he never actually said he had knock...said he has no knock in his first post, then went on to say in another that he's being overly cautious because of all the blown headgasket posts he's read...
Will Increasing Fuel Pressure Increase O2 Readings
- Thread starter mmarlett
- Start date
I guess we can keep going back and forth. I'll keep giving detailed explanations and you can reply with an unexplained statement.
The output/volume of a pump remains constant at any given voltage. As the motor increases its appetite for fuel,when we force more air into it and rev it higher,that demand for fuel will eventually outpace the pumps ability to deliver it. That's why we then need a bigger pump or a second pump.
At an idle we are sending most of the,fuel delivered by the pump to the motor,back to the tank.The pump is moving x amount of fuel at any given voltage.
As we turn up the boost and rev the motor higher the injectors stay open for a longer period of time. This allows more fuel to pass through the injectors nozzles. The pump is still putting out the same volume,but more of it passes through the nozzles and into the motor and less returns to the tank.
The other thing that happens is that the fuel pressure is increased because the boost pressure is acting on the regulator. The reason we increase the fuel pressure is because we are spraying into a pressurized environment. When the fuel moves through the nozzles,the pressure in the intake is trying to push the fuel back into the fuel injector. If we didn't increase the fuel pressure on the delivery side of the injectors,the force of the pressurized air in the intake would impede the flow of fuel. The net result would be insufficient fuel delivery and a lean motor. The pump is still doing the same amount of work,it's just meeting some resistance.
Turning up the fuel pressure forces more fuel into the motor and,again each pump can only deliver so much. If the motor asks for more than the pump can deliver the pressure will start to fall because the pump can't supply the volume the motor is asking for.
In summary turning up the fuel pressure doesn't cause the pump to supply a lesser volume of fuel. It causes more fuel to go into the motor and less to be returned to the tank and ,if the motor asks for a greater volume/amount of fuel than the pump can deliver,the pressure will start to fall and it will fall more and more as we ask the same pump to supply more.
There is one pressure that does causes your pumps output volume to decrease as it increases and that is the pressure in the pressurized intake manifold. Otherwise,it always puts out the same volume at any given voltage.
In his first post he said he had no knock,but only after turning the boost down.
In his third post he said he turned the boost down from 16 to 13 and that he logged 1-2 degrees of spark retard at 16 lbs of boost.
He's getting spark retard at only 16 lbs of boost.
He's richend his fuel to the max chip capability.
His O2s are in the 730-770 range.
Something's not right.
Hello Group,
Tonight I did sereval runs under WOT from 30-40mph and proceeded upward. I started with a warm engine, 184 degrees and fuel pressure with line on at 38psi.
As I opened up (floored it) to WOT, the fuel psi rose to about 44psi within the first few seconds. BUT, as the turbo started to wind-up and produce 10+ pounds of boost, THE FUEL PRESSURE DROPPED TO 35psi and would not increase. At that time I let out of the throttle.
Some basics -
Installed 60lb injectors and matching chip from TT within the past 18 months.
Stock turbo
New Walbro Fuel Pump and hot wire kit within thepast 24 months.
Engine has never been opened up
Tonight I did sereval runs under WOT from 30-40mph and proceeded upward. I started with a warm engine, 184 degrees and fuel pressure with line on at 38psi.
As I opened up (floored it) to WOT, the fuel psi rose to about 44psi within the first few seconds. BUT, as the turbo started to wind-up and produce 10+ pounds of boost, THE FUEL PRESSURE DROPPED TO 35psi and would not increase. At that time I let out of the throttle.
Some basics -
Installed 60lb injectors and matching chip from TT within the past 18 months.
Stock turbo
New Walbro Fuel Pump and hot wire kit within thepast 24 months.
Engine has never been opened up
...further, before my testing tonight, I brought the overall fuel setting on the chip back to a lower 134; knock increased to 3+ retard degrees.
From other earlier responses, I had been getting knock with 1-2 degrees of timing retard with 43psi LO and the TT chip at 134. To stop/lower the knock, I continued to add more fuel through the chip until it maxed out at 154, therefore my problem from the begining of this thread. Increasing the chip fuel helped, but boost could not raise boost above approximatelly 15psi without chains 1-3 deggres of knock.
So, what steps are next to address fuel pressure not increasing lb for lb with boost.
Again, all your expert help is greatly appreciated!
Regards,
Matt
From other earlier responses, I had been getting knock with 1-2 degrees of timing retard with 43psi LO and the TT chip at 134. To stop/lower the knock, I continued to add more fuel through the chip until it maxed out at 154, therefore my problem from the begining of this thread. Increasing the chip fuel helped, but boost could not raise boost above approximatelly 15psi without chains 1-3 deggres of knock.
So, what steps are next to address fuel pressure not increasing lb for lb with boost.
Again, all your expert help is greatly appreciated!
Regards,
Matt
turb0buick57
Member
- Joined
- Oct 10, 2009
Some questions,
1.) what are all your scanmaster numbers at warm idle?
2.) How old is the o2 sensor your using? What type is it?
Last is there any chance your not actually going WOT making a run? I ask because your saying it takes a few seconds for your car to reach 10psi? I would imagine a stock turbo car would spool from 0 boost to 15psi super quick if you put the peddle to the floor, probably 1 second?
Also, around what mph are you seeing knock? When you make a run from 30-40mph its not uncommon to see a few degrees instantly when the car downshifts into 2nd or maybe a few degrees when it shifts into 3rd. I would try to get the car above 60mph and try to start your runs from there to eliminate the shift.
