[hurryinhoosier62]

It's a simple answer: fuel injected engines need LSAs of 112-116 degrees.

[wolf]

Originally Posted by hurryinhoosier62

It's a simple answer: fuel injected engines need LSAs of 112-116 degrees.

Really? Why?

[Steve C.]

From Comp Cams....

8. I’m switching from carburetion to fuel injection. Do I need to change my camshaft?

Quite frankly, it depends on what camshaft is already installed in your engine, but for the most part, yes. The important thing to remember is that factory fuel-injected engines generally require wider lobe separation angles than carbureted engines do. Camshafts with wider LSAs feature decreased overlap, which yields a more efficient combustion process and increased vacuum, which is required by factory engine computers (or “ECUs”).

In order to take advantage of the design characteristics of the high efficiency EFI-style cylinder heads and intake systems, COMP Cams® offers specialized fuel-injection camshafts, such as the XFI™ series. These cams deliver dramatic improvements in performance for today’s fuel injected engines while still satisfying the requirements of sensitive OE computers.

Aftermarket engine computers such as the FAST™ XFI™ system can run cams in street and competition applications that would traditionally be considered suitable for carburetion only, but these ECUs are the exception, not the rule.


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[wolf]

Originally Posted by Steve C.

From Comp Cams....

8. I’m switching from carburetion to fuel injection. Do I need to change my camshaft?

Quite frankly, it depends on what camshaft is already installed in your engine, but for the most part, yes. The important thing to remember is that factory fuel-injected engines generally require wider lobe separation angles than carbureted engines do. Camshafts with wider LSAs feature decreased overlap, which yields a more efficient combustion process and increased vacuum, which is required by factory engine computers (or “ECUs”).

Well that reads like it's still from a 1988 catalog, where recalibrating the OEM EFI wasn't an option, but that's just not the case anymore. Hurryinhoosier62 made the blanket statement that "fuel injected engines need LSAs of 112-116 degrees", and didn't specify "factory" EFI with the OEM calibration, so I was preparing to disagree with that statement. I've had a 106 LSA cam in my EFI Stock Eliminator car since the mid '90s and the National Records it set can attest to how well that cam works, but of course it's with a proper EFI calibration. I've done a ton of EFI calibration work over the years for tighter LSA cams with both Speed Density and Mass Air OEM systems and it's not that difficult to make them work. Now, would I want a 106 LSA cam in a street car? Hell no. But my point is a tight LSA cam has it's place, and can absolutely work with EFI.

[hurryinhoosier62]

Originally Posted by wolf

Well that reads like it's still from a 1988 catalog, where recalibrating the OEM EFI wasn't an option, but that's just not the case anymore. Hurryinhoosier62 made the blanket statement that "fuel injected engines need LSAs of 112-116 degrees", and didn't specify "factory" EFI with the OEM calibration, so I was preparing to disagree with that statement. I've had a 106 LSA cam in my EFI Stock Eliminator car since the mid '90s and the National Records it set can attest to how well that cam works, but of course it's with a proper EFI calibration. I've done a ton of EFI calibration work over the years for tighter LSA cams with both Speed Density and Mass Air OEM systems and it's not that difficult to make them work. Now, would I want a 106 LSA cam in a street car? Hell no. But my point is a tight LSA cam has it's place, and can absolutely work with EFI.

Closed lop or open loop? MOST factory EFI systems with closed loop can't "keep up" with a tight LSA. Most cam manufacturers advise you to stay with a loose LSA IF you're running an OEM closed loop system. I could be wrong, but I believe most aftermarket EFI systems recommend an LSA of 112-116 degrees as well.

[HWYSTR455]

Originally Posted by hurryinhoosier62

Closed lop or open loop? MOST factory EFI systems with closed loop can't "keep up" with a tight LSA. Most cam manufacturers advise you to stay with a loose LSA IF you're running an OEM closed loop system. I could be wrong, but I believe most aftermarket EFI systems recommend an LSA of 112-116 degrees as well.

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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[JLMounce]

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.