Twin Plug 1883 Advance Curve & Ignition System Advice Needed

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Jacques Lefriant
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Re: Twin Plug 1883 Advance Curve & Ignition System Advice Ne

#31 Post by Jacques Lefriant »

Hi Ron
Given there is theorectical advantage why in practice is this not implemented more often on small bore engines? why do 4 valve single plug engines out preform 2 valve twin plug? Why do Turbo 3.6 911 dop the dual plug? why are MSD ignitons touted? i don't need the answers but i think other approaches may have easier implementation.
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Ron LaDow
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Re: Twin Plug 1883 Advance Curve & Ignition System Advice Ne

#32 Post by Ron LaDow »

Jacques,
I made claims and an offer specifically about 356 single-plug, carburetted engines, and I explained the physical laws which lead me to make those claims and the offer.
I stand by the claim, the offer, and the explanation and will mention again that I can be proven wrong.
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Re: Twin Plug 1883 Advance Curve & Ignition System Advice Ne

#33 Post by AlexFord »

I think the ignition systems on these antique motors, unless pressurized electric fuel pumps with accelerated fuel sprays and air induction to match have the limits discussed in prior 356 articles on c/r and unshrouding of the valves and the valve angles. The twin plugging certainly takes care of a lot of the advance problems and the controlled burn can occur with a modified and improve advance so that the connecting rod angle sweet spot can be maximized. The intake valves and locations, according to members with massaged heads still have limitations. The amount of intake charge that can be used with the full broken up droplet pattern have certain limits because of the shape of the Porsche motor combustion chamber & the valve locations and angles. Fuel injection would change some of this but perhaps only to a small degree. Because of the twin plugging, I'm dubious that there would be that much gain with a crank fire ignition, although it solves certain other problems mentioned. Eventually, the application might become ridiculous is a full sensor-set is utilized as in the more modern engines. The Solex with massage of the intake manifolds, velocity stacks and tuned exhaust perhaps can induct the largest practical and usable charge in the twin plug set-up without going to a set-up that involves a set of systems that essentially redesign the engine. At that point, one might one to go to one-off heads designed to, "modernize the engine." However getting the most out of the current engine with a massage, it would seem that sticking to the Solex set-up is the best way to go along with a firing mechanism that is efficient. Because the burn must be controlled, the so-called hotting sparking modification really is overkill.-Zioo

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C J Murray
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Re: Twin Plug 1883 Advance Curve & Ignition System Advice Ne

#34 Post by C J Murray »

The following data was collected today from the test of my 2133cc Porsche 616 pushrod using stock points ignition with one lonely spark plug. It was built for very broad power for street use.
211315-1.jpg
211315.jpg
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Phil Planck
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Re: Twin Plug 1883 Advance Curve & Ignition System Advice Ne

#35 Post by Phil Planck »

It's time for a picture of a twin plug Porsche engine. Gotta admit, it looks pretty cool(except for the exhaust).
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Ron LaDow
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Re: Twin Plug 1883 Advance Curve & Ignition System Advice Ne

#36 Post by Ron LaDow »

C J Murray wrote:The following data was collected today from the test of my 2133cc Porsche 616 pushrod using stock points ignition with one lonely spark plug. It was built for very broad power for street use.
211315-1.jpg
211315.jpg
Get back to us after you get a decent ignition system (and CR) in that thing and find out what it can do.
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C J Murray
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Re: Twin Plug 1883 Advance Curve & Ignition System Advice Ne

#37 Post by C J Murray »

Hi Phil, That's a great picture but a really bad idea. Running engines without exhaust pipes allows cold air to hit hot engine parts, not to mention the loss of performance. I wonder why they were doing that? Cliff
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Re: Twin Plug 1883 Advance Curve & Ignition System Advice Ne

#38 Post by Phil Planck »

"Hi Phil, That's a great picture but a really bad idea. Running engines without exhaust pipes allows cold air to hit hot engine parts, not to mention the loss of performance. I wonder why they were doing that? Cliff"

I assume just for the picture.
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Re: Twin Plug 1883 Advance Curve & Ignition System Advice Ne

#39 Post by Jacques Lefriant »

Hi CJ
They just did not to put the exhaust on backwards since the engine is a spyder engine and the test stand is set up for rear engine.
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Re: Twin Plug 1883 Advance Curve & Ignition System Advice Ne

#40 Post by C J Murray »

Maybe they should have tried a 356 race exhaust for testing? :P
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Re: Twin Plug 1883 Advance Curve & Ignition System Advice Ne

#41 Post by Jacques Lefriant »

Hi CJ
they didn't really race to many 356 in the late 50s with the carrera engine. I have seen pictures of the long spyder exhaust installed in some coupes and it stuck out a foot or so. the next thing they did is shorten the exhaust. the 59 1600 had a nice small dia exhaust and the 2ltr had the elegant Sebring which is my favorite. your peak torque is comprable to a 904 you just need bigger carbs and rev it higher. What carbs did you use and what size venturies??
j
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Re: Twin Plug 1883 Advance Curve & Ignition System Advice Ne

#42 Post by C J Murray »

Hi Jacques,
Remember, this engine is in a mild state of tune. I could get MUCH more power out of it if I tried but I don't know that a 82 mm stroke crank would like to be revved that hard. It might be ok but that stroke is not legal for racing and for a street engine I was aiming to be sort of like a Normal in terms or rpm range used while being somewhat more "peppy". :D

The numbers here are the highest it will see. It has my Solex 44s from my racer with 38 mm venturis. The exhaust used here is a full race Bursch. I tried the carbs and exhaust because the first run with Solex 40s with 36 mm venturis and the crappy sport muffler that I had laying around showed giant torque down low but it gave up way early before making anywhere near equal horsepower up top. I guess I will try some Weber IDF 44s and a better muffler. My wild guess is that it will end up around 155/155 in quiet civilized trim.
Cliff
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Re: Twin Plug 1883 Advance Curve & Ignition System Advice Ne

#43 Post by Jacques Lefriant »

Hi CJ
get real and put 48s or bigger on it run 40 or 42 chokes.
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Re: Twin Plug 1883 Advance Curve & Ignition System Advice Ne

#44 Post by C J Murray »

It has a very mild cam. Do you think it could handle 48/40 IDAs in traffic or are you just yanking my chain?
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Re: Twin Plug 1883 Advance Curve & Ignition System Advice Ne

#45 Post by Vic Skirmants »

"yanking my chain?"
Flush!

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