Hilborn Conversions
The first production TUNED PORT INJECTION (TPI) appeared on General Motors
vehicles in 1985. The GM vehicles built with these systems were Corvette,
Pontiac Firebird & Trans AM, and the Chevrolet Camaro. These systems
according to the manufacturer rendered up to 30 % improvement in Horsepower,
torque and economy over carbureted systems, Independent labratories conducted
numerous test on the TPI systems and indicated these claims were conservative
and that increases of up to 35% in these three areas are attainable.
The 350/5.7L engines from the factory went from 205 HP (1984 Corvette/
crossfire injection) to 245 HP with the addition of TPI. The only differences
were the addition of the TPI (1985) and improvements in the valve train (1987).
Note that this is a 20% improvement over another proven form of fuel injection.
Several modifications have been made to the TPI system introduced in 1985.
The 1985 system used a GM Part #1226870 ECM and had a Mass Air Flow (MAF) sensor
and a MAFS module to control the power and burnoff functions for the MAFS. In
1986 two relays replaced the MAFS module and the Electronic Control Module (ECM)
was changed to a GM part #1227165. In 1989 the cold start injector was deleted
from the system. The primary injectors were used for cold starts via a fuel
enrichment program in the newer EPROM calibrators. In 1990 GM introduced the
speed density system. In essence the MAFS was replaced with a Manifold Air
Pressure(MAP) Sensor. This system uses a ECM GM Part #1227727 for the Corvette
and 1227730 for Camaro.
Another fuel system was introduced in 1992 called Central Port Injection
(CPI) and appeared first on the 4.3L (W) L35 Engine. This system is the
equivalent of TPI for the V6 and will increase horsepower and torque by a factor
of 20% over TBI. A 30 % increase in horsepower, torque and fuel economy is seen
over carburetion.
The LT1 was also introduced in 92, as the basic engine in the Corvette. It
appeared in the Firebird, Z28 (F Body Cars), Caprice, Buick and Cadillac in 93.
1993 was the last year for EPROM's in these cars. Opti-Spark also made its entry
on the LT1 engine in 92.
In 94, OBDI or EEPROM, computers were first used in the Corvette and F Body
Cars. This was the 1st year for Sequential port Injection in these cars.
In 96 the LT4 appeared in the manual trans Corvette, it is rated at 330 HP
and 340 lb ft torque. It looks the same as the LT1, however the heads and valve
train have been modified. The valves are larger 2.00 Int / 1.55 Exh from
1.94/1.50. Air passages are larger to enhance volumetric efficiency, hollow
valve stems, aluminum roller rocker arms and stronger valve springs have also
been added. The camshaft has more lift and a slight overlap at the end of the
combustion cycle eliminating the need for EGR. The compression ratio is (Premium
Gas Only) 10.8:1 compared to the 10.4:1 LT1. This engine makes 330HPat 5800 RPM
and 330 lb ft Torque at 4500 RPM.
For 96 all Chevrolet engines are Sequential Port and are equipped with On
Board Dianostics Phase II (OBDII) PCM's. Sequential Central Port Injection is a
standard on the 4.3L/4300, 5.0L/5000 L30, 5.7L/5700L31, and 7.4L/7400 L29
engines. What's nice about all this ?,...They will fit the old engines, but
heads would also have to be changed on the 4300, 5000 and 5700 engines.
Electronic Control Module(ECM)
The ECM's provided with the original equipment TPI systems are indicated
below:
Y=Corvette F=Camaro ,Firebird, Trans-AM
ECMModel Year GMpartNo Engine
F,Y 1985 1226870 5.0L/5.7L
F,Y 1986-1989 1227165 5.0L/5.7L
F 1990-1992 1227730/16198262 5.0L/5.7L
Y 1990-1991 1227727/16197128 5.7L
Y 1992 16159278 5.7L LT1
F 1993 16159278 5.7L LT1
Powertrain Control Module (PCM)
The PCM is a programmable computer and does not contain a EPROM or
calibrator as did its predecessor. The PCM contains a Electronically Eraseable
Programmable Read Only Memory (EEPROM). This unit must be programed before being
placed in service. These Units can be re- programed for any engine /
transmission combination.
PCM
Model Year GMpartNo Engine
BFY 1994-1995 16188051 5.7L LT1
BFY 1996-1997 16214399 5.7L LT1/LT4
While each of these ECM's/PCM's will provide excellent performancefor the
Port and TPI systems, they are not interchangeable. That is a 1227165 will not
plug in to a 1226870 harness and operate. The wiring for these systems are not
interchangeable, without modifyingthe wiring harness. The LT1 PCM is not
compatible with the earlier ECM's due to significant changes in the distributors
of these engines.