1.) what are all your scanmaster numbers at warm idle?
2.) How old is the o2 sensor your using? What type is it?
Last is there any chance your not actually going WOT making a run? I ask because your saying it takes a few seconds for your car to reach 10psi? I would imagine a stock turbo car would spool from 0 boost to 15psi super quick if you put the peddle to the floor, probably 1 second?
Also, around what mph are you seeing knock? When you make a run from 30-40mph its not uncommon to see a few degrees instantly when the car downshifts into 2nd or maybe a few degrees when it shifts into 3rd. I would try to get the car above 60mph and try to start your runs from there to eliminate the shift.
Ok,now we know you have a fuel delivery problem. This is a serious problem that has to be fixed before anything else can happen. It doesn't matter what O2 sensor or chip you have or scan readings or anything at this point. You have a fuel supply problem and steps need to be taken to fix it. We need to look at voltage to the pump,fuel filter or some other restriction,a leak inside the tank,interrupted boost signal to the regulator,a defective regulator,or a bad fuel pump.
What filter and how new?
Check voltage to the pump.
Check the hot wire fuse for signs of overheating(corroded or black)
Unplug the hot wire relay to look for corrosion.
.
I have 60lb injectors that match the TT chip and the rest of my minor upgrades.
I also noticed that I was not getting any O2 reading on the Scanmaster when making these runs under WOT. The Scanmaster read 000.
Concerning the O2 sensor, I did change this within the past 2 years and 5,000 miles. I do not recal which one it is, but almost certain it was from Autozone.
I cannot recall the mph when the knock occured. I will try some additional runs tomorrow.
I believe I was succesful at getting WOT. The delay I mention above was as the transmisison kicked down a gear and then started to pull...
Thanks
Matt
I also noticed that I was not getting any O2 reading on the Scanmaster when making these runs under WOT. The Scanmaster read 000.
Concerning the O2 sensor, I did change this within the past 2 years and 5,000 miles. I do not recal which one it is, but almost certain it was from Autozone.
I cannot recall the mph when the knock occured. I will try some additional runs tomorrow.
I believe I was succesful at getting WOT. The delay I mention above was as the transmisison kicked down a gear and then started to pull...
Thanks
Matt
Oh no you won't!
We need to look at some things and after finding something and making changes you can drive it to see if we're moving in the right direction.
That's because it is so lean.
turb0buick57
Member
- Joined
- Oct 10, 2009
The reason why I asked about the 02 sensor is because I've recently witnessed bad brand new 02 sensors that read 000 at WOT or some other flaky reading. In my opinion I would change it, try to find a denso, not an ac delco 22, bosch or other.
I asked about WOT, because my buddy would regulary get a few degrees here and there when making a pull with a similiar combo to you. When we looked at his powerlogger files, his TPS was never maxed, usually only around 3-3.7volts or so meaning his foot was not actually to the floor so he had 15#s of boost and some knock activity with this condition. Fully to the floor with a tps at 4.50 he had no knock.
Ttype6 has also given you some good specific things you should check since fp isnt rising properly to rectify that.
I may have missed this info sifting through the couple pages but what type of system are you using to monitor fuel pressure? Hood mounted gauge? an electrical gauge inside the car?
Sorry. Just came back from a few WOT runs before seeing recent posts. I will wait for more input before continuing...
I know for certain that the fuel pressure is not rising when under boost. Again, under 13psi boost, the fuel pressure went down to 35psi LO and would not recover.
I have no knock, but am running at only 13 psi boost.
At WOT at 55+, O2s were only 625-700ish.
I know for certain that the fuel pressure is not rising when under boost. Again, under 13psi boost, the fuel pressure went down to 35psi LO and would not recover.
I have no knock, but am running at only 13 psi boost.
At WOT at 55+, O2s were only 625-700ish.
The fuel delivery problem needs to be addressed first.
Replacing the TPS and/or O2 sensor wont fix the fuel delivery problem.
Let's give the motor the fuel it needs and then we can go from there.
I'm not claiming to be an expert or know more than anyone who has posted before me, or say that any of these other guys are wrong, but i would double and triple check vacuum leaks first, then verify a properly working gauge and regulator, then check the hotwire and voltage drop at the pump. These are easy and CHEAP!
Again I'm not saying anyone else is wrong, but it wouldn't take much time to do all of these first, and if i'm not mistaken all could contribute to your issue. Combining any of them would only compound the situation. Pro's and more experienced folks correct me if i'm wrong.
Again I'm not saying anyone else is wrong, but it wouldn't take much time to do all of these first, and if i'm not mistaken all could contribute to your issue. Combining any of them would only compound the situation. Pro's and more experienced folks correct me if i'm wrong.
Per turbObuick57, I included what I was using to monitor fuel pressure.
Run off the fuel rail to the windshiled through fuel injection hose. Is this ok?
Otherwise, the guage is usually attached to the fuel rail and can only be checked when parked, idling and hood up.
I have noted in previous threads that my fuel system does not maintain pressure after being parked. For example, it has been over an hour since I drove the vehicle and now the fuel pressure guage is reading less than 20 psi. Is this normal or an indication of where my problem might be?
Thanks
Matt
Run off the fuel rail to the windshiled through fuel injection hose. Is this ok?
Otherwise, the guage is usually attached to the fuel rail and can only be checked when parked, idling and hood up.
I have noted in previous threads that my fuel system does not maintain pressure after being parked. For example, it has been over an hour since I drove the vehicle and now the fuel pressure guage is reading less than 20 psi. Is this normal or an indication of where my problem might be?
Thanks
Matt
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