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twin plugging an air head BMW
Has anyone out there had an air head bm that has been twin plugged, if so, how did it improve the bike from the stock single plug head ???
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I was a bit disappointed, after having my R80GS twinplugged. I thought that this would improve (reduce) the fuel consumption, but there was hardly any difference, although I also had the cylinder head smoothed out on the inside, to get the sharp edges away.
It starts better, runs a little smoother. Thats it. Although, for the 100GS it should make more of a difference. The R80 runs smoother than the R100 before any changes done. The effect is said to be much greater on the 1000cc engine. Hans |
Tom Cutter has written the book on this topic. Contact him at:
http://www.rubberchickenracinggarage.com/ Also see: http://www.airheads.org/content/view/281/98/ www.airheads.org is the only resource you need for airhead stuff... Unless you speak German, then there are a few others out there. Kevin ------------------ Kevin http://www.nohorizons.net |
I twin plugged my R100GS (Canadian model, 40mm carbs). I was told to expect an increase to power (5-10%), a reduction in fuel use (5-10%), smoother running, and less or no 'pinging' on <92 octane fuel.
I can say that the pinging on 89/87 octane fuel was reduced to the point where it wasn't a problem. Maybe a slight increase to power, Maybe a slight reduction to fuel economy, but nothing I could clearly measure. I'd do it again, but wouldn't consider it necessary unless you expect a steady diet of <91 octane fuel. |
I had the following mods done on my "89R100: 32mm heads dual plugged, polished intakes. Dyna coils. The result was sharper acceleration, with minor inrease in power and fuel consumption. Motor has to be timed -2 to -3 degrees, i can't remember which. I only burn the cheepest gas, so far i've been happy with the performance, no problems. The bike is also easier to start when cold.
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the main improovement i found with my 100 was it now starts easy peasy on the kick. also added the black box from a kickstart model which also helps.
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Been running twinn plugged since about 1992.
This summer/fall is the first time I ever have had it running well... 16 years of hassle and head-ache! I've run 800cc 8.2:1, 9.2:1, 10.3:1 32mm carbs, 40mm carbs, different air-intakes, different exhausts, jetting laborations, etc and so on... IF you are to go twinn plugged - be prepared to read-up first(!), then be prepared to get a lot of flack. The difference is 1 gearshift at 2000-2500rpm, better and easier cold starting, better burn, slightly lower mileage (some claim more - I have not experience that on my bikes). Would I twinn-plugg my next air-head ? YES! What made my air-head work as it is supposed to after 16 years of testing, reading, etc ? This did: Daniel Dicke: Doppelzündung http://www.derdicke.de/mot/img/doppelzdg.jpg This German recommendation is strickly contrary to Tom Cutter, Oak Oshlen, SnowBums writings. I have NO explanation for this. I can only say that on my R80 this did the trick. |
Mileage increase on R60/6
For what it's worth, I had my 1975 R60/6 dual plugged last winter and put about 13,000 miles on it this summer. My main motivation was to help reduce pinging, particularly as I plan on taking it through central Asia next year. I kept track of mileage both before and after and have had a 3.8 mpg increase on average. I did some other things as well and so admittedly, as an experiment, the variables have not been well controlled. I did reset carb pins to a leaner setting when at higher elevations throughout the summer and switched back from electronic ignition to points at the same time as the dual plugging.
Was it worth it? I think so. It certainly has made a huge difference in the pinging, I think I have more power (hard to say) and there seems to be an overall increase in mileage. It is interesting in that after doing a bit of rough road riding, I notice that it was vibrating and running overall crappy. A little investigation showed that the bottom left wire had been snagged and pulled off the plug. Put the wire back on and back to smooth... so yes, there must be a power difference between single and dual plugging. But maybe not much. Oh yeah... and be prepared to take crap from those who haven't done it. |
BMW themselves released the cure for pinging, cylinder base gaskets at about £7 each.
I have asked on the BMW forums, and no one has answered. Why do BMW's need dual plugging? Other air cooled bikes seem to manage fine without. It does allow later ignition timing, but I sometimes wonder if the timing was retarded without dual plugging wouldn't it still allow the engine to run smoother. It seems to me abit like the big bore kits. The extra CC's produce less power than the original cc's.. IE 20% increase in swept volume=15% increase in 'claimed' power. Mostly things claime dby people who do teh conversion come down to it 'feels like' so and so is better. I can positively state here, every time I clean my bike it feels like it is 5mph faster in all gears, and runs smoother. Very rarely do you get a catagoric measured difference. If you dont belive me try for your self. clean your bike , check the oil and air pressures and ride, It will feel better. As an aside, on top gear they did a test recently and spent £15K adding go faster bits to a car. The road test speed increase was barely measurable. The most effective thing was doing a standard service. |
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Who need dual plugging?
