AE class is in session!
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Joined: Jan 2011
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From: Puget Sound
Starting
You are now about to learn what I was referring to when I mentioned "data sampling rate" when comparing AE to Infinity. With just the 5 PIDs I set up, AE recorded each one once per second. That's 200 milliseconds for each PID, for a total of 1000 milliseconds (1 second) to read them all before it came back to the first PID. It took me 1.5 seconds to start the truck (about 40 degrees, not plugged in). Any guesses how much data I got while it was cranking?
Anyway... I won't repeat all the steps to set up a recording session, but I will show you my playback options... which specifies exactly what I recorded to monitor the starting condition of the truck. I threw IPR in the list, so you can see the lag between what the PCM wants and when it gets it... like nooky. One piece not in there directly (like voltage) or indirectly (like glowplugs revealing themselves with a voltage drop): Fuel Pressure. I have a gauge, so fuel pressure is 62 PSI. I did not play out my pulsewidth over time because I won't show combined ICP and FIPW trends on the forum from this tuner.
I'm just posting screenshots and my notes with no other explanation. If I missed some detail or you want to know more in depth, please say/ask something.
You are now about to learn what I was referring to when I mentioned "data sampling rate" when comparing AE to Infinity. With just the 5 PIDs I set up, AE recorded each one once per second. That's 200 milliseconds for each PID, for a total of 1000 milliseconds (1 second) to read them all before it came back to the first PID. It took me 1.5 seconds to start the truck (about 40 degrees, not plugged in). Any guesses how much data I got while it was cranking?
Anyway... I won't repeat all the steps to set up a recording session, but I will show you my playback options... which specifies exactly what I recorded to monitor the starting condition of the truck. I threw IPR in the list, so you can see the lag between what the PCM wants and when it gets it... like nooky. One piece not in there directly (like voltage) or indirectly (like glowplugs revealing themselves with a voltage drop): Fuel Pressure. I have a gauge, so fuel pressure is 62 PSI. I did not play out my pulsewidth over time because I won't show combined ICP and FIPW trends on the forum from this tuner.
I'm just posting screenshots and my notes with no other explanation. If I missed some detail or you want to know more in depth, please say/ask something.
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Joined: Jan 2011
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From: Puget Sound
So I was getting ready to show how the Injector Pressure Regulator compensates for the drop in RPMs, in order to keep the Injector Control Pressure up with a slower-moving High Pressure Oil Pump. Simply put, the pump slows down and and the valve has to be opened more to keep the oil delivery going at the same flow.
When I zoomed in on the graph, I spotted something I would not otherwise have noticed: I can see the effects of the multiweight oil warming up. The RPMs are constant and the oil pressure is dropping, which I expect because warm engines have a lower Injector Control Pressure. What I didn't expect is the regulator (oil pressure valve) is opening more instead of closing more, to keep the oil pressure (ICP) from falling even faster. The effects of a heavier oil weight is the only changing factor I can think of that would cause this.
So... show of dazed eyes: How many did I lose on that one?
Anyway, here's the significance of all of this: The Low Pressure Oil Pump (LPOP) sends oil up to the High Pressure Oil Pump (HPOP). The HPOP is always the main focus because this powers the injector. The injector gets an electrical signal to be sure (Fuel Injector Pulse Width or FIPW), but that just lets the oil in to squeeze the fuel out of the injector with great force. The higher the ICP, the better the atomization (finer fuel mist) and the faster the fuel squeezes out of the injector (quicker injection means more power and lower EGTs).
We don't need a lot of ICP at idle and cruise, that would make the fuel hard to control at such low power demand... and more ICP is just plain loud. When we first start, the engine is cold, the fuel is cold, the oil is cold... so we need a bump in ICP to get better atomization when cold. As the engine warms and the fuel burns easier, we back off the ICP by about 200-300 PSI.
Now... 15-40 vs. 5-40. My little discovery demonstrates exactly why lower-weight oil works better when cold: Everything moves easier with less effort. Most of you already know this, but now we can actually see it in the performance of the engine.
