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fivelugshortaxle
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 Posted: Tue Dec 12, 2017 11:27 pm Post subject: Dual spark plugs |
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Holy crap.....when did Roy start doing dual plugs on the 050's? What's the benefits to this?
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Pruneman99
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Joined: February 22, 2012
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Location: Oceanside
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| Posted: Tue Dec 12, 2017 11:55 pm Post subject: Re: Dual spark plugs |
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| Aircraft use two plugs.for redundancy. Street/strip use IDK. Two flame fronts for better burn is my guess. Would need a way to fire them at the same time. Unless you are going all out drag, I really don't see the point. |
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fivelugshortaxle
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Joined: May 13, 2011
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Location: Aumsville, Oregon
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| Posted: Wed Dec 13, 2017 12:09 am Post subject: Re: Dual spark plugs |
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About what I thought....and maybe better gas mileage. Interesting either way.
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2332 with lots of goodies....
Rotating assembly balanced by Brothers VW
4340 84mm crank
AA 94mm p&c' s
Total seal 2nd ring, rest are Grants
5.5 h beams
Magnum straight cuts
Steve Long XR310 on a 106
CB 1.4 rockers
CB Magnaspark 2 distributor
NGK D7ea plugs
A1 lowdown 1 3/4 with single muffler
Dellorto 48's with 40 venturies
Kennedy Stage 2 with Daiken disc |
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Lo Cash John
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Joined: February 06, 2004
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Location: Jacksonville, FL
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| Posted: Wed Dec 13, 2017 6:44 am Post subject: Re: Dual spark plugs |
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More thorough combustion and thus better power. Requires less timing advance also.
Big bore engines (101mm and larger) probably see the biggest benefit to dual plug heads since the flame front has to travel so far across the cylinder bore.
There are several ways to fire dual plug ignitions if going that route.
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Dale M.
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| Posted: Wed Dec 13, 2017 7:34 am Post subject: Re: Dual spark plugs |
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Most piston aircraft engines have dual ignition.... IF you have only one ignition setup and it fails, what are you going to do, if you have dual ignition and one fails you are still good...
Dale
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nextgen
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UK Luke 72
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sled
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| Posted: Wed Dec 13, 2017 8:32 am Post subject: Re: Dual spark plugs |
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More compression and less timing = more power and less heat.
J. Raby has done a shit load of twin plug development and states even 94 bore the gain is minimal unless it is a very wild engine. But, in some configurations the comp ratio could be raised a full point with twin plugs while maintaining cool street driven head temps.
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[email protected]
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Joined: August 15, 2002
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Location: Brew City
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| Posted: Wed Dec 13, 2017 8:42 am Post subject: Re: Dual spark plugs |
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| fivelugshortaxle wrote: |
| Holy crap.....when did Roy start doing dual plugs on the 050's? What's the benefits to this? |
I had a fixture made a few years ago when I was building heads for an airplane company. I got tired of paying someone else to do it and figured it would be a good service to offer. The secondary plugs are 12mm and I also have the ability to machine castings for 12mm primary as well. The heads do have to be bored for 92's for me to machine the dual plugs. After I do it, I can always bore them for 94's if necessary but can't do it on heads that are stock bore.
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raygreenwood
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Joined: November 24, 2008
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Location: Oklahoma City
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| Posted: Wed Dec 13, 2017 8:50 am Post subject: Re: Dual spark plugs |
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| sled wrote: |
More compression and less timing = more power and less heat.
J. Raby has done a shit load of twin plug development and states even 94 bore the gain is minimal unless it is a very wild engine. But, in some configurations the comp ratio could be raised a full point with twin plugs while maintaining cool street driven head temps. |
Yes.....I was going to mention this from years back. Also....just going from memory....IIRC...and I may not......I think the engines he was showcasing were also road racing, moderate to high rpm engines.
And....on type 4....which it was.....the required machine work, welding and plug wire routing were extreme amounts of work due to the underneath exhaust configuration. I think I still have the article....and IIRC it was a two or three part series.
Along with all of that.....the twin plug set up would give much better benefit.....with an injected engine with full digital control of spark map...and probably coil on plug direct fire ignition..... items I am pretty sure if memory serves....he was not running with back in the early to mid 2000's when he was doing R&D.
