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BFB Samba Member
Joined: November 03, 2014 Posts: 1694
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Posted: Fri Dec 27, 2019 6:59 pm Post subject: dual spark plug heads |
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i can understand the use of dual plug heads in aircraft for the redundancy factor but whats the point for our application? assume the thought would be a better burn , but does this really do much or is it just marketing crap? |
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vwracerdave Samba Member
Joined: November 11, 2004 Posts: 15280 Location: Deep in the 405
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Posted: Fri Dec 27, 2019 7:09 pm Post subject: Re: dual spark plug heads |
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Yes twin plugs are an aircraft modification. It's marketing crap and completely unnecessary in any street car. It can provide a tiny bit of advantage in a record setting race car. Again totally worthless for a street car. _________________ 2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK
Featured in Dec. 2001 HOT VW's Magazine page 63
Watch my racing video's http://www.youtube.com/user/okvwracer/videos |
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Alstrup Samba Member
Joined: July 12, 2007 Posts: 7183 Location: Videbaek Denmark
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Posted: Sat Dec 28, 2019 5:12 am Post subject: Re: dual spark plug heads |
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Hmm, yeah, it depends heavily on the cylinderhead and piston head design. In most 2 valve engine set ups there can be an advantage. If we isolate it and look at the ACVW type 1 heads and standard piston designs.
There are variations to the statement, but generally there is only marginally effect of twin spark with bores less than 92 mm.
If you do not take advantage of the possibility to run higher CR the gain will also be less. Most twin spark set ups can run 0,7 to 1,2 higher static compression without detonation and other bad side effects.
If you do not reduce timing to take advantage of the faster burn you will not see much gain.
The more perfect the combustion chamber, squish and cylinder filling is the less gain you will see with twin spark and vise versa.
The larger the bore the larger gain you can find with twin spark. (Assuming the plugs can be located in good positions.)
If you use protruding pistons which create a shadow side in the chamber with a std single plug the gains can be larger even at smaller bores. (Not normal in ACVW engines though.)
Engines with semi hemi chambers can benefit a lot from twin spark, even with smaller bores.
Fuel efficiency- and emission wise there can be great gains in all aspects apart from Nox levels per liter exhaust. If you look at it per driven mile it is usually an improvement.
Now, performance gains versus investment. Thatīs where it becomes a little tricky, because almost all known "bolt on" systems are a little expensive. Some are crazy expensive. On the other hand, if you are chasing the last few hp which are typically the most expensive to find, it begins to make sense.
If you have a little technical insight it does not have to be that expensie to make a kit today. Now we have relatively cheap programmable ECUīs like MS , Vems and Speedunio to some extend. With such a unit it is basicly just getting 4 dual coils from some engine with CNP ignition, a crank trigger and a cam position sender. Then program the ECU for sequential ignition and youre in business. You can of course also do it the "mechanical" way with converting a normal distributor to a Nissan CA capīn rotor.
Computronics have a twin spark ignition set up that is based on WS but running off of a cam sync. This is just about the cheapest bolt on possible, - at least that I know of.
Have fun. |
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raygreenwood Samba Member
Joined: November 24, 2008 Posts: 21475 Location: Oklahoma City
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Posted: Sat Dec 28, 2019 9:10 am Post subject: Re: dual spark plug heads |
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As Alstrup noted.....specifically hemispherical combustion chambers....with a matcuing piston... have been the main PRODUCTION beneficiaries of twin plugs.
Ford made millions of vehicles through the 80s across several platforms that ultilized twin plugs. Almost all were their Lima built (and later Brazil) 2.3L four cylinders. The most common vehicle seen with it here was the Ford Ranger Pickup.
That engine had distributorless ignition as well. If memory serves....that engine had pent roof pistons and as such at TDC....the combustion chamber is bisected into two parts....effectively separating air-fuel mixture into two areas so the twin pugs were needed to keep emissions down and power up.....so yes....one could say it was making up for a design issue. I can say after working on a few of these back in the the 90s.....if they had one plug not firing on a cylinder.....it lost quite a bit of throttle response.
They got away from the need for this in the turbocharged versions and by simply goimg to the small cologne V-6.
So.....yes....its all about design. Some designs "might" need twin plugs....so saying its not effective is not "100%" correct......but one could just as easily argue and support Daves point.....that a better deaign would get rid of the need altogether (outside of aircraft redundancies).
