Author Topic: Ignition coils on M42 (Read 7876 times)

Ruger · « **on:** January 18, 2008, 08:44:24 AM »

Hi everyone quick question about ignition coils and using aftermarket items

I noticed people using other bmw coils on their m42's but can aftermarket coils be used? i have a set of 6 Bosch gt40p coils that are brand new for a previous project and i love the look of a set of coils hanging off the side of the engine (not in dangerous manner of course) I know my ignition leads are worn and the coil pack is probably the original from 17 years and 260,000km worth

Does anyone know the specs of the standard coils and if the gt40p's will work?

Cheers,
George.

HaNasich · « **Reply #1 on:** January 18, 2008, 06:13:37 PM »

i managed to match newer coil pack, from later M42 (1996) to the original harness, never thought about using different coils though...

(you can read about it in the M42 DISA swap thread i have in the "Swap"'s section...)

Ron.

Ruger · « **Reply #2 on:** January 22, 2008, 08:21:01 PM »

Well i managed to do it. 4x Bosch GT40RT coils and msd plug wires

runs much better this little car is starting to move. Last engine mod on the list for now is the flywheel that has to wait.

Ill post up pics later today of the setup it looks awesome aswell

D. Clay · « **Reply #3 on:** January 22, 2008, 10:38:10 PM »

How about a picture with some info on the wiring. Are you still using the original Bosch (BMW) computer?

Ruger · « **Reply #4 on:** January 23, 2008, 06:40:56 AM »

still sorting out the coil cover, sanding off the bmw lettering with 4 holes in it for the leads, gloss black paint and a small vinyl roundel in the center

The coils are Bosch GT40 RT w/ MSD Plug wires

In the stock coil wiring loom there are 3 wires, 1 is negative, 1 is positive and 1 is secondary coil ground (afaik cant find any quality wiring diagrams with colors that is clear)

These coils (like they use on some other cars) dont need a secondary ground so we just use 1 negative and the positive wire. The negative we use is the thicker, shielded black wire and the positive is the green wire. Be sure to cut back the shielding because if this gets into contact with the negative terminal on the coil it could blow the coil.

Still running on the stock computer happy as proverbial larry

It does run better but i think thats more to do with old suspect coils/wires. Im getting it on the dyno next week to see how much power shes putting out (moreso state of tune)

I have just learnt im running the wrong coils though and i need to get some ballast resistors for them as our ignition system is triggered off 12v and not 9v (R in the part number meaning it runs off 9v ign) GT40T would be the ideal coil. These are a good strong coil though 40kv of spark im not sure what the stock ones are but if they arent as strong we might be able to get away with more plug gap meaning another 0.5hp yay!

Ruger · « **Reply #5 on:** January 23, 2008, 06:54:19 AM »

also depending on the current draw of these coils vs the stock coils it could blow the dme to smitherines.
I reaaaally need to get the coils meant for electronic ignition systems i think i will do so tommorrow

Jak318 · « **Reply #6 on:** January 31, 2008, 07:26:13 PM »

looks like you could use a new intake boot. Whats with all the electrical tape on it?

Ruger · « **Reply #7 on:** February 01, 2008, 12:34:46 AM »

its split to bits definately need a new intake boot.

N�R-SPEC · « **Reply #8 on:** February 01, 2008, 01:12:11 AM »

i'm running BavAuto COP. fairly simple, no more plug wires to deal with, and looks super clean. i've definately noticed improvements in response, low end torque, and idle. due to the lack of plug wires, i've eliminated resistance. i'm also running resistorless copper plugs at .042 gap. couldn't be happier.

Author Topic: Ignition coils on M42 (Read 7876 times)

N�R-SPEC