Bigstuff 3 also uses a separate map sensor for altitude compensation, at additional cost. It doesn't work............. :( If I had a do-over, I'd use a GM computer and tune it through HP Tuners of Efi Live if altitude compensation was a big factor.

Jody

That pisses me off. If it were me I'd be bitching at Meaney like there was no tomorrow to either get it working or to get a refund for the non-functional add-on! You paid extra for it! :mad:

I hear you on using an OEM ECU, but for this application an aftermarket ECU is just easier-- provided it's the right aftermarket ECU! That's why I know he'll be disappointed in the XFI-- it will not solve his current problem given the forced induction application.

Speed density and altitude compensation can work and the problem has been solved; look at all the old GM speed density EFI stuff from the 80's and early 90's. Granted GM had the advantage of time and money for each engine package, but they did real time barometric updates via one MAP sensor by reading the manifold pressure at specific RPM & TPS settings and then comparing the actual MAP values at that RPM/TPS to a table of "ideal" MAP values at that same RPM/TPS and using the difference between the two for the barometric compensation. That's a lot tougher to do when you're not an OEM and not tuning an ECU for one engine you're going to build millions of, but the principal is the same and can be easily accomplished in the aftermarket with a secondary MAP sensor. Given the wide variety of engines that an aftermarket ECU may be used with a secondary MAP sensor is the most logical choice.

If I stick with my Gen 1 SBC stuff I'm certainly going to upgrade to a more capable ECU such as Lance's 882C, but if I make the jump to LSX I'm going with a factory ECU and EFI Live.

This has become way more interesting than I ever thought it would be. I love learning this stuff. I somewhat mis-spoke though. I get typing faster than I can think.
My immediate reason to upgrade ECU's (to FAST, maybe now) is to be able to retard the timing under boost. Mine's not even doing that now. That's #1 priority. Altitude stuff is just another part of it. I don't really travel from hi to low or vice versa, but it would be nice to not have to screw with it. I will continue my research and check out Lance's. Jody, you know anything about these? Maybe I just need a boosted LS7:unibrow:

I do not have any personal experience with Lance's stuff, but he seems like a sharp guy. The altitude comp isn't a huge deal for me, at least not enough to swap ecu's. I have my high altitude map, only takes 30 seconds or so to swap it if need be. Would be nice if it actually worked though.

Jody