Does a speed density setup (MAP) need live barometric correction?
I have an answer in mind, but also a brain fart. I want to see what the collective intelligence of NYSpeed has to say.
Discuss
Oh, and more specifically in a turbocharged app.
I would think it would be advised in any application, but I really know nothing lol.
i would say no, you dont HAVE to, but it is a good idea . in a situation where elevation change was frequent i would most certainly be using live baro. compensation
If you plan on racing Pikes Peak then yes it would be a good idea. However most applications do not require it. Most stand alone and aftermarket EFI systems take a reading from the MAP sensor before the vehicle is started and set that as the BARO value
Turbocharged cars suffer less degradation of performance (edit: less, if any at all) compared to N/A cars as elevation increases, because the intake charge is compressed.
Assuming you have tuned for a safe AFR, say 11.5, you should have zero problems going from below sea level to a higher elevation. Could you squeeze more power out of it by remapping based on elevation/other factors? Yes. Big gains? Not really. Depends on how lazy you are in the end.
No, it does not need to be live…
my haltech e6x had a provision for barometric correction, it was only advised to set the barometric once at home, and then leave it alone… it was NOT live… dont forget that your MAP sensor will technically sense any effect the changes in altitude/BP will cause on a turbocharged car, because in the end, the only thing that matters is what the pressure is inside the intake manifold, and that reading is live
most modern (1990’s and up) oem map based ecus have a baro sensor and correct for it.
I’m not sure which those would be but any decent unit will have a separate internal baro sensor and trim off it dynamically.
These are the ones I deal with most frequently. They all do this.
Autronic
AEM EMS
Motec
Hydra
Unless you increase boost as you increase elevation, a boosted car will lose a ton of power. For example even on a stock turbo car guys often have to run an extra 5 psi in Denver to equal power output made at sea level. Look at the blower cars when NHRA goes a mile high…
And you can definitely have problems if you significantly change elevation without accounting for it. For example, off the shelf maps by a popular company near Salt Lake City often cause knock on cars around here because of the air density change, and they’re designed to be conservative.
If a turbo pressurizes the intake charge to 15 psi at sea level, and at a certain altitude…there will be NO difference in power change because of the boost. 15 psi on a turbocharger will equal the same power output no matter where the car is, considering all other factors are the same. (That’s also assuming the turbo can get to 15 psi, the air might not be dense enough).
The only thing different at a higher altitude is the amount of work the turbo is doing to pressurize the air…therefore, the intake charge is still the same psi, but much hotter.
Those ‘off the shelf’ tunes are completely worthless. Those should just be used temporarily until you can get your car tuned based on what the car has and how it runs. The knock is caused by increased intake temperatures, not leaning out.
As for the NHRA cars, they are tuned to provide the maximum power output possible…which means it will run much leaner compared to daily driven cars. Any change in intake temperature can drastically affect how they perform…everything on them have very tight tolerances. Nikuk was talking about every day/weekend cars, which essentially have a broader factor of safety in the map.