I cant think of an ACCW that needs it....although.....back in the late 90s or early 2000's....I believe Jake Raby made a few and had an article series on it in one of the mags....that had very good results . Again....it's back to the design. I think that was a very large piston design if type 4. Ray |
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King_vw61 Samba Member
Joined: February 03, 2018 Posts: 1383 Location: Southern California
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Posted: Sat Dec 28, 2019 10:38 am Post subject: Re: dual spark plug heads |
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"I believe Jake Raby made a few and had an article series on it in one of the mags....that had very good results . Again....it's back to the design. I think that was a very large piston design if type 4. Ray"
Tom Schuh did it also in the 90's, made his own duel Distributor. It was with Autocraft 910 heads and 101.5 bore. There was very little to no improvement so they ditched it. He still has one of the distributors(I have the heads) He records tons of data with each pass.
He also tried carbon fiber pushrods, Trying to loose weight were ever they could back then(before the 98mm Turbo)
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raygreenwood Samba Member
Joined: November 24, 2008 Posts: 21475 Location: Oklahoma City
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Posted: Sat Dec 28, 2019 11:54 am Post subject: Re: dual spark plug heads |
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ivkings4 wrote: |
"I believe Jake Raby made a few and had an article series on it in one of the mags....that had very good results . Again....it's back to the design. I think that was a very large piston design if type 4. Ray"
Tom Schuh did it also in the 90's, made his own duel Distributor. It was with Autocraft 910 heads and 101.5 bore. There was very little to no improvement so they ditched it. He still has one of the distributors(I have the heads) He records tons of data with each pass.
He also tried carbon fiber pushrods, Trying to loose weight were ever they could back then(before the 98mm Turbo)
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Yes...but totally different approach.
The concept of the ones you are showing was what everyone was looking at in the 90's....a second strike plug to re-ignite or complete the burn...or keep the flame front cooking... that could not be done with a single plug....or at least that was the theory. I dont think anyone had any notable success with that short of maybe the v-8 crowd for circle track or similar.
The Raby heads had one plug entering from normal direction above...and one from below between the PR tubes. Dual distributor of some kind as well...in fact...going off memory...I think it was using a single V-8 mallory distributor using all 8 plugs.
I remember that Raby got "good" results...but the cost...and complexity. I think that went into one of his clients 550 spyder or 914 builds. I think he moved onto better and less complex designs. I have not heard much about that since then.
Looking for info on it. Here is a thread from 2001. They were 2,666 cc type 4 engines for a 500 spyder.
http://www.spyderclub.com/viewtopic.php?f=7&t=2867&start=15
From 2011
http://www.spyderclub.com/viewtopic.php?f=7&t=7860
260-ish hp
Ray |
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Big Al Samba Member
Joined: June 14, 2014 Posts: 184 Location: Tucson, AZ
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Posted: Sat Dec 28, 2019 12:06 pm Post subject: Re: dual spark plug heads |
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I have a set if anyone needs them.
Al in Tucson |
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Big Al Samba Member
Joined: June 14, 2014 Posts: 184 Location: Tucson, AZ
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Posted: Sat Dec 28, 2019 12:06 pm Post subject: Re: dual spark plug heads |
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I have a set if anyone needs them.
Al in Tucson |
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Alstrup Samba Member
Joined: July 12, 2007 Posts: 7183 Location: Videbaek Denmark
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Posted: Sat Dec 28, 2019 1:22 pm Post subject: Re: dual spark plug heads |
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ivkings4 wrote: |
"I believe Jake Raby made a few and had an article series on it in one of the mags....that had very good results . Again....it's back to the design. I think that was a very large piston design if type 4. Ray"
Tom Schuh did it also in the 90's, made his own duel Distributor. It was with Autocraft 910 heads and 101.5 bore. There was very little to no improvement so they ditched it. He still has one of the distributors(I have the heads) He records tons of data with each pass.
He also tried carbon fiber pushrods, Trying to loose weight were ever they could back then(before the 98mm Turbo)
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Naturally, there would not be much improvement with that second plug location apart from a hairswidth less unburned comming out of the exhaust. Probably hardly measurable. (To confirm that there was an aviation company that dared to be different and did their dual plug cylinderheads almost like that. Normally when you have such an aviation engine with opposing plugs at idle and you cut one row of plugs you can hear the engine drop in rpm. With the side by side solution there is no drop in engine speed.) If you want it to pay off you need to have a plug on each side of the valves so to speak, so you get a double flame front. Also, if you want most possible hp gain the normal non plug side needs to have a different shape. But its a fine line. You do not want to alter the shape in a way that affects the flow, so a little is typically better than any radical changes.
