Dual spark plugs?

[RIDE-RED 350r]

dual plugs on this work just fine

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That cylinder looks very Honda-ish.... And further, looks very ESR-ish/CT-ish/Pro-X-ish (pretty much one in the same as last I knew they all use the same big bore cyl castings).... PLEASE tell me you didn't cut up a set of 250r cases!!! Hoping it is a CR based build...

Either way, fricken cool!

 

[spencerpaving]

You have a good eye....cr based...esr 350

 

[RIDE-RED 350r]

You have a good eye....cr based...esr 350

Very nice!

The ATC250r in my avatar pic has an ESR 350 top end in it as well... As much fun as that engine is in my trike, I can't imagine what it's like in a saw!! Nicely done Sir!

Have you run it on a dyno??

And if it's not being too nosy being a race saw and all, I'm curious as to what porting, carb and dome you are running...

My trike is running a 41.2mm Keihin PWK carb, Eddie Sanders trx9 (mid-top) porting, ESR reedblock (very similar to V-force), 108 oct or higher race fuel dome, and ESR ATC5 pipe and silencer. Thing rips! It takes a pretty stoutly built 450 to outpull my ATC. But it takes nothing short of a Farmall 856 wheel weight hanging from the bars to keep the front end planted as you go up through the gearbox.. LOL!

 

[spencerpaving]

Trx 11 porting...44mm carb...my own pipe

 

[RIDE-RED 350r]

I had a hunch you might be running drag porting in that bad boy!!

 

[Backyard Lumberjack]

Whether it would work or not I will leave to the experts, however, putting spark in another area of the combustion chamber can have an advantage. Such advantages are either to put spark in an area that has to have excessive flame travel to get the fuel burned. Secondly to have more, though not necessation hotter, spark to light heavy or large loads of liquid fuel. Though often hotter is better for this, it takes more juice, so like positive displacement superchargers, the gain must outweigh the power loss detriment. Emissions are likely less as well, though not necessarily.

>Secondly to have more, though not necessation hotter, spark to light heavy or large loads of liquid fuel.

liquid fuel will not burn! only a gas will burn.

but, if there is one I am not familiar with, please tell more about it. a supercharged engine merely has more air/fuel gas... (not meaning gasoline, but the vaporized fuel and air) ie, denser. ie, bigger bang. an additional spark can be as u say, advantageous help flame front... and that is one reason the MSD 6A, for example, wakes up driveability. bit more piston pressure. the MSD 6A will fire the plug 6 times per cycle under, 2500 rpm or so... and above increases the spark dwell. u can hook a car up to a auto clinic type scope and in OFF mode it will show single plug firing on scope... turn it on to MSD and u get 6 blips on scope... per cyl. dry fire an elec or point trigger... and it goes click click at the plug... plug out of engine and grounded... wire in the MSD and it goes ba-rrap! ba-rrap! you can actually hear the plug fire six times...

 

[Backyard Lumberjack]

Great looking saw!

really is! no doubt about it! very interesting, wonder if u can tell us more about it? any vids of it running and/or cutting... almost looks like a racing kart engine modified to power a bar and chain... is the PTO drive direct, ie... no clutch?.... can you tell us approx. hp? and fuel? I assume u built it and compete with it...

 

[spencerpaving]

 

[Chris-PA]

I think that whether it's an advantage would depend on things like the velocity of the flame front. I did a little web searching to try to get some numbers good enough for back-of-the-envelope calculations, but it clearly pretty complicated as the speed depends on many variables. From what I see the flame speed is very slow mediately after spark/ignition, then increases during the main part of the burn, tailing off again as the available fuel is reduced and the mixture leans. So the question is whether igniting it at two places would help? It sort of seems like you'd have two slow flame fronts after ignition and it's hard to see how that would help, given the combustion chamber is small and compact with a centrally located plug, especially considering the cost/weight/complexity of implementing it.

However, most of what I found is for 4-strokes, not 2-strokes at 10,000rpm. With only around 2ms to complete the process, where is the flame front when the exhaust opens? I've seen some evidence in the carbon patterns on the piston top showing shadowing from the ground electrode that there is not much more than the initial flame propagation, and that there isn't much time for mixing and more complete combustion. But that was hardly much of a test and only one unit - maybe the timing was not set well.

Twin plugs in vehicles are usually used where combustion chamber shape is poor, like on rotaries or other elongated shapes.

 

[sawfun]

>Secondly to have more, though not necessation hotter, spark to light heavy or large loads of liquid fuel.

liquid fuel will not burn! only a gas will burn.

but, if there is one I am not familiar with, please tell more about it. a supercharged engine merely has more air/fuel gas... (not meaning gasoline, but the vaporized fuel and air) ie, denser. ie, bigger bang. an additional spark can be as u say, advantageous help flame front... and that is one reason the MSD 6A, for example, wakes up driveability. bit more piston pressure. the MSD 6A will fire the plug 6 times per cycle under, 2500 rpm or so... and above increases the spark dwell. u can hook a car up to a auto clinic type scope and in OFF mode it will show single plug firing on scope... turn it on to MSD and u get 6 blips on scope... per cyl. dry fire an elec or point trigger... and it goes click click at the plug... plug out of engine and grounded... wire in the MSD and it goes ba-rrap! ba-rrap! you can actually hear the plug fire six times...

