Pulling the Trigger: Accurate RPM measurement from FAST™
For any racer or performance enthusiast, engine information is key to efficient operation and performance. And with today’s technology, access to engine information is becoming easier, and the information itself is much more defined and accurate. RPM (Revolutions Per Minute) information is among the most important data an engine provides, because accurate RPM numbers tell so much about an engine’s performance and efficiency. Not only is the information critical. It’s also vital that RPM reporting is accurate.
New Crank Trigger from FAST™
In many applications, RPM is reported from a sensor that’s mounted inside the distributor. This system is essentially a motion train with the RPM data coming from the camshaft rotation. But the total motion really comes from four components; crankshaft, cam drive assembly, camshaft and distributor. Unfortunately, this process is inherently inefficient for RPM accuracy because each portion of the motion train introduces an amount of mechanical play or variance. The result is cumulative and in the end, the RPM signal is inaccurate and inconsistent.
Other applications take RPM readings through the use of flying magnet trigger wheels. These are mounted to the crank which provides more RPM accuracy, however, the down side is they are compromised of thick metal and have bulky inductive pickups. And they’re used at the risk of magnet loss or magnet fragmentation. On a V8 engine, there are typically 4 crank pulses per revolution and if a single magnet is missing, you only get three impulse readings. That means only 6 of the 8 cylinders will be firing, so it’s not just losing some performance, it results in an engine that won’t operate properly.
In either method, inaccurate RPM reading is not acceptable. That’s because the RPM signal is what fuel injection and ignition systems rely on for proper operation. So it follows that that inaccurate and inconsistent RPM signal results in inconsistent fueling or ignition timing.
To eliminate these inconsistencies, engineers at FAST™ set out to develop a solid and dependable way to measure and report RPM. They first began with extensive analysis of the problem as well as seeking the council of OEMs to develop an absolutely dependable RPM measuring system.
The result is a new and revolutionary crank trigger that eliminates any possibility of inconsistent RPM measurement. First, it eliminates the concerns of mechanical play because it’s a wheel that bolts directly to the crankshaft thereby removing the possibility of movement inconsistency. And equally as important is that the new trigger wheel is magnet-free, totally eliminating the possibility of magnet loss or fragmentation.
Cutting-edge computer design was employed in designing the new Crank Trigger
Constructed from very strong ASTM A36 grade steel, the new Crank Trigger from FAST™ is virtually indestructible and is only .125” thick. Because the wheel is thin not only does it weigh less, it also takes up less space than other aluminum versions. In addition, the inductive sensor is significantly smaller than other sensors and it’s hermetically sealed with the connector molded into the body for long lasting performance.
The key to its dependability and accuracy lies in the trigger wheel design. Rather than having added magnets, the FAST™ Crank Trigger wheel has tabs on the outer rim. It’s these tabs that are measured by the inductive sensor as the wheel revolves, which in turn provides data to the fuel injection and ignition systems for accurate RPM measurement. And because the tabs are a part of the single wheel unit, there is no possibility of loss or fragmentation as can be the case in the magnetic style trigger wheel.
Installation is straight forward, and everything required is included. And for those who already use the FAST™ XFI™ system, it’s a virtual plug and play unit. In addition, it’s compatible with any other systems in the market. So when accuracy, quality and reliability are required in measuring RPM, the new Crank Trigger from FAST™ is the right choice.
