Bosch EST
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Original Submission by T:
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[edit] Bosch EST Circuit:
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See also EST VK.
Tom's Shed.
[edit] Overrun Shutoff:
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 Shutoff in EST terms results in reduced emissions.
[edit] 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.
[edit] 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.
[edit] 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.
[edit] 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
[edit] 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 |
[edit] Wiring Diagrams:
[edit] Links:
[edit] Terms:
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