fitech efi

[eschaider]

Speed Density is far from dead. In fact, it is the dominant (in terms of installs) fueling strategy for aftermarket EFI systems. While the MAF-based systems can compensate for the air quality changes as we go higher and lower altitude-wise, the SD systems can have a typically faster response to throttle position changes at a given altitude because they measure air mass differently.

For rapidly changing environments, especially with slower clock speed eight and 16-bit processors, the MAF-based systems used a failed MAF table to use fewer CPU clock cycles to calculate the required injector pulse widthwise. While not entirely fair to give this approach a negative critical review, it can be a few milliseconds slower than a comparable SD system.

That said, if you have to have a vehicle operate properly anywhere from Death Valley to Denver without any intervention from the tuner, nothing today will do that better than a MAF-based system. Both approaches have specific areas where they each stand very tall.

For a n/a engine, the SD system will do an admirable job of properly fueling and protecting the engine from fuel starvation scenarios. For a blown engine where the load can suddenly increase to 100 / 200 / 300 % of a comparable n/a engine load in microseconds, the MAF-based systems have a marginally thicker protective skin but can not save you from stupidity. Both are very, very effective fueling models.

Sometimes the physical layout of the intake system makes one approach more attractive than the other. The one that comes immediately to mind in Cobra Replica country is the EFI system that visually replicates the original Weber carburetors used on the competition cars. The eight individual stacks make it very complicated to force all the engine's airflow through a single MAF — not impossible but very difficult and plumbing-wise, very complex. Weber styled EFI systems are poster children for SD-based EFI systems.

[twobjshelbys]

Originally Posted by eschaider

That said, if you have to have a vehicle operate properly anywhere from Death Valley to Denver without any intervention from the tuner, nothing today will do that better than a MAF-based system. Both approaches have specific areas where they each stand very tall.

And this is the reason that the modern systems are all MAF. The manufacturers couldn't meet emissions standards if going from Death Valley to Denver you went from running horribly rich to horribly lean. (Actually, Denver isn't a good example - going to the Visitor Center on Trail Ridge Road at 14K feet is better stress, and yes, you do see test vehicles there. I70 at the tunnels is another test vehicle section. In fact, the new Ford GT guys got stopped in that area for "excessive speed" when they were doing the altitude testing.

Speed Density EFI is an electronic carb. And a lot more expensive to "tune" than changing jets when going from Death Valley to Trail Ridge.