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Old 06-13-2011, 04:41 PM   #76
anotherguy
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Now that's tuning. Maybe I oughta buy an Airhead Beemer. Looks awful familiar.
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Old 06-13-2011, 04:57 PM   #77
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Quote:
Originally Posted by kbasa View Post
On modern BMW twin spark bikes, the timing of the plugs is controlled independently. IIRC, at low rpms, the sparks are timed apart from each other and, as rpms increase, they gradually get to a point where they occur simultaneously.

My understanding was that this was due to lower amounts of combustion chamber turbulence at lower rpms. I'd have to go back through the old BMW stuff I've got to try and find an answer. I'm not sure I've got paper brochures that speak to this.
I am out of the loop right now but up until just recently I had never heard of that in BMW school or anywhere else. I am thinking it would have to be R12's and later? It would still be news to me. Officially I am R12 certified although that doesn't mean much. I would like to see the info on that. Talk of multi-fire dual plug or not has been around for a while but I have never actually seen any of it before. I new one guy that talked about it all the time but he had a supersonic flow bench too!
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Old 06-13-2011, 05:05 PM   #78
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Quote:
Originally Posted by adrenal View Post
That's one of the advantages of modifying the bean can - you can get an infinite number of timing curves but it requires experimentation.

Would be interested to hear more details about what curves you've seen worked best.

Everyone talks about Boyer, I'm not sure what their latest version has to offer re selectability, but as you are probably aware,there are a number of other options with quite a selection of 'canned' curves as illustrated in the graph below, some of which have been specifically designed for dual plugged airheads.

I borrowed the graph from Basic Gerd's site http://www.zeebulon.de/Mot/bmw_r80gs.htm and added the curve from my modifiied can. Great site, particularly if you understand German!

The black curve labled Serie is the stock airhead timing curve.


I will probably shoot for something around the Two Dignition curves starting at six and ending at around 28.
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Old 06-13-2011, 06:31 PM   #79
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Quote:
Originally Posted by supershaft View Post
You have got to remember that power is relative. You might not have had less top end power at all but more power elsewhere made it FEEL like less on top. I have seen the reverse of that so many times. No you don't have tons of top end power, you just have a lot less midrange!
Yep been there with other mods like 'Y' pipes.
I thought the bike was going really well in the upper midrange and top end cause it kicked at 4,250rpm.

When I measured it all that was happening was a lot of noise and getting back what I had before I created a hole in the power cure with the 'Y' pipe.

With single plug setup I could pull valve bounce in 5th.
With dual plugs 8,000 rpm in 5th was the limit.
No other mods were involved at that time.

Nothing I was capable of doing tuning carbs and ignition could get me back to exceeding 8,000rpm in top with the dual plugs.

I was not motivated to have a 200kph+ dirt bike that ate valves so I'm not saying it's impossible.
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Old 06-13-2011, 07:01 PM   #80
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I would blame your ignition and not dual plugs. There are too many dual plugged machines that don't suffer anything at all like that.
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Old 06-13-2011, 07:32 PM   #81
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Originally Posted by supershaft View Post
I would blame your ignition and not dual plugs. There are too many dual plugged machines that don't suffer anything at all like that.
What area of the ignition would you suspect?
The coil block I'm using is a general motors part for their V6 engines, cut down to 4 outputs wired in paralell.
Each block either upper or lower plugs so live & dead spark on each for load balance , leads are copper , resistance across the coil with leads is 22k.

Trigger is bean can modified advance and ICU is stock. I have no reason to suspect the ICU but a swap out of both ICU & beancan does not alter the picture.

What's the go with plug leads copper or composite graphite?
I've tried both and can't tell the difference.

Happy with what I have but always open for improvement.
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Old 06-13-2011, 08:40 PM   #82
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Old 06-13-2011, 08:43 PM   #83
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I would suspect that coil since that is the only part I have no experience with.

