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Old 03-30-2015, 09:23 AM   #1
DiabloADV OP
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Dual Plug ignition curves

Here are some dual plugged ignition curves.

My application: Seibenrock 1000 kit in a 90/6 block, at a claimed 9.5 compression.

What are the experts thoughts on these curves?

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Old 03-30-2015, 10:57 AM   #2
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Hello, I only have questions, no answers...

Would you mind giving an ignition curve 101? I only just read the wiki page. Did you measure the curves yourself? If so, how is that done?

I can only say the plot looks messy to me. What do the curve numbers refer to?

Single vs dual plugging timing is not different, is it? Maybe you need a slightly advanced timing to make better use of the double-size spark. I'm just guessing.

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Old 03-30-2015, 12:21 PM   #3
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These are selectable ignition curves in the Sachse ignition system.

The standard advice is that dual-plugged advance should peak at 28 degrees. But that advice varies depending on the application...
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Old 03-30-2015, 12:23 PM   #4
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I see we both got our packages from Germany, yah?

But, I am confused. Where is this graph from? Is that what I have or do I have the 7 single plug curves and the two dual plug ones? (I know you don't have the answer to that)

On your graph, I would think curve 3 would be the conventional choice. 5 degree at low rpm, rising quickly, and topping out 28 degrees at 4000.

I've been running #6 (pretty sure now I was looking at the wrong graph) and it does seem like it is too much advance at low rpm.
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Old 03-30-2015, 12:31 PM   #5
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Did you ask for the dual-plugged kit, or the standard?

EME's unit is their own spec...includes single and dual. Otherwise it's the same as Sachse.

Buying direct from Sachse, they sell a single setup and a dual setup, separately. Same hardware, just different curves to choose from.

I ordered the dual kit, and this is the chart they set me. The single plug choices are on their website.
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Old 03-30-2015, 12:41 PM   #6
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I got the dual, but no chart.

I would take a pic of my black box and we could compare, but it will be a few days before I get at it again. The scribble on the label is hard to figure out.

Your selector on the back has exactly nine settings of the arrow, or does it have more?
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Old 03-30-2015, 01:35 PM   #7
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I emailed them asking for a dual-curve chart, and this is it.

Box has "BMW DZ" written on it by hand. DZ is the dual-plug version.
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Old 03-30-2015, 02:43 PM   #8
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They actually look rather similar to my current map up to 100mBar (or full throttle naturally aspirated - North of that timing retards uniformly).
I'm also referenced by throttle state, but in general purple green would be similar to modest throttle accel, red under higher feed.
We're you wondering which one to use?
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Old 03-30-2015, 02:56 PM   #9
chasbmw
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Finishing at 28 degrees should be the important bit.

Try the 2 alternative curves, see which one feels better.

I did a couple of back to back dyno runs at 26 and 28 degrees, the run at 28 degrees was the more powerful, but not by much and not enough so you could feel it. This was using a Silent Hektik ignition. All figures in rear wheel HP.

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Old 03-30-2015, 03:53 PM   #10
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There are three choices that go to 28 -- they differ in how fast they get there.

All else equal, would higher compression mean you want to get there faster or slower...?
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Old 03-30-2015, 04:12 PM   #11
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The Guzzi world is no different. Dual plugging goes on with all the expense and inconvenience by those with no understanding of what it does and the advantages it may bring.

As usual the multiple curves only have 2 or 3 that are even remotely possible.

Think about it. A dual ignition source should mean the expanding gases exert pressure on the piston taster. Your static timing should be just slightly retarded from your OEM static timing. Full advance should be around the same as OEM but it should reach it at slightly higher revs.

That should cut your options down to a single curve.

A slight change in compression will only have a significant effect if the heat from the compression ignites the mix before the spark has its chance. The curve is then irrelevant.
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Old 03-30-2015, 07:08 PM   #12
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Quote:
Originally Posted by anderstornvig View Post
Hello, I only have questions, no answers...

Would you mind giving an ignition curve 101? I only just read the wiki page. Did you measure the curves yourself? If so, how is that done?

I can only say the plot looks messy to me. What do the curve numbers refer to?

Single vs dual plugging timing is not different, is it? Maybe you need a slightly advanced timing to make better use of the double-size spark. I'm just guessing.

Thanks,
Anders
The numbers up the left side are degrees of spark advance. Along the bottom it's RPM.

The timing does need to be different when dual plugged. Back in the late 70s or 80s when guys first started dual plugging, they timed them at TDC, or even retarded, at idle because they felt the fuel ignited so much quicker. And at full advance they found it best to retard the timing a few degrees.

Now days, things are different. We've all discovered that the airheads run best with static timing close to stock, full advance around 28 degrees, and limit full advance till another 1,000 RPM higher - around 4K.

These graphs, as you might have already figured out, display the different timing curves available in this particular electronic ignition that doesn't use the stock mechanical advance mechanism.
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Old 03-31-2015, 01:04 AM   #13
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A dual plugged bmw will start easier and will be smoother, it probably can be jetted a bit leaner, especially if the jetting has been set a bit rich to dampen down pinging.

The main advantage of dual plugging is that it can enable you to run a high compression ratio (9.5 or higher) on any old fuel without the risk of pinging, if combined with other engine tuning such as flowing the ports you can end up with an engine that works much better than stock. This was the reason why some racing cars( Jaguars) used dual plugging despite using old fashioned high octane fuel.

Some tuners reckon that dual plugging can be avoided if the bike has a tight enough squish band that creates enough turbulence in the combustion chamber to prevent pinging.

Back in the day dual plugging timing was a bit hit and miss with various methods used to alter timing, many people just set the full advance at 28 degrees and let the static timing fall where it may. Nowadays we have proper electronic ignitions with a choice of ignition maps.
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Old 03-31-2015, 04:58 AM   #14
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Are you tunning a 336 cam in there Chas?
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Old 03-31-2015, 06:26 AM   #15
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Are you tunning a 336 cam in there Chas?
No, the bike is running the SR 1070 kit including the SR assyemtrical cam. Jim cray built it and as part of the build balanced the engine and ported the heads. It also has a proper 40mm exhaust with Jim's Keihans sports silencers and a pair of 38 mm Dells.

But The bike I use more is my 90/6!
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