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Crane Ignition

In your race engine, getting as much air and fuel lit off in the combustion chamber at the correct moment is the key to making power. The air and fuel part is the domain of your carburetor and induction system, but setting it on fire is all about the ignition. And to make big power you’ve got to have a nice, hot spark that consistently fires exactly when you want it to.

Of course, in a racing environment that is easier said than done. The combination of high RPM, high heat and lots of vibration make it difficult for an ignition to work as well as it does in your street car cruising from stoplight to stoplight.

Crane's Race Billet Distributor is the company's most popular among dirt track racers. It uses the optical trigger technology first developed for NASCAR Sprint Cup racing at a more affordable price than Crane's full-zoot Pro Race Distributor.

Crane’s Race Billet Distributor is the company’s most popular among dirt track racers. It uses the optical trigger technology first developed for NASCAR Sprint Cup racing at a more affordable price than Crane’s full-zoot Pro Race Distributor.

And that is exactly why Crane Cams says they have developed their unique optical trigger ignition system for racing. The optical trigger system originally started out for high-end, big-money race teams, but since it proved to be so helpful is has since migrated to Saturday night racing levels.

Most distributors use a magnetic system that spins an iron reluctor wheel with eight flanges past a magnetic pickup. When the pickup “sees” the flange move past it tells the ignition box to fire. But the problem with a magnetic system is that as the RPM increases it has trouble keeping up and tends to retard the timing. Crane’s optical trigger system is quite different. It attaches a thin steel disc to the distributor shaft that has a small window punched into it. The distributor uses an optical sensor that picks up when the window passes over the sensor and sends a signal to the ignition box.

“What we use is known as an emitter sensor,” explains Crane Cams’ Terry Johnson. “There is a constant signal that goes between the emitter and the sensor, and what we do is put a reluctor wheel between them that breaks the signal. The signal is just a beam of light, and when we break that beam, that’s your trigger event. It works basically like an on/off switch, so it is extremely accurate.”

The difference is with a magnetic trigger the magnetic force between the reluctor wheel and the sensor gets stronger as the reluctor gets closer to the magnet. So the system has to determine the moment of highest magnetic force, or “attraction,” and send the signal. With an optical trigger the light is either hitting the sensor or it isn’t, which helps improve timing accuracy.

“Because you don’t have the inaccuracies inherent with a magnetic signal, it’s impervious to RPM,” Johnson says of the optical trigger technology. “So it doesn’t matter if you’re going 2,600 or 9,600 RPM, it delivers the same signal accuracy all the time.”

The result is something we’ve seen for ourselves in engine tests. Ignition manufacturers and some high-end engine builders have expensive diagnostic equipment that allows them to verify ignition timing on all eight cylinders in a running engine accurate to less than a degree, but you can actually see the difference with something as simple as a timing light. With your timing light pointed at the degree marks on your engine’s balancer, you will probably see the timing bounce back and forth between one-half to three degrees when the engine is revved up to the RPM levels it will see on the racetrack. But with Crane’s optical distributor the timing mark is much steadier and usually only moves less than half of a degree – if at all.

The optical trigger system works by spinning a reluctor wheel on the distributor shaft. When one of the eight windows in the disk passes between the optical emitter and sensor, the distributor signals the ignition box to send a spark to the correct plug.

The optical trigger system works by spinning a reluctor wheel on the distributor shaft. When one of the eight windows in the disk passes between the optical emitter and sensor, the distributor signals the ignition box to send a spark to the correct plug.

Besides helping the engine be more consistent from cylinder to cylinder, Johnson says you can actually use this improved timing consistency for better performance on the race track. “Let’s say you did a series of timing sweeps with your engine on the dyno and determined that it makes the most power at 32 degrees before top dead center. You’d love to be able to run your engine on the race track at 32 degrees, but you don’t want to take a chance with it going into detonation with the timing jumping around, so you have to allow yourself a safety margin and set the timing at 30.

“You can’t truly get the best performance from your engine because you can’t lean on it and set the timing of the true sweet spot. Plus, as your engine gains RPM going down the straights, the spark timing is actually retarding and giving up even more potential power. But now you can set your timing exactly where you want it with the optical trigger because not only is it steadier throughout the RPM range, but it also does not change with RPM.”

