jRock617

hey i came across this on american muscle
http://www.americanmuscle.com/gms-co...s-2v-9904.html

ive heard mixed things about them, some say they dont add anything to N/A cars, is this ture? what about a fully built 2v (heads and cams)?

Stevecooper

I have talking to GMS and they claim that they new sets (like the ones your posted) will add power.

we are going to dyno a twin supercharged lightning with them in two weeks. So we will find out.

cliffyk

Simple answer for any n/a Mustang (GT, Mach I, or otherwise)--NO, not one drop...

DeathRattle

I bought the Accel super coils and put them on when my car was N/A and the engine ran a little smoother...I don't think it added any horsepower tho...you will only gain about 10-15 hp (supposedly) even on a forced induction engine...I'd personally like to see some dyno results with a N/A engine...

ShinobiOfLegends

gms is crap, run away. if you really want to upgrade them, get a set that doesn't mimick the stock design. the only brand worthwhile IMO is WeaponX.

http://www.weaponxperformance.com/ca...products_id=45

cliffyk

Sniper also sells the Weapon X coils, rebranded as Sonic X--they are $399 from Sniper Tuning of South Florida.

However I am forced to once again state that even these will add nothing in the way of performance gains to any n/a engine--zip, zilch, nada...

DeathRattle

Just out of curiosity Cliffyk, what makes you soo sure and adamant in your statements...?? Is there something you know that perhaps nobody else knows about...?? Have you seen or heard of a before and after dyno test or something...??

cliffyk

Mostly it's nearly 50 years of building/repairing/tuning motorised thingys, and then there's that BSME thing as well (MIT '71).

Then there's the fact that it takes a maximum of 18 to 22 kV to ionise the gap on any n/a engine (I don't care how high the CR is) and fire the plug. the firing voltage (once the gap has been inonised) is far less, in the order of 6 to 8 kV. Ignition mods as a quick way to gain performance started to go away when capacitive discharge systems came along in the late 70s, and went away completely when DIS and COP technologies became mainstream...

The OEM COPs are rated as 40 kV capable, which probably a realistic consistently available output rating based on normal under hood temperatures and other factors that automotive engineers (not marketing departments) have to deal with.

The aftermarket people don't have to worry about things like that and can sleep comfortably making bold statements like "up 60 kV output" even if that was just observed once on a stone-cold unit, driven to full saturation with a 16V input.

Further there is that the OEM, and most if not all of the OEM looking aftermarket COPs, are made by the same manufacturer--Micro-Tech. Here's a link to there bragging about the Ford OEM COPs, here's their blurb about their relationship with GMS.

Give them a call, I am sure that if you wanted to buy a sufficiently large quantity of them you could get them in whatever color you like, and branded as DeathRattle-X Super COPs or what ever you like...

Then there are the numerous postings on tuning forums, like this one from the NMRA forum, where people who actually tune cars for a living talk about how good the stock COPs are...

Other than that you're right I should follow my own advice and shut-up when I don't know what I'm talking about.

If someone has come clean non-aftermarket manufacturer sponsored, back-to-back with no other changes, dyno charts showing HP gains from 3rd party COPs I'd love to see them...

DeathRattle

"DeathRattle-X Super COPs"...that would be bad-a** man...I'd get them in black, fake out some dyno pulls and make a killing, haha...so basically, it does not matter that the OEM COP loses kV with each engine revolution because it also requires less kV (due to the gap already being ionized)...in that case it would be irrelevant if an aftermarket COP was to have 40,000 kV anyway, am I correct...?? What about on a supercharged engine...??

cliffyk

Bear with me here, this is what happens when you ask a retired engineer a technical question. My grandson once asked me, when he was 6 or so, how a floppy disk worked--he zoned out well before I got to part about the trade offs between magnetic density, permeability, and retention...

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The COP, OEM or otherwise loses all of its power during every two engine revolutions--except during starting when the COPs on every cylinder pair fire at the same time*--one at TDC on the cylinder that's on a compression stroke, and the one on the cylinder that's at TDC on the exhaust stroke.

To better understand, realise that one primary winding terminal of each COP is connected directly to a +12V source that is constant while the ignition key is in RUN or START. The other primary terminal (which I will refer to as the negative terminal) of each is connected individually back to the ignition controller on the PCM.

At some time prior to needing to make a spark the ignition controller in the PCM connects the negative terminal to ground for a sufficient amount of time to fully saturate the coil electrically (and magnetically). This is a relatively short period of time in the order of 1.5 to 2.0 ms, and is called the dwell time.

Dwell is a term carried over from mechanical distributors, when the contact points remained closed (I.e. dwelled) between the lobes on the distributor cam.

Then, when it is time to fire the plug the controller breaks the connection between the negative primary terminal an ground, and the rapidly decaying magnetic field generates a high voltage pulse in the coil's secondary winding. This voltage builds until the plug gap ionises. then once that happens the voltage drops to 6 to 8 kV while the plug fires. When there's not enough power left to sustain the spark it stops and the remaining voltage dissipates.

This can all be seen in this oscilloscope screen shot, which also shows the primary voltage for the triple firing sequence that happens at idle and lower rpms:



The initial rise shows that the ignition controller has connected the negative primary connection to ground and the coil has been energised. The length of that flat portion after the rise id the dwell time.

The downward spike at the beginning of each firing represent the voltage rising to the point that the gap ionises; after that the plug fires, that's the squiggly upward rising trace.

In the first firing, due to the longer dwell, when the plug does fire the voltage drops so quickly from the ionisation level to the firing level that it actually creates a spike in to opposite direction. The remaining firings do not exhibit this because the shorter dwell times between the multiple firings do not saturate to coil as fully.

The first two actual plug firings are cut short by the ignition controller once again connecting the negative side of the primary to ground. On the last firing you can see the characteristic ringing of a natural energy decay.

The ringing after the 3rd firing is the remaining energy being dissipated back through the primary winding.

This trace also serves to show that the COP has got more than enough spherical stuff to fire three times in rapid sequence, less than 6 ms for all three dwells and firings.

For reference, at 6500 rpm the entire cycle for each cylinder, from intake to compression to power to exhaust, takes 18.5 ms--the first single firing shown in the trace last 2.5 ms, I.e the OEM COP get to rest for 86% of each cylinder's cycle.

In the last your are spot on, 40 kV is more than enough to ionise the gap on any n/a engine, and also on most high compression and boosted engines as well.

However it is possible, when chamber pressures get way up there in very high compression and boosted engines, for there not to be enough voltage available to ionise the gap**; that's when some sort of booster on the primary, or a better engineered COP is needed--but not until that point has been reached.

I am highly suspicious of higher voltage claims made by the purveyors of OEM "lookalike" aftermarket COPs. I am certain I could mount an OEM on a test fixture and get a peak reading of 60 kV while having it "fire" a optimised test gap, or maybe even just a plain old spark plug with a 1/4" gap. There's no magic available to make to make a coil of the same dimensions and weight as the OEM unit, and have it be 150% more powerful.

This said, it is quite possible that the improved design of the Weapon-X/Sonic-V COPs can do this, and if were running high boost or a seriously tricked out engine I would take a serious look at getting a set.


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* - When the engine is first turned over the cam sensor signal is unavailable and/or unreliable for a bit, so the PCM just fires both COPs for the cylinders that are coming up to TDC regardless of what part of the cycle they are in.

** - As compression and temperature rise more voltage is needed to get gap inonised so the spark can begin/