I like that dual Mallory distributor though
One of the reasons to why twin plugging became sort of obsolete in newer times is that almost every new engine design is with pentroof and 4 valves per cylinder. With that design you can place the plug right in dead center of the chamber. When you do that and the chamber is good (which almost all new designs are) the flame travel becomes so efficient that the addition of a second plug in one of the sides (preferably on the exhaust side) makes so little difference that it is simply not worth it neither performance nor emissionwise unless the bore is really big. I do not know where the line is, but Iīd suspect at least 4,2". I see some of the 580 CUI tractor pulling and drag engines use dual plugs, but i donīt know much else about these engines.
Last edited by Alstrup on Sat Dec 28, 2019 1:31 pm; edited 1 time in total |
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gears Samba Member
Joined: October 28, 2002 Posts: 4391 Location: Tamarack, Bend, Kailua
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Posted: Sat Dec 28, 2019 1:27 pm Post subject: Re: dual spark plug heads |
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I think it was Dave Folts who made that dual distributor. He showed it to me many years ago as something he had made .. _________________ aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com |
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bugguy1967 Samba Member
Joined: January 16, 2008 Posts: 4338 Location: Los Angeles, CA 90016
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Posted: Sat Dec 28, 2019 9:42 pm Post subject: Re: dual spark plug heads |
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Funny that this came up, as I just posted today that I needed someone to modify my CU Remmele heads for a second plug. What had me interested in the dual plug addition were the same reasons as listed above: you can pull timing, add compression, and make gains in that respect. Torben, I was going to contact you because I'd like this to preferrably be done on the European side of the world before coming to me. I'll message you. _________________ "A petrol engine can start readily, run smoothly and give every appearance of being in good order, without necessarily being in good tune." - Colin Campbell, "The Sportscar Engine" |
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FreeBug Samba Member
Joined: March 12, 2012 Posts: 4278 Location: deepest, darkest Switzerland
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Posted: Sun Dec 29, 2019 1:16 am Post subject: Re: dual spark plug heads |
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vwracerdave wrote: |
Yes twin plugs are an aircraft modification. It's marketing crap and completely unnecessary in any street car. It can provide a tiny bit of advantage in a record setting race car. Again totally worthless for a street car. |
I seem to remember the Alfa T-spark twin spark system was just for emissions issues.
Ideally, I think both plugs would work best if on opposite sides lengthwise, not top-bottom like it's done....(and probably extra advance on the exhaust-side plug) but that is a design "impossibility"... |
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Alstrup Samba Member
Joined: July 12, 2007 Posts: 7183 Location: Videbaek Denmark
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Posted: Sun Dec 29, 2019 4:21 am Post subject: Re: dual spark plug heads |
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Yes, the Alfa Romeo 1,7, 1,8 & 2,0 twin spark engines got the mod mainly to meet the new (at that time) Euro 1 norm, and did it. But they got taken with their pants down, because EU mnade a regulation that ALL passenger cars were to have cats by the end of 1992 if memory serves. In the process Alfa were able to gain 10 hp instead of loosing 5-10 as most other engines at the time. When they released the 1,8 and 2,0 16 valve twin spark engine they were the production engine with the highest ABP still with peak power below 6500 rpm in the world, naturally aspirated that is. But almost naturally evolution caught up with it, so within about 4 years other engines could do the same.
While the 2,0 twin spark is of course the most powerfull the 143 hp 1,8 twin spark is absolutely awesome for its size. At the time there was nothing that came even close in stock form. These engines could cruise all day long at 18-1 afr and do very well fuel efficiency wise and with a blip on the loud pedal it would turn into a spirited mountain climber and eat 2 liter GTIīs for breakfast. (In the 147 body. The 155 body was somewhat heavier)
The main reason to why they stopped using this technology is actually political more than enviromental. The twin spark technology as they used it gave higher numbers in Nox levels due to a leaner burn which was/is both difficult and expensive to pacify. (The Euro 5a norm) About 15 years later "we" have learned how to do that in a safe and financially efficient way, sortof, so in theory they could reinstate the twin spark solution. But with the evolutional design improvements of the pentroof chamber along with the introduction of more modern and powerfull ignition systems the gains are most likely minmal.
