duel plugs

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shackles

duel plugs

Post by shackles » Wed Jun 16, 2004 12:08 pm

I am looking in to building a set of type 4 heads for a 6- stud case. While moving the plug holes for clearance I thought adding a second plug would this increase combustion? wht type of distributor would be needed?

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Post by MASSIVE TYPE IV » Wed Jun 16, 2004 12:20 pm

I have done this, it was featured in VW Trends a few years back, I think in 2001.

It would be a pain to do with a distributor. The only way I would imagine it could be easily done is with a dzzy from a Mazda Z22 engine (8 plug 4 cylinder)

If you want it done I can sell you my modified direct fire system, it bolts right on and has the correct firing order. No dizzy used at all.

shackles

duel plugs

Post by shackles » Wed Jun 16, 2004 12:42 pm

Does this add any performance advantage over single plugs? What's the terriff on a system like this? On a side note I have a DTM on a stock 2.0 With my new stroker block, if deck height increases will I have trouble fitting a DTM on this engine?

thanks

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Post by MASSIVE TYPE IV » Wed Jun 16, 2004 1:01 pm

The DTM allows for .250" shim on EACH SIDE before it needs grinding..

Power differences were not great with dual plugs, since our chambers and pistons are just a modified compact wedge..

geddes66
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Post by geddes66 » Wed Jun 16, 2004 11:18 pm

The big reason for dual plugs is dependability. They are usually restricted to aircraft engines as a type of failsafe. It helps to prevent running out of airspeed, alititude and ideas at the same time. I have also seen them used on giant, stationary industrial natural gas engines though, with a bore of 12 inches those may be installed as a combustion enhancing device.

Tristessa
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Post by Tristessa » Thu Jun 17, 2004 12:07 am

MASSIVE TYPE IV wrote:It would be a pain to do with a distributor. The only way I would imagine it could be easily done is with a dzzy from a Mazda Z22 engine (8 plug 4 cylinder)
Would the dizzy from a Nissan NAPSI motor work any easier? They also had 8 plugs in 4 cylinders.

Just curious.

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Post by MASSIVE TYPE IV » Thu Jun 17, 2004 12:21 am

its about the same.... Direct fire is the way to go.

farmer
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Post by farmer » Thu Jun 17, 2004 5:05 am

Back in the mid 90´s there were a couple of US based guys that worked with that on big cc turbocharged T4´s (103 mm bore) I talked a bit with them because at that time I was working on a dual plug setup for a turbo engine. (But ditched the idea)
They claimed that they could pull another 22 hp + som torque out of it (using the Nissan dizzy) - AND they got much better burn. Consumption was improoved by 3 mpg over sgl. plug comparison.
But then again, this was on a big bore where there would be a theoretical gain in flame travel.
A guy in GB uses twin plugs on a race car with Porsche heads and 104 mm bore (I think) His car is definitely faster after he got the twin plug system up and running.
But it is a rather complicated and costly affair to make it work.
T.

Guest

Post by Guest » Thu Jun 17, 2004 8:06 am

I guess one of the main reason I considered dual plugs is for the fact that stock plug hole must be re-located to allow for 6th stud. A plug on both sides of orignial location would would be better than, one off-set to one side or the other? Just a thought

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yilon
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Post by yilon » Thu Jun 17, 2004 9:47 am

Back in the 1920s and 1930s in Europe racing were getting smaller and smaller and it was necessary to wring every last bit of power out of them. Dual plugs were one of the 'last bit of power' strategies. The effectiveness of the dual plug setup was apparently not that great, as the idea was more or less abandoned.

Ford used a dual plug setup in one of its four cylinder engines, but for smog, not performance reasons.

Some older two stroke engines used two plugs, not dual plugs. Only one plug was active at a time. The plug in use tended to foul, while the inactive plug would clean itself.

The dual plug idea seems like a lot of work for very minimal power gain.

JMHO.

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dstar
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Post by dstar » Thu Jun 17, 2004 9:54 am

I read somewhere that dual plugs were not a cost effective measure
until the bore went over 98mm.

Then it is advantagous because of flame travel time.

I wanted to use the piston as the ground with four electrodes on the plug,
but couldn't come up withg the backing(read $$$) to have it developed.
:-(

I STILL think it's a great idea....
:lol:

Don

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Post by MASSIVE TYPE IV » Thu Jun 17, 2004 10:29 am

I thought about the same thing... BUT DAMN if it ever detonated- it would be wild!~

Guest

Post by Guest » Thu Jun 17, 2004 6:08 pm

in the direction of like "OOOOHHHHSHIIIIT!"!" :wink:
Alfa Romeo did the twin plug thing for some yrs. (Actually they still do I think.)
They started at it again, when Cathalytic converters became mandatory here in EU. They were able to create a burn that was just as clean as a 1. generation CC. But they had to have the converters anyway, so more or less wasted efforts. however they kept working on the idea both for power and for emission issues. And even today Alfa twin spark engines are some of the cleanest "burning" sportscar engines in the world. They do not ignite at once, but a few millisecs apart to creat that "wawe" which is needed in their combustion chamber.
OK. Enuf water here.
T.

Guest

Post by Guest » Thu Jun 17, 2004 7:39 pm

There is a company claiming a 10hp gain from an otherwise stock aircooled Ducati when a second plug is added...
It has alot to do with the chamber shape and the location of the exsisting(SP) plug. If you could center it like in high perf. two stroke things would be different..

J.

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raygreenwood
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Post by raygreenwood » Thu Jun 17, 2004 7:55 pm

Twin plugs can have their uses. I watched my brother building a 520+ hp 327 for a corvette last year. Serious port work. The pistons were what everyone would call "supersquish". They were exact mirrors of the entire chamber...squishing the mixture into a boundary area about 3/32" deep or so...around the entire chamber surface with "mirror" flat spots...not angled reliefs...cast into the piston for the closed valve margin. By the way....he noted that what we called supersquish design....is very old hat. Effective...but been around for a while. Anyway....the spark plug was completely bisected from the other side of the chamber by the piston dome. It was necessary to machine a "flame trough" across the center of the dome in order to allow that fuel pocket to combust. Even at that, the delay and directional travel started by that trough...was opposite the flame travel that was ideal. He noted that twin plugs would greatly improve things in this instance. Ray

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