Simple 8973 question...

Discussion in 'PSI Superchargers Tech Questions' started by Scouder, Jul 27, 2010.

  1. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    8973

    I'm not an electronics expert and never claimed to be. As I've stated in the past, I'm a bottom line kind of guy. If I see the box do some stupid things myself, I talk to some pretty damn good racers in both TAD and TAFC who kept hurting motors when the box was legalized, took it off and quit hurting motors. At that point, I don't have to know why the box is killing motors. If I wanted to move the timing around a bunch, I could put multiple six shooters on it to create the same curve. I can do anything that box does digitally with analog devices and lose the risk of the box doing something on it's own.

    As I have said numerous times, the box seems to have less problems with the Pro Mod cars. Maybe it's the steel firewall, I don't know.

    Yes Mike I had two retards on at once. I had launch retard with 9 degrees and 9 degrees out at 0.0 seconds not realizing that 0.0 was active while on the transbrake. When I hit the brake the motor would go completely silent for about a second, then come back to life popping and gurgling until I released the transbrake. After a few shots at rewiring, we took a racepak pull while this was going on, and it showed the timing going from 26 to 72 degrees of timing on the transbrake. According to MSD's own words the retards should have been cumulative and it should have pulled 18 degrees out and shown 8 or 9 degrees. I realize the box can't "add" timing but it can retard it enough it starts cross firing or something. Yes we had the big cap on it. We quit running the car a short time later, but at the next few races, I talked to other people running the box who kept killing motors due to detonation related problems, pulled the box off, no more detonation related problems...

    Fast forward a couple of years later to a car I helped who ran the 8973 box with no crank trigger. Against my urges, the racer wanted to keep the box on the car. We go to one race set the mag at 26 and make a run. At the next race (a week later, mag was never touched) I start the car up and the timing is 29. We change mag clamps and make a run, resetting the timing to 26. We make a few runs, come back and the timing is now showing 32. There is no way a mag can advance itself. If it comes loose, it will retard. I back the timing off back to 26 and go get another racers timing light. Mind you nobody has touched the car in the 5 minutes it took to go get this light. We fire the car again and the timing is back to 32 with both lights. All timing retards were zeroed out in the 8973. This was checked by MSD. I don't want to bring the racers name into this, but he has been hurting pistons since I helped him for reasons he can't seem to track down.

    These boxes have a track record of failures in TAD/TAFC. I don't know why. Maybe shake, RF, where the box is mounted, etc. MSD seems to take the attitude there is no problems rather than try to tackle the problem. That in mind, I gave up on the box and strongly recommend anyone against using it in a dragster/fc/altered. In my opinion it doesn't have enough good features to offset the risk. Not to mention they are a pain in the ass in general to deal with. If I go look at the starting line and want to make a timing change, I have to lug a laptop around. Instead of just changing chips, I have to pull the program up, redo the curve, then upload it. The box does maybe 7 or 8 things an alcohol racer will actually use and about 75 other things we'll never use.

    All I'm saying is use at your own risk. I think there have been enough failures to inform new users that may not be aware of this. If they continue to use it, it's on them.
     
    #21
  2. Scouder

    Scouder New Member

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    Will,

    Thanks for the detailed response. The quote above concerns me a little bit now. I had mine setup for 34 base and took another 2 out with a step retard that is always on, for a total of 32. Same thing, never changed the mag position, but I do take the drive out to prime oil before each race. Mag drive is offset with the bolt that pins it in position on the support bracket. No place for anything to move. Checked the timing a couple of nights ago and it was at 39 with 2 out for a total of 37. This 5 degree increase is a mystery to me. Like you, I assume a loose clamp will retard, not advance.

    I loosened the clamp and moved the mag back to 32, and am going to watch it like a hawk. If it advances again there will be another 8973 for sale. Personally, I don't think it will, but after your post I'm not gonna take any chances.

    -Brian
     
    #22
  3. Mike Canter

    Mike Canter Top Dragster
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    Before you all read this I would first like to say something about Will and I. Just because we have a difference of opinion on the 8973 does not mean that we are enemies or we hate each other or anything like that. I respect Will and his tuning capability and am glad that we know each other. If will says that he saw the timing advance then I believe him. What I don’t believe is the cause of the advance in timing.

    Will, I can’t explain all the problems you have seen with timing on cars equipped with the 8973 because I wasn’t there. I will tell you this that is a blown alcohol really goes from 26* to 76* in ignition timing it is going to either blow the supercharger off the top of the motor or just totally shutdown. Like what MSD told you the 8973 software can retard the ignition but CANNOT advance the ignition over what the Pro Mag is set at. That is physically and electronically impossible. That would be like making gold out of lead. Since the motor did not destruct with 76* of advance in it I would be real suspicious of the Racepak ignition timing being interfered with and giving you a false indication of timing. I do agree that having a cumulative timing retard of 18* would make a motor go real silent real fast. Again stop and think…..there is no way that the 8973 can give you advanced timing over what the Pro Mag is set at. How would that be able to do that? It is absolutely physically impossible. Also you seem to have forgotten that the car that you claim was advancing the ignition timing by a few degrees when checking with a timing light was Steve’s car. You are the only person on that car who has ever seen that car jump from 26* to 32* that one time. It has never been seen again by anyone on the crew and is watched very carefully. The only way a car can advance timing over what the mag is set at is by something going wrong in the mag and not in the 8973 or by false indications. I have to believe that if you say that a car advanced to 76* or it advanced to 32* that you really had an indication that it did “appear” to happen and there has to be an explanation other that an 8973 performing an impossible function. As far as Promods we have a mixture of the 8973 being mounted next to the mag right by the motor and having them mounted inside the car and we do not see any interference problems or mystical timing advances.

    Brian, I would be looking elsewhere for your problem other than the 8973 malfunctioning. Next time you start the motor do it with a laptop plugged into the 8973 and look at the upper left quadrant of the screen at the MONITORS to find out what retards are turned on or off. IF a retard was turned on and you set the timing then the retard was turned off then your timing will suddenly appear to advance. When you see this happen again the check the MONITORS real carefully.The other thing that can trick you is that when you start the car the 8973 will be in the Run Retard Curve which is the bottom right graph on the laptop and will stay there until you momentarily apply 12 volts to the 8973 Blue Wire then it will switch to the Launch Retard Curve which is the top graph. So if you have anything other than zero degrees in the Run Retard Curve then that will be active when you check or set the timing. Also the motor has to be above 800 rpm to have all the features work on the 8973. It is a good procedure that immediately after you start the car that you apply 12 volts to the Blue Wire either by the clutch switch or the transbrake switch before you check or adjust the timing.And finally don’t get me wrong. I understand the Six Shooter and the Leahy Timer and they work well and I am tuning some cars that have them. There is nothing wrong with either configuration and they both have their Pro’s and Con’s. I have had problems with the Six Shooters and with the 8973s and they all end up being either in the wiring or operator problems.You should all appreciate his long post because I typed it on my BlackBerry phone and my thumbs are killing me.
     
    #23
    Last edited: Aug 6, 2010
  4. aj481x

    aj481x Member

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    "It is a good procedure that immediately after you start the car that you apply 12 volts to the Blue Wire either by the clutch switch or the transbrake switch before you check or adjust the timing."

    Bingo !! ;)
     
    #24
  5. Bottlefed

    Bottlefed New to Blowers

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    Mike the post is pretty good, but what really impresses me is typing that whole thing out on a blackberry with your thumbs and not having any typos....
     
    #25

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