On the other hand, you can extend the life of your fuel pump if you
install larger injectors and drop the fuel pressure with an adjustable
regulator. Be sure not to drop it more than about 20psi. Such
low pressures can effect the spray pattern of the injectors during idle
and they may fail to atomize the fuel properly. If you have to bring
the pressure that low, then your injectors are too big. See the Regulating
Fuel Pressure section for more info on how to lower your fuel pressure.
To go to a larger set of injectors requires you to know what injectors
you currently have. See the chart below to reference your engine
and lookup the flow rate of the injectors you have (big thanks to Garry
McKissick for this data):
|1985 - 1988 2.2L Turbo I *||27 lbs/hr|
|1987 - 1988 2.2L Turbo II||32 lbs/hr|
|1988 - 1993 2.5L Turbo I *||34.85 lbs/hr|
|1989 - 1990 2.2L Turbo II||34.85 lbs/hr|
|1991 - 1993 2.2L Turbo III||34.85 lbs/hr|
|1989 - 1990 2.2L Turbo IV||34.85 lbs/hr|
|Mopar Performance "803s" (P4452803)||27 lbs/hr **|
|Mopar Performance "804s" (P4452804)||34.85 lbs/hr ***|
|Mopar Performance +20% (P4529495)||42 lbs/hr|
|Mopar Performance +40% "Super 60" (P5249452)||52 lbs/hr|
The trick is to go to the next size up. As you can see Mopar Performance
supposedly sells oversized injectors for this type of application.
The problem is that these injectors are not what they appear to be.
The "803s" and "804s" turn out to be defective stock early Turbo I and
II injectors that flowed too much fuel. The supply of over-flowing
injectors has run out and current 803s and 804s flow the same as a stock
injectors (they are actually the same part numbers now). It's hit
or miss with these and you are likely to miss. Fortunately, the Mopar
Performance +20% injectors are what they claim to be. Here is a chart
to help you choose the right oversized injector for your engine:
Your Engine Type
|Your Flow Rate
Get This Injector
|New Flow Rate
|1985 - 1988 2.2L Turbo I||27 lbs/hr||Mopar Performance "803s" (P4452803)||30 lbs/hr ***|
|1987 - 1989 2.2L Turbo II||32 lbs/hr||Replacement for 1989 Turbo II (5277895)||34.85 lbs/hr|
|1988 - 1993 2.5L Turbo I||34.85 lbs/hr||Mopar Performance +20% (P4529495)||42 lbs/hr|
|1990 2.2L Turbo II||34.85 lbs/hr||Mopar Performance +20% (P4529495)||42 lbs/hr|
Now that you have an oversized injector, you will need to get an adjustable fuel pressure regulator and set it so that the new injectors will flow the same as your stock injectors did at stock fuel pressures. See the Regulating Fuel Pressure section for information on how to do this. You also have the option of fine-tuning your setup to run richer or leaner, if you desire. If you are installing a Super 60 computer or an ND 3-bar computer, then you MUST use the Super 60 +40% injectors. DO NOT use these injectors for any other setup unless you really know what you are doing (such as using your own custom computer, a MASC device, or a adjustable FPR with a lot of boost). Dropping the fuel pressure on these injectors too far may begin to effect the spray pattern of them. Bigger is not always better!
For information on fuel injector flow rates and part numbers, see Gary
Fuel Injector Data
Page. It lists the current part numbers for various replacement
injectors and as you will see, he hates the "804s" too. His chart
for current part numbers is confusing, but it is useful if you have a set
of injectors an want to know what you have. Basically, it shows how
all the old part numbers have been changed to four, basic numbers.
The 1984 Turbo I, the 1985 - 1987 Turbo I, the 1988 2.2L Turbo I, and the
2.5L Turbo I and 2.2L Turbo II, III, and IV injectors. Here is a
simplified chart showing the current part numbers. Big thanks to
Gary for figuring out this big mess.
|1984 2.2L Turbo I||4275312||27 lbs/hr|
|1985 - 1987 2.2L Turbo I||4418474||27 lbs/hr|
|1988 2.2L Turbo I (early) *||4418475||27 lbs/hr|
|1988 2.2L Turbo I (late) *||5277895||34.85 lbs/hr|
|1989 - 1993 2.5L Turbo I||5277895||34.85 lbs/hr|
|1987 - 1990 2.2L Turbo II||5277895||34.85 lbs/hr|
|1991 - 1993 2.2L Turbo III||5277895||34.86 lbs/hr|
|1989 - 1990 2.2L Turbo IV||5277895||34.86 lbs/hr|
There are three different Turbo I part numbers because the style of
the fuel injector and fuel rail changed in 1985 and again in 1988.
They actually increased the fuel flow to the early Turbo II engines from
32 lbs/hr to 34.85 lbs/hr. This is equivalent to adding 10psi of
fuel pressure! If you have to replace your early Turbo II injectors,
you'll probably want an adjustable fuel pressure regulator to lean your
mixture back out. While the computer can compensate for the richer
mixture during normal throttle operations, the 1987 Turbo II logic module
cannot compensate for the richer mixture during cold start and WOT.
Later computers could, to some degree.
For applications were the stock fuel rail does not flow enough, custom
fuel rails are available through LRE.
