Having adequate voltage in the electrical system is a huge deal in racing, especially dirt track racing. In most stock car classes, stock-style ignition systems are used. These are inductive ignition systems that are hampered by output-voltage efficiency under heavy load and high-RPM conditions. Unfortunately, this is where dirt track stock cars live the majority of their lives.
Many racers used to drop some weight and parasitic engine horsepower loss by removing the charging system’s alternator. This solution worked alright for short races where the existing ignition technology kept engine rpm lower.
Older factory stock ignition systems were great for road use but lacked in high-performance situations. The ignition coil stores battery voltage and transforms it into high-voltage, so the current can jump the gap in the spark plug electrodes. At high RPM, the coil has less time to charge fully , and therefore, routinely fails to reach the maximum output. This means less power when you need it most.
The automotive aftermarket industry figured this out decades ago and countered the problem with ignition boxes that produced a stronger spark, or multiple sparks, to help promote combustion. These ignition boxes require a specific range of voltage to work correctly. So, racers who used a total-loss electrical system (no alternator) were subject to angry ignition boxes when the voltage supplied from the battery dropped too low. Racer’s found it necessary to have an electrical charging system again.
Potential Problems And Solutions
We reached out to the experts at Powermaster Performance, to get the lowdown on charging systems, and how to get the most from our charging system. You could say we were told to start at ground level by company President John Babcock. “One of the most important things in the charging system — in fact, the entire electrical system — is a quality ground path,” he states. This is a priority Babcock has reminded us of for several years.
“We recommend running a ground cable from the alternator housing directly to the engine block or common chassis ground,” he continued. “This ensures a path which can help in the case of coated brackets or mounts that may not provide the necessary ground path.”
Likewise, the importance of the charge wire cannot be understated. A crusty, small-gauge charge wire is not going to handle the output of today’s high-performance race alternators. Especially, when you move the battery from the stock location.
Many of the automotive manufacturers placed the stock battery location at the front right of the vehicle — the worst place for a heavy component when it comes to chassis cross-weight on an oval track. Running a high-quality, heavy-gauge charge wire is a necessity. “You could have the highest output alternator, but without a smooth path for all of that current to get back to the battery, it will do you no good,” Babcock reminded us. “This is one area where overkill will certainly not hurt. The further away from the battery, the lower gauge wire you need.”
Belt tension and alignment is critical. We’ve all see cars that continuously fling alternator belts in every heat race and the main event. If you’re standing in the infield, you can hear the belt hit the sheet metal and simultaneously see the clumps of clay jump off the hood where the belt hit. Most of the time, this is a dead giveaway the engine has a pulley misalignment condition.
Almost every wrencher we’ve seen will use a pry bar to make sure the belt tension is strong enough to keep King Kong from pulling the belt off of the pulleys. “Powermaster deals with a lot of issues when it comes to improper tension,” says Powermaster Representative Todd Ryden.
A loose belt will result in excessive vibrations of the belt causing it to come off the pulley. – Todd Ryden
“A loose belt will result in excessive vibrations of the belt, causing it to come off the pulley,” he explained. “The goal is to have both sides of the belt making equal contact with the sides of the pulley.” Ryden stressed, “equal contact.”
“Belt diameter is critical as well,” he added, “If the belt contacts the bottom of the pulley, the side force, or contact area, will not be correct and result in slippage.” Obviously, if the belt is slipping, the system is not charging correctly. This will result in a low electrical charge stored in the battery and poor ignition.
Pulley Ratio And Output
Bigger isn’t always better. Here’s the key to solving the alternator pulley ratio requirement: Alternator output is not a linear rate. Alternator output performance is a lower rate at lower rpm but picks up, as speed increases — to an extent.
According to Ryden, “Powermaster rates most of its alternators at 7,500 rpm, which is about where peak output occurs.” The takeaway from that statement is there is no reason to run the alternator at up to twice that rpm with thoughts of gaining more charging output. “That taxes the unit,” says Ryden.
