[eschaider]

Ti Automotive makes five fuel pumps using that Hellcat form factor, Kevin. The part numbers and corresponding specs look like this

Form Factor..... Part #.... ... Flow.......... Pres Relief...... ... MAX PSI

Hellcat ..........F90000262.. ...405 LPH............Yes.....................87 psi
Hellcat.......... F90000267... ..430 LPH.............Yes.....................87 psi
Hellcat.......... F90000274..... 430 LPH............ Yes ..................187 psi
Hellcat...... ....F90000285.... . 470 LPH........... Yes....................150 psi
Hellcat....... ...F90000295 ... ..540 LPH............ No....................150 psi

This table is an F90000274 pump being run at 12 and 13.5 volts. The pump goes to a zero flow at 160 psi

This is a pump flow graphic at varying pressures up to pump stall and the voltage and amperage required to drive the pump;

TI Automotive publishes this data for all their pumps to help us select the proper pump for our application.

A worthwhile data point to remember is the amperage to drive these pumps at elevated fuel pressures, our electrical system's ability to power the pump at these performance levels, and of course, the impact the additional head has on their flow performance.

Considering where TI indicates the pressure relief blows off on a F90000274 pump, the performance graph seems to indicate they test pump performance without a working check valve.

 

[eschaider]

TI Auto has most of the info on its site Kevin, however it is not intuitively obvious where they have it located. Here is a link to a significant chunk of it; click here => https://aftermarket.tiautomotive.com/technical-info/#flow-charts.

Discovering the rest of it is akin to playing that original computer game Colossal Cave. Colossal Cave, if you recall, is the original classic text-based adventure released in 1976 by Will Crowther for the DEC PDP-10 computer, which predates most of us on the site here. In the game, the player explores a vast and extensive cave network, seeking treasures within. Along the way, you will encounter a variety of tools and characters, some of whom will attack you and some of whom will help you. It is sort of the same thing on the TI Automotive website, but without the tools and characters — the game is more fun.

If you have never experienced the original text-based game that literally started the gaming industry in the mid 1970's, you can get a taste of what it was like back then in a demo version available here => Colossal Cave When Colossal Cave was first released, computers were ASCII terminals on an RS-232 link back to the minicomputer they were attached to. There were no graphics or colors like we have today so the developer(s) had to build the video images in your mind with words — quite a feat and quite a game. If you have never experienced it, it is worth a few minutes to explore — it might actually help you on the TI-Automotive website.

 

[eschaider]

Ashford nailed it, Kevin. When you look at the flow chart for a single pump and read the head the pump is pumping against, you will see the voltage and amperage the pump is drawing. If we increase the head and reduce power (voltage or amperage), then the system will experience a corresponding reduction in volume flow (mass flow). Because the metric used to fuel our engines is a mass flow metric, AFR (lbs of air per lb of fuel), the engine operation is sensitive to these sorts of power delivery perturbations.

With a finite delivery orifice and a computer-controlled duty cycle (injector on time), the addition of increased pumping capacity will not result in a linear increase in delivered fuel mass at the injector or measured pressure in the fuel system. When you add to this the increasing load it places on the fuel pump's electrical system, you've added yet another dimension to an already complex physical process.

The best fix I have found is to run the fuel system with the most robust power delivery capabilities we can package into the back of the car, run the base system pressure at 39 psi, and select injectors that will allow you to operate at less than a 75% duty cycle. While nothing is perfect, this does allow for an operating fuel system pressure of only 60 psi while using up to 20 lbs of boost. If you are looking at a race scenario where you will be using 25, 30, 40 psi of boost and higher, you will need to go to a mechanical pump. The power draw of an electric pump goes off the wrong end of the chart and becomes very difficult, if not impossible, to consistently control and supply.

There are other challenges that also appear along the way. A big one is the low speed, read idle, flow characteristics of the injectors. Some big injectors, not all, and usually older design big injectors can have poor idle characteristics because the injector flow at low pulse widths becomes both non-linear and inconsistent with the same injector's flow at higher pulse widths.

The basic problem is attempting to build a race engine power level for a daily driver type application. We simply run out of operating range with some components. Either the low-speed fuel delivery is inconsistent, or the high-speed fuel delivery is beyond the operating range of the components (pumps and injectors). The basic admonition is to be careful what you wish for and attempt to build.