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 Post subject: 7AL-3 or Digital 7 ??
 Post Posted: Wed Nov 07, 2007 6:06 pm 
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I need some input here. On this build I am buying everything for the first time with the dragster.
In this application, which MSD ignition is the right choice? 7AL-3 or the digital 7.  :-k

John

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 Post Posted: Wed Nov 07, 2007 6:22 pm 
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Digital 7 is the way to go. It's lighter,smaller,has more features and if you spend the extra $$$ like Ken did you can get the programmable one =;  =;


While your at it get a data logger you can really have fun with that piece.. \:D/  \:D/

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 Post Posted: Wed Nov 07, 2007 6:55 pm 
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Mine proved to be invaluable with marginal tires last year as I pulled 15* of timing out at the hit, ramped it back in .8 seconds later and made those tires last till the cord was showing.  The short times looked like xerox copies!  Yeah the car slowed down but I got every ounce of use out of those slicks!

That box has more stuff than you'll know how to work with at first but time and reading and fooling with the software will fix that.  I just setup a high gear timing retard on mine the other day.  Another nice feature I might add.  

So, if you don't mind spending the money for top drawer stuff then go for it Bubba!

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 Post Posted: Wed Nov 07, 2007 7:11 pm 
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Since you mentioned "software" I am assuming that I will need a laptop to program it. Is this neccessary at the start or can the laptop wait?

John

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 Post Posted: Wed Nov 07, 2007 10:22 pm 
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You don't need a laptop unless you want to change s**t at the track and download the RPM graphs for each run.  Then it's a necessity.  I got a hand held box with mine that is suppose to allow you to change the launch RPM and a couple of other things right from the seat but I've never used it.  You will need to be able to connect it to a computer at your shop though so you can set it up.  

I originally bought this one when I had that last hard tail dragster cuz I wanted to be able to retard the timing at launch on marginal tracks or tires.  I never did put it in that car before I sold it and installed it in the Camaro last year in August when the Goodyears were going south.

The 7531 box I have has a feature in it that is considered to be traction control, ie, slew rate is programmable and will control tire spin down track via timing retards once the RPM accelleration rate has exceeded the set point.  Nice feature also and I wish I had of had that part working week before last.  It would have kept my car going straight when the tires started to turn loose.  

It doesn't take much of a computer to do the programming and if you want to carry a desktop PC with you in your trailer like I did at first, it's not that big of a deal.  The laptop just makes ita little nicer is all.  Dell is selling NEW laptops for under $500 now and that would be the way to go IMHO.  

7AL-3 boxes have been somewhat problematic over the years.  I've known some guys locally that had problems with them.  The 7AL-2 is rock solid and cheaper but with less features.  The Digital 7 box it pretty much an "all in one" deal as it's the rev limiter, two step, three step and RPM activated swich also along with the timing retard features.

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 Post Posted: Wed Nov 07, 2007 10:30 pm 
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Hey Ken, didn't you have a problem when you had a 7AL-3?


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 Post Posted: Wed Nov 07, 2007 11:27 pm 
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slow72velle wrote:
Hey Ken, didn't you have a problem when you had a 7AL-3?


Well, not really Don.  I did change it out with the AL-2 I have in the Studebaker but it turned out that it was a fuel problem not ignition.  That AL-3 box had been back to MSD though as it had a repair sticker on it.  The guy I got the car from had sent it back to them before I bought the car.

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 Post Posted: Thu Nov 08, 2007 4:31 pm 
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The Digital 7 is the way to go. The start retard alone is worth the difference. You can use just about any laptop with a serial port, a $200 to $300 used one will work.There are defaults but at least hook it up to a computer to set the initial parameters. You could do that on a home computer and hook up the MSD to a battery. The ignition has to be energized to load changes as well as the main power and ground.


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