[DeTomaso] Quella Low Pro MAP?

[Ken Green]

Will,
 
    the following is from the FAST XFI Manual:
 
- A Speed/Density setup uses engine speed and manifold absolute pressure (read with a MAP sensor linked to the intake manifold by a vacuum hose) to determine fuel injector pulse width and ignition timing. Typically, an injector pulse width and a spark advance value are simply looked up from two manifold absolute pressure vs. engine RPM lookup tables. The FAST XFI system uses this technique for ignition timing. But it differs from most engine management systems in the way it handles fuel calculations. It uses the intake manifold absolute pressure and the intake charge air temperature (read with an air temperature sensor located in the air intake tract.) to calculate the density of the air entering the engine. Density is mass/volume. So if the ECU knew the volume of the air entering the engine, it would be able to determine the mass of that air. The ECU calculates this volume of air by using engine RPM (read from a crank pickup or a factory ignition
 system), the engine’s displacement (entered by the user in the Fuel Calc Parameters screen) and a volumetric efficiency number (entered by the user in a manifold absolute pressure vs. engine RPM lookup table). Knowing the density and volume of the air entering the engine, the ECU calculates the mass of the air. From there, the ECU looks up the desired air/fuel ratio (entered by the user in a manifold absolute pressure vs. engine RPM table) and determines the amount of fuel required to achieve that ratio. Finally, the ECU uses the number of injectors and the injector flow rate (both entered by the user in the Fuel Calc Parameters screen) to arrive at the required injector pulse width.
 
- In Alpha-N mode, the manner of operation is much simpler. An injector pulsewidth is simply looked up from a throttle position vs. engine RPM lookup table. The intake air temperature sensor and the MAP sensor are used to measure ambient air temperature and pressure. There is a user-definable correction curve for adding or removing fuel based on air temperature, and a generic barometric compensation curveis applied internally.
 
-In most applications, Speed/Density mode will provide the best overall performance. Neither mode will produce more power than the other, but Speed/Density will allow for much better drivability tuning than Alpha-N.

they go on to say:
 
You should use Alpha-N mode if you have an individual runner intake manifold such as a Kinsler, Hilborn, or Crower. However, it is possible to use speed/density mode with some modifications to the manifold. A small manifold with a vacuum connection to each runner can be created and used to provide a manifold pressure signal to the ECU.
 
    It sounds like Speed/Density is better for a street car, and if you run lines to all 8 runners after the throttle bodies, you can connect a MAP sensor.  
 
Ken

--- On Thu, 11/27/08, Will Demelo <wdemelo at cogeco.ca> wrote:

From: Will Demelo <wdemelo at cogeco.ca>
Subject: [DeTomaso] Quella Low Pro MAP?
To: detomaso at realbig.com
Date: Thursday, November 27, 2008, 8:26 PM

I have Quella's low-profile IR set-up and I'm converting to a current
EFI system. Can someone confirm that  there is no MAP sensor on the IR manifold?
With no MAP signal, I'll have to tune in alpha-n mode, correct? How does the
system know when there is engine load?
Will
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