Drag Racer - - Contents - Text by Ben Mozart Pho­tos Courtesy of PerTronix Per­for­mance Prod­ucts

EARLY IN 2017, A NEW CA­PAC­I­TIVE DIS­CHARGE (CD) IG­NI­TION SYS­TEM EMERGED. An in­no­va­tive phi­los­o­phy de­rived from new soft­ware—a pro­pri­etary al­go­rithm, in en­gi­neer­ing jar­gon—it prom­ises sub­stan­tially more than pre­vi­ously avail­able.

De­signed to op­er­ate with a sin­gle coil dis­trib­uted spark, which in­cludes most car­bu­reted drag rac­ing ap­pli­ca­tions, it’s re­puted to be smaller in size than any CD de­vice with sim­i­lar fea­tures. Of greater sig­nif­i­cance, it’s more en­ergy dense, main­tain­ing mul­ti­ple spark ac­tiv­ity from idle to 7,000 rpm, as well as gen­er­at­ing greater spark­ing power.

There are two com­mon types of ig­ni­tion sys­tems: ca­pac­i­tive and in­duc­tive. The coil is sup­plied power by one or the other. In­duc­tive, which is still the most com­mon, and em­ployed on most road-go­ing pas­sen­ger cars, charges the coil with 14.6 volts and dis­charges be­tween 200-300 volts into the coil’s sec­ondary wind­ings.

In­duc­tive sys­tems are any of those ig­ni­tion sys­tems that do not have a ca­pac­i­tor en­er­giz­ing the coil. In­duc­tive sys­tems have power ap­plied to the coil for a pe­riod of time, but their elec­tro­mag­netic prin­ci­ples are the lim­it­ing fac­tors as to how quickly the coil charges and how much en­ergy it dis­charges. Prop­erly seen, the stan­dard in­duc­tive ig­ni­tion sys­tem is de­signed to start a car at 20°F be­low zero, and it doesn’t sup­port high com­pres­sion ra­tios, high horse­power or high rpm.

Ca­pac­i­tive ig­ni­tion sys­tems, on the other hand, are de­vel­oped for high-per­for­mance and rac­ing ve­hi­cles that op­er­ate at high rpm and gen­er­ate higher cylin­der pres­sures. Higher cylin­der pres­sures mean the spark plug gap is harder to jump. Also, as en­gine speed in­creases, the time to cre­ate en­ergy de­creases, and the fir­ing events oc­cur much faster. In both cases, ca­pac­i­tive dis­charge tech­nol­ogy out­per­forms in­duc­tive.

A stor­age de­vice, the CD ig­ni­tion sys­tem re­ceives bat­tery volt­age, steps it up, stores it and then dis­charges to the coil. From the coil the en­ergy is trans­ferred to the dis­trib­u­tor, which di­rects it to each spark plug. This huge acquisition of en­ergy stored in the ca­pac­i­tor is gen­er­ated by a DC-to-DC step-up trans­former, which re­sides in the CD box. Like a toi­let tank when flushed, it pro­duces lots of vol­ume and pres­sure.

“CD is about the in­ten­sity of the spark,” says PerTronix’s Gar­rett Weaver. “Nat­u­rally

We’ve suc­ceeded in spark­ing two more times within the same 20 de­grees of crank­shaft rotation, and it is this that has given us the abil­ity to de­liver mul­ti­ple sparks to 7,000 rpm. —Gar­rett Weaver

as­pi­rated, high-com­pres­sion en­gines, as well as turbo, su­per­charged or ni­trous en­gines, have much higher cylin­der pres­sure and need more spark en­ergy to com­bat those con­di­tions. This is why most rac­ers tend to grav­i­tate to CD over in­duc­tance sys­tems.”

