Bosch EST

From Holdenpaedia
Jump to: navigation, search

Original Submission by T:

Back to the Engine Section

Manual Transmission EST VK Commodore ECU. Photo by T. Click to Enlargen.

Bosch EST Circuit:

A Crank Angle Sensor is mounted at the Rear of the Engine and receives info from three rotating Magnets implanted in the Flywheel (Manual) or welded into the Flexplate (Automatic). The CAS is also called a Speed Sensor.

EST VK:

Electronic Spark Timing was only fitted to Carburettor 6 Cylinder VK Commodores. EFI VK Commodores do not use EST. They use an HEI Distributor with Balance Weights and a Vacuum Advance Module similar to those used in VC, VH, WB 6 Cylinder Engines.
See also

EFI VK 3.3.

Operation:

A Digital ECU reads the CAS Pulses as well as information from the Engine such as Manifold Pressure, Coolant Temperature and Throttle Position to calculate Spark Timing for the Engine.

ECU:

The ECU collects all the information needed to determine the Spark Timing and it's the ECU that triggers the Coil.

ECU Types:

EST VK ECU's come in AUTO or MANUAL types. Neithe unit has any control over the Gearbox and they don't even monitor any Gearbox Top Gear Switch. It is most likely that the spark advance plots are different for each Engine.

Coil:

The EST VK uses the same Coil as WB, VC, VH and VK 6 Cylinder and V8 Holdens the Bosch HEC-716 Coil. 

Distributor:

The EST VK uses a special Distributor that has no Balance Weights or Vacuum Advance Module. The Distributor only houses the Rotor Button and the Distributor Cap. It uses a Special Rotor Button.

Throttle Position Switch:

This allows the ECU to determine when the Throttle is closed or open.

Manifold Pressure Sensor:

This Device plugs into the Inlet Manifold and produces a Resistance that changes with the Manifold Pressure.

RPM Based Advance:

RPM based Advance uses information stored in ROM in the ECU. The required Advance for each specific RPM is held as a value which tells the ECU how long to wait once a CAS Pulse has been recieved before the Coil is Triggered. The delay reduces with the increase in RPM. Dynamic Advance is determined by a pressure sensitive device connected to the Inlet Manifold.

Overrun Retard:

When the Throttle is closed the Throttle Position Switch sends an unique signal advising the case. If the Engine is spinning above 900 RPM and the Throttle is closed, 6 degrees of Advance is produced.
Overrun Retard in EST terms results in reduced emissions.  

The Trimatic in the rear is from an EST Commodore. Note it has an Hole drilled in the top for the Crank Angle Sensor and provision for a removable Inspection Cover.  Click to Enlargen. Photo by Stuart.

 
EST VK Commodore Engine and Trimatic. Note the Bellhousing has an Hole drilled in the top for the Crank Angle Sensor and provision for a removable Inspection Cover.  Click to Enlargen. Photo by Stuart.

 
EST VK Commodore. Click to enlargen. Photo by Tom1569.

Another shot of the Computer with the cover removed. Click to Enlargen. Photo by HZ Tonner and image enhanced by Circlotron.
 
A shot of the Magnetic Pickup. Photo by HZ Tonner.
 
Another shot of the Magnetic Pickup. Click to Enlargen. Photo by HZ Tonner.
 
A shot of the EST Distributor. Click to Enlargen. Photo by Two Heads.
 
Air Injection holes blanked off by grub screws on a factory EFI head. Image by 265Grunt. Click to Enlargen.
 
Improved Spark from Bosch EST. Click to Enlargen. Photo by LMH.
 
Distributor and Coil from an EST VK (6 Cylinder) Commodore. Note the Distributor body is very thin because it does not hold any balance weights and there is no provision for fitting a Vacuum Advance Unit. Click to Enlargen. Photo by Kenscars.

Limp Mode:

Any time the circuit loses an input or cannot make rational sense of the Sensor Voltages, the B Voltage is forced to a maximum. When this happens the Ignition Timing runs at a static 6 degrees of advance irrespective of the Engine's Speed or Sensor Voltages.

Starter Signal:

There is also a Starter Signal which the EST Computer responds to. When the Engine is cranking, the advance is forced to 6 degrees.

Test Wire:

There is a test wire taped to the wiring harness at the back of the Rocker Cover. Test Mode is activated by connecting this wire to earth. Once this wire is activated the Computer will signal coded information to a dash mounted warning lamp indicating if there is a fault in any Engine Sensor Circuit.

