5.7L FIRING BOTH PLUGS AT ONCE
Moderator: scottm
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5.7L FIRING BOTH PLUGS AT ONCE
Hi,
Has anyone tried rewiring the plug wires on the hemi to provide BOTH plugs firing at the same time on each cylinder?
Hemis, traditionally, are high in Volumetric Efficiency but not great with Combustion Efficiency.
I thought maybe if BOTH plugs fired at the same time, it may help low-end torque and perhaps mileage.
Ron Miller
Calgary
Has anyone tried rewiring the plug wires on the hemi to provide BOTH plugs firing at the same time on each cylinder?
Hemis, traditionally, are high in Volumetric Efficiency but not great with Combustion Efficiency.
I thought maybe if BOTH plugs fired at the same time, it may help low-end torque and perhaps mileage.
Ron Miller
Calgary
I've had my plug wires switched around to fire both plugs at the same time for a about a month or more now...running great!
'03 silver Ram 1500 QC Hemi 4x4 Laramie 3.92s
Custom air intake, 3" magnaflow exhaust w/ high flow cat, 0-25K ohm adjustable IAT sensor mod, helix power tower, 195 degree t-stat, Superchips Hemi tuner, BFG A/T 325/60R20s.
Custom air intake, 3" magnaflow exhaust w/ high flow cat, 0-25K ohm adjustable IAT sensor mod, helix power tower, 195 degree t-stat, Superchips Hemi tuner, BFG A/T 325/60R20s.
How do they fire?
I always thought they did fire at the same time. How does the system actually work?
To perform this modification, are you simply connecting the coil to itself via the spark plug wire?
jason
To perform this modification, are you simply connecting the coil to itself via the spark plug wire?
jason
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5.7L Firing Both Plugs At Once
Well, when #1 fires, it also fires #7 exhaust, then #8 and #? exhaust, and so on; which tells me Chrysler needed to do this to burn ALL the unburned gas in the cylinder to meet emissions.
Personally, I would rather have the plugs BOTH fire in the same cylinder if that what it takes so the gas money I spend goes into power production.
The old 426s offered a dual plug head for a reason.
Like I had mentioned in the original post, Hemis are NOT very combustion efficient.... So if we can help them out we should !!
Ron Miller
Calgary
Personally, I would rather have the plugs BOTH fire in the same cylinder if that what it takes so the gas money I spend goes into power production.
The old 426s offered a dual plug head for a reason.
Like I had mentioned in the original post, Hemis are NOT very combustion efficient.... So if we can help them out we should !!
Ron Miller
Calgary
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This is from Hakan Osman (product engineer, ignition systems) at Chrysler.
With the Hemi's 1-8-4-3-6-5-7-2 firing order, the parent/companion pairings are:1/6, 8/5, 4/7, and 3/2. Therefore, to fire the two plugs on cylinder No. 1 at the same time, coils 1 and 6 are triggered, resulting in four spark plugs firing-two on cylinder No. 1 on compression stroke and two on cylinder No. 6 on the exhaust stroke. Since the plugs firing in cylinder No. 6 during the exhaust do not work, they are termed "waste spark", and in turn the entire ignition system is referred to as a "waste spark ignition system."
Another person from chrysler said the two plugs on the #1 cylinder fire at "nearly the same time"
I have done tests with timing lights which neither prove or disprove whats really happening. People that have swtiched the wires says it definatly makes a difference. I think this part of the Hemi is still alittle bit of a mystery.
With the Hemi's 1-8-4-3-6-5-7-2 firing order, the parent/companion pairings are:1/6, 8/5, 4/7, and 3/2. Therefore, to fire the two plugs on cylinder No. 1 at the same time, coils 1 and 6 are triggered, resulting in four spark plugs firing-two on cylinder No. 1 on compression stroke and two on cylinder No. 6 on the exhaust stroke. Since the plugs firing in cylinder No. 6 during the exhaust do not work, they are termed "waste spark", and in turn the entire ignition system is referred to as a "waste spark ignition system."
Another person from chrysler said the two plugs on the #1 cylinder fire at "nearly the same time"
I have done tests with timing lights which neither prove or disprove whats really happening. People that have swtiched the wires says it definatly makes a difference. I think this part of the Hemi is still alittle bit of a mystery.
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I wouldn't think doing this would cause Piston damage or any damage to the engine. Basically your just getting a better spark. As long as the A/F ratio is kept correct and their is no lean condition then the MORE spark the better.
Wouldn't adding a MSD box and Coil on a Conventional Ignition system be the same principal. Everyone knows that a MSD Ignition only provides benefits due to it's more powerful, hotter spark.
Wouldn't adding a MSD box and Coil on a Conventional Ignition system be the same principal. Everyone knows that a MSD Ignition only provides benefits due to it's more powerful, hotter spark.
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Converting to dual plugs has been a popular modification for years on the Harley Davidson shovelhead motor, which is a true hemi head. I've never heard of any problems with piston damage and the conversion is proven to make more power. I had a friend who used to own a bike shop and did this conversion to several engines. He would break the motors in on a test stand running on just one plug per cylinder. After the break-in he would hook up the second plug setup, and he said he always had to reset the idle, as it would go up several 100 RPM's.
Owner of the Poor Man's Hemi Cuda
Multiple people testing it for a couple months with answers to your questions and even more questions to confuse you: http://dodgetruckworld.tenmagazines.com ... p_modmaybe
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Twin Plugs
Ive done it already . nothing to it ..
pictures at my website
pictures at my website
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twin spark plugs
Allen click on the" Mopar Nationals Plaque " There is pictures of my 55 Dodge custom royal convertible with a New 2004 5.7 HEMI
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This sounds like a safe and logical mod. Coil fires both plugs on compression stroke and no plugs are fired during exhaust ( waste ) stroke. Besides a little extra heat during the compression stroke what more could happen?? This mod sounds like controversy over the intake mod I did on my 98 mustang. Guys started using the 99 mustang intakes on the 96-98 stangs. The ports were not the same and everyone said it would never work and ruin the engine, Well after 5K miles and 20 rwhp proven on the dyno, my intake switch was a sucess. I imagine this mod will prove to work safely, maybe not a huge HP mod but it sounds like it could help. Just my 2 cents.
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well fellas i have been doing some research on this topic and i liked what i was finding but couldnt be sure until i tried it myself so i did it took me about 10 min and she fired right up now i am finding that from a start and from a low rpm it made one heck of a difference high rpm not much of a difference but i have a lot of hills here in pa and i go up and down them alot and today i never kicked out of overdrive like i would have normally so with a combination of disabling my tmr and the wire switch i know i increased the horsepower some nothing major but what can you ask for when it is free
I haven't seen any true gains reported. Here is a dyno from about two weeks ago where someone tested this mod. No gains. I've seen some folks try it at the track w/ no gains either.
http://dodgetruckworld.tenmagazines.com ... ?id=122080
http://dodgetruckworld.tenmagazines.com ... ?id=122080
1971 Plymouth Cuda - 451 stroker
2003 QC 4x4 Dodge Hemi - STS Turbo, KRC 6005 heads & rods, Ross pistons, 6.1L crank & cam, ARP main/head studs, JBA headers, SMT6, APS converter: 575rwtq/492rwhp @ 9psi
2005 Chrysler 300c
2003 QC 4x4 Dodge Hemi - STS Turbo, KRC 6005 heads & rods, Ross pistons, 6.1L crank & cam, ARP main/head studs, JBA headers, SMT6, APS converter: 575rwtq/492rwhp @ 9psi
2005 Chrysler 300c