MSD Ignition Box - PT. 24: Spark Box

Computerized Timing Is Here To Stay

Mike Petralia Aug 1, 2004 0 Comment(s)
Sucp_0408_09_z Msd_ignition_box Spark_timing 1/14

Since the timing controller can not put advance into the system; it can only take timing out by retarding the spark, you must lock out your distributor and install it at a timing point higher than you want your total advance to be: i.e. 40 degrees in DM's case. The computer can retard timing up to 25 degrees max in 0.1-degree intervals at any point to give you the advance curve you want. So, for 15 degrees at idle, we'd program in 25 degrees of retard and for 38 degrees total, we'd program 2 degrees retard from something like 5,500 rpm to redline, etc.

It Gets Even Weirder
Since peak numbers are only a small part of the power making game, we've grown accustomed to analyzing average power gains to determine if a change was worth the effort. Well, this month's test averages perplexed us as well. Even though power was up at the low end, the drop at the top made average gains net zero! At least in the torque department. Average horsepower actually fell off by 3, which really sucked, considering how hopeful were going into this test. One positive note about this month's test was that in a car, the motor would have pulled harder off the line this month than it did last month. But we'd have to short-shift it and that's not really an advantage to in our book.

Dyno Testing Part 24Instead of comparing this month's test, Number 40, to the last test from last month as we usually do, we're comparing it to the second test from last month, Number 37. That's because in that test we were running locked-out ignition at 38 degrees and 91-octane gas. This is the combination that was detonating and losing the most low-end power, so it was the one we wanted to compare to. Ironically, this month, in test Number 40 DM did not detonate, even though the engine set-up was exactly the same. The two exceptions this month were fuel from a different source and testing done at a different facility.

Danger Mouse specs for Part 23-Test 37*

*Previous test from last month: 355 cid, 12.5:1 cr, 4.030-bore 4-bolt Motown block, 3.48-stroke Lunati crank, 5.7-inch Lunati rods, Lunati flat-top forged pistons, Total Seal ductile iron Gapless top rings, Edelbrock Victor Jr. heads (64cc chambers, 215cc runners, 2.08" intake valves, 1.60" exhaust valves), Edelbrock Super Victor intake manifold, COMP Cams XR286R solid roller camshaft installed @ 105 intake CL (248/254 @ .050, 286/292 adv, .606/.612 lift w/ COMP 1.6:1 rockers, 110 LS), Carb Shop modified Holley HP950, 38 degrees locked-out ignition advance, 91-octane

Danger Mouse specs for Part 24-Test 40:

Same as above but with 35 degrees ignition advance starting at 2,400 rpm, ramping up to 38 total at 5,500 rpm, 91-octane

We're always looking for new ideas. Do you have a better one for Danger Mouse? Send your test suggestions to:

Super Chevy MagazineAttn: Danger Mouse
720 Hundley Way
Placentia, CA 92870
Or e-mail: terry.cole@primedia.com

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