Interestingly, there is also an option to upgrade the standard optical pickup with a fiber optic unit that can increase timing accuracy even further. “We actually developed that technology for these distributors several years ago when NASCAR came out with what they were calling the Car of Tomorrow,” Johnson says. “The way they had closed off the nose on those cars caused the temperature underneath the hood to really spike. It was elevated way beyond the survivability of a lot of parts under the hood, and the design of the motors at the time was really causing a lot of harmonics. For instance, they were exploding alternators on the cars because the temperature was so high and there was so much vibration. The manufacturers had to go in and redesign a whole new alternator for those things so that they would live through a race.

This is the standard pickup in the Pro Race unit. The guts of the pickup are all sealed in epoxy to protect the unit from moisture, chemicals and vibrations so that it can provide a consistently timed spark race after race.

This is the standard pickup in the Pro Race unit. The guts of the pickup are all sealed in epoxy to protect the unit from moisture, chemicals and vibrations so that it can provide a consistently timed spark race after race.

“We didn’t have a (distributor) failure, but we knew that it wouldn’t be too long because the temperature was way beyond the threshold of what these triggers could stand. We already had experience with fiber optic pickups for some private customers and decided to develop it for the distributor pickup. That stuff doesn’t care how hot it is, and it doesn’t care how much you shake it, so it works really well in that environment. In fact, with the fiber optic technology, they are rated at 200°C. And instead of a regular emitter sensor, we actually incorporate a laser so the speed of the signal is actually almost faster than we can capture on a scope. We don’t service the NASCAR Cup teams anymore since they moved to fuel injection, but we still sell a lot of the fiber optic pickup systems in our distributors. It is more expensive, but we have many dirt track racing teams that use them because they demand that accuracy and resilience.”

Here's a shot of a standard magnetic pickup. When the iron reluctor swings past the pickup it triggers the spark. But as the RPM increases a magnetic system tends to retard the spark. Also notice the mechanical advance up top. The extra mechanical movement also harms timing accuracy. That's why many engine builders lock it out, but that can make a hot race engine difficult to start.

Here’s a shot of a standard magnetic pickup. When the iron reluctor swings past the pickup it triggers the spark. But as the RPM increases a magnetic system tends to retard the spark. Also notice the mechanical advance up top. The extra mechanical movement also harms timing accuracy. That’s why many engine builders lock it out, but that can make a hot race engine difficult to start.

Another factor with the optical pickup system is mechanically it is extremely simple. There’s just a disk on the distributor shaft and an emitter/sensor assembly mounted on one side of the distributor housing. Crane doesn’t even have an option for mechanical advance in the distributor because the extra moving pieces allow slop into the system that can throw off timing accuracy. Instead, Crane’s engineers developed an ignition box that actually has a digital timing retard baked right in to help aid cranking a heat-soaked motor. The feature is standard equipment on Crane’s most popular ignition for circle track racing, its HI-6RC ignition box, and it works by automatically retarding the timing 20 degrees on startup. The timing retard is turned off as soon as the engine hits 600 RPM and is shut out so that it cannot be triggered by accident. The only way to get it back on is to completely power off the engine and ignition and then crank the engine again. That way, if your race engine stalls on the track, the automatic timing retard will kick in and make it easier to re-fire before the tow truck shows up to ruin your night.

 

 

The next time you check the timing on your engine, take a moment to see how much the timing marks jump around. If it is more than a degree, you are losing out on potential power.

The next time you check the timing on your engine, take a moment to see how much the timing marks jump around. If it is more than a degree, you are losing out on potential power.

 

Although Crane's optical trigger distributors will work with most brands' ignition boxes, Crane's HI-6RC ignition box is incredibly popular because of its accuracy, consistently strong spark and built-in electronic ignition retard that doesn't use any moving parts.

Although Crane’s optical trigger distributors will work with most brands’ ignition boxes, Crane’s HI-6RC ignition box is incredibly popular because of its accuracy, consistently strong spark and built-in electronic ignition retard that doesn’t use any moving parts.

Source

Crane Cams

(866) 388-5120

www.cranecams.com

 


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