Hey guys i have teh Accel regulator, will unscrewing the adjustment rais eor lower pressure?

 

PLEASE leave the stocker on if you have no way to measure this and monitor the results. We do not want to hear you are building a new engine because you cracked a piston or washed out the bearings.

AFPR as a tuning device are best left to OTHER vehicles where the pcm is not so very cheap and easy to retune.

A FEW guys can use them as part of making a fuel system support the power goals thay have but if you are asking this that does not yet apply to you, put the stocker back on and leave that one on the shelf for now.

 

umm sorry maybe I shoul dhave updated my sig and such, I have MTI stage III heads, CC306, 1.6's and everything else. have order fuel pressure gauge just isnt here yet, AFP reg has been on car for a while now as i got this set up from afriend of mine complete. he was running 36#ers and I am just runnign running 28#ers since i am not spraying mine so i was just looking for a quick bit of advice. . but thanks.

 

I was talking to a guy at a machine shop today. He was saying one of the best upgrades you can do is an ajustable fuel pressure regulator. I dont think I would doubt him too much beings how he has built more then a few lt1's in his day.

 

I'll disagree with your "guy at a machine shop"..... why does he feel an AFPR is "one of the best upgrades"? After 12 years of working on these cars, I'd put an AFPR at the bottom of the list of usefull mods. I bought into the AFPR "hype" in 1995 right after I bought my car. Quickly realized that it provided no valid purpose on a "bolt-on" application, and returned the fuel pressure to stock. Even with my 800HP (with dry nitrous) setup, the AFPR is just there to baseline the fuel pressure at the 58psi that I determined would provide me with the optimum fuel supply system, but its not used for "tuning" in any way, shape or form..... its been set at 58 psi for 5 years now.

 

If you were still running the stock fuel pressure, you would have to use larger injectors than you're using now though, right? Plus, the stock fuel pressure on the LS1 is 58psi (4 bar); there has to be a reason for that.

 

umm all of this is valid points in many peoples minds, this is what is on my car alreay, and i was just wondering which way would lean it up a bit.

 

unscrewing the screw will lower fuel pressure...tightening the screw will place more pressure on the spring and diaphram, thus raising the fp

 

Thank You Husker.

 

Turning it either way will NOT lean it out at all.... that's the point.

If you decrease the fuel pressure, it will reduce the fuel flow for any given pulse width. That will TEMPORARILY lean it out. The O2 sensors will see the leaner A/F ratio in closed loop, and the PCM will increase the long term fuel corrections (BLM's) to increase the pulse width. Bottom line - in closed loop it is running at exactly the same A/F ratio it was before. BUT.... when you push the throttle to the floor, and the PCM enters power enrichment (PE) mode, because the BLM's were adding fuel, the PCM will use long term correction cell 15, and the BLM's that are in it..... in effect causing it to run at exactly the same A/F ratio it was running at before you changed the fuel pressure.

Alternatively, you could increase the fuel pressure. That will TEMPORARILY richen the A/F ratio, the O2 sensors see the richer mixture and the PCM pulls down the BLM's, cutting the pulse widths and bringing the A/F ratio right back where it was before you raised the fuel pressure. Now, wneh you go into PE mode, the PCM will not default to the cell 15 BLM's. When the BLM's are cutting fuel, the PCM defaults to a BLM of 128 (0% correction) and the engine is now running way rich in PE mode becuase of the higher fuel pressure.

You don't "tune" with an AFPR. You reprogram the PE mode tables to reduce the "target" A/F ratio. Stock tuning will usually produce a target A/F ratio in PE mode of approx 11.7:1..... too rich. To get it to a more desirable (a generalization - each engine is different) 12.8-13.2:1 ratio, you alter the PE mode tables, which are used to calculate the target A/F ratio.