As of this writing, the TI Automotive F90000267 is the standard fuel pump to run on high boost street/strip cars running ethanol blended fuel. While this is currently one of the highest performing electric pumps available, the safety relief valve is a weakness that needs to be considered if you're pushing your fuel pressure past 80 psi.
TI Automotive publishes the following performance curve for a new F90000267. Detailed performance data between 80-90 psi is not provided, but the change in the slope of the performance graph indicates the relief valve may actuate anywhere in between 80-90 psi and still be in specification.
Broken-in pumps perform better than new pumps; however, repeated actuation of the relief valve causes degradation in the relief spring. In order to find out "which one" wins, we took a used pump (that had spent some time at high pressures) and tested before / after the modification. As you can see, performance before relief valve actuation is better than the new pump, but performance after the relief valve could be unsafe for some cars...especially if the valve is allowed to degrade under repeated actuation after the initial tune.
APPLICATIONThanks to Tony and his crew at T1 Race Development for pushing us to get more out of these pumps and proving out the effectiveness of these changes. He was gracious enough to provide the following screen before/after captures from a couple R35s at his shop:
HOW TO MODIFYFirst off, you have to completely remove the fuel pump from the hanger/module. If you are using one of our cartridge based modules, it is best to plan ahead an purchase an o-ring kit for reassembly...the o-rings will likely tear when you take everything apart.
Drill a 4.5mm hole as shown...(but try to do a better job of getting the hole on center...CNC is our thing...not necessarily hand tools):
Use a M4 screw to find the depth of the spring seat, then adjust the jam nuts so you can press the spring seat down another 1.5mm. (FYI, two turns on a M4 screw = 1.4mm) Done.
Here's what you did. There is a spring behind the ball...you simply pressed down the spring so that the ball doesn't spring open at 80-90 psi.