Chrysler Turbo Sequential Multiport Injection Fuel System
Fuel Injector Flow Chart
and Horsepower Levels
Chrysler uses a Speed/Density-based,
Sequential Multiport Injection system with the 1990-91 Turbo SBEC to
control the fuel delivery. Unlike a mass air flow system the speed/density
system does not recognize the increase in air flow and hence tends to lean out
at higher power levels (not a good thing at higher boost levels, if you like
your pistons! Just remember: LEAN = MEAN, but FUEL is POWER)
Sequential Multiport
systems offer better control of the injector at low and high pulse widths do to
several facts. Earlier (1989 and earlier) Mopar "Batch Fired"
systems fire half the injectors at once and the injectors are fired every engine
revolution. Sequential systems fire each injector just like the spark
plug, each injector can be controlled as to the time it fires relative to the
spark (phasing), the amount of fuel delivered and any cylinder fuel trim
desired. The Sequential system fires once every two engine revolutions
(once every 720 degrees) on
a four cycle engine.
Also, when higher HP outputs require that injectors are chosen with
"low impedance (Z)" coils (Mopar chose low-impedance, 2.4-ohm
injectors) and large flow rates are required, these low-Z injectors must often
operate at very low pulse widths at idle. Hence the double fire, batch
or bank/bank operation modes can not offer the desired idle quality.
On the other hand, Sequential-fired
injection systems can offer individual cylinder control often used in racing
where air flow to different cylinders is not the same and small corrections are
desired to make the air-to-fuel ratio to all cylinders exactly the same to get the
ultimate performance possible. The sequential system will have also have greater
control of the injector at high pulse widths and slightly extend the injectors
usable working range.
The numbers you see listed in
this chart represent what have generally been reported to be safe dyno-measured
horsepower levels for these
different sizes of injectors. Remember, with a speed/density-based
ECM system, if you increase or adjust static fuel
pressure you will increase the horsepower level you can attain, within
reasonable limits. This is where an
adjustable (or rising rate) fuel pressure regulator can help you bridge the gap between injector
flow rates.
To meet our desired output
goals of 100 bhp per litre, (250 bhp), we'll be using the +20% (P4529495) 42 lbs/per
hour injectors, which theoretically max out at 260 hp.
Turbo I '84 - '88
( 88-1/2 changed to 34.85 #/hr)
Part Number lbs. per hour @
55 PSI Max Hp level
Stock
(varies)
27 #
167 hp
803's (P4452803)
27 #
167 hp
Turbo I '89 -
'93, All Turbo II's, Turbo III's, Turbo IV's
Part Number
lbs. per hour @ 55psi Max Hp Level
Stock
(5277895)
34.85 #
193 hp
804's (P4452804)
34.85 #
193 hp
+20% (P4529495)
42 #
260 hp
+40% (P5249452)
53 #
327 hp
NOTE: In both charts the
horsepower levels are figured at 85% injector duty-cycle
with a .55 Brake Specific Fuel Consumption (BSFC) factor. Fuel system static
pressure used is 55 PSI.
Formula used
(where # = pounds):
#/Hr x
Number of injectors x Duty Cycle % = BSFC
(BSFC) is Brake Specific Fuel Consumption (or Crankshaft Horsepower)
Read a good explanation of formula
terms here. Essentially, BSFC is the amount of fuel (measured in pounds per
hour) an engine consumes per horsepower per operating hour (lbs/hp/hr).
Roll your own Injection Flow
Calculations (including Rising Rate Regulators projections) with this Free
downloadable
software from Jeff Chojnacki
Also see: (great for cross
referencing other injector applications)
Stan Weiss' - Electronic Fuel Injector (EFI)
Flow Data
Tables
Fuel Pump Modifications:
As the stock tank-mounted "modular" fuel pump (in 1993) was fitted in to all engines (TBI four and
MPFI six cylinders) and is approximately equal to the capacity of the 89-90 Turbo
Minivan pump, the stock fuel pump was successfully used during the break-in period.
A high-pressure 255 ltr/hr Holley (Walbro)
pump will be fitted before going beyond the stock SBEC and
804 injectors limits with boost cutout-limited to 12-13 PSI. After 1992, Mopar
began using a dedicated fuel pump relay, which is better suited to handling the
high current demands of the Walbro pump (see chart below).
Note: In 1991 (and
newer) the Gen-2 Mopar Minivans began using a "modular" design fuel
pump. Fitting the Walbro pump to the modular-style hanger requires
modifications to the stock modular hanger system.
Fuel pump flow rate and
current draw at 13.5 volts
Pressure
(psi) |
"high pressure"
255 ltr/hr pump
(gal/hr) |
"high pressure"
255 ltr/hr pump
(amps) |
| 0 |
84
|
5.1 |
| 10 |
82
|
5.4 |
| 20 |
78
|
6.1 |
| 30 |
73
|
6.8 |
| 40 |
68
|
7.6 |
| 50 |
64
|
8.4 |
| 60 |
59
|
9.2 |
| 70 |
55
|
10.1 |
| 80 |
46
|
10.9 |
| 90 |
38
|
11.9 |
| 100 |
19
|
12.9 |
| 110 |
9
|
14.0 |
1990-92 VNT Adjustable (Bosch) Fuel Pressure
Regulator
or
Accufab
GM-Type (BREG) Adjustable Fuel Pressure Regulator:
With the stock
804's (P4452804) injectors, static fuel pressure is set to 60-62 PSI. (With vacuum cut off to the regulator,
this should be 60 PSI on the Fuel Pressure
Gauge. Applying normal idle manifold vacuum --15 in hg @ 4800 ft
above sea level) and at idle gauge drops about 8 PSI to 52 PSI.)
With the +20% larger (P4529495)
injectors I've set the fuel pressure to 50-52 PSI static. This yields about
42-43 PSI at idle at my altitude.
TurboNation --
Fuel Pressure Gauge Kit
