|View single post by subwoofer|
|Posted: 12-13-2008 09:27 pm||
I dare to disagree that it should be the same as with a carb, and will claim that it has all the same problems as the BMC/Rover heads, compounded by the long throat, but I will admit that it is based on logic, not actual experiments.
There is one significant difference between an actual carb and an "electronic carb" or TBI system, which is likely to bite in this particular configuration. In a carb, fuel delivery is a function of air mass flow, while in the case of EFI, fuel delivery is a function of time. The two are effectively one and the same if air flow is evenly/symmetrically distributed for the four-stroke cycle, but in the case of a dual carb 4 pot, it isn't.
The distance from the intake ports to the TB only makes the problem more difficult to solve, because of the pressure propagation time lag, causing the ideal moment for injection to move around with respect to the crank angle, RPM dependent.
Of course, I could be completely wrong, the length of the intake runners could smooth out the air flow speed fluctuations, causing the TBI system to behave closer to an actual carb, but the fact that intake runners are tuned to length for different RPM power peaks suggests to me that the air flow is not evened out, but pulsates.
Just some late night speculation on my part, does anyone else have any opinions?