so i got a 350 with headers, no cat, flowmaster 3" exhaust, open element airfilter, msd coil, msd cap and rotor, new plugs and wires, a chip from tbichips and i was wondering about my fuel pressure regulator, i want to mod my stock one but i dont know how much to adjust it because i dont have an oxygen sensor to tune it with. any suggestions? or advice on how much i should adjust it? also pics of the modified ones would be nice, thanks

 

Aren't you going to have to have an O2 sensor if you are staying with TBI? What's the ECM going to base fuel adjustments off of if there's no O2 sensor? Won't you throw a code and the engine will run like crap?

Anyway - for carbed motors (ie no O@ sensor either) we tune by vacuum - we tune the carb to get the most vacuum at the lowest "streetable" idle - don't know if that helps any.

 

FP would be set according to the fueling tables in the chip.

 

Your ECM will adjust the mixture to a certain degree as needed. If the car is running ok you might not have to change anything. Is there an adjustable regulator for the TBI setup avaliable? To get an idea of what you need you will have to get a scanner and read the integrator and block learn specs from your ECM as it is now.

 

my engine runs fine but if i put an o2 sencor on it will i get more power? or mileage?

 

Thats new to me, I did not know TBI would work fine without the 02 sensor. You sure you are not messing with us? Or do you only drive WOT?

 

no lie. i bought the car from a friend who put headers, a custom Y-pipe, no cat, 3" exhaust, he just took the o2 sencor off, it runs fine, the check engine light and another light was on but i just pulled the bulbs out, i get around 16mpg, mixed city highway, and thats beating on it once in a while. i have 308 rears in the rear with a t5 tranny the rpms are at 2000 when im going 80mph. so is this milege expected or should i put an o2 sensor in?

 

that makes no sense at all cause when my O2 went out my car stunbled and stall all over itself.

 

I just re read this, a must from time to time.
https://www.thirdgen.org/open-loop-closed-loop
A working 02 should help mpg (eccept if you are running really lean right now), though without a cat some functions may no longer be used. Your set up is basically running like a carb without taking advantage of the capability to adjust it self using sensor's imput (open loop).

 

If you wish to tune an EFI car by adjusting the FP only give it a try. Only way to tell if you are on the sweet spot is with plug checks or a WB02 sensor. I have never heard of anyone removing the NB02 sensor as a performance enhancement. Some will run the engine in open loop and "turn off" closed loop in the chip. I ran that way for a couple months but gas mileage sufferred. CL feedback when environment or elevation temps change is critical to an efficent running engine. Closed loop is my friend.

 

so do u think i should put an o2 sensor in or just leave it how it is?

 

The 02 will be a nice improvement for all around driving. No performance gains at WOT sice it does runn on pre established tables but can also be used to analize WOT datalog, though a additional WB02 will be much better in this situation.

Thats yes for the 02 and additional WB02 is a big plus.

 

what type of o2 sensor is the best or are they all pretty much the same?

 

If your set up is so radical(cam/heads) and it wont run well in CL then OL is an option. CL adjusts for changes in air temps, barometric pressure if you are in a State with varying altitude, as well as wear within engine components. CL will save you $$$ on your gas bill. Also there is a benefit in CL runnning in that PE looks at last BLM and calcs the power enrichment A/F off of it. So if you wish to run say 12.5/1 for PE or WOT, CL will help you stay close.
best sensor is GM heated.

 

alright thanks so when i do get an o2 sensor how should i go about knowing how much to adjust my fuel pressure?

 

12-14 lbs is where you want to be. Stock TBI fuel pump wont support much more under load.

 

just put an o2 sensor it the car, how much do u think i will get for mpg now?