Microsquirt Wasted Spark with Carbs

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Microsquirt Wasted Spark with Carbs

Postby Markos » Thu Dec 28, 2017 11:18 am

Hi Folks,

Apologies in advance for my ignorance. I mainly want to get my idea down 'on paper', and hear your thoughts about wasted COP. I'm a quick study but I'm just getting started with this. I have decided that I want to use Megasquirt to drive the ignition on my old BMW. The motor is an early 2.8L M30. I plan to use a 60-2 wheel from a M30B35, which was availbel from 1989 through the 90's. You can find the engine in 5 and 7 series from that time. The wheel and sensor will bolt onto my 1971 block without issue. Although MS is less common on classic BMW's, most people that drive these cars chose to ditch the points on their distributor. This was done on my car before I bought it, and I plan to unravel that stuff. I would like to take the tunability up a knotch.

Although I am modifying my car, I want it to look mostly period correct. I like the low profile of the microsquirt setup, and I think it meets nearly all of my needs given that I don't need to control fuel at all. Here are some things that I would like:

major control of the ignition timing
electric fuel pump control, priming and shutoff
rev limiting (I'm interested to see how bad this will be if the carbs are still pumping fuel, I've seen the videos of flaming exhausts which isn't my end goal).
digital dashboard - I like the idea of reading and logging the various sensors from my laptop - particularly reading the AFM which is critical to carb tuning. I don't intend to install a permanent LCD monitor.

Microsquirt Box
Quad Spark or Bosch 211 unit (I would prefer to run the bosch unit unless directed otherewise)
3 coil pack, six outputs - not sure which one yet
I will make the wiring harness using the proper ends that match my hardware. Wiring will be quite minimal
I would like to add a TPS to the mix, likely from an e36. They work well with megasquirt and they are only about $35

I am really interested to know if I could run wasted COP with Microsquirt. I know that the microsquirt box won't run sequential COP, but I am assumign that Microscquirt doesn't car where the coil is located. The difference is that MS is firing one signal to a coil that fires two plugs. I'm not sure if I can split that signal to fire two coils. I believe that I may need to run two quadsparks or 211's, but I don't fully understand why. The main reason is that I could ditch the plug wires and could keep the original look and feel of the car. I would run a quad spark or equivelent inside the distributor cap and run the low voltage wires through shielding that looked similar to plug wires. Other than the bulky plug plug ends it would look a bit closer to factory. I'm still researching this option, as there doesn't seem to be much on the subject. I really wish somebody made coilpacks that looked like a distribor cap but I haven't found any. I'll be honest in that I'm a bit confused on what type of COP's I can use if it works at all. I dont want to run COP's with a bulky pack on the end. Can pencil coils handle wasted spark or is their 'duty cycle' too low?

It is possible that I may upgrade to fuel injection in the future once the novelty of my triple webers wears off. I'm not opposed to getting a more capable box when that time comes. This is a very low risk, reversible effort for me so I'm definitely going to give it a shot.
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Re: Microsquirt Wasted Spark with Carbs

Postby Matt Cramer » Tue Jan 02, 2018 9:56 am

Sure, you can wasted spark with per-cylinder coils - you just don't want to run two coils off one channel on the ignition module. You'd need two QuadSparks or two 3-4 channel Bosch modules.
Matt Cramer
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Posts: 13736
Joined: Thu Apr 16, 2009 8:08 pm

Re: Microsquirt Wasted Spark with Carbs

Postby Markos » Tue Jan 02, 2018 1:51 pm

Matt Cramer wrote:Sure, you can wasted spark with per-cylinder coils - you just don't want to run two coils off one channel on the ignition module. You'd need two QuadSparks or two 3-4 channel Bosch modules.

Thanks Matt! I'm slowly unearthign this stuff. My next area of inquiry is to determine if I can use pencil coils or if I need to use the more robust individual coils with the big pack on top.

I have an update on the TPS however. It turns out that weber makes a TPS kit for around $160.

After digging in deeper, I determined that the TPS in the kit is also used on a 90's Ford Festiva. You can buy Weber the mounting brackets from Dellorto.co.uk for around $20. The Ford TPS sensor can be found online for $12! So for the cost of an e36 sensor, I can have a bolt-on TPS with no fabrication required.

http://www.miparts.com/detail/sensor-th ... kvwnt-nHdV
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