Anyone running an Adjustable fuel pressure regulator on their 540i?

[ninetyseven1]

Anyone running an Adjustable fuel pressure regulator on their 540i? I wanted to get some info on this.

[edjack]

How much pressure do you need? Are you running some mods that require more fuel? If so, you may need injectors that provide a higher flow rate.

The stock regulator is set to circa 50 psi.

[JimLev]

Answered your PM.
Yes, tell us what mods you have that require more fuel?

[bimas]

Isn't the stock FPR more than enough to deliver enough pressure to the stock injectors?

I always thought that you have to match up fuel pressure to the appropriate injectors (for example, M5 setup). No?

But maybe, you have some cool injectors. Please share.

[ninetyseven1]

Isn't the stock FPR more than enough to deliver enough pressure to the stock injectors?

I always thought that you have to match up fuel pressure to the appropriate injectors (for example, M5 setup). No?

But maybe, you have some cool injectors. Please share.

I'm after a certain. Fuel trim number. Preferable
Closer to 0, that's where my car runs the best and makes the most low end torque

[gmak]

I'm after a certain. Fuel trim number. Preferable
Closer to 0, that's where my car runs the best and makes the most low end torque

I may be off-base here, but the fuel trim number shouldn't have an impact on torque. trim is the amount of fuel being added or subtracted by the DME to ensure that 14.7 air / fuel ratio is maintained on the exhaust side. Whether you are at zero of 3%, the same amount of fuel is going into the cylinders. It's based on the amount of air that the DME thinks it has. the only time there would be some kind of impact would be when the limits of what the DME can do are reached and you wind up running true lean or rich - and get a CEL to show this.

[ninetyseven1]

I may be off-base here, but the fuel trim number shouldn't have an impact on torque. trim is the amount of fuel being added or subtracted by the DME to ensure that 14.7 air / fuel ratio is maintained on the exhaust side. Whether you are at zero of 3%, the same amount of fuel is going into the cylinders. It's based on the amount of air that the DME thinks it has. the only time there would be some kind of impact would be when the limits of what the DME can do are reached and you wind up running true lean or rich - and get a CEL to show this.

Fuel trim most definitely effects performance , I have been tuning gm ecms for years. when my fuel trims are high cause if let's just say, a vacuum leak then then I will have a positive fuel trim like +7 but increasing fuel pressure will bring that number down and the car is significantly more powerful , this can be seen by simply driving in the rain. The car skids and loses traction with the minimal effort . I can also feel being pushed back in the seat harder . The butt dyni measures torque , if you feel it then torque is what u feel , torque is felt. Also lowering the fuel trim number will also increase power through the whole rpm band.

[topaz540i]

The leaner you run an engine the more power it will create at the expense of heat . Run it too lean and you'll blow it up.
this is what makes tuning so hard

you need air fuel ratio to determine stoich (14.3?) for the safest tune. Ignoring a/f readings you are asking for trouble

[Mach540]

I have been tuning gm ecms for years. when my fuel trims are high cause if let's just say, a vacuum leak then then I will have a positive fuel trim like +7 but increasing fuel pressure will bring that number down and the car is significantly more powerful
This is because in your scenario, you have a problem in the system that the AF ratio is compensating for. Not a good analogy.

You can make the fuel trims say whatever you want if you change the calibration on the MAF sensor. Bottom line is that the correct AF mixture will give the best performance, regardless of what the fuel trim numbers are used to get you there.

[Mach540]

Sitting around waiting for my JB Weld to set up, I thought of an interesting experiment regarding fuel trims and how to manipulate them.

Follow along closely......

If the size of the MAF is approx 3.5 inches, this is about 10 square inches. (Numbers made up fir easy math)

If you take a 1 inch square piece of tape and place it on the MAF, (not near the sensing wire, duh) this would make the MAF assume it is flowing 10% more air than it actually is. And the engine would be running rich right off the bat.

If you run it like that, I would assume that the STFTs would quickly compensate, and they would be in negative numbers. After a while, the LTFTs would come down also.

Now, my assumption would be that a 10% change in air flow should equate to a 10% change in FTs.

Thoughts??