You are correct when you say liquid fuel will not burn, however for certain fuels under certain conditions, they will. Gas and alcohol need air, however nitromethane carries air (oxygen) with it due to its chemical composition. Rocket fuels do this as there is not enough air in space. This is why tuning it can be completely different than with other fuels. If you throw a match on gas or alcohol it will light where nitomethane will not. It requires other conditions such as pressure and heat to burn. Of course supercharging gives even more air into the mix, however the combustion chamber on a modern nitro engine is on the edge of hydraulicing. This is also why one must back down one of those engines before attempting to turn it over with a starter. This procedure does not happen with gas or alcholol. These engines are fired with magneto's rather than conventional ignitions. Nitro is a slow fuel so it needs to be lit early. With a single mag we could set it at 70 degrees BTDC with dual mags we went to 55 degrees as the was easier to get a better burn so more advance was not necessary.
As for MSD units, one of their functions also tends to be firing over a much wider degree of crank rotations and not just many more times at the original point of firing.

 

[maico490]

Back in the day when I was younger and racing dirt bikes, I had a 1972 Suzuki TM-400R Cyclone. Long story short, it was highly modified from the frame, to the suspension, to the engine.

I had an over-sized Mikuni carb on it, was well as a full port job on the jug, and the head had been milled. I got the idea of a two spark plug set-up. It had a CDI electronic ignition on it. I purchased an additional coil for it and wired it into the ignition system.

Because I had installed a "frame handling kit", the engine sat approx. 1.5" lower in the frame, thus exposing the area under the fuel tank. I had a fiber-glass after-market Maico tank on it. When I installed the extra spark plug in the head, it was very obvious that the engine was running two plugs. It looked trick as all Hell.

Whether or not it made any actual difference was hard to tell. I had modded the bike so much, that it was pretty much anyone's guess as to how much of a difference all the mods made. Even with the frame handling kit, it was still a handful. The engine itself was making extreme power and that was both good and bad at times. If there had been a line drawn in the sand, as to indicate where not to cross, I'm sure I went well beyond that line.

By doing all the mods, I had dropped the bike's OEM weight by almost 15 lbs. I increased the engine's power, and it was very obvious, but I had no way to gauge the degree or amount.

I still have a picture or two of the bike in all it's glory after all the modifications........somewhere. If I ever find the pics, I'd love to figure out how to post them. It even sat in a Suzuki dealer's showroom alongside some stock TM-400R's for a month or two, on display.

It took a brave man to ride a standard TM400 let alone a modified one:http://motocrossactionmag.com/more-...s/the-worst-bikes-i-ever-raced-by-jody-weisel

 

[Backyard Lumberjack]

yeah, rite on! thanks. powerful. I am going to guestimate hp at 20 - 40, maybe more... since I would call V8 chain saws the T/F dragsters... your saw imo definitely is a Comp Eliminator! maybe even as much as a B- Altered!! A+ in any event... pun intended!

 

[1Alpha1]

It took a brave man to ride a standard TM400 let alone a modified one:http://motocrossactionmag.com/more-...s/the-worst-bikes-i-ever-raced-by-jody-weisel

Even with a fly wheel weight, it was still terrifying. I thought that a frame kit, re-sprung front forks, some better rear shocks, and of course, more power ( ) would help it.

Of course back in the days, we had all a certain mindset. "If you didn't mind......it didn't matter".

Well.........that and being young and dumb and stuff................

 

[Backyard Lumberjack]

You are correct when you say liquid fuel will not burn, however for certain fuels under certain conditions, they will. Gas and alcohol need air, however nitromethane carries air (oxygen) with it due to its chemical composition. Rocket fuels do this as there is not enough air in space. This is why tuning it can be completely different than with other fuels. If you throw a match on gas or alcohol it will light where nitomethane will not. It requires other conditions such as pressure and heat to burn. Of course supercharging gives even more air into the mix, however the combustion chamber on a modern nitro engine is on the edge of hydraulicing. This is also why one must back down one of those engines before attempting to turn it over with a starter. This procedure does not happen with gas or alcholol. These engines are fired with magneto's rather than conventional ignitions. Nitro is a slow fuel so it needs to be lit early. With a single mag we could set it at 70 degrees BTDC with dual mags we went to 55 degrees as the was easier to get a better burn so more advance was not necessary.
As for MSD units, one of their functions also tends to be firing over a much wider degree of crank rotations and not just many more times at the original point of firing.

MSD - over wider degree of crank roatations? hmm, I can buy over wider # of degrees... but it's basically over as piston rolls over TDC.

