Quote:
Originally Posted by HWYSTR455
I believe that is a correct statement, that most aftermarket EFI suppliers do recommend a 112-116 LSA.
There are some caveats to that though, for example, throttle body injection as compared to multiport. Mutliport systems are more sensitive to LSA, or at least that's what I've seen/heard.
I have also seen/heard folks having issues with throttle body injection systems when the LSAs get into the 106-108 range, to a point where some either ditch the system or change the cam. In those cases closed loop is ineffective, and many statically map the fuel curve. When you think about it, you're pitching one of the basic reasons most even switch to EFI.
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It's not entirely that a closed loop system can't keep up with a tight LSA cam, it's more to the point that the tuning is hard to undertake. Closed loop system rely heavily on data tables that are manually created. It's far easier to tune these tables when the engine is acting in a more linear and even fashion. Narrowing the LSA narrows the power band, which makes the tuning more difficult.
THe OEM's obviously have teams of people devoted to this, where joe-bob down the street does not. It adds considerable additional expense to have the car tuned by a professional that knows what he's doing. Depending on what needs done you could be adding $400-$1000 fairly easily.
With the newer systems on the market that employ wideband sensors and operate primarily in an open loop fashion, it's become less of an issue.
I pulled a 280H that has a 110 LSA and made about 8" Hg from my 462. The FiTech system I'm running didn't care that it had a LSA on the tighter side and didn't make crap for vacuum.