Twin Plugging?

[nissan2ner831]

Alright, I'm fairly new here (though I've been a lurker for over a year), and to the L-series engine in general (I'm young XD).

 

Anyways, I have a lot more experience in my 20 years of life with air-cooled engines, in particular the VW Type 4 engine and the Porsche 912 4-cylinder engine, the same one found in the Porsche 356. Now I know (from all my various information gathering and some work experience on them) that almost all the air-cooled Porsche and VW engines can benefit greatly from twin-plugging the heads (not on its on, but what it can allow the engine to do...and expensive modification, but one I would have done had I continued with that world, though I plan on returning to it someday in the future, the costs for a college student were just too high).

 

Anyways I was looking at some build ups of several L28 heads, and noticed the spark plug placement is very similar to that of a stock Type 4 or Porsche 912 engine, that is off to the side of the valves. So it piqued my interest if anyone had tried to twin plug the L28 engine, and I couldn't find anything on it. Is there a specific reason for this? Head design doesn't allow for a second plug to be drilled in on the other side of the valves? The cost unjustifiable? Just curious as I know it is quite common in the air-cooled world for high performance builds (it's limited to those due to the cost) and am wondering why it hasn't been explored with the L-series (or if it has, I may have just missed it).

[smokeybear]

Wow this is a very interesting topic. I have not seen anything done like this before with the L series but someone more experienced than myself may have done it.

 

Subscribing to see where this goes, I am sure it is good information either way .

[MAG58]

I'm not sure how this would work on a Z, but with some twin plugs and especially with rotaries, the twin plugs is to ensure flame front propagation across the entire combustion chamber. With only one plug on a Porsche or a VW with a deep CC and a tall dome, you tend to get sides of the combustion chamber area that is occluded from the flame front until after the the piston begins it's travel down. I'm not sure what kind of thermodynamic benefit one would achieve with twin plug heads so I'd like to see what some others think of this idea.

[PanzerAce]

Interesting, but TBH, I'm not seeing a really good way to use it on a L series. I'm more familiar with the concept because of aircraft engines, but the L series doesn't really seem to fit with it. We don't have huge chambers, lots of dish, or heads with huge cc numbers.

 

Plus, there just isn't alot more room in the heads...:

 

 

 

 

 

(this head looks like it's already been modified, but you get an idea for the depth of the head CC with it):

 

As you can see, not really alot of room to play. Though....it could be an interesting project to both weld up the chambers AND twin plug them

 

Also, some answers to your questions: The head really doesn't allow for another plug, since opposite the plugs are the intake and exhaust systems. Non crossflow heads leave us plenty of room on the spark side, but none on the other. Cost I don't think really enters into it (we've got people doing completely one off custom intake manifolds, dumping mucho dinero into the stock heads, or doing plenty of other crazy stuff).

 

Any chance you could post some pictures of the twin plug setups on VWs? Might give some of us with too much time and too many heads an idea

[Daeron]

Panzer: that last pic you posted, I am pretty suure, Is a head that Monzter is building. It was a welded P90 that he actually totally (but subtly) relocated the spark plug holes.

 

I am going to cast a vote here saying this idea won't pan out on our engines. It is a throwback to an ear of much larger combustion chambers and big domed pistons. and there isn't any room. There are other methods to fight a battle on similar fronts (the Battle for Complete and Efficient Combustion and Harness of Power) that will yield much greater results for the effort in our L-6. Cylinder head cooling modifications, flat top pistons with proper shaped reliefs on high quench heads, tweaking R/S ratios..

 

I may be wrong, and I would be interested to be proven wrong... and even if I am right, plenty of old Datsun motors have been built using big open chambers and domed pistons, so the idea could yet be put to use... but it still probably would be better to start elsewhere for most people. HTH

[Mack]

Im going to go ahead and say, that aside from the cost and space aspect, it wont work on our engines because they are liquid cooled. If you start drilling into our heads to try and stuff another sparkplug in there, chances are you will hit a coolant flow passage.

[PanzerAce]

Panzer: that last pic you posted, I am pretty suure, Is a head that Monzter is building. It was a welded P90 that he actually totally (but subtly) relocated the spark plug holes.

 

 

I knew I recognized it from somewhere. I just keep associating Monzter with the plenum that he built over here: http://forums.hybridz.org/showthread.php?t=127863

[BRAAP]

Panzer: that last pic you posted, I am pretty suure, Is a head that Monzter is building. It was a welded P90 that he actually totally (but subtly) relocated the spark plug holes.

 

 

Sorry fellas, that head in the picture was built by me for another HBZ member a few years back, details of the head are in this thread;

http://forums.hybridz.org/showthread.php?t=108398

It’s an N-42 head, customer had the chambers welded up prior to sending it to me. MONZTERS monster is way nicer with angle plugs, etc.

