Dual Plugs in a TWIN CAM?

[build it]

Steve, is this something you plan on moving forward?

[Steve Cole]

Correct, Nascar is well beyond the lean burn engine numbers today. The numbers I posted were early 1990's carb. vintage numbers and you can see thing have improved since then. EFI is going to move things again but as soon as they go faster they will change the rules to slow them back down again. It appears as though Nascar will limit them to keep the cars at 200 mph on the big tracks. As soon as someone starts topping that number the rules get changed yet again.

[qtrracer]

Correct you are Steve, 200mph is kind of a glass ceiling that they want to avoid breaking. The best teams figure out the new rules the quickest!

[Hillside Motorcycle]

High performance / high compression Pan Head and Shovel Head motors definitely benefited from having dual plugs when utilizing the original combustion chambers and high domed pistons. It's simply a way to burn the complete fuel mixture, or at least as much as possible. The high domed pistons and hemi heads with the spark plug off to one side, inherently has a loss of complete burn, due to the fact that the high piston dome inhibits the mixture from burning completely. And as Scott stated, you would shorten the plug gap to 0.022 to 0.025. The two sets of Shovel Heads I had owned (with dual plugs) both had a smaller spark plug on the right side of the motor. I can't remember the Champion number, but it was a 10mm thread I think, and was the same heat range and plug style as the N12Y on the other side.

Evo and Twin Cam motors using a flat top or slightly domed piston with the stock combustion chamber shape would benefit very slightly, if at all from dual plugging. In the event that you ran extremely high compression on the Evo or Twin Cam, you may start seeing benefit. Essentially a racing condition may warrant dual plugging.

I think it was Head Quarters that offered a bathtub chamber modification for Shovel Heads, and would utilize a slightly domed piston. I always wanted to try a set of those, but never did. I'm not sure that they are even offered anymore. 

added: (with dual plugs)

Our AHDRA racer liked .020", but then again, it was @ 17.25 cr............
Scott

[1FSTRK]

Because both plugs in the cylinder are triggered by the ignition at the same time if you mess with these again you might want to try setting the plug with the shortest plug wire .003-.008 tighter gap than the one with the longer wire and see what happens. I have seen .026 and .020 on the stock side allow more fuel to be added.

[Steve Cole]

The higher the cylinder pressure the harder it is to get the spark to jump the gap in the plug. So the higher the cranking compression the hard it will get. Just as the leaner the mixture gets, the hard it is to get the fuel burn started. Dual plugs help in getting the burn going in two places and if done properly the burn will get done 1/2 from each starting spot when it burns together. Tighter gaps help the spark jump the plug gap in higher pressure conditions.

[akjeff]

"It's really slick that in development they have eliminated the starter all together! Just turn the key and with direct injection the engine will start on its own when told to. Have to see how well they can make it work on a two cylinder but for now they have 4, 6 and 8 cylinder engines doing it."

While really cool, wouldn't that hammer the piss out of the rods, crank, etc? Seems like the starter kinda gets things up to a rolling start before the first kaboom happens? Just thinking out loud. Would be awesome if it works in practice, over a long period of time though. Get rid of the weight of the starter, the ring gear on the clutch basket, a smaller, lighter battery. A lot of free horsepower there!

Jeff

[Hillside Motorcycle]

One Iron XL stroker we built for a local guy years ago with a Dyna S, dual plug/single fire ignition,(used a lot of those at one time)more times than not, once warm, when he turned the key switch on, would fire one cylinder enough to roll the engine and it would light right up, without the use of the stater button.
We used to get a laugh out of that.....
Scott

[Karl H.]

I believe the next big thing is going to be direct injection as the materials can now take it and the systems are already into production automobiles. It's really slick that in development they have eliminated the starter all together! Just turn the key and with direct injection the engine will start on its own when told to. Have to see how well they can make it work on a two cylinder but for now they have 4, 6 and 8 cylinder engines doing it.

