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Sun Sep 08, 2013 8:51 pm

... but do you know of anybody doing this stuff commercially?

Sun Sep 08, 2013 8:51 pm

... but do you know of anybody doing this stuff commercially?

Mon Sep 09, 2013 3:19 am

58 Plastic Tub wrote: ... but do you know of anybody doing this stuff commercially?

http://www.stanpobjoy.com.au/#!dual-ignition

This is in Australia though

Mon Sep 09, 2013 8:33 am

58 Plastic Tub wrote: With that in mind, is anybody currently doing this correctly (with the bottom plugs aimed at the exhaust, and so everything clears the P/R tubes)?

... and probably equally important, is anybody building dual plug distributors or adapters?

I always centered them in the combustion chamber and angled them in. The pointing towards the exhaust is a bunch of BS as far as im concerned.

I made a few distributors. Even have some castings around somewhere that fit the 81 Nissan 720 cap. As far as I know it is the only 4cyl 2 plug cap in production. The problem with it is that it has low dielectric strength so you cant run a high energy ignition on it. Maybe you can but I couldn't ever get it to stay stable for a reasonable amount of time.
Your best bet is to megasquirt it.

Mon Sep 09, 2013 8:49 am

I asked DRD if he did this work and he doesn't. He told me Rimco can do the modifications to dual plug.

I have a set of dual plug aircraft 040 heads that I picked up at a swap meet. They are the older style with the access cover plates (for socket wrench) inside the valve cover area.

Steve

Mon Sep 09, 2013 9:10 am

Jimmy111 wrote:
The pointing towards the exhaust is a bunch of BS as far as im concerned.

Well, when your racing customers know better, and you aim to please, you figure out a way to give them what they need.

Mon Sep 09, 2013 10:23 am

I do what ever they want. If they want to pay for it its their baby.

There are lots of theories of why to do this but the only one that makes any sense is to cool the electrode to prevent preignition. This dosent work on ACVW because the spark plug is on the wrong side to begin with and not in the airflow stream.

However in general, ACVW's have no electrode projection. Not like SBC's that have lots of it. This makes for a very cold plug. No need to expose the electrode which is not exposed anyhow to the incoming charge for cooling.

So whats the point?

Mon Sep 09, 2013 12:46 pm

When it comes to engines, there's a lot I don't understand, so I don't pretend to .. like how does an additional spark plug DOWNSTREAM of the exhaust valve make a top fuel car go faster?

Tue Sep 10, 2013 6:12 pm

Jake Raby wrote: .I made 250HP on pump gas last year with a 2.9 Twin Plug engine in my Wife's GL Vert and it still averaged 30 MPG.

I think that is more better power to mpg than the 2013 Beetle. Hummm......

Wed Dec 04, 2013 9:38 pm

So it seems this thread recomends either Great Planes, expensive pre tapped heads or do-it yourself. If I do contract Great Planes to do it will it mess with the quench area? I'd like to run a 0.040" quench but it looks like the plugs may protrude. Is there anyone else for the job?

Thu Dec 05, 2013 9:53 am

Juanito84 wrote: Is there anyone else for the job?

RIMCO

Thu Dec 05, 2013 10:02 am

Steve Arndt wrote: Juanito84 wrote: Is there anyone else for the job?

RIMCO

Muchos thank yous!

Thu Dec 05, 2013 11:48 am

I can already machine my heads for 12mm plugs. I will be able to do dual plugs within 30 days.

Please e-mail me direct with any pricing questions.

Thu Dec 05, 2013 1:21 pm

Raby recommends 10mm plugs on the bottom side.

Thu Dec 05, 2013 3:39 pm

SGKent wrote: it is done in aircraft for redundacy. Twin magnetos twin plugs. They can't just pull over when it comes to problems and fix a wire.

Yes, And not only that, If you are running twin mags that are timed close together and you are running low octane gas, watch out. When the sparks occur nearly simultaneously, two flame fronts can collide and cause some serious engine damage over time. The cure is to time one mag slightly later than the other so that its spark is essentially wasted. Fred

Thu Dec 05, 2013 4:45 pm

Fred Winterburn wrote: SGKent wrote: it is done in aircraft for redundacy. Twin magnetos twin plugs. They can't just pull over when it comes to problems and fix a wire.

