Calculating Jetting

Aquamist Jetting Calculator

Calculating jetting for Aquamist systems is quite easy as we will walk you through a few simple steps, then some examples. At the bottom of the page you will find some conversion factors if you are using other jets and systems.  Please follow through the examples below, but if you don’t have the fuel injector size, or all else fails, you can use this simple formula to get you in the ballpark.  CC = 1.5 x  hp.  This generally holds true for a 50:50 mix or above.  So for a 300hp car, you’d use 450cc of jetting.

Example 1
1) First, you will need three pieces of information. Fuel injector size, number of cylinders, and peak boost pressure.

2) Take the number of cylinders and multiply by the injector size. For example, let’s use a 4 cylinder with 800cc injectors. This car would have a total of 3200cc of injectors.

There is a general rule of thumb for injection. Three guidelines are below:

For 100% water target 10% – 15% of fuel flow
For 50/50 mix target 15% – 20% of fuel flow
For 100% methanol target 20% – -25% of fuel flow

For this example we will use a 50/50 mix. So find the range of jetting you need by the following:

3) Multiply your total fuel injector number from step 2 by 15% and 20%.

3200cc x 15% = 480cc
3200cc x 20% = 640cc

4) Subtract your peak boost pressure from the system running pressure on the chart and find the appropriate jetting range.

Jet Flow Chart

For the example being discussed we want to target 20% which would be 640cc. We also know our peak boost is 30psi. The new Aquatec pumps run at 165psi, the older Shurflo pumps at 125psi. We have a brand new HFS-4 installed in our test car so we use the 165psi starting point.

4) We start at the 165psi line, and subtract our 30psi boost pressure. This means we need to look at a phantom line of 135psi. So we have our 640cc target, we look down the columns and estimate that between the 130 and 140 columns 640cc is going to fall around…….wait, it’s off the chart. We need to use two jets. So, we split the 640cc in half and see that 320cc falls between the 130 and 140 columns right right between the .7mm and .8mm jet range. In this instance we will pick two .8mm jet as we can always trim the flow down with the gain functions.

IMPORTANT NOTE

It is best to test your jetting into a container and measure the flow. Since every build and configuration is different this will be your best measure of the system performance.


Example 2
6 cylinder, 1000cc injectors, 35psi boost and we will run 100% methanol.

6 x 1000cc = 6000cc.
6000cc x .25 = 1500cc
1500 / 3 = 500cc for each jet.

Now we are getting close to the edge because the HFS series systems max out at about 1500cc of flow. Since we are calculating right at the limit we should be fine. NOTE: FAV’s post 9/2012 flow 1500cc, pre-9/2012 FAV’s rated at 1300cc)

From the chart we can see we will need 3 jets to get the job done. So we look down the 130psi line (165-35 peak boost = 130) and find the 500cc for each jet falls just above the 1.0mm jetting. In this case we would probably pair 2 x 1.2mm with 1 x 1.0mm jets to hit the 1500cc target. If running a split plenum that requires 3 equal size jets, 3 x 1.0mm would be recommended. The best test to see your actual flow is to measure the flow into a container through the system.

We would be happy to help you out with any jetting or application questions you may have, just contact us.

Conversions from other systems
1 GPH = 63CC/MIN

GPH jets are calculated at 100psi. Since most systems vary the pressure to the jet to vary flow it’s easiest to use a chart to find your actual GPH jetting rate.  The Aquamist chart has equivalent GPH numbers (Mx.x) next to the cc/min.

Even though your pump is rated at 250psi, in reality it probably never injects at that pressure, especially with bigger nozzles. Use 150-175psi for realistic numbers when estimating what jetting you may have now.

Notice that the M nozzle chart is not linear; it is a square function. So the jump in flow from 100-200psi is not the same as the 200-300psi flow change.