Msd 8973

Are you using solid core plug wires. MSD states that all their products should be used with shielded wires. We have never had problems with our 8973 and I have never actually experienced problems with any other 8973's. There may be a lot of rumors being passed around about problems. Over 90% of ignition problems with magnetos are caused by old or bad plug and coil wires. With a ProMag 44 your should change the plug wires at least 2-3 times a season and the coil wire more often than that. The insulation on plug wires break down and short the spark out to anything metal. They wil still check good with an multi-meter.

 

One other thing to consider. A 8973 does not act different from one cylinder to another. It fires the same way for each cylinder. I believe it is impossible for an 8973 to cause a miss in just one or two or three cylinders. It either works for all or none. I would look for other problems.

 

the death toll rises...

while i ran one earlier in the year, i'm rapidly losing faith in not only the effectiveness of the msd 8973 box, but of the overall reliability and safety to run one.

i know of at least 6 motors this year that have been seriously hurt with the culprit being the msd 8973 box. ask snyder and thacker.

i was a big believer in the features of the box earlier in the year. knowing what i know now, i would stay away from them. the box has some issues, whether msd wants to admit it or not.

msd will swear up and down the box doesn't have the ability to add timing, but i saw it add 50 degrees of timing on the jackstands on our racepak. the timing was jumping to 77 degrees. how i didn't have the blower sitting in my lap, i dont know. the reason why it threw a fit was because i had two retard settings on top of each other, so yes, there was user error involved. but it did demonstrate when something goes wrong on this box, it goes bad wrong....not just half ass.

what i did wrong was i had 11 degrees out on the launch retard setting (transbrake) and 11 degrees out at 0.0 seconds, thinking that the launch retard was my button setting and the timing would transition to the 0.0 setting once the button was released. what i later found is 0.0 is also taken out on the button, so it was 'stacking' the retards. it threw a fit and would damn near die, spit sputter, pop, u name it. we spent a day on the jackstands trying to diagnose it. now once got rid of the launch retard, it ran fine. BUT, the way that box works, it says if two retards are on at once, they will have a cumalitive effect, which should have retarded 22 degrees. instead the racepak showed the timing going from 27 to 77 on the button (flatlined i might add).

while i'm not going to speak for marty, mick and others who have had serious engine failure associated, the failures were just stupid things happening that went away when they quit running the box.

until msd admits there is a problem i would stay away from the box and just run a six shooter.

thats a highly recommended opinion. i can't back it up with a factual reason 'why' the boxes are failing, but i go to a lot of races, talk to a lot of races, and i wouldn't run one right now, period.

 

Will, I respect your knowledge and by no means want to start anything but I would have to question if that cumulative timing jump through a worm hole was really there and it was not the Racepak reading erroneous data on the timing. Like you stated with 77* advance on the mag the blower should have been sitting in your lap but it didn’t. The MSD does not utilize an advance system it only retards ignitions so it would be very hard to add a feature that is not designed into the box.

The software and electronics used in the 8973 originate from a tried and proven Digital 7 Ignition system which has been in use outside the blower world for almost ten years that I know of without problems. I have been using Digital 7 systems that long also. The only real problem that I know that can still happens with both the analog and digital MSD ignitions is the false triggering from the crank trigger by electromagnetic interference picked up by the older type unshielded trigger cables.

When the Digital 7 systems were first introduced there where all kinds of stories how they messed up motors. They were blamed for everything.

We have to also look at how many other MSD 8973 systems are being used on blower cars without any problem.

 

good ones/bad ones? vibration?

mike,

i think it's safe to say you're the resident expert on msd stuff. not disputing that at all, just comparing field notes.

i'm not an electronics person by any stretch. i look more at end results than linger in the 'why'. i guess that's why i'm not an engineer.

one explanation for the 8973's apparent problems in the alcohol ranks could be the extreme vibration and tireshake alky cars are exposed to.

the people that are having problems are pretty sharp people that relatively the same parts before/after the 8973. generally when someone thats been running for a while hurts parts, takes the box out of the equation, then quits having those problems, it's a pretty bold statement against the box.

in reference to my timing experience, the motor would go completely silent when i hit the transbrake button, then recover, but be spitting and sputtering. we had just installed diodes in the transbrake circuit to prevent feedback through the transbrake button from the solenoid to the msd box. so our first reaction was we wired something wrong. we checked it, changed the grounds just for grins, then tried it again, same results. then we started checking things to make sure it wasn't mechanical (trans). we disconnected the diodes, same result, finally we cut the wire to the 8973, no problems. well, we changed some more grounds, changed a blown blower oring, then did another warmup, this time with the racepak on. with the transbrake button applied, the timing would go from 27 to 77 on the racepak. i toggled through it a few times, but same result. we had our mind made up we had a bad box and was about to load up and go home (note-unlike a clutch car, it's not an option to run a torque converter car w/o retard, so no need to test doing burnouts). we had ran the car the weekend before with no problems. however, i was new to the software and was trying to click -11 on '0.0' on the graph rather than drag the retard curve to -11. we had spent a lot of time going over our 'new' ignition file, even tried uploading it from two different laptops to make sure it wasn't a windows vista issue on the new laptop. our last ditch was to take an ignition file from the previous weekend and not so much click on anything besides upload. we downloaded it to the box, no problems at all. as mentioned in above post there was user error on the setup. point being, this thing threw a major shit fit. we're very lucky it was a situation that presented itself as an obvious major problem on the jackstands instead of driving over the crankshaft on the track.

getting more into the methodology of my recommendation for alcohol teams NOT running it:

- the potential problems outweigh the potential gains. especially for clutch cars. i've worked with some very fast cars, and the need for an elaborate mapped timing curve just isn't really there. a normal analog six shooter can map a curve just fine, and if you need more, it's easy enough to add another six shooter to give you 11 timing points down track.