In ad­di­tion to spark en­ergy, hav­ing an ef­fec­tive mul­ti­ple spark func­tion is a vi­tal fea­ture in the de­sign of any modern CD ig­ni­tion sys­tem. The chal­lenge is to charge the ca­pac­i­tor and trans­fer the en­ergy to the coil very rapidly at high en­gine rev­o­lu­tions. Mul­tistrike spark­ing from idle to 3,000 rpm has been the stan­dard for some time, but in 2017, the Cal­i­for­ni­abased ex­haust and ig­ni­tion spe­cial­ists at PerTronix an­nounced a new ca­pac­i­tive dis­charge in­no­va­tion that not only charges the coil with 530 volts, it also ex­tends multi-strike to 7,000 rpm. It’s called Dig­i­tal HP.


For sev­eral years, PerTronix, in com­mon with its CD ig­ni­tion ri­vals, bat­tled with the time lim­i­ta­tions as­so­ci­ated with charg­ing and dis­charg­ing ca­pac­i­tors above 3,000 rpm. How­ever, the com­pany made a break­through when de­vel­op­ing a new al­go­rithm and cir­cuitry that proved suc­cess­ful in gen­er­at­ing mul­ti­ple sparks up to

7,000 rpm.

“It’s a sat­is­fy­ing de­vel­op­ment,” said Weaver, “be­cause the mul­ti­ple sparks func­tion is per­ceived by most rac­ers as a more pow­er­ful, more re­li­able spark for high­com­pres­sion and high­per­for­mance ap­pli­ca­tions.”

We don’t know how it was achieved, nor should we, be­cause that’s the way in­vest­ment in re­search and de­vel­op­ment works. Those who in­vest the ef­fort should re­ceive the re­ward. Nonethe­less, Weaver does re­veal some in­for­ma­tion, “We’ve suc­ceeded in spark­ing two more times within the same 20 de­grees of crank­shaft rotation, and it is this that has given us the abil­ity to de­liver mul­ti­ple sparks to 7,000 rpm.”

Prob­a­bly so, be­cause ba­sic physics states that it takes much more en­ergy to im­pel a body at rest into mo­tion than it does to ac­cel­er­ate or sus­tain some­thing al­ready in mo­tion. The same is true with elec­tric­ity. It takes more en­ergy—five or six times more— to jump the gap of a spark plug than it does to main­tain spark plug arc­ing.

Be­yond this, the true scale of the achieve­ment can be bet­ter ap­pre­ci­ated when you con­sider the in­te­gra­tion of a three-step rev lim­iter, rpm-trig­gered out­put and ad­justable start re­tard, among other pro­vi­sions.

First, the built-in three-step rev lim­iter pro­tects the en­gine from fa­tal over­revving. Sec­ond, it lim­its max­i­mum en­gine rev­o­lu­tions dur­ing launch as well as dur­ing the burnout pro­ce­dure.

The rpm-trig­gered out­put is de­signed to ac­cu­rately con­trol shift lights, so­le­noids and other rpm de­vices.

Fi­nally, the sys­tem’s start-re­tard pro­vi­sion pro­motes eas­ier start­ing for high-com­pres­sion and dif­fi­cult-to-start en­gines. It al­lows the ig­ni­tion tim­ing to be re­tarded dur­ing start­ing and then ad­vanced to its most ef­fec­tive set­ting, in­stead of crank­ing it at full tim­ing. En­gine builder Greg Brown of Ham­mer­head Per­for­mance En­gines says, “The more com­pres­sion you have, the harder it is on parts. I’ve seen them kick back so vi­o­lently they al­most broke the starter mo­tor off the en­gine. Most rac­ing en­gines with higher com­pres­sion have the dis­trib­u­tor locked. So you don’t have the op­tion of crank­ing the en­gine at, say, 25 de­grees be­fore TDC and then re­turn­ing it to it op­ti­mum set­ting. On high-com­pres­sion en­gines it’s very im­por­tant to have start-re­tard func­tion.”

PerTronix’s new Dig­i­tal HP ig­ni­tion box

Pro­gram­ming is done with a dial in­ter­face.

Small de­sign ac­com­mo­dates many in­stal­la­tion op­tions.

Lock­ing, weath­er­proof con­nec­tors of­fer ex­cel­lent wire re­ten­tion.

PerTronix’s T3001 crimp tool makes wire ter­mi­na­tions sim­ple.

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