Fuels - interesting. I knew that nitro got lit earlier, and carries lots of O in it, but dint know so many degrees BTDC. clearly a powerful 'fuel' and slow to burn as evidenced by each cyl's intake charge ... still lit and aflame as it exhits the zoomies. nothing quite like a T/D run down the quarter... well, maybe a rocket launching! i see they are pushing now over 10,000 hp! I like your avatar! I am quite experienced with supercharging, more so with gasoline... and used to design and build supercharger kits... we would make the patterns, I took them to the foundry... got the raw parts, tooled up for them, and then cut manifolds etc... and made the drive systems... used AM blower... I always like the dual MSD triggers on the diggers....

 

[Backyard Lumberjack]

Even with a fly wheel weight, it was still terrifying. I thought that a frame kit, re-sprung front forks, some better rear shocks, and of course, more power ( ) would help it.

Of course back in the days, we had all a certain mindset. "If you didn't mind......it didn't matter".

Well.........that and being young and dumb and stuff................

right on! warriors! ever the warrior! ba**s to the wall, kick the tire and light the fire... first one into the air is the Leader... lol

ahh, yes... as u say: back in the days,

 

[1Alpha1]

right on! warriors! ever the warrior! ba**s to the wall, kick the tire and light the fire... first one into the air is the Leader... lol

ahh, yes... as u say: back in the days,

Looking back, it's a good thing that as we grow older and mature, we learn from our life lessons of the past.

If we didn't, most of us wouldn't be alive today.

 

[Rx7man]

From the reading I've done, Nitromethane also decomposes (burns) in 2 stages.. the first is where you get the most power from, and the second is *very* slow, which accounts for the flames coming out of the header pipes of top fueler drag cars, as well as the *incredible* noise that pretty much turns your guts inside out...
I'd love to try it in a saw just to blow it up.. Perhaps start with the XL12? then one the the Husky 65's?

The only way you can make a dual plug system work on one coil is if the high tension side of the coil isn't grounded at one end, but each end of it goes to one of the two plugs... There are many vehicles that use this method to fire 4 cylinders with 2 coils.. It's called "Waste spark".. Coil 1 will fire the plug of cylinder 1 and 4, coil 2 will fire 2 and 3..
When coil 1 fires to light cylinder 1, cylinder 4 fires as well, but since it's at the end of the exhaust stroke, it doesn't do anything.. I did hear it helps keep the plug clean though..

 

[RIDE-RED 350r]

yeah, rite on! thanks. powerful. I am going to guestimate hp at 20 - 40, maybe more... since I would call V8 chain saws the T/F dragsters... your saw imo definitely is a Comp Eliminator! maybe even as much as a B- Altered!! A+ in any event... pun intended!

Based on what I have learned about Honda's 250r's over the years, and building up my own shown in my avatar pic that is running the same 350 big bore that Spencerpaving is running on his saw but with slightly less carb and not being drag ported.. I would say that 55hp is very realistic, if not a conservative estimate of what his saw is putting out.

Just as a for instance and not intending to jack the thread, but I own another '85 ATC250r just like the one in my pic.. It is a stock engine with just the usual bolt-on mods, ie better carb, exhaust, and reedblock. In bone stock config, a 250r was stated to be right around 36hp. You could reasonably expect to be close to 40 with descent bolt-ons, and a bolt-on modded 250r is nothing to scoff at, but the modded 350 big bore R makes the other feel slow! And I am not exaggerating one bit. I have seen dyno sheets from an ESR 310 (which is 295cc actual on it's first bore) with similar add-ons as my 350, except a smaller carb and different brand of pipe, Paul Turner if I recall... That motor peaked out at 49 hp. So yes, I would say 55-60 hp pretty easy on his drag ported 350cc saw.

That thing RIPS Spencerpaving!!! Thanks for sharing the vid!

 

[RIDE-RED 350r]

From the reading I've done, Nitromethane also decomposes (burns) in 2 stages.. the first is where you get the most power from, and the second is *very* slow, which accounts for the flames coming out of the header pipes of top fueler drag cars, as well as the *incredible* noise that pretty much turns your guts inside out...
I'd love to try it in a saw just to blow it up.. Perhaps start with the XL12? then one the the Husky 65's?

The only way you can make a dual plug system work on one coil is if the high tension side of the coil isn't grounded at one end, but each end of it goes to one of the two plugs... There are many vehicles that use this method to fire 4 cylinders with 2 coils.. It's called "Waste spark".. Coil 1 will fire the plug of cylinder 1 and 4, coil 2 will fire 2 and 3..
When coil 1 fires to light cylinder 1, cylinder 4 fires as well, but since it's at the end of the exhaust stroke, it doesn't do anything.. I did hear it helps keep the plug clean though..

I doubt like hell you would even get a "normal" saw to fire and run on that fuel... Nowhere near the compression required, let alone the timing.

 

[firmwood]

Holy. I just coughed up a shot of moonshine. Dammit!

/me replays video.

Wow.

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