This has turned into a pissing contest - I'm not going to comment further.
Sorry, if my attempt to add clarity to some misinformation came across as anything but trying to be helpful. That was my only intent. Unfortunately, as I read the responses I see I missed the mark completely.
Pissing match? I do not see how having a discussion of the facts, or one’s opinion for that matter, could be construed as a pissing match.
I can see how there could be some confusion with the information, as my comments were specific to the SDS system and may not be applicable to other systems. So my comment stating “Altitude compensation is not needed with a MAP based system” was specifically related to the SDS system. If we were discussing the SDS system in an Alpha-N configuration, then I would not have made this comment.
Regarding a Speed-Density based system and barometric compensation as related to other systems such as OEM, Megasquirt, Haltech, etc.; we can discuss why the OEMs have the tuning strategies they have, and why other systems may or may not need a separate sensor [and tuning table] to compensate for barometric changes. For now, lets set these aside and keep the scope of this discussion related to the SDS system. This will help keep the discussion on-track and hopefully, minimize any additional confusion.
Not including the ‘altitude compensation’ discussion, I addressed your other specific comments [misunderstandings] regarding the SDS system. Given that you have not responded to these, I can only assume that you stand corrected on these points and we can move along and address the ‘altitude compensation’ question.
Another comment was that it is 'utter utter crap' that a separate barometric sensor and/or ‘altitude compensation’ is not needed with the SDS system.
If you would be so kind and allow me to ask a few questions as this will help me better understand how you arrived at the comment that it is 'utter utter crap', when, in this matter, dealing with the SDS system and not other EFI systems.
In my post I mentioned that during a recent road trip a SDS equipped vehicle ran up to a 11,438 foot elevation change with no adjustments to the fuel map. If what you claim is true and accurate regarding the SDS, then how could this vehicle make the 14,000 foot climb with no adjustments to the fuel map? I understand that this is second hand information and you can not verify this, so lets jump to some facts which can be verified.
Given the length of time and the number of SDS systems installed on land based vehicles, it is estimated that the system has logged well over 20 million hours of operation. If the system worked as poorly as you describe, how could this company still be in business after 20 years of supplying the same basic product?
The SDS systems are also used on [experimental] aircraft. There is a large installed base of airplanes running the SDS system. The total operation time is well over 200,000 hours. This probably exceeds most, if not all other automotive based EFI systems used in this type of application. Airplanes experience elevations changes [climb rates] which far exceed what a typical automobile will ever see. If the system required constant fiddling with the fuel map, or the mixture knob, to keep the engine running, this would not be acceptable in an airplane application. Given this, why do so many airplanes use the SDS system?
The SDS system is also used on UAVs. Not in a few examples, but a few hundred. A UAV, by definition, is unmanned, so there is no one available to fiddle with the fuel map or play with the mixture knob. If what you state is correct, then how do these UAVs fly with out constant adjusting of the fuel map?
Once again, I hope this does not come across as bold or arrogant, as I am only trying to impart accurate information, specific to your comments regarding the SDS system. We could discuss engine management and engine operation theory to our hearts content, but that would probably only muddy the waters more. In this case, stating the simple facts and actual operation of the SDS system seems to be a much more direct and straight forward way of conveying the needed information.
My offer to help your friend with his SDS system still stands. There is no reason why he should have to put up with his engine running poorly. That takes all the fun out of driving the car. I am not claiming that I can make his car run perfectly and maybe there will be no improvement; who knows with out giving it a try? All I am saying is I am available to help and if we can make his car run better, great. If not, we tried. Either way, it did not cost him anything. What is there to loose?
If you would also like to lend a hand with his tuning, that would fantastic. I would be please to work with you, while we both help your friend to get his engine running better. I am sure you would add some much needed insight and tuning assistance into the mix.
Ray