Slightly off topic, but then again not |
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rayjay Samba Member
Joined: March 26, 2008 Posts: 1501 Location: Buford GA
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Posted: Sun Dec 29, 2019 6:17 am Post subject: Re: dual spark plug heads |
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gears wrote: |
I think it was Dave Folts who made that dual distributor. He showed it to me many years ago as something he had made .. |
Look at the address label on the box the cyl head is sitting on. |
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rodeking Samba Member
Joined: October 09, 2017 Posts: 367 Location: near Buffalo NY
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Posted: Sun Dec 29, 2019 7:34 am Post subject: Re: dual spark plug heads |
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I'm not sure what the thinking was behind the twin plug head shown above? Maybe the design of those heads didn't allow the second plug to be located on the opposite side? It's no wonder it showed little improvement, it's essentially a bigger spark but just on one side of the chamber. Almost any air cooled Porsche race engine ran twin plugs (ex. 934), even the DOHC 917 ran twin plugs.
Faster burn, less advance req'd, less combustion pressure before TDC where you don't want it, more torque.
Whether it's worth it or not on these engines comes back to how much you're willing to pay for HP. It's an exponential curve and this is up towards the top. |
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gears Samba Member
Joined: October 28, 2002 Posts: 4391 Location: Tamarack, Bend, Kailua
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Posted: Sun Dec 29, 2019 9:15 am Post subject: Re: dual spark plug heads |
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According to guys who know more than I, the bottom plug should be angled slightly toward the exhaust, so as to be least disruptive to intake flow .. so that, along with the ability to change plugs without removing any other part is what dictated the location I chose.
Gary Peloquin claimed the mod gave him 7% hp increase in his drag car (with the Scat heads shown below).
In my street Ghia, seat-of-the-pants was a small hp increase (or maybe it was just crap .. hard to tell the difference at my age)
_________________ aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com |
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King_vw61 Samba Member
Joined: February 03, 2018 Posts: 1383 Location: Southern California
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Posted: Sun Dec 29, 2019 9:53 am Post subject: Re: dual spark plug heads |
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gears wrote: |
I think it was Dave Folts who made that dual distributor. He showed it to me many years ago as something he had made .. |
Dave made them with his CNC machine off of Toms design.(4 were made) Both Dave and Tom are very smart but dave will be the first to tell you that Tom is on another level when it comes to engineering things. |
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Alstrup Samba Member
Joined: July 12, 2007 Posts: 7183 Location: Videbaek Denmark
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Posted: Sun Dec 29, 2019 12:44 pm Post subject: Re: dual spark plug heads |
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gears wrote: |
According to guys who know more than I, the bottom plug should be angled slightly toward the exhaust, so as to be least disruptive to intake flow .. so that, along with the ability to change plugs without removing any other part is what dictated the location I chose.
] |
Exactly. On a type 1 head Thats not so easy on one side. Wasted a few heads trying. Maybe There is little more room on the split port heads |
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gears Samba Member
Joined: October 28, 2002 Posts: 4391 Location: Tamarack, Bend, Kailua
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Posted: Sun Dec 29, 2019 1:34 pm Post subject: Re: dual spark plug heads |
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Oh, it's a tedious task, for sure. There's really only ONE possible position for all parameters to be met on plug #2 .. not to mention precise depths for optimal indexing of the plug electrodes.
While Scat heads accept 12mm lower plugs, Type 1 heads require 10mm motorcycle plugs IF you wish to easily remove them. I had no junk Scat heads to practice on, so machining Gary's already-prepped race heads were a pucker-up afternoon ..
Pattern Type 1 head
#1 plug
#2 plug
OD ground & shortened 10mm sparkplug socket
_________________ aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com |
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bugguy1967 Samba Member
Joined: January 16, 2008 Posts: 4338 Location: Los Angeles, CA 90016
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Posted: Sun Dec 29, 2019 3:02 pm Post subject: Re: dual spark plug heads |
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Gears, so it looks like you'll do whatever it takes to come up with the right angle. Wanna give my Remmeles a shot? I can provide stub pipes as well so you'll know that everything clears. _________________ "A petrol engine can start readily, run smoothly and give every appearance of being in good order, without necessarily being in good tune." - Colin Campbell, "The Sportscar Engine" |
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