ignition timing moving

[Jim Comet]

Well I finally made it to the track this year for the first time. Over the winter I completely rewired the car, added a crank trigger and a data logging system. The car fired up better than ever and ran really well in the garage and loading onto the trailer. Little did I know. When we got to the track we drove the car around the pits and it ran great. When our 1st time trial came up my son did a burnout and staged. As you can see from the datalog #2 the timing was steady but the motor wouldn't rpm. This became very apparent when he launched the car and he let off and basically cruised down the track and back to the pits. With only a few time trial available before eliminations I decided to run the ignition off of the MSD's magnetic pickup and retime it which solved the rpm problem allowing the motor to rev past 5000. One thing to note is how much more the timing "sewing machines" in the datalog #13 which is a pass using the MSD's distributors magnetic pickup. The car and really consistent the rest of the weekend so I did not spend more time on the crank trigger. Today it dawned on me that for some odd reason I have had to run my ignition box on the "points rising trigger" setting to make the MSD distributor work in the past. I think if I change my ignition box setting to magnetic falling it will solve my issues with the crank trigger. I guess that will teach me to go to a competitive race weekend with zero test passes on a new combo. Jim

[6667fan]

Looks like you are using an RPM data logger. I like their stuff and their customer service has been really great.

How is the timing captured by the logger? Is there a sensor for that or is it a box connection that is reading what the trigger is doing?
You said car ran well later. Any improvements over last year?

[Jim Comet]

There is a separate sensor similar to the crank sensor that mounts on the opposite side of the trigger wheel. There is a calibration function that you can enter into the data logger to compensate/match the timing output of the crank trigger. The car ran really consistent but only had a best ET of 11.19.  The da was about 3500 ft. with an air temp of 80+ all weekend. I am sure once I get the crank trigger sorted out I will be back in the high 10.s. We ran a best mph of 120 this weekend where the last time out with the old setup and better air we were consistently running 123-124mph through the traps. Jim

[6667fan]

Jim, wouldn’t mind seeing a pic of that timing sensor.
What is the engine supposed to be timed at for peak power? I see via the graph that it’s moving around a few degrees

[Jim Comet]

Here are a couple of pics of the sensor during setup. I had to make the timing sensor bracket. Jim

[Jim Comet]

Well long story short, I removed the dash adjustable timing control from my system and now my timing is perfectly flat through the rpm range. It didn't make any ET differences, but I feel better without the zig zag 2-4 degree timing changes throughout the rpm band. The timing is the top flat line and that is 2 back to back runs overlaid. Jim

[My427stang]

Thanks for the update!  Glad to hear it worked out

Sort of a KISS lesson, or as my wife says, less gadgets are better