Chips/Proms
The chip is a Programmable Read Only Memory (PROM) Chip which is installed
in the ECM. It is this device that provides specific information for the ECM and
allows for different timing characteristics,and injector pulse width for the
5.0L / 5.7L engines. A Calpak, a separate chip on the Calibrator Modules,
normally provides the information to the ECM for rear axle gear ratio on pre 90
models. Information for the vehicle Anti Theft system, auto / manual
transmission, and emission control system, typically resides in the EPROM. To
allow for the various Engines, transmission, gear ratio combinations and to meet
national, international and state standards for emissions,a wide variety of
these Calibrators are available from GM. After 1987 some calibrators incorporate
a vehicle anti theft system (VATS). The ECM will not fire the injectors until it
receives the proper signal from the VATS module. The 1985 TPI calibration is
contained in a EPROM (Eraseable Programmable Read Only Memory) and is a 32K
chip. The 1986-89 ECM contains a 128K EPROM, 90-92 ECM's use a 256K EPROM. The
94 Plus EEPROM is even larger. The factory ECM/PCM has a Learning capability
which allows it to make corrections for minor variations in the fuel system to
improve performance and driveability. There are two learning features. The
Integrator and Block Learn (I and BL) and Block Learn Memory (BLM) cell. The I
and BL feature is normal with a value of around 128. If this value is higher
than 128, it indicates that the ECM is adding fuel to the base fuel calculation
because the system is running lean, a value lower than 128 indicates that the
ECM is taking out fuel because the system is running rich. The integrator is a
short term corrective action while the BLM is along term correction. The BLM
value will change if the integrator has seen a condition which lasts for a
longer period of time. There are from two to sixteen different cells which the
ECM modifies, dependingon RPM, airflow or manifold air pressure and other
conditions suchas AC "ON" or "OFF", etc. The ECM learns how much adjustment is
required in each cell, retains it in memory, and applies these adjustments when
the engine operates in that cell or RPM - Load Range. These features of the OEM
ECM allows the system to adjust itself AUTOMATICALLY to your engine and assure
peak performance for stock and other than stock engines. When the vehicle power
is disconnected for repair or to clear diagnostic codes, the learning process
has to begin all over again. To TEACH the ECM, drive the vehicle at operating
temperature with moderate acceleration and idle conditions. Performance
Calibrations typically change the parameters for fuel flow, fuel cut-off and
spark advance-timing and will allow increased fuel flow and modify the spark
advance curves during rapid acceleration.
WHAT THE ECM - PCM DOES: The 1985-1988 TPI system utilizes the following
sensors and devices to control the engine: Mass Air Flow Sensor, Manifold Air
Temperature, Coolant Temperature, Oxygen Sensor, Throttle Position Sensor, Cold
Start Switch, Cold Start Injector Fuel Injectors, Idle Air Control Valve,
Distributor Electric Spark Timing, (Module in distributor) Electric Spark
Control, Module and Knock Sensor.
When the starter is engaged and the coolant temperature is less than 100 deg
F. The cold start injector provides a spray of fuel, of 8 seconds duration max,
to each cylinder via a air distribution system built into the intake manifold.
If the engine temperature is greater than 100 deg F, the cold start injector is
disabled by the cold start switch. Upon startup the ECM utilizes information in
the calibrator to establish the initial pulse rate for the injectors and the
engine starts. At this time the engine is operating in open loop mode and will
continue to do so until the engine warms up. After the warm up period the ECM
scans the sensors, if all sensors are operating and within their proper range,
the engine then goes into closed loop operation. This means that the sensors are
dynamically controlling the engine. In the event the information received is
higher or lower than the normal range, a code will set in the ECM, and the Check
Engine or Service Engine Soon light will come "on". The ECM receives information
on air flow, engine temperature, air temperature, exhaust gas oxygen content and
throttle position. This information is used to calculate the proper pulse width
for the injectors and fires the injectors for the calculated period. This
procedure is repeated continuously in very rapid sequence to maintain the
optimum fuel air ratio. The electronic spark control components provide maximum
advance, if engine knock is detected the spark is automatically retarded. This
too, is a continuous process. It should be noted that the following components
are MATCHED for optimum performance; Distributor - EST module, ESC module, knock
sensor and ECM calibrator. These components are not interchange able between
5.0L - 5.7L engines. 5.7L components referenced are recommended for 327 - 400
CID engines. 5.0L components are recommended for 265- 305 CID engines.
