drag race engine ignition systems

General engine tech -- Drag Racing to Circle Track

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bill jones
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Post by bill jones »

-I think the issue of seeing timing differences between MSD's analog versus their digital boxes---when triggering with a crank trigger wheel----has to do with when the box fires in relation to the rotating reluctors or magnets.

-Using a sensor that has a magnetic core and using steel reluctor tabs---the timing actually happens just slightly after the reluctor passes the centerline of the trigger-----at least on the analog boxes.
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-I'm not exactly sure but I think maybe when using the flying magnets and/or the digital boxes-----that the spark is designed to be triggered just slightly before the tabs or magnets align with the trigger.

-this disparity could very well be about 10 to 12 degrees or so.
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-You guys might want to get into the habit when you are checking the timing---to always also check and correct rotor index---and shine the timing light onto the crank trigger and get an idea of exactly what the relationship is of the rotating part to the stationary trigger.
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-On my ignition testing machine I have a variety of distributor caps that have holes cut into them so that I can look at rotor index AND also so that I can see clear inside to view the relation of the rotating reluctor or the shutter wheel etc in relation to the trigger centerline.
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-And to add to all this----all you guys who are using the electronic retardation features of the MSD ignition boxes and and/or the simple timing retardation boxes, start retards & timing retards for nitrous etc---you need to be looking at what happens to the rotor index as any of those retardations are being applied.

-those retards ALL electronically change the rotor index so the further you are moving the timing the worse the rotor index gets----and it may very well move way off to either side of what you thought was a perfectly indexed rotor.
aussie mouse
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Post by aussie mouse »

fastvette wrote:I have it the other way, 7AL on the dyno and digital 7 in the car and see at least 10 degrees differance in timing. That don't bother me much, but what about at peak power? What is the timing doing? Do both boxes do the same thing?

Randy
Even though I have a msd box on my dyno, I encourage evey customer to use the exact igntion box and coil that they will use in the car/boat whatever

As I said on top timing vairations and compensations built into the boxes for affects of timing retard, different MSD and Crane boxes or whatever often have different spark dwell, this will affect what is required.

So using the excact box from the car/boat etc covers any issues, plus you get the chance to "dyno test the whole igntion system"
And I have found issues on more the one occaision (other then timing issues) with customers igntion boxes.
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ep33510
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drag race engine ignition systems

Post by ep33510 »

Wow Larry way to start thread! :)

All the above mentioned info is right on the mark, so let me try to throw my two cents into the pot. If you want dead on timing then the crank trigger setup is the way to go. That said you need to take the time to walk the sensor in to the correct spot for the engine. ( Usually a Dyno ) Then don't touch!!! Yes there are differences between the analog boxes and the digital boxes. So as mentioned above you need to dial in the timing each time you change between them. Also keep in mind to keep things set on kill you should be checking you timing if you ever swap out the same model boxes. They each have a sweet spot if you are trying to stay on your game. As for which is best, it all depends on your program. If your a plug and play racer and don't want to play with a PC hooked to the digital box then stay with the analog units. If you do go digital please take the time to get some test runs under your belt. We have found that doing this with digital boxes allows you to find that sweet spot your motor is happy with. Just consider it like getting the jetting right, once there it is easy to to go to any track and spend alittle time to adjust and then go Play! As with any electronics a good install goes along way to making sure you have a flawless operation with no operator installed Gremlins! :)
Pat Collins

TechWest Racing Services
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MSD®Ignition Upgrade & Repair Service
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