kineticSpicyMSP
Member
Ok something just hit me as typed that. Joe P being the tuner he is..... Why would he call it fuel cut, or FUEL CUT DEFENSER? if it was the spark...
I DONT" KNOW
I DONT" KNOW
Am I experiencing the "Fuel Cut"?
- Thread starter kineticSpicyMSP
- Start date
Damn how did i miss this thread?
HHMMM some very good points here. Let me clarify a couple of things.
First the MAF will read airflow. It doesnt control anything.
Secondly the reason the ECU "sees" denser air is thru calculations it will make from the following sensors: Air temp, Baro sensor, coolant sensor and MAF. It will look up the inputs on a preprogrammed table and respond accordingly.
Now the infamous "fuel cut" is there on every vehicle.
It is basically an ENTIRE system shut down. The airflow thru the MAF will trigger the ECU to shut down the injectors and the ignition system together. The trigger on the MSP is based on preprogrammed airflow values that it is "supposed to see" at certain atmospheric conditions. That is why some MSP'a will cut at lower than 5.0 volts. I have seen some cut at 4.3volts. The stock MAF though if it sends a "noncorrected " signal of 5.0 volts to the ecu it will cause the unit to cut all fuel and ignition until it sees the system drop in RPM, LOAD and AIRFLOW.
Every protege i have seen and tested had the cut occur at or below 5.0 "noncorrected" volts.
The reason you will see your gauge go to full rich is that the vehicle is not combusting the mixture . Just passing the valves and being "seen" by the O2 as unburned fuel.
HHMMM some very good points here. Let me clarify a couple of things.
First the MAF will read airflow. It doesnt control anything.
Secondly the reason the ECU "sees" denser air is thru calculations it will make from the following sensors: Air temp, Baro sensor, coolant sensor and MAF. It will look up the inputs on a preprogrammed table and respond accordingly.
Now the infamous "fuel cut" is there on every vehicle.
It is basically an ENTIRE system shut down. The airflow thru the MAF will trigger the ECU to shut down the injectors and the ignition system together. The trigger on the MSP is based on preprogrammed airflow values that it is "supposed to see" at certain atmospheric conditions. That is why some MSP'a will cut at lower than 5.0 volts. I have seen some cut at 4.3volts. The stock MAF though if it sends a "noncorrected " signal of 5.0 volts to the ecu it will cause the unit to cut all fuel and ignition until it sees the system drop in RPM, LOAD and AIRFLOW.
Every protege i have seen and tested had the cut occur at or below 5.0 "noncorrected" volts.
The reason you will see your gauge go to full rich is that the vehicle is not combusting the mixture . Just passing the valves and being "seen" by the O2 as unburned fuel.
It will happen anywhere between 9psi to 13psi. Depending on how the ecu "sees" and calculates the airflow thru the meter.1st MP3 in NH said:
The cut is based on the MAF and temp sensors i listed above.
Then the ECU will shut down the injectors and stop the firing of the coils.
They are not really the same thing. The end result may be but how they come about are are different.1st MP3 in NH said:
It happens more on the MSP because of the program installed into the ECU. It is a boosted vehicle from the factory. For safety and anti detonation characteristics the company chose to be more conservative in the settings so as to be safe. Hence the 9-10:1 A/F ratios on boost and WOT. (AKA hesitation problem) (AKA bulls*** flash fix) (cough cough)
kineticSpicyMSP
Member
wow that was alot. I understood some of it, some of it i didn't.. . . but it helped.