For some details klick here:
http://www.etas.com/data/RealTimes_2006/rt_2006_01_34_en.pdf

Bosch has a limited system running already (with starter motor support):
http://rb-kwin.bosch.com/en/powerconsumptionemissions/gasolinesystems/startstopfunction/distart.html:

Karl

[Ohio HD]

One Iron XL stroker we built for a local guy years ago with a Dyna S, dual plug/single fire ignition,(used a lot of those at one time)more times than not, once warm, when he turned the key switch on, would fire one cylinder enough to roll the engine and it would light right up, without the use of the stater button.
We used to get a laugh out of that.....
Scott

I never had one that would start, but I did have a 98 inch Shovel with Dyna S and single fire and dual plugs, that when the key was turned on, motor hot, about 50% of the time it would fire residual fuel in one of the cylinders. Motor would just turn slightly. That motor had the Sifton 575 Outlaw in it, not much static compression to start that easy.

I guess Tom Sifton isn't around anymore, was a real pioneer in HD performance at one time.

[Steve Cole]

With direct injection the fuel being fired into the cylinder doesn't need to worry about valve position. When the engine is shut off the ECM remembers the crankshaft position, at start up the ECM fires a small amount of fuel into the cylinder that is just past TDC and then fires the plug. This starts the piston down the hole softly and on a multi cylinder engine you just fire a few cylinders and it's up and running. The trick is as the amount of cylinders decrease and odd fire patterns come into the mix there may not be enough energy to make it go. Therefore in those applications they add a much smaller starter to assist it.

These systems have been running in the lab for 4-5 years that I know of and I saw it about 3 years ago in action. It's a good idea as long as they can work out all the conditional bugs from it. The big driver of it is to shut the engine off each time you stop the vehicle and have a quick start when you want to go. So each stop, in heavy stop and go traffic, ect. the engine shuts off, saving lots of fuel and reducing the emissions output across hundreds of thousands of vehicles.

[akjeff]

Makes more sense now, thanks for the info Steve! People can mourn for the old days all they want. I say technology has made the "good old days" right now, and tomorrow. The power, and efficiency of today's engines, is really incredible.

Jeff

[Hillside Motorcycle]

One Iron XL stroker we built for a local guy years ago with a Dyna S, dual plug/single fire ignition,(used a lot of those at one time)more times than not, once warm, when he turned the key switch on, would fire one cylinder enough to roll the engine and it would light right up, without the use of the stater button.
We used to get a laugh out of that.....
Scott

I never had one that would start, but I did have a 98 inch Shovel with Dyna S and single fire and dual plugs, that when the key was turned on, motor hot, about 50% of the time it would fire residual fuel in one of the cylinders. Motor would just turn slightly. That motor had the Sifton 575 Outlaw in it, not much static compression to start that easy.

I guess Tom Sifton isn't around anymore, was a real pioneer in HD performance at one time.

We used a lot of Sifton 440's, and 412's at one time.
Also the 468S's.
They always ran pretty dang good.
Now Tedd's Cycle somehow owns the name, and has Chinese parts being pushed out with that name on them.
Scott

[strokerjlk]

One Iron XL stroker we built for a local guy years ago with a Dyna S, dual plug/single fire ignition,(used a lot of those at one time)more times than not, once warm, when he turned the key switch on, would fire one cylinder enough to roll the engine and it would light right up, without the use of the stater button.
We used to get a laugh out of that.....
Scott

My ole 69 mag fired iron motor would light off when you started forplay with her. (Just touch the kicker)
She would act like she was ready, but she never was. Just a tease.
Hardest cold starting bitch I ever had. Once she was hot , she was easy.

Speaking of mags ... Durwood had a good suggestion. Run 3 plugs and 3 mags like the Automotive guys do.   
got a fixture to do this on a twin cam scott?

[Ohio HD]

One Iron XL stroker we built for a local guy years ago with a Dyna S, dual plug/single fire ignition,(used a lot of those at one time)more times than not, once warm, when he turned the key switch on, would fire one cylinder enough to roll the engine and it would light right up, without the use of the stater button.
We used to get a laugh out of that.....
Scott

I never had one that would start, but I did have a 98 inch Shovel with Dyna S and single fire and dual plugs, that when the key was turned on, motor hot, about 50% of the time it would fire residual fuel in one of the cylinders. Motor would just turn slightly. That motor had the Sifton 575 Outlaw in it, not much static compression to start that easy.

I guess Tom Sifton isn't around anymore, was a real pioneer in HD performance at one time.

