Author Topic: Which Transistors & How: Driving 16 Coils for twin spark V8  (Read 6035 times)

Offline 190E_Will

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Which Transistors & How: Driving 16 Coils for twin spark V8
« on: October 04, 2018, 05:05:14 pm »
Hi All,

I'm planning on using a VEMS v3 to control a Mercedes 5.4l M113 V8 engine from a 1999 e55 w210, transplanted into a mercedes w201 chassis (190e). I am a complete novice but trying to learn as much as possible from reading!

My main concern at the moment is how to control the 16 spark plugs. I want to utilize the x8 original Bosch twin fire coil packs which mount nicely to the rocker covers. They fire both spark plugs in a cylinder simultaneously. The problem is these are dumb coils with no built in transistors.

       [Twin Fire Coil Spec Sheet: http://www.powerongroup.it/BOSCH/pdf/Injection%20&%20ignition/Ignition%20coils/2x1.PDF ]

Seeing as these twin fire ignition coils are basically 2 coils in 1 package, its more like controlling 16 ignition coils. Considering the current rating of 2x7.5 amps per coil pack I think paralleling them directly (15 amps) would send too much current through normal IGBTs and would cause them to fail. For example the max collector current for a Bosch BIP373 IGBT is 16 amps, (not enough margin in my opinion).

My first idea was to use x4 Bosch IM4 (4 channels each) Ignition modules, original equipment on VAG 1.8T engines. The 8 logic level ignition outputs from the VEMS would be split/paralleled to create x16 logic level outputs to feed the ignition modules and in turn the ignition coils. However, genuine Bosch IM4 units are expensive and 4 of them are quite bulky.

       [Bosch IM4 ignition module Spec Sheet:                                                                                                                                                       
                 http://www.bosch-motorsport.com/media/catalog_resources/Ignition_Module_IM_4_Datasheet_51_en_2778345099pdf.pdf ]

My next idea was to essentially do they same thing (paralleling the x8 logic level outputs to create x16) but using the 16 Original ignition transistors I de-soldered from the car's ECU (Bosch 30046 [no data sheet available]) to make a purpose built 16 channel ignition module to be controlled by VEMS.
This would cut down on costs and make a more compact ignition module. I could also use other similar transistors such as BIP373 for this purpose.

My third and most recent idea was to build a similar ignition module using only x8 ISL9V3040P3 IGBT ignition transistors. Since these have a higher current rating of 21 amps, I thought it might be possible to connect both sides of each ignition coil together (15 amps) and drive them using only x8 IGBT. This would be pretty low cost and very compact.

          [ISL9V3040P3 Transistor Data Sheet: http://www.onsemi.com/pub/Collateral/ISL9V3040P3-D.PDF ]

Another concern I have is that although the data sheet say 2x7.5 amps for primary current, the primary resistance is 0.42 Ohms. By my logic using I=V/R the primary current when driven by 12 Volts would be around 28.5 amps per channel. Obviously 28.5 amps is a lot different from 7.5 amps, and i'd like to know where my confusion lies. 

Any information from experts or people with experience with this sort of thing would be greatly appreciated and help me make the best decision as to how to fire these 16 spark plugs !


 

Offline MWfire

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Re: Which Transistors & How: Driving 16 Coils for twin spark V8
« Reply #1 on: October 05, 2018, 09:49:54 am »

Offline 190E_Will

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Re: Which Transistors & How: Driving 16 Coils for twin spark V8
« Reply #2 on: October 06, 2018, 09:31:14 pm »
Thanks MWfire,

It’s good to know that option works! Have you also fitted vems to M113 V8?


Offline MWfire

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Re: Which Transistors & How: Driving 16 Coils for twin spark V8
« Reply #3 on: October 06, 2018, 10:29:50 pm »
I don't know mark of engine, but was sl500 year around 2007. Also add 1.5bar of boost :).