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Discussion in 'Old's Cool' started by supershaft, Jun 10, 2011.
He is correct. NAPA stocks a high quality Belden solid strand wire that is sold off of a spool.
What Craig explained to me was that the combustion chambers were redesigned for the gas and running the unleaded stuff in the earlier engines were the ones benefiting from dual plugs.
Any hemispherical chamber with a domed piston will benefit from dual plugs. Fuel burn rate is no longer tied to octane as it once was. There's a myriad of chemicals in "gas" that can be used to tailor flame speed. Pump fuels are are designed for new engines which sport very small,compact combustion chambers and through design promote turbulance. Very hot ignitions are used to light difficult to ignite lean mixtures for emissions standards. Did you know fuels are held to emissions standards too? Large displacement hemis require large valves to work well and because of this a centrally located plug is often difficult.
Some engines with very large bores benefit from dual plugs as well. Rotax,Honda and Kawasaki all have had models with dual plugs from the factory.
Anyway this leaves those of us with old vehicles with an issue. Rotten combusion,detonation and poor starting. Compounded by poor ignitions. To put it simply lighting from both sides and meeting in the middle promotes a more complete burn,more torque and easier starting. From the flame front's increased exposure to the charge the burn is completed faster thus retarding timing is needed to allow peak cylinder pressure to occur at the right time. It also allows throwing some fuel at it for a few more ponies. Makes the engine more tolerant of crap gas as well allowing those economically minded individuals to run regular w/o detionation if they tune for it.
just to show ya there is nothing new under the sun................
I've never taken an electronic bean can apart beyond prying the inspection door off and spraying the guts out with contact cleaner. Planning to dual plug the GSPD when it goes back together (using a pair of brown Dyna 1.5ohm coils because A. I have them [thanks Rapid Dog] and B. The GSPD has run for 40k miles with a 3ohm Buell coil without issue) and am wondering how to achieve the necessary advance curve to suit dual plugs. My only experience with dual plug ignition involved the pre '79-style whose exposed advance weights and springs were fairly easily modified to suit.
Can similar simple spring and post tricks be played with the advance mechanism in the bean can electronic ignition units?
My limited understanding (based solely upon what I've been told and what I observed through my arse at tracks like Grattan, where I was sure my single plug engine pulled harder at the top end, though softer off the bottom) is that the stock curve is useful from idle but needs to be contained 4 degrees or so at maximum advance.
I am at your mercy. Do your worst.
No need to over think it? And you are bringing Snowbum up in the same breath? Basically, coil wise, I am following the bum's advise. Like I have always said, he makes sense half the time. Not that he came up with the notion to try to keep the coils at the same resistance but . . . . I am sticking with Dyna brand wise, however. I like the way Dyna's fit and how the plug wires attach. Plus, I have a lot of experience with them and know they are good coils.
Same resistance or not, I don't know anybody that runs points dual plugs without a booster. Rick and Chris sure use them with points. I have seen points fail real quick when the booster fails (they use to on a semi-regular basis).
Timing dual plug? That's where I part from the bum, Oak, and Cutter although according to, I believe, the latest dual plug plug article in Airhead tech, Cutter came around to leaving the timing stock at idle like others have been doing for some time. Snowbum mentions that method but then goes on and on about the older Oak advise of backing the timing back off from idle on up and then goes even further backing that method up more with some bad theory. His theory has some serious flaws that show in his advise. I think Yunick and Dr. Curve have a lot better grasp of what is really going on in there and explain it better to boot. Denish in The V Twin Tuners Handbook II explains the theory well too. So does Cameron but I think he falls a bit short on rod length ratio concepts.
I guess Snowbum's dual plug article is where the often repeated story of Bosch no longer making non-resistor plugs got started? That's another myth.
It seems as if your great detective work DM has also broken the heavy veil of secrecy surrounding my identity. Man you guys are good! Nevertheless, it is supposedly strictly against forum rules to bring up other forum's content such as your Funholi . . . although I sometimes wonder if the rules mean anything around here. IMO, there are good reasons for them and that is why I am here and not there. Despite an idiotic conspiracy theory to the contrary, my identity has NEVER been a secret. I just choose not to use it openly on the idiotnet as do most others. Let it go.
I forgot to add that good plug wire is hard to find sometimes. I use /2 BMW wire readily available at dealerships and the price is fair.
