MSD 6al digital

[flyinlow]

Any reviews of the MSD 6425?  Thinking about upgrading and giving the MSD Street Fire to my son. My Charger is a street car , so dependable is at the top of the list. The SF has been dependable.

[cuda66273]

Most and I stress Most MSD Products work very well, dependability is something you'll need to do some research on.  I can't give you an unbiased opinion as we don't sell MSD Products and we have our reasons.

You may also want to ask what country it's made in?  The Street-Fire probably has the same CoC (Country of Origin)

Street car?  Why do you think you need a CD ignition system?
CD Ignition will add no performance to your application if the system you already have is up to the task which it sounds like it is. 

CD Ignition fires a multiple spark on each cycle.  If you have extremely low Cylinder pressure from valve overlap on a big cam shaft, low CR combined with a cam profile that doesn't match the rest of the build then the Multi Spark may help you.  race cars have big cams, low cylinder pressure at low RPM and the Multi spark works well.

If you have a nice performance build with a correct cam for the application then it'll fire with a quality conventional ignition just fine and you'll see no improvement for your $$$.

Burn time.... Simply explained this is the length of time the spark is actually occurring within the combustion chamber on each cycle.  CD (Capacitor Discharge) Ignitions like Daytona-Sensors, Crane, MSD and others generate a very short burn time on each fire point so up to 3000 a Multi spark or a series of short sparks may be needed to be sure you achieve ignition, it's really a band aid for the characteristics of a CD System not so much of a benefit as these companies would like you to believe.  It works well but in a street car application it probably won't offer you any improvements.

A conventional ECU system offers up one long spark which in most cases lights off the combustion process just fine as long as it's up to the task.  As you build more top end power in the engine the cylinder pressure starts to drop at the low end as described above and a CD Ignition may be needed to get it light off clean.
 
A good alternative to a CD Ignition for a hot street/race application is the new Pertronix Ignitor 3 distributor, this has the best of all worlds, double spark from crank to 10,000 RPM, built in REV Limiter, stand alone unit with a 2 wire connection.  They are a little tricky to curve perfectly but we figured them out and do things a little different than the factory supplied info and parts and they work really well with great performance and reliability.

50,000 Volts! Or more as some claim, here's the truth, the ignition system will only generate enough voltage for that energy to find a ground which hopefully is the ground strap on the spark plug. 

Think about the whole system for a moment, what can cause the plug to require 50-80KV to fire the plug if it's only generating the voltage it needs to find a ground?

Have you ever welded?  It's the same principle, the welder builds voltage until it can jump to ground.  If you have the welder set at low voltage you have to get the wire very close to the material and it's cooler for thin metals, if you crank it up it'll jump 1/2" or more to find that ground and it'll be much hotter and may even melt away thin material almost like a cutting torch.

So it comes down to "Resistance" starting in the distributor ....How far is the rotor tip from the cap contact points? Back "In the Day" we would file the rotor tip to increase the gap and force the system to generate higher voltage.

Plug gaps... does it make sense to you that the wider the plug gap the more energy it will take for the spark to jump to ground?  Wider gaps force everything to work harder build higher voltage=Heat and will shorten the life of the plugs dramatically.

Ambient resistance...  As your engine builds HP and RPM it creates more cylinder pressure, the A/F mixture gets richer as the carb starts to release more and more fuel as velocity through the booster increases.  This whole chain of events creates and a much denser ambient air condition within the combustion chamber building more and more resistance between the electrode and the ground strap therefor forcing the ignition system to push more and more voltage to find a ground.  This all takes an ignition system that can handle the task.  A Pro Stock car will build cylinder pressures in the 3800 4000 PSI range, everyone I talk to about this seems to evade the question about how much pressure they build, I'm sure there's some 12 year old MIT freshman that could figure that out based on weight, MPH and ET but I never quite got that far in the higher education system.  I do know from reliable sources that you'll probably never see a pump gas motor make over about 2400 PSI at tops.

So armed with all this info you can see that a 80,000V systems will run at about 25% throttle on a street engine and maybe up to about 30-34KV at WOT up around 6500-7000.  Our test nitrogen pressure tank we operate at 3000 PSI which simulates a pretty stout race motor. We have the gaps set at .050 which allows us to Dyno an ignition system to determine it's max output within these parameters, 1000 RPM idling it will pull about 16KV then at a 2200-2800 RPM street driving simulation it takes about 22-24KV to fire the plugs and at 7000 it will pull 34-36KV.

These numbers are not actual facts but just a baseline that we use and compare to.  The point is if the big red letters on the box say 80,000V output that has no relevance on what portion of that you'll need to run your car, it sure isn't the 80KV unless of course your Allen Johnson or V. Gaines (old guys rule).

