Mechanical Fuel Injection

Sample Reports

Standard Flow Tag - This is our most basic fuel pump flow tag. Some flow tags floating around out there do not specify the pressure at which the flow was measured. This means the flow number is nearly worthless! The flow of a pump against a precise known back pressure is critical to determining a safe tuneup and evaluating pump health.

Our basic pump checkout includes observations under two standard conditions; 1800 pump RPM and 50 PSI back pressure and also at 4000 pump RPM and 100 PSI back pressure at a standard 68F and .792 specific gravity (methanol). If you use a different fuel, we can deliver numbers that are real-world for your application. Along with a flow test, pumps are disassembled for inspection of bearings, rotor, impeller, body, and overall wear. All parts are thoroughly cleaned, internal clearances reset, and a new front seal is included.

To help keep you from misplacing your flowtag, ours are DECALS. Stick your flowtag inside your logbook, toolbox lid, the wall of your trailer, etc. We use a thermal printer so it's impervious to smudging when exposed to water or fuel.

Click the images below to view the full size PDFs

Advanced Pump Profile - This complete pump flow profile gives you the whole picture of what your pump is or isn't doing. In addition to the two standard tests, cleaning and inspection described above, a pump flow profile graph is generated. Your theoretical maximum system pressure is calculated using your nozzle and main jet combination. We then run your pump up to 4000 RPM and achieve that maximum pressure and record the flow. We then reduce the RPM in 250 RPM increments noting the flow at each point. This tells you how your pump performs under different pressure and RPM conditions. Most pumps (but not all) gradually flow less as pressure increases. Due to internal turbulence and harmonic pulsations that differ from pump to pump, most will exhibit slight "humps and bumps" on the graph where flow is slightly more or less than would be expected. Pump output is not exactly linear with RPM and these translate to "rich" or "lean" spots on your overall fuel curve. You should know where these are! In addition to the report at the upper left, you also receive the advanced flow tag DECAL pictured at the right.

In cases where pumps exhibit severe turbulence and diminished flow at certain speeds (resulting in lean spots), some mild porting of the pump is called for. Casting flash and irregularities in the pump ports can cause very non-linear flow. The more linear your pump output is with repect to RPM, the easier it will be to find a tuneup that works consistently well. A straight reference line is super-imposed to make it easy to see the trend in pump flow.

Nozzle Flow Report - Nozzles from the same set can differ greatly in flow, especially at high pressures. Some manufacturers don't flow test or match their nozzles at all. They drill a hole in a piece of brass and call it a nozzle. The size isn't the only thing that's important: the shape of the entry, the exit, and the surface finish of the orifice are extremely important at high pressures. Some companies rate and match their nozzles at a standard low pressure. It's easy to get orifices to flow the same at low pressure, at higher pressures it is very difficult! Hopefully, you don't run your mechanically fuel injected motor across the finish line at only 30 PSI. The higher the pressure, the better fuel atomization you'll get. This results in more fuel actually burned and more power produced.

At higher pressures, all orifices are not created equal! We check the flow of each nozzle at 30 and 70 PSI (or any customer specified pressure) to see that they match well. We also check and record the "terminal flow" pressure for the nozzles for the specific gravity fuel that will be used with it. Normally, as pressure behind a nozzle increases, a corresponding increase in flow through it results. Eventually however, every nozzle quits flowing in a linear fashion and it will reach a point where it will not flow any more liquid regardless of how much the pressure is increased. The pressure where this occurs is called the Terminal Pressure. Terminal pressure also changes as the specific gravity of the fuel changes. Terminal pressure will be different when running 100% alcohol or 20% nitro or 60% nitro through the same nozzle. In cases where people are running small nozzles and small main jets, system pressure can be very high. If any of the nozzles reach their terminal pressure before the finish line, engine damage can result. At the very least, power output can suffer dramatically. In most cases, nozzles that aren't flowing like the others can be corrected, but you have to know about them first! In cases where we correct the flow and match a set of nozzles, we deliver before and after flow numbers as well.

Full System Flow Report - Typically, when we flow an entire system, three separate multi-page reports like this are generated. One for the "optimal tuneup" on paper, and then two more: one step richer (and safer) and two steps richer for a safe place to start. The system is flowed with the customer's actual pump, nozzles, bypasses, and jets. In some cases, the customer's barrel valve and fuel tank are also used to ensure real data. We find the best possible main jet combination on the flow bench and plot a line on the graph to show the actual fuel flowing into the motor. Then, we tune the high-speed bypass jet and cracking pressure and overlay that on the graph so the customer can easily see its effects. We also plot an Air/Fuel Ratio (AFR) curve along the top so the effect to the fuel curve can quickly be seen and interpreted. A super-imposed air flow line is also placed on the graph. This is the theoretical linear airflow requirement of the motor. The very best data to use for this "reality line" would be dyno torque curve information and/or an EGT graph or actual airflow data from a dyno session. Since most people don't have that, this is a good indicator even though this line will not really be straight and linear in real life. The *ANGLE* of this line on the graph shows the trend and is a reality check for what the fuel curve should roughly mimic up to peak torque.

On another page, the actual fuel flow, pressure, and AFR at each RPM increment is displayed for a particular tuneup. For a particular main jet and high-speed bypass setting at wide open throttle, the data is clear to see. From this, one can easily extrapolate what a change in bypass cracking pressure would do, etc.

Also included is a procedure sheet to help the customer get through the tuneups logically to find the very best performance as well as a setup sheet with all the initial settings and adjustments along with a legend of all the ports as they are labeled.

Sometimes, a racer just wants to put his whole setup on the fuel flow bench, put in their best tuneup and see what it looks like. Nearly always, places are found where improvements can be made.

Atmospheric Effects Report - Given either theoretical data from a known good tuneup or actual flow bench numbers, we can calculate exactly how your tuneup will change due to weather conditions or altitude. Given a customer specified baseline altitude or temperature/barometer/humidity, we can precisely calculate how things will change for different conditions. For example, we can customize the report to show how much of a main jet and high-speed change to make for a 1000' difference in density altitude. What if the temperature increases 20F and the barometric pressure drops from 30.08" to 29.88"? What if the relative humidity changes 25%? No problem! Given any particular weather scenario, you'll know what to do. This information is customized and calculated using the customer's particular equipment and altitudes calculated are chosen by the customer.


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