Need Help with Fuel Pressure Regulation
06-05-2002, 09:43 PM
#1
Three Wheelin'
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Need Help with Fuel Pressure Regulation
I want to look into reducing the fuel pressure in my 1981 928 with Callaway Turbochargers
The car has high flow injectors, plus two additional injectors in the air stream. Being that the fuel management is stock (except under boost), I get a very rich mixture under normally aspirated conditions....so much so that I have to run the car in open loop to get it to idle. If I plug the O2 sensor in, the idle hunts (computer shutting down the injectors I guess).
My thought is I can keep the high flow injectors, but cut back on the fuel pressure?
Has anybody installed an adjustable fuel pressure regualtor on an 81 928?
Can the pressure be decreased from stock, or just increased with the regualtor (maybe I could go back to stock injectors and run a higher pressure I the regualtor won't go lower?)
Any help would be greatly appreciated!
The car has high flow injectors, plus two additional injectors in the air stream. Being that the fuel management is stock (except under boost), I get a very rich mixture under normally aspirated conditions....so much so that I have to run the car in open loop to get it to idle. If I plug the O2 sensor in, the idle hunts (computer shutting down the injectors I guess).
My thought is I can keep the high flow injectors, but cut back on the fuel pressure?
Has anybody installed an adjustable fuel pressure regualtor on an 81 928?
Can the pressure be decreased from stock, or just increased with the regualtor (maybe I could go back to stock injectors and run a higher pressure I the regualtor won't go lower?)
Any help would be greatly appreciated!
06-05-2002, 11:31 PM
#2
If you keep the high flow injectors and reduce the fuel pressure, you will be leaning out the mixture under normally aspirated conditions. You would also be leaning the mixture under full throttle conditions too though. Do NOT do that unless you're looking for an excuse to do an engine rebuild. An adjustable fuel pressure regulator should allow you to either increase or decrease the fuel pressure. Make absolutely sure you have a safe full throttle air/fuel mixture if you do any fuel pressure adjusting. Are you sure your O2 sensor and it's wiring are good?
06-06-2002, 04:28 PM
#3
Three Wheelin'
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Yes....the O2 sensor is good, it is new. When they did the conversion it had been removed. The voltage reading off of the sensor is nearly 1 volt, so I know I am rich at all locations on the map.
I figured I can start out with stock pressure and make minor adjustments, then read the voltage off of the sensor in open loop. Once I get it close, I should be able to plug the sensor in and let it do a minor correction. Right now, the comuter can't correct the mixture when the sensor is plugged in, so I have to run in open loop and go back to the uncorrected map in the computer. It runs great when it is really cold out, but in the heat it feels sluggish. I also want to clean up the exhaust, since it runs very, very rich right now.
Does anybody have figures on the stock fuel pressure and the range of the Bosch adjustable regulators?
I figured I can start out with stock pressure and make minor adjustments, then read the voltage off of the sensor in open loop. Once I get it close, I should be able to plug the sensor in and let it do a minor correction. Right now, the comuter can't correct the mixture when the sensor is plugged in, so I have to run in open loop and go back to the uncorrected map in the computer. It runs great when it is really cold out, but in the heat it feels sluggish. I also want to clean up the exhaust, since it runs very, very rich right now.
Does anybody have figures on the stock fuel pressure and the range of the Bosch adjustable regulators?
