Question - digital-7 and a 44 mag

I'm currently running a 44 mag with a 8145 box on a 565/14-71 BBC blown Alky motor in a boat. To soften the launch I'm using a Digital-7 connected to the 44 mags 8145 box to limit the RPM at launch. Since I'm only using the Digital-7 as a rev limiter, the 44 mag rotor phasing and the crank trigger does not need to be in phase.

My question is if I want to use the retard function in the Digital-7 what is the best method to phase the 44 mag rotor to the crank trigger?

Thanks, Joe

 

Use the mags internal trigger to phase it. If you are going to pull out a lot of timing you might run the mag a little retarded. EXample if you run 30 degrees total set the mag at 25. Then set the crank trigger at 30. That way when you retard the cap is a little closer to correct phase. I set ours both the same because I don't care if it has proper phasing when i'm killing power anyway. If you go extreme enough out of phase it can misfire but it takes a lot with a big cap 44 mag.

 

phasing

One of MSD Bulletins explains it. Go to there site If you have a problem let me know, I will find it. I have it printed somewhere. Don

 

We phase the mag in at half the total retard. For instance we ran 25* total timing, but left the line at 5*....so we phased the mag in the middle at 15*. Crank trigger set at 25*.

Josh

 

Thanks guys for all the input. I can see that both methods are used, pulling out timing and riding the dots.

Now my question is which is the better method on a blown alky motor, pulling timing or rev limiting the motor at the launch or both?

Thanks again, Joe

 

dots

Riding the dots is difficult in a car because it breaks the blower belt when you hit them hard.
Any rev limiting is hard on the belts. Thats why a lot of guys keep the injector closed on the starting line with an air controller in conjunction with the 2 step rev limiter.The boost stays down so it loads the belt less.
Timing is the way to soften the power. We ran the digital 7 for years but have switched to the 8973 because the 7 bases timing off rpm. The 8973 is based off time.
It makes it easier to soften the car at different points on the track.

 

belts

Mike, we never had a belt failure on the starting line but it would fail a few hundred feet out usually after the shift like most cars. A lot of guys have good luck with belts by changing them often. We run them 40-50 passes and have never lost one without the rev limiter involved. I've seen video of the belt on a 2 step and it looked like it was having a hard life.
2 years ago almost everybody was saying you had to launch wide open on the 2 step. Now most all the adrl auto cars leave with the blades shut.
We ran a superman roots at 37% with 14mm stuff.
Now we are setting up a D rotor and i'm concerned with anybodys thoughts on belt life.
Sorry to hijack the thread.

On the digital 7 topic. The slew rev limiter was designed originally for offshore boats with the props coming out of the water...first time i've heard of one in a boat application .lol.

 

Launch Retard

The Digital-7 has a Launch Retard function capable of retarding the motor up to 25*, up to a maximum time of 2.5 sec. At the line I set it with a push button switch on the steering wheel and activate it by removing the supplied 12 volt activation voltage at launch. I first start the motor at full advance, 25*, then hit the button which retards the motor ~10*. Once I launch, the 10* retard is removed linearly over the 2.5 sec, or any time up to 2.5 sec, with the Digital-7.

Note: Digital-7 are used mostly on nitrous motors. They have three Step Retards and a 2.5 sec timed Launch Retard. Digital-7 have many neat functions and are used mostly on multistage nitrous system motors. Since I used a two stage nitrous motor on the boat in the past I wanted to incorporate it into my current bower motor and try to save some bucks.

Thanks, Joe