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

[Jon K]

I am trying to find out what dwell i need to run these coils to keep them from catching fire when I go full standalone - I am thinking if they're anything like the Bremi coils they will be 3.3 ms, but I don't want to guess it.

The full part number on the coil looks like this:
0 221 504 410
1 748 394

Haven't found any tech sheets for it yet, any help?

[joshua43214]

This is the stock coil, correct?

If you know someone with an old fashioned osciliscope, you can hook it up and measure the "dwell". Just get a set of scrap ignition wires to jumper from the coil to the plug, you do not need the #1 reference if all you are doing is watching a single firing line. I have done this for diagnosis purposes in the past with good results on DIS cars. make sure you run a smal ground wire from the coil to the head, its probably not needed on a BMW, but its best not to take risks with electronics. On the older Jags, it would blow the instrument cluster if you cranked the car with a coil ungrounded.

Or even better, use a lab scope to check it, but not even many pros have them.

I would be surprised if running it at anything other than stock dwell would make much diference. BMW has always been a bit tight mouthed about this type of figure, so I am not sure its published anywhere.

[Jon K]

Stock coil yes -

I did find the numbers for the Bremi model, but when I looked up on some part supply websites, it says do not substitute a Bremi for a Bosch or vice versa - not sure if the dwell are different or the overall resistance, but something is different - they said its fine to replace 6 bremis with 6 bosch, but not a single one... so I think it'd be a resistance thing (want to load the ignition drivers properly across the whole ECU) but not sure. Crap this sucks.

[winfred]

i swap coils and see cars with different coils all of the time, id suspect they have very close spec's from brand to brand as they all run with the same series of computers

[joshua43214]

I agree with Winfred, I see cars with multibrand coils and they seem fine. If you have bremi specs, they will should be right for bosch too. The computor handles the dwell time, it doesn't care what brand coil you use, just so long as it has the right resistance properties and can charge at the right speed.

[Rustam]

Stock coil yes -

I did find the numbers for the Bremi model, but when I looked up on some part supply websites, it says do not substitute a Bremi for a Bosch or vice versa - not sure if the dwell are different or the overall resistance, but something is different - they said its fine to replace 6 bremis with 6 bosch, but not a single one... so I think it'd be a resistance thing (want to load the ignition drivers properly across the whole ECU) but not sure. Crap this sucks.

It's not resistance but "turns ratio" that affects the time of charge...

[632 Regal]

just like say, the turns of wire in a coil? lol
It's not resistance but "turns ratio" that affects the time of charge...

[Jon K]

It's not resistance but "turns ratio" that affects the time of charge...


That's not my point - Bremi and Bosch have different resistance spark plug boots . I think one is 1.8k ohm and the other 1k ohm. Thus, you wouldn't mix Bremi and Bosch because it would load the ignition drivers differently. That is my theory of why they say not to mix them - the dwell has to be the same... the ECU is programmed to handle a certain dwell, it is not variable.

[Jon K]

just like say, the turns of wire in a coil? lol


Too easy

[joshua43214]

It's not resistance but "turns ratio" that affects the time of charge...

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.

[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?