This is sort of like the fuel pump rule, you can run a Aerospace 400GPH pump on a 273 2 barrel and it'll work fine as it's regulated by the Fuel Pressure Regulator and Needle and seat.  I think we can all agree that it would be a huge waste of money to put a pump of that magnitude on a 273.  Same goes for ignition, it's controlled by rotor gap, plug gap, Ignition Wire resistance (Another whole subject) ambient air quality within the combustion chamber, all these meter how much voltage it takes to fire the plug.  You wouldn't put a $700.00 80KV CD Ignition system on that 273 but a good upgraded ECU will help it some, same for your Hot Street Car or light bracket car, use an adequate ignition system to handle the task and you'll maximize the potential power and reliability of the motor and car.

Of course one of most important things you can do for the performance, longevity and reliability of your car is getting that distributor curved correctly to the application and be sure that it's the correct distributor for the application, don't put a locked out Pro Billet in that 273 and expect it to actually run.

This is just the sugar glaze, it would take days/months to give you the whole doughnut but hopefully it will help you in your decision making process and help preserve a few of those hard earned dollars in your wallet.

My philosophy on Rev Limiters...  We all have a REV Limiter we carry with us all the time, it's better know as a wallet.

Please do not leave messages on this board if you have a question email me direct or jump on my Live Chat accessed on my website I'll be happy to answer your questions.
www.4secondsflat.com

Pertronix, Daytona-Sensors, FBO Ignition, Andover, Aerospace Components are all products Made in America.

Help Keep America working, shop with consideration of your Family and Friends.

[firefighter3931]

I like the Analog 6 series MSD boxes....been running them for years. Never had one crap out on me yet ! 

The digital boxes have some nice add-on features but unless you're planning to race a lot and need a 2-step or delay box then it's overkill....inmho 

The digital boxes are also more sensitive to EMI so you need to isolate and shield the power wire and keep it away from the alternator. This is not an issue with the analog 6AL or 6A



Ron

[flyinlow]

Thanks for the replies.    The Street Fire seams to work fine. I like the dial adjustable rev limiter. I have about 28K. miles on it. When I bought the 73 it had a 318 with the stock box. It was old and rusty ,but worked. Actually ,I have never had a problem with a stock Ignition, but I was going to put a 440 with Eddy heads and a mild cam and put the S.F. on it. The 318 seamed to run a little better with it,but it needed some carb work (never got it). The 440 has never been run without it, so I cannot say if it helps it. I have an old points distributor I take on road trips,to get home with, never needed it.
Not trying to win a voltage war, I hope my plugs never need more than about 25-30 k. volts to fire. Years ago when I put 440's on a Sun analyzer , warm plug firing voltage was 5-10k. idling and 15-20k. under load with resistor wires. Good information on the CD ignition. Thanks.
Made in America counts. Ron, I am looking at a made in Canada gas tank for a winter project. I like analog dependability (DC9,B727,MD80)  I have heard about the digital sensitivity elsewhere.

Craig

[Chryco Psycho]

I have lost count of how many MSD boxes I have seen fail , mostly analog , all on customer cars as I don't use them on mine . I have less failed Mopar ECUs in the pile !

[mhinders]

You can make any electronic box fail by using a coil with a lower resistance/inductance than the box is specified for. You simply pull more current thru the transistors than they are designed to handle.

[Chryco Psycho]

so the typical setup of a MSD 6AL & a Msd vibration Blaster coil is a bad one ?
I guess a warning of only using a given resistance coil in block letters might help !!

[mhinders]

We customers are kept in the dark, there is no specification on the MSD 6AL-2 for minimum resistance.

Of course there is no problem with stock coils, these are high resistance/low current coils. When it comes to higher performance coils you have to stick to MSD coils simply because they don't give the data needed that would enable you and allow you to safely choose other brands.
This is copied from the MSD data file:
----------
COILS
The MSD 6AL-2 Ignition can be used with most stock coils and aftermarket coils designed to replace
the stock coils. The line of MSD Blaster Coils are great for street and mild racing. For extended high
rpm operation the Blaster HVC, PN 8252 or HVC II, PN 8253, are recommended. For more information
on recommended coils, check with our Customer Service Department at (915) 855-7123.
----------

Not a word about minimum allowed resistance, and you are in the hands of MSD when it comes to choosing a coil.

[mhinders]

I had a look at the more powerful coil they recommend for the MSD 6AL-2 box, the

HVC-2 Coil, 6 Series Ignitions, Part No. 8253

Here they state that the resistance is as below:
Primary resistance:   .16 OHMs

I think one can assume that any coil having 0.16 Ohms or more can be used with their MSD 6AL-2 ignition box. However, you get the most energy to the plugs with a 0.16 Ohms coil.
The resistance is however not the full story, the inductance also plays a role, but the resistance should have a bigger impact on the reliability of the ignition system.