In 1989 the cold start injector was deleted. The calibrator provides a wider
pulse width on startup to provide a richer mixture for a cold engine. All other
features are the same. In 1990 the MAF was replaced with the MAP sensor, in 94
the MAF returned with a MAP sensor. The1990-92 TPI system still operates the
same except that Manifold AirPressure is used to calculate injector pulse width
as opposed to airflow. The 1990-94 TPI - LT1 system also uses a more
sophisticated VATS system to disable the injectors. A resistor is embedded in
the ignition key. The resistance is read by a VATS module (Camaro, Firebird and
Trans AM) or a Command Control Module (CCM) for the corvette. If the key is the
right resistance a signal is sent to the ECM enabling the injector circuit. If
the sequence or the resistance is not correct,the engine will not start.
The PCM introduced in the 1994 Corvette, Camaro and Firebirds forthe LT1
engine accomplishes the same functions as the earlier models in much the same
way, but there are some significant differences. The 94 and up LT1 is a
sequential port fuel injection system. The injectors are fired in coordination
with the opening of the intake valve. The distributor and electrical spark
timing system, now referred to as "Opti-Spark Control", has an optical sensor
which counts light pulses through a perforated disc in the distributor. There is
NO timing adjustment for the LT1. The Mass Air flow sensor is back in 94 andi s
one of the primary sensors for fuel control. The MAP sensoris a backup for the
mass air flow sensor. All other sensors are the same except that the TPS is no
longer adjustable. The only adjustment is idle control, and this too is factory
set.
The 96 OBDII engines all use EEPROM computers making Chip technology
something from the past. These PCM's have the ability to determine a cylinder
misfire and will even tell you which cylinder midfired. Opti-Spark is now the
standard ignition system on 5.7L LT1-LT4 engines. For 96 a combination
crankshaft position sensor and cam shaft position sensor perform the timing
functions on all the 4.3L, 5.7L and the 7.4L engines. The LS1 is now the new
small block appearing in the Corvette in 97 and the Camaro / Firebird in 98.
CASTINGS
The 1985-86 intake manifolds will fit the older small block heads without
modification. In 1987 and up, the heads were designed with vertical bolt taps
for the two center bolts on both sides of the intake manifold. With a little
drilling the newer manifolds will fit the older style heads. The intake
manifolds are therefore interchangeable for all small engines. The plenum is
interchangeable for all model years thru 1990. The 1990 and up have tapped holes
for the mounting of a MAP sensor (right rear of plenum). The throttle body is
different on 90 and later models, modifications can be made to the plenum to use
the 90+ Throttle Body by drillling a hole in the front of the plenum. Intake
tubes (runners) are interchangeable for all model years, however the left intake
tube through 1988 has a mounting for the cold start injector, for 89 and up this
mounting is deleted.
NOTE: Throttlebodies 85-88 are the same and must be matched to plenums 85-88.
To work properly on 90 and up plenums a hole (1/2") must be drilled, between the
intake openings where the throttle body mounts, to allow for passage of idle air
from the IACV to the plenum. 89 and up throttlebodies will work on earlier
plenums without modifications.
The fuel rails have a few differences. If the left side fuel rail has a
fitting at the end close to the firewall it is from a 1985-88system. The fitting
is for connection of the cold start injector fuel line. The left side fuel rail
is stamped at the factory to identify same with the engine. The Fuel Rail
Identification Table above will assist you in identifying your system as a 5.0L
/ 5.7L and the injectors furnished with those systems.
Distributors
All 85-86 systems used a GM HEI distributor. The connector for the
distributor is keyed differently than previous model years. 87-92Camaro and
+Pontiac systems use a small diameter distributor with an external coil. 87-91
Corvette's still use the HEI distributor. Either distributor will work, however
the connectors are different.We can furnish adapters to make them interchange.
The HEI Distributor for the 85-86 5.0L engine has the number 1103679 stampedin
the aluminum casting at the base of the distributor. The 85-91 5.7L HEI unit is
stamped 1103680. The smaller diameter (72mm) distributor is stamped 1103479 on
the metal plate beneath the distributor. The72mm Distributor was furnished with
5.0L/5.7L engines on the Camaro,and Pontiac engines 87-92.
As mentioned earlier the LT1/LT4 has an optical sensor and is significantly
different than the HEI system. Distributors are not interchangeable for these
different engines.
Fuel Pumps
The OEM fuel pump for TPI/LT1 is an "in tank" fuel pump with an operating
rating of 50 PSI and 24 GPH. This pump is recommended for all vehicles with
in-tank pump mountings. We also offer a chassis mounted fuelpump which has an
operating rating of 60 PSI and 30 GPH. This pump is also an AC DELCO unit. It is
important to note that Throttle Body Injection systems operate at 12 PSI. Almost
all carbureted systems operate at low pressure utilizing a mechanical pump. An
electric pump is definitely required as referenced above for all Port Injection
systems. A return line is required to the fuel tank. A 3/8 or 5/16inch supply
line is required. 3/8 is recommended. 5/16 inch is recommended for the return
line. The fuel tank must be vented so as not to buildup pressure. Recommended
location for the fuel pump is close to the fuel tank.