Air Injection Grub Screws:


Submitted by lovemyholden on Sun, 10/06/2007 - 08:41.
By the way those grub screws are 5/8 UNF x 3/4 inch. I just got some the other day. Thought you might like to record that somewhere. Cheers LMH
End of submission by LMH

IC's List:

Integrated Circuits Used in the EST Design
 Type  Description Quantity 
 4011  Quad Dual Input NAND  3
 4069UB  Hex Inverter, unbuffered version  1
 4520  Dual BCD Down Counter  1
 2732  Eprom 4096 bytes  1
 74LS537  1 of 10 Decoder with Tristate Outputs  1
 CPU SC85056  Possibly a custom version of a 6809.  1
 74LS00  Quad Dual Input NAND  1
 MC14443L  A/D converter  1

   

Image One. A shot of the original 6 Cylinder EST VK Computer with the cover removed. Photo by LMH.
Distributor and Coil from an EST VK (6 Cylinder) Commodore. Note the Distributor body is very thin because it does not hold any balance weights and there is no provision for fitting a Vacuum Advance Unit. Click to Enlargen. Photo by Kenscars.
 
EST VK Engine. Note the Air Injection Pipes. Click to Enlargen. Photo by Tom1569.

EST VK Engine. Click to Enlargen. Photo by Tom1569.

EST VK Engine. Click to Enlargen. Photo by Tom1569.
 
I always like to clean the threads on the manifold studs to remove burrs and rust. This ensures a smooth torquing of the nut, and maximum "pull down" as opposed to the nut binding which is not desirable. I'm using a 3/8" UNF Nut die for the job The image also shows the Air Injection holes drilled, threaded and leading into each exhaust port. Click to Enlargen. Photo and info by LMH.
 
Everything is ready. Gasket surfaces are clean, block painted to re seal the metal after years of leaks and spillages. Grub screws are installed in the air injector ports, and brass block-offs in the old TVS (Thermal Vacuum Switch) ports.
LMH. Click to Enlargen. Photo and info by LMH.

 
The manifolds have now been installed and the Weber adaptor installed. Note I still use the Varajet heat shield. Don't forget to use a gasket both bottom and top side of the heat shield. I have installed 3 Weber base gaskets to ensure the linkages clear the adaptor. This may seem a little dodgey but in practice it actually works very well. In previous installations I have had several years usage without any problems. These are a very dense gasket, and act as a good heat insulator as well. LMH. Click to Enlargen. Photo and info by LMH.
 
The Photo shows the EST Crankshaft has a Dowel  for positioning  the Flywheel so that the Trigger Magnets will be precisely positioned.  Click to Enlargen. Photo by Stuart.
 
EST VK 3.3 Engine. Click to Enlargen. Photo and Info by Stuart.

       

 
The Crankshaft Boltholes are drilled offset meaning the Flywheel of Flexplate can only be fitted in one position.  That's true for any red/blue/black 6. Click to Enlargen. Photo by Stuart.
 
EST VK Commodore. The Smog Pump can be seen on the right hand side of the Engine. Click to Enlargen. Photo by Kyle.
   
EST VK Commodore. The Red Arrow shows the Manifold Pressure Sensor Hose. Click to Enlargen. Photo by Kyle.

 

 
A shot of the Computer with the cover removed. Click to Enlargen. Photo by HZ Tonner.

 
Rear View of Manual Transmission EST VK Commodore ECU. The Power Transistor is has a black Plastic Cover.Photo by T. Click to Enlargen.
 
Connector of Manual Transmission EST VK Commodore ECU. Photo by T. Click to Enlargen.

   

L P Trimatic Half Bellhousing from a 6 Cyl EST VK Commodore. Note the Hole in the Top for the Speed Sensor. This is the only Trimatic to have the Top Hole and use a Speed Sensor.  Click to Enlargen. Photo by 383HGBrougham.
 
L P Trimatic Half Bellhousing from a 6 Cyl EST VK Commodore.  Click to Enlargen. Photo by 383HGBrougham.

 

Part Numbers:

 Part Description Bosch P/N0
GMH P/N
 Coolant Temperature Sensor 0 280 130 026  92017805
 EST ECU Manual
 9 220 066 008  92020763

 

Wiring Diagrams:

Wiring Diagrams

Links:

VK Workshop Manual

Bosch EST

Campbell's Shed

Tom1569's Shed

Stuart's Shed

Kyle's Shed  

Terms:

Terms

Back to the Engine Section