Fuel Delivery Rates

Folklore teaches that we must increase fuel flow when using ethanol instead of gasoline. Gasoline has a greater chemical energy density per volume than does ethanol. Since fuel is metered through the injectors as a timed fluid flow, it is substantially metered as a volume. Consequently some arrangement must be made to open the injectors for a greater duration, or employ injectors with a greater flow capacity, or a combination of both. The rule of thumb is a 30% flow increase.

There is, however, a contingent of people who believe that predominant folklore is overly pessimistic. hey claim that ethanol enjoys efficiencies in an internal combustion engine that are not shared by gasoline. Specifically, ethanol creates less waste heat and loses less heat to the block and coolant. It is reportedly observed that ethanol engines have cooler exhaust temperatures than does gasoline. They argue that the flow increase to compensate for energy density should be only 15%.

There is a further consideration. Classic Saabs perform better under boost conditions with ethanol than gasoline. This makes it more interesting to operate the car at higher boost levels than a Saaber may be accustomed to, and this requires more fuel. Adding an further 15% fuel flow rate serves this purpose.

Our conclusion is that building in the potential for a total 30% greater fuel flow rate over stock will allow for performances somewhat better than achieved with the stock installation and fuel. 15% is for equivalence and 15% is for fun.

Stock Injectors

Stock injectors for 1986 900T are Saab part 7560170 and Bosch 0280150712.

Technical specifications are

  • Ohms: 16.2
  • LB/HR: 20.35
  • CC/MIN: 213.9
  • Stock vehicles: 1985-1988 Saab 900 16V Turbo

Larger Injectors

Two larger capacity injectors are suggested for use with performance tuning Saabs. Both are Bosch (Ford Motorsports) parts with red tops. 0280150945 delivers 29lb and 0280150431 delivers 34lb. The 30lb recommended elsewhere as the way to go for a moderate (gasoline) upgrade and without doing much else to the motor. The 34 pound are used for racing.

Technical specifications for Bosch 0280150945 (Saab xxx)

  • Ohms: 14.4
  • LB/HR: 28.55
  • CC/MIN: 300.1
  • Stock vehicles: 1993 FORD 3.8L V6 S/C(IC-083)

Technical specifications for Bosch 0280150431 (Saab 9142449 or 30551847)

  • Ohms: xxx
  • LB/HR: 34.15
  • CC/MIN: 358.9
  • Stock vehicles: 1994-1996 9000 Aero (T5 system) Aret there any othr T5 Saabs?
  • Stock vehicles: SAAB 2.3L Turbo(IC-735), Saab 4-2.0l Turbo, 4-2.3l Turbo

[ref: Injectors technical summary]