less and less accurate, which could cause over-boosting or under boosting along with other troubles. It simply requires a re-tune (essentially adjusting the formula for the MAP sensor).

So if your moving somewhere permanently its fine get it tuned. for me I do long drives over very varying elevations. so unfortunately an MAF makes more sense for me, even though id love SD.

but someone correct me if i'm wrong.

 

well a map sensor is an absolute pressure sensor, so it knows what altitude you are at. The problem is that at higher altitudes the engine is less efficient. So your turbo is going to have to spin faster to hit its target PSI/Load which will change its efficiency and thus may require compensation in the tune.

 

Ok guys and gals, I'm now pulling the trigger on speed density, already got my SD intake, omni 4 bar sensor, gm 3 port, muse short route uicp and turbosmart raceport vta bov. Along with SD, I'm doing the fitronic flex fuel setup, so I can run 91 and e55 they have here in AZ. So now I'm thinking of picking up a turbosmart wastegate actuator, either the 22psi or 26psi model. Just wondering if its worth it, just wanting boost to hold longer on my stock evo 9 turbo. Thoughts?

 

Well, pulled the trigger on the Turbosmart 22 psi WGA, since I'm wanting to get everything out of the factory 9 turbo until I upgrade in the distant future. Hopefully I'll get retuned with Tom for Speed density, flex fuel and with the WGA soon, and results and thoughts will get posted on here afterwards