CDI box

bspower · Post by **bspower** » Wed Jan 28, 2015 1:25 pm

I am currently trying to tune a cbr600f4i engine with the megasquirt 3 pro and i was wondering if anyone knew if i had to use a CDI box or not?

I was told by several people yes and a couple no's as well.

thanks

dontz125 · Post by **dontz125** » Wed Jan 28, 2015 6:20 pm

I *believe* the CBR coils were inductive, so a CDI box wouldn't be particularly efficient (high primary resistance). What you DO need is a coil driver box like DIY Autotune's QuadSpark. The MS3Pro doesn't have on-board high current coil drivers, so you need an external unit to actually switch the coils on and off.

ewflyer · Post by **ewflyer** » Thu Jan 29, 2015 12:54 pm

I'm using ’05 Honda CBR-600RR (Denso Corp.) Coil on Plug sticks and a DIYAutotune Quadspark box on my current motorcycle project (Suzuki GSF400 Bandit), running in Wasted Spark mode. Works fine so far.

This project is still a work in progress, I'm looking forward to springtime weather so I can get back to riding and tuning the bike. I've got the dwell set at 2.5ms right now (I'm taking a conservative approach in the early days of this project) but my internet research has shown me that people tend to run the CBR600 coil sticks at 2.8 to 3.0 ms of dwell.

I'm guessing that using a dwell time of up to 3.0 ms would be okay based on the math: The GSF400 engine redlines at 14000 rpm, so 60,000 (milliseconds in a minute) divided by 14000 means each 360 degree rotation of the engine takes 4.286 ms.

bspower · Post by **bspower** » Tue Mar 17, 2015 8:28 am

i am running a QuadSpark with the MegaSquirt, however i was unaware that i would need an external unit to switch them on and off. i feel no question is stupid so why would i need to switch them on and off?

elaw · Post by **elaw** » Tue Mar 17, 2015 8:59 am

The driver takes the place of points and condenser on older systems. It turns the current in the coil primary on and off to create the spark.

The quad spark *is* a driver, so you should not need anything additional.

A CDI box is a different kind of driver (and should only be used with CDI-specific coils) and would take the place of the quad spark.

ewflyer · Post by **ewflyer** » Tue Mar 17, 2015 9:30 am

bspower wrote:i am running a QuadSpark with the MegaSquirt, however i was unaware that i would need an external unit to switch them on and off. i feel no question is stupid so why would i need to switch them on and off?

Well, not quite sure where the logical disconnect actually exists, but maybe this will help: the QuadSpark is the "external unit" so you've already got the necessary hardware in hand. As Dontz125 pointed out, the MS3Pro doesn't have on-board high current coil drivers. And the statement, "switch the coils on and off" refers to the act of Dwell-timing your CBR600 coils (so they fire the spark plugs with the necessary/optimal amount of energy).

In the case of your setup, MS3Pro-to-Quadspark-to-CBR600 stick coils, this means: The MS3Pro is wired to the QuadSpark by nothing more than 5Volt "logic level" inputs, these logic level inputs ("on" = 5Volt, "off" = 0Volt) control the length of time the QuadSpark will Dwell the CBR600 coils (dictating how long the QuadSpark should ground each CBR600 coil to negative/earth, allowing 12Volt current to flow through the coil's primary winding before removing that ground which causes the electrical field in the primary winding to collapse, which causes the coil's secondary winding to do the same at a much higher order of magnitude which fires the spark plug).

Firing spark plugs is a messy, high-power business (an electrical storm in miniature, thousands of times a minute). Because of this it's simply a safer/simpler choice to keep it at an "arms-length" from the vehicle's ECU.

dontz125 · Post by **dontz125** » Tue Mar 17, 2015 9:37 am

bspower wrote:i am running a QuadSpark with the MegaSquirt, however i was unaware that i would need an external unit to switch them on and off. i feel no question is stupid so why would i need to switch them on and off?

The MS controls the QuadSpark, the QuadSpark switches the current on and off through the coils. If you're not sure why the current is switched, do a quick bit of reading on Kettering ignition systems.

bspower · Post by **bspower** » Tue Mar 17, 2015 11:16 am

Thanks guys i just keep having people tell me you need a CDI. I always thought the quadspark and stock denso coils that came with the bikes were fine.

dontz125 · Post by **dontz125** » Tue Mar 17, 2015 1:22 pm

Part of the problem is that, over the years, the black box on EVERY bike became known as "the CDI", even when it was actually a TCI / Kettering system. The fact that the two systems are very different, don't work the same way, and WON'T work if you try to wire one up as though it was the other has created a great deal of confusion for many people.

Based on the PM you sent me earlier, you have exactly what you need to fire your bike's plugs.

kaeman · Post by **kaeman** » Fri Mar 20, 2015 9:14 pm

nope just use the Quad spark and the denso coils you will be fine.

Fabius72 · Post by **Fabius72** » Sat Mar 21, 2015 4:51 am

ewflyer wrote:I'm using ’05 Honda CBR-600RR (Denso Corp.) Coil on Plug sticks and a DIYAutotune Quadspark box on my current motorcycle project (Suzuki GSF400 Bandit), running in Wasted Spark mode. Works fine so far.

This project is still a work in progress, I'm looking forward to springtime weather so I can get back to riding and tuning the bike. I've got the dwell set at 2.5ms right now (I'm taking a conservative approach in the early days of this project) but my internet research has shown me that people tend to run the CBR600 coil sticks at 2.8 to 3.0 ms of dwell.

I'm guessing that using a dwell time of up to 3.0 ms would be okay based on the math: The GSF400 engine redlines at 14000 rpm, so 60,000 (milliseconds in a minute) divided by 14000 means each 360 degree rotation of the engine takes 4.286 ms.

I'm also running CBR-600RR CoP (installed four years ago) with bip373 drivers put on the MS2 case. Many thousand KMs made with no problem.
So I could confirm that we don't need a CDI box.

About dwell time, I have taken a picture showing my o-scope.
This is the shape of the current flowing through the coil.

Bobine CBR600 - dwell.JPG

After the point marked by the red arrow, the current stops rising.
Since I have taken this shape as standard to make calculations for all volts during tests, could someone please tell me if this is a too late point or just right?
Thanks.

Just to share, these are the values that I found for that type of coils:

2.3ms @14.4v

V --- ms --- % --- TS table
06 = 5,4 = 235 --> 236
08 = 4,5 = 196 --> 196
10 = 3,6 = 157 --> 158
12 = 2,8 = 122 --> 126
14 = 2,4 = 104 --> 104
16 = 2,0 = 87 ---> 86

Cheers,
Fabio

dontz125 · Post by **dontz125** » Sat Mar 21, 2015 4:07 pm

That's a beautiful shot of the current as the coil goes into saturation, where current flow is now purely based on the resistance of the circuit - thanks for sharing! Assuming the horizontal ticks are 0.1ms, you could probably back off 0.1ms without changing anything, but you aren't at the point where you're overheating your coils or drivers either. It ain't broke, don't fix it!

Fabius72 · Post by **Fabius72** » Mon Mar 23, 2015 3:08 am

dontz125 wrote:...but you aren't at the point where you're overheating your coils or drivers either...

Thank you Don.
Fabio

bspower · Post by **bspower** » Mon Mar 23, 2015 11:43 am

Thanks for sharing Fabius thats useful info for me as well

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