I guess the general consensus is that not all airheads need dual plugging. Not sure that anyone ever said that they did. Mid-late 70's high-compression models are the only ones I know that really benefit from it. They don't do well on swill, and often ping on even Chevron Superduper when under load. Dual plugging helps there. The thicker base gaskets lower the compression but can also lead to lower combustion temperatures, increased carbon, pre-ignition and eventually higher compression and here we go again.
When looking for a bike for my trip, I was trying to avoid one with a high-compression engine, but got swayed by the other good characteristics of the /6's. I figured that dual-plugging needed to be worked into the cost of the bike. And pinging my way all the way up the hill to my house on it's maiden run was just as expected. Had it dual plugged and now it's quiet even on regular. :thumbup1: That's all I know. Don't know about big bore kits or 15k go-faster kits. |
The Egyptian Police commissioned a special edition of the R80. 800cc barrels with 1000cc 44/40 heads and 40mm Bing carbs.
This should result in about 7.0:1. This edition was only made for and sold to the Egytian Police. To get the best mileage L/dollar one needs to raise the compression ratio. The plug is places off set in the beemer and VW air-cooled heads. Krauser 4-valve heads have the plug placed at the center which is the best position. The 1200 oil-heads have 11:1 and dual plugs... Recomended reading: * 4-stroke performance tuning, Graham Bell, Haynes Books * Internal Combustion Engine Fundamental, Prof Heywood, MIT. * Oak Oshlen - Dual Plugging * Tom ... ABC home-site - Dual Plugging * Snowbum - Dual Plugging * Daniel Derdicke - Dual Plugging * Technik BMW 2-Ventiler etc Then test a dual-plugg vs a single plugged; do not guess - test and try for yourself before you decide what you think about 4 vs 2 plugs on the 2-valves. As far as I know there are no available Dyno Tests on signle vs dual plugged 2-vales. All I have found is one (1) test, and that was on a Duccati by an American motorcycleshop. |
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You can't just dual plug and ride off. You then need to reset the idle ignition timing and limit the amount of ignition advance. |
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If you spend the same amount of time doing a normal service ( include diaphragms, needles and needle jets I believe you will get the same or better results. Running a low compression will reduce the mpg slightly, but early post war 1945-50 Triumphs had 7:1 and would run happily on 'pool pertrol' ( 65 octane). One of the reasons I chose my BMW was because that model was designed fo modern fuel and has an 8,2 CR. It runs absolutely fine on 3 star. It has been stated that the pre monolever bikes with high compression engines are the ones with the problem. To fix the compression ratio ( poor modern fuel) problem lower the compression ratio with BMW's own fix at £7 a go. Spend the rest on petrol and beer. Only BMW's seem to suffer, no other biking forum I am on mentions it. I think in part it is caused bytheir use of a wasted spark which heats up the plugs more than a non wasted spark system. |
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When I changed from Bing 40 (worn) to dell'orto PHM 40 (new) mileage dropped from about 6.5L/100km to about 5.6L/100km. The dell'ortos are tuned for 8.2:1 single plugged heads and were used with dual-plugged heads with 10.5:1 (venolia pistons) 45/40 highflow valves... my plugs were quite black... so mileage will be much better when the carbs are properly tuned. BUT - as you point out; not even I have tested to run my engines with single properly tuned and then retuned to the dual-plugged heads. The only "testing" I have done was back in 1992/93 when I did not have the dual-pluggin set-up - my bike consumed about 6.7-7.0L/100km and dropped to about 6.5-6.3L/100km when the second plug was activated. Coincidens ?... The bike have been running really hot causing lots of overhauls and repairs since 1992 - up till this very summer, 2008, when I fiddled with the ITU in accordance to Derdickes homesite/tips - now it is running well, but mileage is still at 6.4L/100km or so (and topping 6.7 or there about now at winter with the studded tires). Summation: - I agree. On what does these milage claims rest ? Service, wishfull thinking or facts ? - If there are solid facts; please do present them -:) - My view on dual-pluggin does however remain as solid as ever; I'm for it -;) |
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