 

 

Twin plugs.. Hmm interesting. Being a non cross flow head, there really isn't any room to locate spark bolt on the other side of the valves to help expedite flame front travel to all regions of the chamber, (intake and exhaust ports are occupying the real-estate the plug would need to be.)

 

MAG58 is on track with centrally located spark bolt in the chamber... Mercedes twin cam head on the L-28 block.

[nissan2ner831]

Here's a quick few things I found. There's a variety of VW Type IV engines, Porsche 6 cylinder engines and Porsche 4 cylinder engines:

 

4 Cylinder VW head (I believe)

 

Porsche 911 with twin plug (whole engine bay of course, but notice the 12 wires running from the distributor. That engine cost a small fortune)

 

Pic of a engine built by Jake Raby, one of the most knowledgeable people in building high performance 4 cylinder air cooled engines:

 

Porsche 356/912 engine with twin plugging

 

I'm short on pictues of the actual heads, but the first picture gives you the idea.

 

And yeah, I can imagine it might be more difficult with our engines, but if people are rewelding up combustion chambers and redesigning them as it is, wouldn't it be an interesting option to explore? Granted, the actual design of the head may get in the way...but I've also wondered if you could just technically fill up say the exhaust port with metal, and then just reroute it to the opposite side of the head XD I'm thinking you would run into water jacket issues though, and that may indeed be a problem preventing twin plugging from being used on these heads. Just some musings of mine, something I was thinking about in my spare time =P

[z-ya]

Sorry fellas, that head in the picture was built by me for another HBZ member a few years back, details of the head are in this thread;

http://forums.hybridz.org/showthread.php?t=108398

It’s an N-42 head, customer had the chambers welded up prior to sending it to me. MONZTERS monster is way nicer with angle plugs, etc.

 

Paul, This is an N42? It looks like a "P" head to me.

 

[e_racer1999]

Paul, This is an N42? It looks like a "P" head to me.

 

 

No, it's an N42. They welded up the combustion chambers so it's a closed design. You can tell by the depth of the CC.

[johnc]

With only one plug on a Porsche or a VW with a deep CC and a tall dome, you tend to get sides of the combustion chamber area that is occluded from the flame front until after the the piston begins it's travel down.

 

Exactly! John Benton's shop (http://www.bentonperformance.com) is across the alley from mine and over beers after work we've talked many times about the things needed to make power from the Porsche flat 4. Twin plugs are a band-aid - although a very necessary one in some cases. Absolutely not needed for the L6.

[z-ya]

No, it's an N42. They welded up the combustion chambers so it's a closed design. You can tell by the depth of the CC.

 

OK, I can see where the open chamber was welded up. Very cool.

[nissan2ner831]

Exactly! John Benton's shop (http://www.bentonperformance.com) is across the alley from mine and over beers after work we've talked many times about the things needed to make power from the Porsche flat 4. Twin plugs are a band-aid - although a very necessary one in some cases. Absolutely not needed for the L6.

 

Yeah John, with all the pictures of these heads being posted of the L6 it doesn't seem like there would really be such a need as with the VW heads and Porsche heads I've seen. With the way all of those combustion chambers are shaped on the L6, it doesn't seem like twin plugging would be necessary.

 

haha and yeah they can be a bit of a bandaid, but they do allow one to raise compression ratio's or increase boost (much more of a common thing on a Porsche flat 6 than found on the Porsche flat 4...and there is a reason why Porsche started twin plugging the Porsche 911 Turbo =P) or if nothing else, can help an engine continue working reliably. I know many people don't use it as a way to gain power by increasing the compression or upping the boost, but as more of a reliability thing...though that seems an awful expensive upgrade for some "reliability" to me =P

[nissan2ner831]

I believe it was a picture like this that made me think about twin plugging the L6 engines:

 

 

None of the race prepped heads or ones with the shapes show in this picture would benefit from it, but this combustion chamber is much more open =P

[PanzerAce]

it certainly *looks* that way, but there isn't actually alot of depth on the left side of those chambers (upper in the picture, opposite the plugs). Add that to the lack of space on that side of the engine and the very small dishes we usually run (or flattops often), and it starts making less sense.

[MAG58]

Like many are saying, if you're gonna put more holes in your L series head, fill them with Valves! We've got plenty of spark for what we're doing.

 

[BRAAP]

...

If you're gonna put more holes in your L series head, fill them with Valves! We've got plenty of spark for what we're doing.

 

I see a signature quote in this..

[nissan2ner831]

haha yeah that's the gist I'm getting. Like I said, I just tend to think about things a lot when I'm bored, and when I noticed the more more open head I just got thinking =P

[Daeron]

I see a signature quote in this..

 

Me too..... "fill the holes in your head with Valves to keep from losing the Spark..."