Fuel Pressure Regulator Questions & FPR mod

Was looking to purchase a new OEM fuel Pressure Regulator Assy.
P/N 16740-MFT-641, one on bike is not bad, just a squirrel thing  
in shopping cart at Ron Ayers, waiting to make free shipping amount

So, I did a internet search JIC and several non oem popped up on Evilbay, listed using same Honda p/n , but out of Poland and made by "Tre Rosso"

Yes, I'm getting to the point, you can get them in 3 different fuel pressure settings   is there any real benefits/experience from changing fuel press. on the SW ? or they are just blowing smoke up ...    

OEM spec. 294 kPa, 43 Psi fuel press. at idle.
Clones Pressures. 300 kPa/43.5 psi, 320 kPa/46.4 psi, 350 kPa/51 psi

IAC, similar price to oem when you factor shipping, etc. good feedback on seller and fast shipping, etc., the 46.4 is in my watchlist.

Side Bar, these pressure modified regulators were kinda the cheap fueling fix, for the VFR's, Blackbird's and other Honda sport bikes of that era and it worked. The SW is from that era  

IMO there’s nothing “lacking” by staying with the OEM FPR.

What could be gained by an increase in fuel pressure? The scoot will go 110 mph as it is. So maybe bumping up the fuel pressure might get you there a moment faster. But it’s still scary business at that.

What were the results from increasing fuel pressure on the other bikes you’ve mentioned?

Most of the ones that bought high press. FPR's or modified their own FPR (sometimes with a calibrated hammer blow !!) reported improved drivability at lower to mid rpms, IOW it corrected the lean factory settings on stock bikes, but more so on ones with performance exhaust and high flow air filters, etc. This is about 17 years ago  

Keep in mind that some of these early fuel injections on Honda motorcycles where kind of basic, wax choke, actual idle speed adjustments and did not have a 02 sensors (as in early SW600) a "Open Loop" system, preset fueling parameters, so an increase in fuel pressure would affect all throttle positions.

In "General" on a "Closed Loop" system, the O2 sensor only plays a part at idle or constant throttle settings, usually below 50% (low power), it will adjust to the most efficient mixture by controlling injector on/off time. In theory adding a high-pressure fuel pump to a close loop system will only affect/benefit, acceleration and high-power settings, otherwise the O2 adjusts to best fuel economy/emissions values.

Here's a modified pic, from VFRD owner's board, circa 2005 on a 1998/VFR800, it worked!  

What is he trying to accomplish here? Kinda looks like he’s trying to delicately crush the diaphragm body of the regulator. If that the case then how could that increase the fuel pressure over normal?

Cosmic_Jumper wrote:

What is he trying to accomplish here? Kinda looks like he’s trying to delicately crush the diaphragm body of the regulator. If that the case then how could that increase the fuel pressure over normal?

"Delicately" , yes his basically beating on the diaphragm metal cover to bend it in and preload internal valve spring, thus increasing fuel pressure, 2-3mm was the desired range for 4-6psi pressure increase, some guys tried to simplify or "Rube Golberg" the mod , by doing it while still installed on the fuel rail, with punches, pry bars, wood wedges, etc., etc. against frame, good results/success where limited at best,

Ah ha! Preloading the spring. So in our case which end of the FPR is the spring? The fuel rail or manifold vacuum end?

The Honda FPR of aprox. circa year 2000 +/-, where all almost identical physically, the difference was the pressure settings for different bikes and orientation of hose fittings, the increase pressure mod was possible on any bike. You could also install one from a different bike with known higher pressure, like any special interest group mod, a bit of "Tribal Knowledge" played a part.

Here's a pic/diagram to visualize better.

OEM PGMFI is designed to run on preset fuel ratios and Emission standards when manufactured. The standard is 14.7 :1 for best overall fuel to oxygen burn but that doesn't make the most power. Increasing pressure will richen it up and make more power. 12.8:1 ideal but leaves a bit more unburned fuel going out.

Modify the intake or exhaust flow and it will start to go leaner than desired making less power and hotter running engine. O/2 sensor will compensate at a steady throttle but not all the time. Increasing A/F ratio will give more power all the time.