what to expect from an 800 ft altitude change?

kanenas · Post by **kanenas** » Fri Feb 03, 2006 2:27 pm

Somewhere in the MS manuals i came upon the altitude variation problem, unfortunately i can't remember where and what was discussed. Now that the tuning is in high gear on the old Benz, I was wondering how much of a problem i am going to have when i go from sea level to an altitude of about 800 ft. Can the experts comment on a possible compensation scheme?

Post by **efahl** » Fri Feb 03, 2006 3:15 pm

Here's a thread you should find entertaining.

http://www.msefi.com/viewtopic.php?t=5707

The bottom line is that it depends on the restrictiveness of your exhaust system. 800 feet from sea level is 2.9% change in pressure, speed density automatically compensates the intake side, MAF compensates both intake and exhaust sides, alpha-N neither. So, if you're running SD and baro correction for your motor is about 70% (typical), then 3%*70% = 2.1% VE correction will be required for 800 ft, easily within the range of the typical EGO correction.

Eric

kanenas · Post by **kanenas** » Sat Feb 04, 2006 12:30 am

Thanks, that takes care of the issue:)
btw, what's MAF?
d.

whittlebeast · Post by **whittlebeast** » Sat Feb 04, 2006 4:06 am

Mass Air Flow is a method of measuring the air flow with a device using most often some sort of heated wire. MAF is used by about 1/2 of the OEM installs. This is an option when using the late versions of Extra. Many Ford MAF's can easily be adapted to Megasquirt and very cheep at local junkyards. Look for the ones with a 4 wire connector. A GM stlye MAF is useless for our application. Lots More Info or From the Extra Site

Hope this helps

AW