Fuel Injectors
There are a number of Fuel Injectors on the market today. The following
injectors have been furnished on GM OEM systems: Lucas Bosch, Rochestor and
Multec. The prices vary considerably and performance differences are hard to
detect. Basically they are sized for application. The 5.0L injector is sized to
deliver approximately 4.05 milligrams of fuel with a 2.5 millisecond pulse or
18.13 lbs per hr at approximately 36 PSI. The 5.7L injector is sized to deliver
approximately 4.83 milligrams of fuel with a 2.5 millisecond pulse or 23.92 lbs
per hr at approximately 43.5 PSI. This information is typical for all
manufacturers and flowrates will vary slightly even between identicle injectors.
A wide variety of flow rates are available to include 19lb/hr, 24lb/hr,30lb/hr,
36 lb/hr. These are all 16.2 Ohms and will work well with all GM TPI's Rochestor
injectors are presently furnished for the 90-94 GM 5.7L engine. It has an all
metal nozzle and performs well. Bosch injectors an excellent choice at approx
$37.00 to$50.00 each.
While there are significant differences between the TPI and LT1 induction
systems and computers, the injectors are essentially the same. Sequentialport
injectors and batch fired injectors are sized in the same manner.
Wiring Harnesses
The 1985 Engine Harness for all vehicles incorporates a
MAF module which plugs into the harness in the vicinity of the ECM. If you are
purchasing a system thru a salvage yard it it always a good idea to just buy the
unit and upgrade the electronics to speed density 90-92.It is neater and simple
to install and it performs like a 90 to 92. The 1986-89 Harness has three relays
and the ESC module mounted in the engine compartment. The 89 harness does not
incorporate connectorsfor the cold start system. Please note that a mass air
flow sensoris required on all systems thru l989. Please note that while the
connectors for the 85 ECM and the 86-89 ECM are the same, they are NOT
interchangeable.The ECM's are different.
The 90-92 systems are considerably different than their predecessors. The
90-92 systems use a Manifold Air Pressure (MAP) sensor in lieu of the Mass Air
Flow Sensor. This system is referred to as a Speed Density System. The Electric
Spark Control (ESC) module is also incorporated in the ECM. All hardware
components remain the same ie., intake runners, fuel rails, throttle body,
distri butor and intake manifold. The EST module, in the distributor and knock
sensors are different than the earlier models and must be matched. All hardware
components are interchangeable with earlier models.
While the 90-92 systems are cheaper to manufacture, it is questionable as to
whether Speed density is better than the Mass Air Flow System, especially when
GM brought the MAF back in the 94 LT1. But who are we to question GM
engineering. All systems appear to perform very well indeed. The 90-94 system
has a single relay for the fuel pump mounted in the engine compartment. There is
no ESC module as previously discussed. These functions are performed by a module
in the ECM/PCM. The ECM's for the 90- 92 Camaro and Pontiac are different than
the 90/91 Corvette.
The Pontiac and Camaro use a 1227730 ECM and the Corvette uses a 1227727 ECM.
The difference between the two is in the ECM enclosure and ECM connectors. The
Corvette enclosure is built for mounting in the engine compartment. Camaro/
Pontiac are built for mounting in the passenger compartment. Internally they are
the same. Calibrators are interchangeable. It should also be noted that the
Assembly Line Diagnostic Link (ALDL) connector ISNOT normally part of the
Factory Engine Harness. It is normally part of the instrument panel harness. The
factory engine harness also includes a number of connectors which are not
required for "Off Road Use". These connectors are Air Management, Transmission,
EGR, Electric Fan, Instrument Panel Oil Pressure Sender, Water Temperature
sender, AC High Pressure Switch, VSS and VATS module to mention a few.
From 94 and up its the PCM and no calibrators. The PCM for the LT1 is the
same in the Corvette, Camaro, Firebird, Buick and Caprice. This unit is
Programmable as previously discussed. These units are completely different than
their predecessors. We can program these units for any LT1/engine transmission
combination. Performance and special calibrations are also available.
VORTEC HEADS and TPI
Since GM offered the new Vortec cylinder head many
customers have ask if a TPI unit would bolt up.At a glance you can see that it
will not due to the lack of bolt holes and the wrong bolt angle.We now offer a
service to put the required holes in the Vortec cylinder heads so TPI will bolt
up to these awsome heads. The modification is $125/pr.Port matching required.
Telephone - 410-465-9569
Toll Free 1-877-465-9569
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