LT5

Was wondering what the best and or recommended fuel pressure regulator is for my 1994 Z28 6 speed. I bought an Accel one in the past that was adjustable but wasn't really sure why i needed it. This car will stay mostly bolt ons only for now and will always be an NA car. Any help would be great

shoebox

Best for you would be a stock regulator. No need for anything else.

Injuneer

+1

LT5

So how much hp is the stocker worth? Just curious

Injuneer

No idea what you are asking. A healthy stock unit accurately regulates the fuel pressure. They are very reliable. Even if there was a minor departure from specified fuel pressure, the PCM can compensate using the long term fuel trims (LTFT).

Some people opt for an adjustable fuel pressure regulator (AFPR), in the belief they can gain HP. Can't, unless the fuel injectors are too small and the engine is running lean, with 90% + injector duty cycle. Raising fuel pressure increases flow through the injectors. Causes engine to run rich, O2 sensors tell the PCM, and in closed loop the PCM uses the LTFT's to reduce injector pulse widths, reducing fuel flow, returning the A/F ratio to the stoichiometric target value (14.7:1). = no change.

Go wide open throttle, PCM enters power enrichment (PE) mode and sets a new, richer target A/F ratio (typically 11.7:1 with stock programming) to increase power and torque. Because the PCM was reducing fuel flow in closed loop (LTFT below 128), it defaults the LTFT's to 128 and the engine runs excessively rich, losing power and torque. The stock PE mode target A/F ratio is already too rich at 11.7:1. The first place a tuner will go to pick up 10-15 HP on a stock tune is to lean out the PE target A/F ratio.

So.... let's lean it out by REDUCING fuel pressure with an AFPR. Doesn't work. Lower pressure = lower injector flow = a bit lean, so the PCM increases the LTFT's to return the A/F ratio to 14.7:1 = no change in closed loop. And now, when we go WOT, the PCM sees the LTFT's were adding fuel in closed loop (above 128), so to play it safe it continues to use the above 128 LTFT's in PE mode, offsetting the reduced fuel flow due to reduced fuel pressure = right back where we started from, with the overly rich 11.7:1 target A/F ratio.

Bottom line, there is no HP to be gained or lost with a stock FPR, and there is no HP to be gained with an aftermarket FPR or AFPR.

Again, if you are running stock injectors and making more than 350-375 HP at the flywheel, increasing fuel pressure would increase the flow through the injectors, and allow them to exceed that HP limit. You would have to reprogram the injector size in the PCM. But the best way to handle big HP is bigger injectors.

LT5

So basically its worthless to get one, just stick with a good quality one and get bigger injectors and worry about a tune later on? Pretty simple....and very very well put!

Injuneer

Stock regulator is fine.

Of course there are always people who think it if costs a lot, has a lot of impressive tech hype, or comes from a big name company, it must be better. Perfect example is the Aeromotive adjustable fuel pressure regulator for the LT1. Expensive and looks beautiful, and Aeromotive makes good stuff..... well mostly. When I see a post that involves a problem with an AFPR, the first question I ask is "what brand?". Invariably, it's an Aeromotive.

LT5

Yeah well the stocker is like 70 bucks at autozone.....i saw one on summit that was like 50....ill test mine before i replace it hopefully mines fine. Thanks for all the info! Saved me money cause i was thinking of getting a nice adjustable one again but knowing i dont even need one yeah good thing.....just want a quality one that will work really well.