The advantages of dual plugging are really the advantages of running higher compression. It improves off cam performance and midrange the most but it surely doesn't hurt high rpm performance either. Snowbum claims that single plugs work better at high rpm and they don't. Most dual plugged race engines are not that concerned with low rpm performance. XR750 Harleys are a perfect example. Absolutely everyone has been dual plugging them for decades. Drag race engines are another perfect example.
Restrict (don't extend it like Snowbum suggests) the curve by bending the weight stops. Extending the curves rpm range is tougher because the weights still need to hit the stops but you do it the same way by removing weight and testing.
Lighten up a little, Shaft. I've enjoyed reading your posts on both forums.
I agree with you regarding restricting the advance by bending the stops. I tried just retarding overall timing when I first put my RS back together, but I didn't like how it idled and started.
To me, bumping the compression and dual-plugging is a no-brainer to squeeze more power from today's alcohol fuel blends that have less energy per unit of volume.
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.
It sounds like I need to in your case DM. Thanks for the heads up! Surely you can't blame for being a bit touchy for all the crap I still get from some of that crowd.
They run so much better not timed like Oak, Snowbum, and Cutter suggests from their articles that I have read.
Now that's a loaded comment! Your bucking a lot of airhead tuners as well as tuners and designers of other engines from all across the motorsports spectrum.
Trend? How many decades does it take to not be considered a trend any more?
I would love to see it!
Sounds like you're a devotee of Mr. Chapman.
Mr. Moore, can you please elaborate? I'd love to hear more from a man of your experience.
To me, the dual-plugging and is an inexpensive way to increase combustion efficiency without spending huge dollars, or pounds, on a set of custom pistons. I'm working with factory BMW parts.
I'm going out on a limb here and guessing that ambient temps and fuel quality are likely factors in Mr. Moore's tuning direction. Cooler temps and better fuel (in addition to Mr. Moore's attention to detail in the combustion chambers) might just negate the pressing need for dual plugs?
Anecdotal and completely accidental evidence - My bike runs fine with single plugs at comparatively high compression ratios. And it runs even better in the cooler months. I'm dual plugging in hopes of finding even higher levels of efficiency throughout the rev range. My local HP guru has been advising it for years.
Please don't make me close this thread. Leave the baggage of other forums behind, please.
Supershaft, can't answer your original question, however I mucked around quite a bit with spark timing when I dual plugged my 1981 R100RS (first of the bosch electronic ignition with hall effect beancan) including conducting an experiment to work out which was better: Stock beancan with timing retarded at idle or modified bean can (weights/springs & travel) with timing at idle set to around normal.
Did back to back dyno runs with both beancans. The shape of the charts were crap for other reasons but they did serve to illustrate the difference between the two timing approaches. Though not fully definitive, the test showed that leaving the timing at idle close to the stock figure and modifying the beancan to stretch the timing curve up to a maximum of 28-29 degrees resulted in a marked improvement over just retarding a stock beancan. The magic 28-29 dgrees is a number that quite e few people have independantly arrived at.
Bit off topic but folks might find it interesting.
I wrote about it in a blog including details of how I modified the beancan, too wordy to repeat here but here's the link:
BTW, I took the advice readily found from sources already mentioned and used 2 x 0.7 ohm twin post coils in series, copper leads and 5000ohm NGK caps. The coils are PVL, which is a tried and tested brand popular in Europe and available here in Aussieland from a couple outlets. Keep in mind, this is for post 1981 bikes with the Bosch electronic ignition.
I tried dual plugging but saw no benefits what so ever. I used the 6v aircraft coils supplied by Steve Scriminger http://www.scriminger.co.uk/10380/info.php?p=8&pno=0
Don't waste time messing with your bean can settings. Boyer do an ignition module replacement (with the correct curve for dual plugged airheads) and will even supply it with a pair of coils for less than $200.
As do Silent Hektic, Omega, Dignition - All of whom offer a range of curves to choose from. But thats all too easy! What's left for us incurable fiddlers to fiddle with? Ok..don't answer that..
Actually, the beancan mods are pretty straight forward if you have an ounce of mechanical nouse. Cheap fun for this little black beemernerd.
Interesting link BTW
The valve seats were changed for unleaded then changed again by the time it got to your model.
The combustion chamber shape is AFAIK identical to other models.