I do not like graphite wires. They do work while they are working. Other than that, I have nothing good to say about them. No one that I know uses them on anything serious.
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Old 06-13-2011, 10:07 PM   #84
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If you're only running the one stock ICU, I'd suspect that as the reason. The extra two sparks do make a big difference, and at higher RPMs much more current is needed. Try an extra ignition amp.

Quote:
Originally Posted by Rucksta View Post
What area of the ignition would you suspect?
The coil block I'm using is a general motors part for their V6 engines, cut down to 4 outputs wired in paralell.
Each block either upper or lower plugs so live & dead spark on each for load balance , leads are copper , resistance across the coil with leads is 22k.

Trigger is bean can modified advance and ICU is stock. I have no reason to suspect the ICU but a swap out of both ICU & beancan does not alter the picture.

What's the go with plug leads copper or composite graphite?
I've tried both and can't tell the difference.

Happy with what I have but always open for improvement.
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Old 06-13-2011, 10:17 PM   #85
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I have never seen that done. Who runs them like that? Is it hard on the halls effect?
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Old 06-13-2011, 11:21 PM   #86
adrenal
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Quote:
Originally Posted by supershaft View Post
I have never seen that done. Who runs them like that? Is it hard on the halls effect?
SS, if you are talking about the 2 x Ignition Modules (amplifiers) in parallel, this is apparently not uncommon practice in Germany. But downside is that you are drawing twice the beans from electrics - approx 150W which has other ramifications.

There is a discussion of it here by Basic Gerd (scroll down a bit):
http://www.advrider.com/forums/showt...=476893&page=4

Gerd himself did not go down this path as he was happy with results from PVL coils and 1 x amplifier as I was.

As with all these discussions, what works is as much a matter of what your trying to achieve e.g. chasing micro HP at the giddy end of the RPM range for racing or looking at producing a more robust, tracktable street machine...etc etc

Pardon me wirespokes - I butted in!
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adrenal screwed with this post 06-14-2011 at 12:09 AM
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Old 06-14-2011, 09:02 AM   #87
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Thanks! I have never had an issue with the stock charging system but if I do have a issue with my new ignition setup, I can always update my charging system for two ICU's. It sounds like the hall effect sensor does not care how many ICU's it is squaring off its signal for.

I truly am a revver so I will soon have my own opinion of how the .7x.7x stock setup deals with high revs! If for nothing else but bikes handle way better way revved! Especially beemers!
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Old 06-14-2011, 12:04 PM   #88
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Quote:
Originally Posted by moorespeed View Post
I have never found a need to twin plug, on my road or race engines, and I now have over 100bhp at the rear wheel. you need to look closer at combustion and not follow the trend like sheep.
Just enliven this discussion, Dirk Scheffer of Edelweiss Motorsport is claiming 108ps. It looks like he is in the flock of sheep that uses twin plugs.

http://www.tourenfahrer.de/index.php?id=152

Ok, ps and hp aren't exact, but they are close. 1 horsepower = 1.014 PS


Edelweiss Motorsport:

http://edelweiss-motorsport.de/class-motorrad/

Moorespeed Race/Rally Fabrication and Tuning:

http://www.moorespeed.co.uk/
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Old 06-14-2011, 02:34 PM   #89
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That was a good read of an older post you linked adrenal.

I learned a LONG time ago that a big fat blue spark wasn't the best deal right after I put a CDI ignition on my two stroke. Way smaller LOOKING spark, way more power. Burning alcohol is another story! Well, that story is really more like my dad putting a CDI on my two stroke! I was doing a lot of things to my dirt bikes at a very early age but my dad always timed them himself till I was out of high school!
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Old 06-24-2011, 06:47 PM   #90
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For those that are interested, there's a schematic for wiring two ignition modules in parallel and other info on modifying the bean can here:
http://www.derdicke.de/mot/dz.html
Though in german, can still get the jist.
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