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Originally Posted by Dana E.
There is plenty of misinformation in this thread. Yes, multiport injection is better than a throttle body, but a modern TBI system is still better than a carb.
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No one said, suggested or implied a carb was better.
Quote:
Originally Posted by Dana E.
The Holley Sniper/Terminator systems are self-learning systems. In a nutshell: they don't need retuned if you change your air cleaner or drive to a higher elevation.
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Most EFI systems available today offer a self learning capability. The self learning capability is not the same as getting the engine tuned. It will get the engine running fairly well, at least well enough to begin the tuning process yourself or allow you to drive the car to a professional tuning shop.
Quote:
Originally Posted by Dana E.
The Edelbrock ProFlow4 is a speed density multiport system. No, I don't have a Sniper system. Yes, I use both the Terminator and Edelbrock systems.
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Other than having used multiple systems the point you are making is not intuitively obvious..
Quote:
Originally Posted by Dana E.
Do the speed density and Alpha-N strategies work? Yes. Will the world end if you don't use a MAF system? Not hardly.
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The progression of systems sophistication was from early Alpha-N systems to Speed Density and finally to Mass Air Flow systems. MAF based systems are where manufacturers and professional race teams ended up in the natural evolution of EFI systems.
Whether it was Detroit with their EPA mandated emissions limits or the F-1 teams where the smallest edge can translate into a win because of how evenly the cars are matched, MAF based systems are what the people and design teams that could use anything they wanted, ended up using.
While no one is talking about the end of the world, the challenges identified with the Speed Density Systems are real. Does it mean you should not use one? Not necessarily, beauty after all is in the eyes of the beholder.
On the other hand if you are attempting to optimize an engine for power, fuel economy, drivability, emissions (not likely with our crowd) or any of several other metrics the systems that have consistently won the roses are the MAF based systems. Does it mean the others are bad? Not at all. Does it mean the best fueling models are available to you using MAF based systems — absolutely!
There are some scenarios where even if you wanted to use a MAF based system the implementation would be extraordinarily difficult and a Speed Density model would be not just easier but the prudent choice to implement. Examples would be individual runner intakes like the EFI systems that spoof the appearance of Webers. Fitting a MAF to the air inlet path would be quite difficult.
A similar example would be the tuned length Individual Runner EFI systems where the intake runners lay over the opposite cylinder bank. Same problem, managing intake air to a single path through a MAF and then to the individual intake runners. Impossible? No, but quite demanding.
Most IR scenarios are just easier to implement as a Speed Density system. Intake systems that do not employ the individual runner geometry are much easier to implement as MAF based systems.
It is worthwhile noting that MAF based systems include both Speed Density and Alpha-N logic in their code. There is a reason for the inclusion. Each fueling model has particular strengths and can perform some aspect of the engine fueling model better than either of the other two.
When you use a MAF based system you actually have all three systems included in the EFI system's logic. In normal operation the EFI code will switch dynamically between the three different fueling models selecting the best model for the environment at hand.
In the final analysis, Detroit could not meet the strict EPA imposed emissions standards everywhere in the country with a Speed Density system. Similarly in the thin air of F-1 racing the engine designers / developers could not reliably produce optimum power across varying weather, climate and altitude conditions without using MAF based systems.
Even a basic grocery getter with the lowest purchase price point will use a MAF based EFI system because of the EPA imposed mandate to meet very specific emissions targets — everywhere in the country. We, or at least most of us, do not need to worry about emissions. What we do intuitively want however is an engine that will reliably and predictably start in all weather, at all altitudes and in all climates. It should be as reliable and predictable as that grocery getter you drive to the corner in. A MAF based system will do all this and properly tuned, do it in spades.
Ed
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