Also.....once you have all of that.....adding sequential to the injection can finally probably show more benefit than just slightly better economy.
There have been a few mass produced vehicles with twin plugs.....and the way they were set up and timed....it made a large difference. The Ford Ranger truck comes to mind.
Aside from cost and maintenance cost.....most mass produced cars do not need a second plug....because the factory on new cars has full "clean sheet" control when they design an engine....over combustion chamber shape, piston shape, timing and fueling.
I see a twin plug application as mainly trying to get better performance out of chambers and existing parts you do not have full control of the shape and design off. Ray |
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mark tucker
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| Posted: Wed Dec 13, 2017 10:45 am Post subject: Re: Dual spark plugs |
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I take everything raby did with a grain of sand., so i dont have a clue as to what he wrote. but now after seeing the new mazda diesiel gas engines (detonation spark) I can see where 2 or MORE PLUGS CAN BE USEFULL.  gas is slow burn and somany losses incur. diesel is a big bang at the top of the cylinder so you have massive force for a lot longer peroid. so higher cr and duel or tripple plugs(if there is room for it) you can somewhat simulate the diesel affect of the big bang theory by getting the charge going sooner in a bigger explosion for more tq. and then there is the blond thats always nice to look at   , knock, knock, knock penny!!knock knock knock penny!!like a diesel only different. |
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FreeBug
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Location: deepest, darkest Switzerland
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| Posted: Wed Dec 13, 2017 11:51 am Post subject: Re: Dual spark plugs |
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From what I've read, if you do it right, you can reduce timing and/or increase C/R.
Best results in some cases came from NOT sparking at the same time.
And in the VW head, the plug placement is not ideal, it would probably be better to have a plug on either side,but left/right, not up/down, but that's just not happening...
Multispark with just 1 plug and good chamber turbulence can do things, too
But if you'r going all-out, and are itching to spend more money on your project, why not? ...apart from almost doubling maintenance costs and they're probably a pain to change without a lift... |
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UK Luke 72
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Alstrup
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| Posted: Wed Dec 13, 2017 1:56 pm Post subject: Re: Dual spark plugs |
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What Ray said.
Twin sparking type 1 engines does work. The claim that there is no benefit with small bores is not entirely true. Even on stock 85,5 mm bore and high CR/semi high rpm some guys over here made the twin spark mod and saw a consistent 6-7 hp increase when the second plug was fired up. This is with a classic dual distributor set up to be able to compete in the classic races.
I have the parts for building a 1914 twin spark engine, but absolutely no time. Maybe next winter.
I built a 1720 616 engine some years back that was twin sparked with a system from Precission engineering (Or something like that) elgin 7017 cam, Twin 40 IDF´s 68/69 and a Bursch header. That engine pulled a solid 10 hp more with the second plug activated plus much more midrange torque, - and as almost always with 616 engines, the idle and low end was improved significantly.l There have been more than one enthusiast that mistook the engine for an 1880 until they were told what it really was.
With todays technology it is relatively easy to control and activate the second plug. But as said before, if you really want to take advantage of the second plug you need to know what youre doing. just adding it to "X" engine might get you very little except a thinner wallet.
T |
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raygreenwood
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Location: Oklahoma City
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| Posted: Wed Dec 13, 2017 2:20 pm Post subject: Re: Dual spark plugs |
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| Alstrup wrote: |
What Ray said.
Twin sparking type 1 engines does work. The claim that there is no benefit with small bores is not entirely true. Even on stock 85,5 mm bore and high CR/semi high rpm some guys over here made the twin spark mod and saw a consistent 6-7 hp increase when the second plug was fired up. This is with a classic dual distributor set up to be able to compete in the classic races.
I have the parts for building a 1914 twin spark engine, but absolutely no time. Maybe next winter.
I built a 1720 616 engine some years back that was twin sparked with a system from Precission engineering (Or something like that) elgin 7017 cam, Twin 40 IDF´s 68/69 and a Bursch header. That engine pulled a solid 10 hp more with the second plug activated plus much more midrange torque, - and as almost always with 616 engines, the idle and low end was improved significantly.l There have been more than one enthusiast that mistook the engine for an 1880 until they were told what it really was.
