Need info on Bosch coil 0 221 504 410...

[Jon K]

I was mixing apples and oranges a bit, sorry. I only mentioned resistance since if it is incorrect it can cause the drivers to shut off.

The plug boots are part of the secondary ignition system, so the ECU does not see them when it charges the coil. The time it takes for the primary windings to saturate will remain the same regardless of how much resistance there is in the secondary.

I should have said that any coil that is listed as a replacement part will have the correct properties for both the safe operation of the ECU and required dwell for proper operation of the coil itself.

That's what I was thinking Joshua - so if I found a Bremi coil dwell time is 3.3ms, it would be "safe" to assume that a Bosch (an OEM replacement) should have the same 3.3 ms dwell time?

[Bill R.]

dme and it varies according to engine rpm and load.. that was one of the big advantages of electronic ignition over the old points system that it could vary the dwell. Each manufacturer of coil for bmw has different firing characteristics. Here you can see the differences and why you don't mix and match them.

That's what I was thinking Joshua - so if I found a Bremi coil dwell time is 3.3ms, it would be "safe" to assume that a Bosch (an OEM replacement) should have the same 3.3 ms dwell time?

[Jon K]

dme and it varies according to engine rpm and load.. that was one of the big advantages of electronic ignition over the old points system that it could vary the dwell. Each manufacturer of coil for bmw has different firing characteristics. Here you can see the differences and why you don't mix and match them.

Yeah I figured dwell was controlled by ECU - so now the question is, since my new ECU also controls dwell... how do I find out what dwell the coils are happy at? It seems even a millisec too long and the coils burn up.

[joshua43214]

Nice chart, going to borrow it to show my point.

I think all this discusion aplies to the base dwell time at idle. The time it takes for the coil primary windings to reach saturation is based on the charactistics of the coil. You will notice that all 4 coils have the same dwell time provided by the ECU, the difference you see with the bosch coil is a lower firing line and hence a longer burn time as compared to the bremi coil. The difference in firing voltage can come from 2 causes. the Bosch coil is unable to reach saturation in the dwell time provided, or the the ratio between the primary and secondary windings are less optimal. Either way, The 4 coils shown all have the same dwell time but react differently after the coil is released.

[Bill R.]

am not really sure what your asking for. If you want dwell at idle and with what battery voltage or dwell at the maximum expected engine rpm etc etc, If you ask Mark D, i'm certain that he has the dwell maps for the dme, these maps may give you a better idea what the average dwell is , or what the dwell is at idle .. the dwell map will show dwell at x rpm and x battery voltage.
The higher the battery voltage the shorter the dwell time needed for the coil to produce adequate firing current and the system is mapped accordingly.

Yeah I figured dwell was controlled by ECU - so now the question is, since my new ECU also controls dwell... how do I find out what dwell the coils are happy at? It seems even a millisec too long and the coils burn up.

[632 Regal]

looks like the Bosch has less voltage but a longer burn period, that I think is preferred?

[Jon K]

Bill what are the units on the X axis?