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Old 03-18-2001, 12:00 PM
stevebfl stevebfl is offline
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
The real problem with getting into re-engineering systems is that many of the design criteria are not published (often trade secrets).

To give an example: I think the 300e is not current limited and I think they use about 6-7 amps. I have "current ramped" a number of MB coils but don't remember which are which. Current ramping is the act of using an inductive current probe with a high resolution DSO (digital storage oscilliscope). Each event can be captured and analyzed. The current starts at zero and either peaks and holds (current limitation - looks like a ramp to a maximum and then a horizonatal to the point of ignition where an almost vertical drop to zero occurs) or rises unlimited to a value regulated by the components of the system.

One thing that can't be determined is which components are doing the regulating in the last senario. Modern controllers are so good that instead of limiting current they plan on starting the event at the appropriate time so that the coil gets saturated at the precise moment of ignition (controller opens the circuit) In this case the ramp gets to 6-7 amps because the ramp slope and time used were part of the calculation. If you change the design of the coil the slope of the ramp changes throwing these precise calculations for a loop.

Basically I am saying that I don't know the specs. I know where to find them if I suspect a deficiency in operation. I, like most driveability techs, look at the effects with quality testing eqiptment, but very seldom get into the redesign of the system. I know the guys that designed it know way more than I do (especially in MBs case). They also have more time than I do. Real design changes that work take lots of engineering. Figuring how the system works exactly, is probably the first step.
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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