Yes, And not only that, If you are running twin mags that are timed close together and you are running low octane gas, watch out. When the sparks occur nearly simultaneously, two flame fronts can collide and cause some serious engine damage over time. The cure is to time one mag slightly later than the other so that its spark is essentially wasted. Fred

Of course, based on a little internet snooping, it depends on the engine. I was referring to a 65HP Continental engine as fitted to a J3 Cub, not a Porsche. This is a good link for explanation for why a twin plug set up would be a good idea. In this case it seems to be a band aid for a poor combustion chamber design. Fred http://rennsportsystems.com/letstalk-2/gasoline-detonation-twin-ignition/

Thu Dec 05, 2013 5:28 pm

Fred Winterburn wrote: SGKent wrote: it is done in aircraft for redundacy. Twin magnetos twin plugs. They can't just pull over when it comes to problems and fix a wire.

Yes, And not only that, If you are running twin mags that are timed close together and you are running low octane gas, watch out. When the sparks occur nearly simultaneously, two flame fronts can collide and cause some serious engine damage over time. The cure is to time one mag slightly later than the other so that its spark is essentially wasted. Fred

I'm afraid the flame front collission theory is a myth. First of all making them out of sync won't keep two flame fronts from "colliding". And what damage could two flames coming together really do? However there is one danger involved with twin spark. With two flames the cylinder pressure can rise over twice as fast. If it gets two high then detonation can set in. Usually you want the flames to end around 10 to 15º ATDC. Since two flames burn faster than one that's why dual spark engines should be timed retarded when compared to single spark.

You are right about combustion chamber design. A poor design leads to a slow flame. In ICE's the faster the flame the better short that of detonation.

Thu Dec 05, 2013 6:43 pm

Juanito84 wrote: Fred Winterburn wrote: SGKent wrote: it is done in aircraft for redundacy. Twin magnetos twin plugs. They can't just pull over when it comes to problems and fix a wire.

Yes, And not only that, If you are running twin mags that are timed close together and you are running low octane gas, watch out. When the sparks occur nearly simultaneously, two flame fronts can collide and cause some serious engine damage over time. The cure is to time one mag slightly later than the other so that its spark is essentially wasted. Fred

I'm afraid the flame front collission theory is a myth. First of all making them out of sync won't keep two flame fronts from "colliding". And what damage could two flames coming together really do? However there is one danger involved with twin spark. With two flames the cylinder pressure can rise over twice as fast. If it gets two high then detonation can set in. Usually you want the flames to end around 10 to 15º ATDC. Since two flames burn faster than one that's why dual spark engines should be timed retarded when compared to single spark.

You are right about combustion chamber design. A poor design leads to a slow flame. In ICE's the faster the flame the better short that of detonation.

Well, I stand corrected and what you describe explains why there is detonation with cheap fuel in the Continental aircraft engines. Having one spark well retarded means the first and only flame front has taken more time to burn and hence no detonation. With higher octane fuel the flame fronts would expand more slowly and not result in detonation. You have solved the paradox that was threatening to short circuit something in my brain. However, I disagree with what you said about timing them differently not resulting in colliding flame fronts. Given how fast combustion actually occurs, retarding one spark far enough will effectively make it a wasted spark. That's how detonation was and is prevented with cheap fuel and twin mags in some aircraft engines. Thanks, Fred

Thu Dec 05, 2013 7:24 pm

Yep, you got it!

As far as retarding one over the other not causing flame "collision" depends on several factors. The flame lasts for several degrees, picking up speed as it burns. Some flames can take over 50 degrees of crank rotation from start to finish even in ideal conditions. Lets say one is timed at 20 BTDC and the other at 0 TDC. The goal is that both end between 10 to 15 ATDC but may last longer in poor conditions. The flames really don't get rolling until after TDC meaning the second plug has a very good chance of starting a flame. With the increasing pressure and heat caused by the burning fuel between 0TDC and 15ATDC both flames will take off and collide. Of course the first will be bigger but I'd imagine it would take a spark at at least 5 ATDC to not cause a second flame.

Thu Dec 05, 2013 7:35 pm

Combustion chamber shape and chamber filling have everything to do with proper twin plug placement and flame propagation.

The larger the bore and the bigger the chamber, the more efficient an opposing twin plug arrangement will be.

There are benefits from chaning dwell times, splitting up the timing and etc, but I typically only found those gains beneficial when hunting for high MPG. Thats how I got 51 MPG from a 140HP engine back in 2005.

Two flame fronts colliding is whats supposed to happen, thats why twin plug engines optimize with much less overall timing, in my experience 22-24 BTDC is maximum timing for a twin plug engine. With twin plugs my CR starts at 11:1, else there's no benefit.