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1985-1998 [Subscribe to Daily Digest] |
of the boost control motor spring and compression thereof. The trionics pretty much sets the pulse rate of the Boost Pressure Solenoid (BPS) up to the point where above ambient is reached (+ delta P with ambient). This point is variable depending on the volumetric efficiency of the air pump and the barometric air pressure being pumped, which is understandable. We have found there is a difference in the trionics controlers for a T25 pump and the TD04 pump and the wastegate responses/positions. When this was queried to Engineering it was stated that the dynamic response rates were different but went no further to explain the difference.
The plug information and data was undertaken to determine why so many were having early failure of the DIs and rough running cars. I have cars that go well beyond 200,000 mile with no problems and never a rough runner. Really don't understand this if one is sensitive to those things which cause failures. But it certainly seems to be endemic to the HOT engines.
The DI looks at manifold pressure and VA (watts) required to fire the plug, as the plug increases the gap, more VA is required to ionize the area around the plug. If the fuel octane is too low for the BMEP requested (throttle position) the flash ignition propogation advances across the plug face too rapidly. This disrupts the ion corona of the plug and detonation is recognoized by a rapid decrease in VA of the plug. LIght to pending detonation adjusts the spark advance (Low octane fuel) but heavy detonation (excess boost) changes both spark and frequency of the BPS This causes the DI to hold the BPS open and vents charge pressure to the near ambient of the inlet. We found that large plug gaps completely destroys the smooth operation of the trionic control of the BPS and the wastegate looks like it is confused. I don't know if this is an frequency interference or a frequency change in the signal to the BPS or a sharp shift in timing -or all of the former. Normally a knock detection is a shift in frequency to the BPS causing a smooth opening of the wastegate or retardation of the timing, initially- we probably could go further and solve but recent conditions in my health has slowed things with my investigation and plans.
We did not try with anything disconnected since we were trying to emulate a "normal" response situation. I will tell you we disconnecterd the speed sensor input to the car so that it would revert to a pure base boost condition while retaining a completely normal engine condition. This also gave some interesting information on the wastegate motion - essentially a very smooth response regardless of plug gap I am still scratching my head on that one. - maybe the RATE comes into action early because one of the variables is not in the software equasion. I don't know if this is the place to get into this her but it is "technically" a Saab discussion. Scott you there? OK?
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