PROMO Nexsys Motorsport N54 Ignition Coil Upgrade Kit

bahn

Corporal
Platinum Vendor
Nov 5, 2016
231
370
0
Iowa
Thanks. Resistor in stock VC model boot?
No resistor as it's not needed in a performance application. There seems to be misinformation being spread around about what the resistor does. I've seen claims that the resistor keeps the coil spring from melting or burning due to the high energy output of the coils which just isn't true. Resistors in-line with the spark path have two uses, first being EMI reduction and second being increasing spark voltage. If we look at it from an EMI standpoint 1 kOhm (resistor inside B58 coil boot) is not sufficient for EMI suppression. Instead automotive spark plugs used these days have built-in resistors for suppressing EMI. In the case of the N54, N55 and B58 motors there is a 5 kOhm resistor inside the spark plug for suppressing EMI and is designated as a Resistor Spark plug by the "R" in the spark plug model (for example SILZKGR8B8S).

So if EMI reduction isn't the reason it exists what is? After the primary side of ignition coil is energized and the path to ground is removed (DME switches it off suddenly) a magnetic field is generated as the current in the primary coil has no where to go. This magnetic field then induces a high voltage in the secondary side of the coil and since there's no path for the current to take (because there's an air gap at the end of the spark plug) the voltage continues to increase until it is sufficient to ionize the gas between the spark plugs electrode and ground strap at which point the current is conducted through the ionized gas as a spark. The key take away here is that added resistance in that path increases the voltage at a cost of secondary spark current. An increase in spark voltage from the added resistance is useful in an OEM application with extended spark plug change intervals as the gap will continue to increase as they wear. This is why the increased voltage is not useful in a performance application as we are running smaller gaps than the stock B58 plugs (0.030") and replacing spark plugs more often than once every 40,000 miles. Instead for performance you want a stronger longer lasting spark (more secondary current) with sufficient voltage to reliably ionize the mixture between the electrode and the grounding strap.

As for burning/melting the coil spring, our springs are 0.8 mm thick (stock B58 is 0.5mm) which is equivalent to 20 AWG wire which can carry a constant 10 amps. Pulsed short duration bursts of 0.184 amps have no chance in melting or burning the spring. Any spring burning is due to insufficient spring contact causing a gap that is crossed by a spark which burns and erodes the material.
 

turbohugh

Private
Nov 13, 2018
47
11
0
Ride
E92 335
My parts arrived last week. Excellent work thank you. I understand shipping is slow. Just be patient everyone, it's worth the wait.
 
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bahn

Corporal
Platinum Vendor
Nov 5, 2016
231
370
0
Iowa
My parts arrived last week. Excellent work thank you. I understand shipping is slow. Just be patient everyone, it's worth the wait.
Thank you for the kind words and your support!

Our N55 and S55 kits are now live for pre-order on our website. See details here.
 
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JAKWAGN

Lurker
Jun 14, 2021
11
5
0
Edmonds Wa
Ride
2014 335i
No resistor as it's not needed in a performance application. There seems to be misinformation being spread around about what the resistor does. I've seen claims that the resistor keeps the coil spring from melting or burning due to the high energy output of the coils which just isn't true. Resistors in-line with the spark path have two uses, first being EMI reduction and second being increasing spark voltage. If we look at it from an EMI standpoint 1 kOhm (resistor inside B58 coil boot) is not sufficient for EMI suppression. Instead automotive spark plugs used these days have built-in resistors for suppressing EMI. In the case of the N54, N55 and B58 motors there is a 5 kOhm resistor inside the spark plug for suppressing EMI and is designated as a Resistor Spark plug by the "R" in the spark plug model (for example SILZKGR8B8S).

So if EMI reduction isn't the reason it exists what is? After the primary side of ignition coil is energized and the path to ground is removed (DME switches it off suddenly) a magnetic field is generated as the current in the primary coil has no where to go. This magnetic field then induces a high voltage in the secondary side of the coil and since there's no path for the current to take (because there's an air gap at the end of the spark plug) the voltage continues to increase until it is sufficient to ionize the gas between the spark plugs electrode and ground strap at which point the current is conducted through the ionized gas as a spark. The key take away here is that added resistance in that path increases the voltage at a cost of secondary spark current. An increase in spark voltage from the added resistance is useful in an OEM application with extended spark plug change intervals as the gap will continue to increase as they wear. This is why the increased voltage is not useful in a performance application as we are running smaller gaps than the stock B58 plugs (0.030") and replacing spark plugs more often than once every 40,000 miles. Instead for performance you want a stronger longer lasting spark (more secondary current) with sufficient voltage to reliably ionize the mixture between the electrode and the grounding strap.

As for burning/melting the coil spring, our springs are 0.8 mm thick (stock B58 is 0.5mm) which is equivalent to 20 AWG wire which can carry a constant 10 amps. Pulsed short duration bursts of 0.184 amps have no chance in melting or burning the spring. Any spring burning is due to insufficient spring contact causing a gap that is crossed by a spark which burns and erodes the material.
For over a year now I have been running MHD stage 2+ 93 octane on stock Bosch plugs with stock gap with BAV auto coils (2 of which have gone bad in the last 2 months so stock coils on those 2 plugs now). I get a peak of 21psi & I have no issues/misfires with my n55. I would really appreciate any thoughts or info about what gap I should run on the stock b58 plugs & coils (Eldor) I am going to install as soon as my kit gets here.
I thought part of the benefit of this conversion was to be able to run stock gaps.
I do plan on a custom tune or ethanol in the near future to bump up hp to 500 or so. My AWRON gage says my engine makes 450 HP now but I'm not sure if it's true.
 

jzx_andy

Specialist
May 22, 2019
63
82
0
Perth, Western Australia
Ride
2008 E92 335i 6MT
What is the consensus re: best plugs to use for B58 coils on N54 using this set up?

My car is currently stock but will do a "stage 2" tune up to 16-18 psi, targeting 350-400whp. Eventually want to aim for high 500s with upgraded hybrids when the time comes to replace stockers.

Any thoughts re: plugs?

I am running NGK 97506's on my mild N54 with basic bolt ons, flexfuel and the B58 coil kit. These are colloquially referred to as the 2 step colder plugs. I don't see any need to change them, and my understanding so far is that they are perfectly adequate for upgraded turbo setups.

I've also heard the factory B58 spec NGK plugs are a good match for modified N54's, as you can open the gap a little more on them than you can with the 97506's.