We used a lot of Sifton 440's, and 412's at one time.
Also the 468S's.
They always ran pretty dang good.
Now Tedd's Cycle somehow owns the name, and has Chinese parts being pushed out with that name on them.
Scott

I always liked how guys would tell about their 0.468" lift Sifton 468S cams...     They were actually 0.445" lift, they just called them the 468S, and were actually cataloged as 104 Silencer. But they were good cams.

Yeah, a shame that his name is getting mixed in with imported crap.

[Admiral Akbar]

I always enjoy that video.  You can see the benefit of having high-er valve lift, good port velocity, flat top pistons and a good tulip valve. Thanks for sharing that DB.  -Tutt

Just curious as to can see that in this video.. I don't.. Especially the good tulip valve.. I'd say based on the valve margins and the distance between the intake and exhaust it's not a real high performance motor..

Max

[Admiral Akbar]

Because both plugs in the cylinder are triggered by the ignition at the same time if you mess with these again you might want to try setting the plug with the shortest plug wire .003-.008 tighter gap than the one with the longer wire and see what happens. I have seen .026 and .020 on the stock side allow more fuel to be added.

What difference does plug wire length make? Propagation delay is in the nanosecond range..  Are the wires real inductive?

Max

[Admiral Akbar]

"Snip"
Honda came up with a nice way around it years ago by making a very small prechamber into the head that was feed a rich mixture. The plug fired in the prechamber area and the flame from it got the lean mixture in the cylinder to light off very well and controlled. Downside was the NOx emissions when out of sight, so with today's rules it doesn't work but for power and fuel economy it was great.
"Snip more good stuff"

Steve, I thought that the main reason for the CVCC motor was to reduce NO emissions and delay the requirements for a catalytic converter?

http://en.wikipedia.org/wiki/CVCC

Was it other emissions (other than NOX)  at that they were more interested at the time that they wanted to reduce?

Max

[Deye76]

"What difference does plug wire length make?'

voltage drop? 

[Karl H.]

Was it other emissions (other than NOX)  at that they were more interested at the time that they wanted to reduce?

Max

The early 2-way converters in the 70s were capable of reducing CO an HC emissions only. NOx reduction has not been the main focus of the early CARB regulations. Lower NOx limits came later and forced the 3-way converters.

Karl

[Jaycee1964]

"Snip"
Honda came up with a nice way around it years ago by making a very small prechamber into the head that was feed a rich mixture. The plug fired in the prechamber area and the flame from it got the lean mixture in the cylinder to light off very well and controlled. Downside was the NOx emissions when out of sight, so with today's rules it doesn't work but for power and fuel economy it was great.
"Snip more good stuff"

Steve, I thought that the main reason for the CVCC motor was to reduce NO emissions and delay the requirements for a catalytic converter?

http://en.wikipedia.org/wiki/CVCC

Was it other emissions (other than NOX)  at that they were more interested at the time that they wanted to reduce?

Max

Exactly,  When I worked for Hyundia when they first came to the US the Excel in 85 had a "jet valve" with the early Carb models.  It was actuated off of the intake rocker arm and opened a small valve in the intake.  Had issues with them burning out all the time.  Had everything to do with emmisions.  Ran a primary cat off the exaust manifold and a secondary cat back a bit.  Still struggled to get them to pass emmisions.  They were horrible....

[Steve Cole]

"Snip"
Honda came up with a nice way around it years ago by making a very small prechamber into the head that was feed a rich mixture. The plug fired in the prechamber area and the flame from it got the lean mixture in the cylinder to light off very well and controlled. Downside was the NOx emissions when out of sight, so with today's rules it doesn't work but for power and fuel economy it was great.
"Snip more good stuff"

Steve, I thought that the main reason for the CVCC motor was to reduce NO emissions and delay the requirements for a catalytic converter?

http://en.wikipedia.org/wiki/CVCC

Was it other emissions (other than NOX)  at that they were more interested at the time that they wanted to reduce?

Max

It reduced HC and CO which back then were the big things the government was pushing. Since then NOx and CO2 have been added into the mix and the CVCC engines could not help them all so it went by the way side. What it did show was a way to improve the burn in the cylinder and it's benefits.

[Admiral Akbar]

Thanks Karl and Steve for the additional info..
Max

[strokerjlk]

ok ready. where does it go?

[1FSTRK]

Harley went and put the compression release right in the chamber where the second spark plug is supposed to be.