Calculating Supercharger RPM for RAM TRX with Aftermarket Pulley Upgrades
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If you own a RAM TRX with a supercharged engine and you're considering aftermarket pulley upgrades, you can use the following steps to calculate the supercharger RPM based on the pulley sizes:
Step 1: Determine the size of the engine's crankshaft pulley
The crankshaft pulley on the RAM TRX is located at the front of the engine and is easily accessible. Measure the diameter of the pulley in inches. This will be your "Crankshaft Pulley Diameter" (CPD).
Step 2: Determine the size of the supercharger pulley
The supercharger pulley on the RAM TRX is located at the front of the supercharger housing. Measure the diameter of the pulley in inches. This will be your "Supercharger Pulley Diameter" (SPD).
Step 3: Calculate the ratio between the two pulleys
To calculate the ratio between the two pulleys, divide the CPD by the SPD. For example, let’s take a stock lower with a 2.85 upper. if the CPD is 8.18 inches and the SPD is 2.85 inches, the ratio is 2.87:1 (8.18/2.85 = 2.87).
Step 4: Determine the engine's RPM
To determine the engine's RPM, use a tachometer or other engine RPM measuring tool. This will be your "Engine RPM" (ERPM).
Step 5: Calculate the supercharger RPM
To calculate the supercharger RPM, multiply the ERPM by the pulley ratio. For example, if the ERPM is 6,500 and the pulley ratio is 2.87:1, the supercharger RPM is 18,655 (6,500 x 2.87 = 18,655).
If you're planning to install an aftermarket pulley on your RAM TRX, keep in mind that it will affect the pulley ratio and the supercharger RPM. Most aftermarket pulleys are smaller in diameter than the stock pulley, which increases the supercharger RPM and can result in more boost and horsepower.
For example, if you install a 2.85 upper on a RAM TRX with a stock CPD of 8.18 inches and an SPD of 2.85 inches, the pulley ratio will be 2.87:1 (8.18/2.85 = 2.87). If the engine is running at 6,500 RPM, the supercharger RPM will be approximately 18,655 RPM (6,500 x 2.85 = 18,655).
It is important to note that changing the pulley size can affect the engine's performance and reliability. It is recommended that you consult with a reputable builder, tuner, or performance shop before selecting pulley combinations. If they are tuning the truck they may want to see certain things or keep the truck within a certain Blower RPM. They can provide guidance on the appropriate pulley size for your specific needs and ensure that the installation is done correctly and the truck is reliable. To learn more about RPM limits, visit our Supercharger Porting Theory Write-Up.
If you found this helpful or interesting and would like to see more, we'd love to feature a topic or discussion you'd like to learn more about. Please fill out our Topic Submission Form and we can review it and act accordingly.
Step 1: Determine the size of the engine's crankshaft pulley
The crankshaft pulley on the RAM TRX is located at the front of the engine and is easily accessible. Measure the diameter of the pulley in inches. This will be your "Crankshaft Pulley Diameter" (CPD).
Step 2: Determine the size of the supercharger pulley
The supercharger pulley on the RAM TRX is located at the front of the supercharger housing. Measure the diameter of the pulley in inches. This will be your "Supercharger Pulley Diameter" (SPD).
Step 3: Calculate the ratio between the two pulleys
To calculate the ratio between the two pulleys, divide the CPD by the SPD. For example, let’s take a stock lower with a 2.85 upper. if the CPD is 8.18 inches and the SPD is 2.85 inches, the ratio is 2.87:1 (8.18/2.85 = 2.87).
Step 4: Determine the engine's RPM
To determine the engine's RPM, use a tachometer or other engine RPM measuring tool. This will be your "Engine RPM" (ERPM).
Step 5: Calculate the supercharger RPM
To calculate the supercharger RPM, multiply the ERPM by the pulley ratio. For example, if the ERPM is 6,500 and the pulley ratio is 2.87:1, the supercharger RPM is 18,655 (6,500 x 2.87 = 18,655).
If you're planning to install an aftermarket pulley on your RAM TRX, keep in mind that it will affect the pulley ratio and the supercharger RPM. Most aftermarket pulleys are smaller in diameter than the stock pulley, which increases the supercharger RPM and can result in more boost and horsepower.
For example, if you install a 2.85 upper on a RAM TRX with a stock CPD of 8.18 inches and an SPD of 2.85 inches, the pulley ratio will be 2.87:1 (8.18/2.85 = 2.87). If the engine is running at 6,500 RPM, the supercharger RPM will be approximately 18,655 RPM (6,500 x 2.85 = 18,655).
It is important to note that changing the pulley size can affect the engine's performance and reliability. It is recommended that you consult with a reputable builder, tuner, or performance shop before selecting pulley combinations. If they are tuning the truck they may want to see certain things or keep the truck within a certain Blower RPM. They can provide guidance on the appropriate pulley size for your specific needs and ensure that the installation is done correctly and the truck is reliable. To learn more about RPM limits, visit our Supercharger Porting Theory Write-Up.
If you found this helpful or interesting and would like to see more, we'd love to feature a topic or discussion you'd like to learn more about. Please fill out our Topic Submission Form and we can review it and act accordingly.