MODs List:
CAI
colderplugs
FLASHED! dammit
thats it
MODs List:
CAI
colderplugs
FLASHED! dammit
thats it
Joes fix was somewhat "temporary" it increased resistance inline with the MAF to the ecu. This just delayed the inevitable. In other words the voltage the stock ECU saw would have been less at a given RPM, LOAD and ACTUAL airflow reading. You would be able to increase the boost and show less of a reading to the ecu. That is why the MSP ECU is easier to work with when using a piggyback. But dont forget that the car would go into open loop much sooner than the mp3's and such. It would rely on the MAF for input to achive its A/F goal.1st MP3 in NH said:
BremertonMSP
Member
- :
- 95 F-150 4x4, 89 Mustang Turbo Coupe, 87 Thunderbird Turbocoupe
perfworks said:
Hmm, so the MAF output is being changed throughout the entire range of airflow. If that's how it's being done, I would rather use a voltage clamp circuit. That way, you can limit the the MAF output voltage to say 4.5V at max airflow. Then the MAF signal sends a true voltage reading under 4.5V. But then again, I would think someone else would have thought of that by now.
MSPDAVE125
Member
kineticSpicyMSP said:
A front mount will cool the charge air going to the throttle body after the MAF sensor.
Your MAF sensor will read the ambient temp air passing through it, going to the turbo.
The colder the air the denser the air blah blah blah. Fuel cut is iminent.
BremertonMSP said:
I'm with Bremerton on this. If the Fuel Cut Defenser merely adds an inline resistor to the MAF signal, that would skew ALL the voltages that the ECU receives. Assuming the ECU is continually altering the fuel/timing maps based on the MAF sensor readings, if this signal was altered, you'd potentially be using the wrong fuel/timing maps across the board. Not good.
Therefore, a voltage clamp would be the right solution. All you'd need is a 5V fixed voltage regulator and a diode as a barebones solution. Am I right?
BremertonMSP
Member
- :
- 95 F-150 4x4, 89 Mustang Turbo Coupe, 87 Thunderbird Turbocoupe
praetor said:
I think a Zener diode is what needs to be added. But it's been so long since I've worked at the component level, I can't remember LOL!! I'll have to ask one of my EE buddies. I suppose I should cut down on the (beer) (thinkbeer (drinks) !!
Correct to a degree. The ecu will see some malfunction at some point as your RPM would increase and the flow would stay the same.praetor said:
But the real problem is the fueling. What happens when the MAF signal is clamped? How will the ECU know what to do.
It is alot more compliacted then just adding a resistor and such. Myself and Joe have been down this path before.
BremertonMSP
Member
- :
- 95 F-150 4x4, 89 Mustang Turbo Coupe, 87 Thunderbird Turbocoupe
perfworks said:
But the scale isn't infinite to begin with. At some point the voltage max.s out right? My suggestion is that if for example, the voltage max.s out at 5vdc, the clamp it at 4.5Vdc. It really all depends on what voltage level the PCM starts cutting spark/fuel. I don't know what that value is, so I don't know where to clamp the voltage at. Hell, I'm not even sure what type of MAF these cars are using, Hot Wire?
I'm just curios how Joe's FCD works. If it's just a resistor that is dropping part of the MAF voltage, then the PCM won't see full MAF voltage at max airflow either. Also, if FCD is keeping the PCM from seeing the true voltage at any airflow, then the AFR is going to be leaner then what it should be for that given airflow. Right? Or is it scaled the other way? Geez, it's been so long since I've played around with this stuff, I have a bad case of CRS. LOL!!
(crazy)
Again very good points. The whole reason why the joe p FCD was brought on was to offer something to these guys who wanted to boost higher.BremertonMSP said:
Anyway, The voltage does increase in a linear upward slope . Usually following the load curve . This will help in timing and more importantly fueling. The FCD did make the system a bit leaner. BUT that was only up top where the car was allready in the 10:1 A/F zone. It actually NEEDED to be leaned out a little. The reason he coulnt go too much with the resistor was partially due to the fact that it was a constant "load" seen. That would decrease the key on and idle voltage. The car wouldnt start or would briefly then die.
My point above was when you clamp the voltage then you (in lamens terms ) "stop" the fueling. In other words at that point the ECU will go to a somewhat fixed duty cycle. How much boost do you think you would be able to add at that point till you are running dangerously lean?
And yes it is a hot wire sensor. The voltage is very tricky in this MAF. The ecu ALSO has alot to do with it. Depending on IDC, throttle position and rpm it may hit cut whether you are clamped or not.