If you used the oversized injector guide in the Fuel Injectors section, then you need to know what fuel pressure to set them to with your new adjustable fuel pressure regulator. To do this, you will need a fuel pressure gauge. This can be purchased at some auto supply stores. You can either get a guage with a schrader valve fitting that can screw right on the fuel service valve on the fuel rail, or you can hook it up with a cheaper make-it-yourself pressure guage. See my Make A Fuel Pressure Gauge page for more information. Install the fuel pressure guage as described on that page.
To take a fuel pressure reading, you have to remember that during idle,
the vacuum causes the fuel pressure regulator to lower the fuel pressure
to maintain 55psi between the fuel pressure and the manifold pressure.
For every 1inHg of vacuum, there is a 0.49psi drop in pressure at the rail.
So, 15inHg of vacuum will make about 47.6psi of fuel pressure on a stock
regulator. To accurately set the fuel pressure, you either have to
calculate the proper fuel pressure by measuring the manifold vacuum, or
you need to unplug the vacuum line from the regulator. This will
make the regulator think the manifold is at 0psi of pressure and the fuel
pressure will rise to 55psi. Do not leave the regulator unplugged
when you are done! If you drive your car with the regulator unplugged,
the engine will lean-out and severe engine damage could result!
While at idle, the engine will run rich because of the rise in fuel pressure,
so don't do it for too long. With your fuel pressure now at a constant,
atmospheric pressure, you can reliably adjust it. To lower the fuel
pressure, turn the adjusting screw on the adjustable regulator counter-clockwise.
To raise it, turn it clockwise. With the engine idling, you will
see the pressure change on your guage. To set the pressure of an
oversized injector to flow as the stock injector did (using the chart provided
in the Fuel Injector section), use this chart:
Your Engine Type
Your Oversized Injector
|1984 - 1988 2.2L Turbo I||Mopar Performance "803s" (P4452803)||44.55psi|
|1987 - 1989 2.2L Turbo II||Replacement for 1990 Turbo II (5277895)||46.37psi|
|1989 - 1993 2.5L Turbo I||Mopar Performance +20% (P4529495)||37.87psi|
|1990 2.2L Turbo II||Mopar Performance +20% (P4529495)||37.87psi|
To make this calculation by yourself, use this equation: the new pressure equals 55psi times the desired flow rate squared, divided by the base flow rate (at 55psi) squared. Here is the equation put more simply:
p = 55 * (Rdesired^2 / Rbase^2) where "p" is the required fuel pressure, "Rdesired^2" is the desired flow rate squared, and "Rbase^2" is the flow rate at 55psi squared.
These values assume that the injectors are flowing to spec, which they
don't always do. You must have a air/fuel guage installed
to fine tune this setup (see the Choosing Your Gauges
page). Once you have set this base pressure, disconnect the fuel
pressure guage and reconnect the vacuum line to the fuel pressure regulator.
Go for a careful test drive and watch your A/F guage. You want to
see at least 8 lights at WOT. If you get less than 8 lights, then
you are too lean and you need to raise your fuel pressure a couple of psi.
If you are seeing 10 lights, then you need to lower your fuel pressure
a few psi.
The appeal of these regulators is that they can properly compensate
for rises in boost pressure. Matching each psi of manifold pressure
with 1psi of fuel pressure is not enough. The computer normally adds
even more fuel by increasing the duty cycle of the fuel injectors.
If you are "fooling" the computer with a MAP sensor modification and don't
want to use extra injectors, you can try this method. It requires
a lot of tuning and fiddling around, but it works. An extra injector
is usually more appealing.
Typical Stock - 34 gal/hr (129 L/hr) Mopar Standard Turbo fuel pump
P5249511 - 60 gal/hr (227 L/hr) Mopar Performance Super 60 fuel pump
GCA 724-2 - 50.2 gal/hr (190 L/hr) Walbro fuel pump
GCA 723-2 - 67.4 gal/hr (255 L/hr) Walbro fuel pump
Other pumps are available, but most require some modifications to your setup for it to work. All of these, except the Super 60 pump, mount right into the fuel tank the way it was meant to. For more information on the fuel delivery characteristics of the Walbro fuel pumps, try this page.
Another consideration for fuel pumps is the power feed. The power to the fuel pump is drawn through a long chain of wire and connectors, which creates a significant voltage drop. It goes from the ASD Relay, through a 14 gauge wire, to a 20 amp fuse, through a 16 gauge wire to the left body connector, and then through a long 14 gauge wire to the pump. Voltages of 8V to 12V at the pump are not uncommon (when the system is at 14V), You can get rid of a lot of this loss by running a 10 or 12 gauge wire right from the ASD relay to the fuel pump. Be sure to install your own 20A inline fuse. Also check the ground for the pump, which often is fed by a ground lug in the trunk.
Keep in mind that in-tank fuel pumps depend on the gasoline inside the tank to keep the pump cool. Frequently running on a dry tank of gas can cause the pump to run hotter and shorten its life.
Lastly, if you are installing a large pump, then you may want to consider
upgrading the fuel lines. The stock fuel lines are 5/16" OD steel
lines. Upgrading to at least 3/8" OD will be sufficient. For
most engines, the stock fuel lines are sufficient, as long as they are
in good shape.
|Return to the Mini-Mopar Turbo Performance page|
This page is maintained by Russell W. Knize and was last updated 06/03/99. Comments? Questions? Email email@example.com.
Copyright © 1996-2003 Russ W. Knize