Pulley ratio is the comparison of the crank-pulley diameter to the alternator-pulley diameter. The actual ratio is the result of dividing the diameter of the crank pulley by the alternator pulley. For example, a six-inch-diameter crank pulley used with a two-inch-diameter alternator pulley results in a 3:1 ratio.
For the mathematicians in our sport, the equation can be written like this: Ratio = Crankshaft pulley diameter / Alternator pulley diameter.
This combination of pulley diameters results in the revolutions of the alternator. At 6,000 engine rpm with a 3:1 ratio, the alternator is spinning at 18,000 rpm. Running at that sustained high-RPM can take its toll on an alternator.
An alternator rotor RPM that is too high will overcome the efficiency of the alternator. This results in increased heat, loss of output, and exceeding the mechanical capabilities of the unit’s bearings and cooling capacity. “Short bursts up to those kinds of dizzying RPM are okay, but over the long run will be tough on any alternator,” added Ryden.
Typical stock cars on surface streets use a pulley ratio of 3:1 or a touch higher. Ryden explained what we should see on dirt ovals. “For dirt track racing, the sustained higher-RPM and longer duration, Powermaster recommends a 1:1 or 1.5:1 pulley ratio.”
Helpful Tips For Diagnosing Belt Problems
- Squealing sound: The drive belt slipping
- Chirping sound: Misalignment of the drive pulley
- Frayed belt edge: Misalignment of pulleys
- Polished belt edges: Belt slipping
- Fluid contamination: Oil, power steering, or coolant leak
- Excessive cracking: Severe old age
- Rhythmic noises occurring at engine speed: Delaminating belt backing or foreign object(s) embedded in belt groove
- Grinding sound: damaged bearings in driven accessory
- Belt coming off: Pulley misalignment
Diagnosing Belt Noise
Belt noise can be hard to isolate but can be diagnosed with a spray bottle of water. With the engine running, when the sound is audible, lightly mist the contact side of the belt with water. If the noise disappears or lessens, but then shortly returns, the problem is probably a misaligned pulley. If the noise immediately increases after the belt is misted, the belt is slipping.
We’ve seen old-timers diagnose noisy belts by reversing the belt. That is, they take the belt off and reinstall it, so it travels in the backward direction as initially installed. If the noise goes away or gets much quieter, the problem is a misaligned pulley. This works because flipping the belt changes the direction of misalignment from the belt’s perspective. If reversing the belt does not temporarily eliminate the noise, the problem is something other than misaligned pulleys.
Parallel And Angular Misalignment
Pulleys can have parallel misalignment where the pulley is too far, or not far enough, on the component’s driveshaft. This results in a pulley that doesn’t line up with the other pulleys on the engine. Angular misalignment exists when a component’s pulley is at an angle to the other pulleys due to worn bearings in an accessory.
The pulley parallel alignment can be checked with a steel rule or straightedge. Place the straightedge flat across the two pulley faces. If it doesn’t lay flat, one of the pulleys is misaligned. The ultra-pro way to check pulley alignment is with a laser alignment tool.
Sometimes pulleys are pressed onto alternators and power-steering pumps by the manufacturer, which can cause problems when the component is replaced, and the new pulley doesn’t line up with the other pulleys. The pulley will have to be removed and pressed back on to the shaft to line it up. This requires special tools.
Pulleys can also experience angular misalignment due to worn bearings in the component. Turning the part by hand can generally give an indication of the amount of wear. The accessory will turn noisily or will feel sloppy as the shaft rotates. If the bearings are worn enough, the pulley may even wobble or have excessive end play.
Hopefully, we’ve given you enough information to diagnose and solve drive belt and charging system problems on the mechanical side of things. If you would like more information on alternators or other electrical engine components, please visit Powermaster Performance online at www.powermastermotorsports.com.