- not user friendly. i work with computers every day and i even made a mistake with the software. there are a lot of alcohol racers that barely know how to pull up racepak and the davenport software and that's it.

- crank trigger/timing monitoring - first off if you're using digital or analog timing retard on a mag trigger instead of crank trigger, you're absolutely wasting time. i was leery of the crank trigger set up when we started a couple years ago, i thought it was another potential part to fail. so i had the beefed up mag drive and shaft, fresh bronze gear and almost no endplay in the camshaft. our first race with the racepak timing monitoring was a real eye opener to how much timing changes on the mag trigger. 4 to 6 degree changes in the gear changes were normal, not to mention being a 'squiggly' line. so here we are agonizing whether or not to put a '9' or '10' chip in the six shooter...only to find out with the mag trigger we were completely pissing in the wind. shortly thereafter we had crank trigger. nice flat line on the timing, goes where you tell it to. if you're moving timing around, you need to have timing monitoring of some sort to make sure it's doing what you tell it to. not only that, it's a very valuable tuning tool to overlay your timing curve to corresponding events in the driveshaft rpm and engine rpm. that's why we have flowmeters, to make sure your fuel system is doing what it's supposed to, the same for timing.

maybe there are some good boxes and bad ones? some very respected names in the sport have had problems with the box that have not presented themselves without the box. in my book, it represents a problem.

until msd gives it a good look and actually listens to the racers rather than tell them how there is no way their box can be the problem, i'll stay away from the box. maybe they've dealt with individual racers differently than me, but when i've brought the topic up at the msd trailer, you get dirty looks and the like, get told why it's not the box, etc. this is the same trailer that is commonly regarded as a waste of time testing something by most racers in the pits.

 

Will let me explain myself better. (I do work for a large aircraft company as an engineer.) The reason I said that the 8973 cannot advance timing is that it uses a trigger/pulse from the generator through the points box to the 8973. This trigger/pulse can only be delayed electronically from the time that it is transmitted by the generator and this delay is where the retard(s) comes from. There is no way in the 8973 for it to go bad and to move that trigger/pulse to come in the future before the generator triggers it so therefore no advance can be added to that trigger because it hasn't happened yet. That is what I meant by a worm hole in my other post. You would have to invent a time machine to get that trigger or pulse in advance of when that generator is sending it. It can't happen regardless of how much you shake or bang the box around. The only way to appear to be in the future is to have the box be randomly triggered via electromagnetic interference (EMI) being picked up by the crank trigger cable. Now this random triggering can fire a spark at the wrong time and make it appear so far out of sequence that it matches the arrival time of a different plug in the firing order and may appear to be way in advance. This is what I was also talking about in my earlier post. This will happen on the Digital 7 and the 7AL2 and 7AL3 and I am sure it will happen on the 8973 IF the crank trigger cable is not shielded and not grounded. Having an unshielded ungrounded crank trigger cable can make the motor randomly fire and appear like detonation. This used to be common in the early nitrous promod days but we all learned what you have to do to prevent it. It maybe that the blower guys are now or a steep learning curve. This is NOT a malfunction within the box. Our crank trigger cable and all other cables are shielded and grounded to the chassis. If you don't use a crank trigger then this is not a problem.

 

310?

Is it possible it's retarding it an extreme amount? Don't know. Like I said, I don't know exactly why, or 'what' happened to some of the cars hurting motors, just know the end result.

You make good points on shielding the trigger wire...regardless of a 8973 problem. Do you run a Leahy or MSD trigger? Does the Leahy trigger need additional shielding?

RE: Worm hole....maybe MSD has found something they don't know they have......it was kind of weird...we warmed up and I swore the clock had just said 2:30 five minutes ago...

 

Sorry it took so long to reply. My wife dragged me up to Maine and most can't even spell WiFi so I couldn't hook up. I use the MSD crank trigger with the steel armor and I ground the armor to the chassis. For the crank trigger cable back to the 8973 I use the MSD shielded crank trigger cable part number 8862 which I have made to the correct length. That cable has a shield ground which I connect to the chassis. I still route all the wires as far away from all other wires and the plug wire and the coil that I can. It appears that it is the mag system that interferes and ransdomly fires the crank trigger. On nitrous cars it could be the eloectric water pump, electric fan or the electric fuel pumps especially if you ran the crank trigger cable in a wire bundle with other wires.