With todays technology it is relatively easy to control and activate the second plug. But as said before, if you really want to take advantage of the second plug you need to know what youre doing. just adding it to "X" engine might get you very little except a thinner wallet.
T |
There is also a lot to be said....and benefit to be gained...for spark position relative to mixture flow and valve location in the cylinder.
For example....as thousands of others and Jake Raby as well have found...the plug angle and location in the 914 2.0L head...is good for an honest 10% increase across the board. With the actual chamber shape itself not being very different than the 1.8L and even when the same valve size is used...this plug angle has been shown to be the BIG difference in that head.
If one can gain benefit from plug angle...they can gain benefit...when its tuned for...by plug location.
At high rpm....burn time...or more accurately time allowed for burn becomes an issue. Having a second plug in sequence to the first can help insure fuel combustion of richer mixtures during hard enrichment, high rpm periods.
Also...others are correct. From memory...what Jake was exploring...was very tight deck and higher compression to start and complete as much of the combustion up in the head and the top say....1/4 of teh cylinder...more of a complete initial "bang"...instead of trying to fight to combust fuel air mixture all the way down the cylinder. Expand the gas to its maximum early and keep the heat up in the head.
The added benefit....of being able to greatly reduce spark advance...is that if you do not have to start combustion at 30-40 degrees ....15-20 degrees of crank rotation.... before TDC.....you are not putting extra resistance against the piston while it is already under stress compressing the mixture. If memory serves this is where and why Jake Raby was seeing use for twin plugs.
This frees up HP and lowers heat. If you have enough engine controls....spark timing, advance timing and fuel....there are or should be a lot of benefits to this.
You see some of this very type of tuning being done in modern cars even though they may not be using two plugs as part of the recipe. You see some of this theory in action in the Atkinson cycle and in the VW Budack cycle ...which is a mix of the Miller and Atkinson cycle.
Ray |
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vilihardrada
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| Posted: Wed Dec 13, 2017 2:28 pm Post subject: Re: Dual spark plugs |
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| You take your Cessna down to the end of the field and bring it to full power, standing on the brakes of course, then remove one of the mags from the system if you see a 45 to 50 rpm drop you know that mag is working. |
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timvw7476
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| Posted: Wed Dec 13, 2017 4:32 pm Post subject: Re: Dual spark plugs |
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the other advantage with big aviation radials at least,
was spark near the exhaust port fired earlier due to exhaust-mixed mixture
being slightly weaker than the fresh charge near the intake valve.
Not that a VW combustion chamber will ever end up that huge. |
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oprn
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| Posted: Wed Dec 13, 2017 4:53 pm Post subject: Re: Dual spark plugs |
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| vilihardrada wrote: |
| You take your Cessna down to the end of the field and bring it to full power, standing on the brakes of course, then remove one of the mags from the system if you see a 45 to 50 rpm drop you know that mag is working. |
Yup that tells you there is a benefit. And it's at much lower rpms too!
P.S. My aircraft mechanic source just informed me that you look for a 75 to 100 rpm drop at 1700 rpm. That's significant!
Last edited by oprn on Wed Dec 13, 2017 4:59 pm; edited 1 time in total |
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boxkiteflyer
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Location: Taylorsville, KY
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| Posted: Wed Dec 13, 2017 4:58 pm Post subject: Re: Dual spark plugs |
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| There can be a benefit of having the plugs fire at slightly different times depending where and how the flame travels within the 'squish'. I got this info on one of the aircraft racing societies/clubs I belong. I have no practical knowledge. |
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HotStreetVw
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| Posted: Wed Dec 13, 2017 7:09 pm Post subject: Re: Dual spark plugs |
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The claim that RPM drops when the second ignition is shut off is not an indication of power, or a decrease in power, compared to your standard single plug system.
If you can run less timing due to the redundancy, and then remove one point of ignition, it operates like everyone else does with less spark advance, the spark advance is the reason for reduced power.
If the tech was great, increased power, increased efficiency, we would see all major auto manufactures doing it. We don't.
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