When I zoomed in on the graph, I spotted something I would not otherwise have noticed: I can see the effects of the multiweight oil warming up. The RPMs are constant and the oil pressure is dropping, which I expect because warm engines have a lower Injector Control Pressure. What I didn't expect is the regulator (oil pressure valve) is opening more instead of closing more, to keep the oil pressure (ICP) from falling even faster. The effects of a heavier oil weight is the only changing factor I can think of that would cause this.
So... show of dazed eyes: How many did I lose on that one?
Anyway, here's the significance of all of this: The Low Pressure Oil Pump (LPOP) sends oil up to the High Pressure Oil Pump (HPOP). The HPOP is always the main focus because this powers the injector. The injector gets an electrical signal to be sure (Fuel Injector Pulse Width or FIPW), but that just lets the oil in to squeeze the fuel out of the injector with great force. The higher the ICP, the better the atomization (finer fuel mist) and the faster the fuel squeezes out of the injector (quicker injection means more power and lower EGTs).
We don't need a lot of ICP at idle and cruise, that would make the fuel hard to control at such low power demand... and more ICP is just plain loud. When we first start, the engine is cold, the fuel is cold, the oil is cold... so we need a bump in ICP to get better atomization when cold. As the engine warms and the fuel burns easier, we back off the ICP by about 200-300 PSI.
Now... 15-40 vs. 5-40. My little discovery demonstrates exactly why lower-weight oil works better when cold: Everything moves easier with less effort. Most of you already know this, but now we can actually see it in the performance of the engine.
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Joined: Jan 2011
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From: Puget Sound
I was worried I ventured too far out there. If I have a specific question, I can do a better job of clarifying things.
Did I skip over too many steps to record... or playback? Too much alphabet in the soup? Would it help if I demonstrated how our injectors do their thing?
We'll park on this start thing until everybody is comfortable with it... I just need some feedback, questions, a "go to hell"... or something.
Did I skip over too many steps to record... or playback? Too much alphabet in the soup? Would it help if I demonstrated how our injectors do their thing?
We'll park on this start thing until everybody is comfortable with it... I just need some feedback, questions, a "go to hell"... or something.
More Turbo
Joined: Mar 2011
Posts: 683
Likes: 1
From: cincinnati, oh.
I was worried I ventured too far out there. If I have a specific question, I can do a better job of clarifying things.
Did I skip over too many steps to record... or playback? Too much alphabet in the soup? Would it help if I demonstrated how our injectors do their thing?
We'll park on this start thing until everybody is comfortable with it... I just need some feedback, questions, a "go to hell"... or something.
Did I skip over too many steps to record... or playback? Too much alphabet in the soup? Would it help if I demonstrated how our injectors do their thing?
We'll park on this start thing until everybody is comfortable with it... I just need some feedback, questions, a "go to hell"... or something.
I'll catch up.
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Joined: Jan 2011
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From: Puget Sound
I slept on it and I now have a better grasp of what needs to be done.... the basics. I got ahead of myself, sorry.
Let's start with the injector, because everything in starting is all about getting fuel into the cylinders. Once we have rotation (the starter doing its part) and compression (the engine doing its part), we just need some fuel please, thankyouverymuch (at the right timing). Think of it as a frat party... waiting for beer. As soon as the beer shows up, 8 lunkheads make a racket. If nobody gets beer, no party. If only some of them get beer, there's a fight, which involves a lot of bucking and kicking. If the tap on the keg just dribbles, the party stalls.
In order to get those pesky HEUI injectors to cough up some “beer”, we need:
Believe it or not, fuel pressure is not so critical for firing... but enough fuel flow to refill each injector before it gets fired again is paramount. The closest we can get to seeing if there's enough flow is to look at the pressure, so the pressure gauge is a proxy for a flow gauge. Think about it, if a specific pressure value was so critical (on this truck), where's the fuel pressure sensor? Do you think they just overlooked it... after they went into convulsions on sensors for the oil? You're probably thinking “The fuel part of the truck must have been engineered in a different department and those guys are idiots.” Well... while this has some merit, the fuel system is pretty basic: If you hear the pump and you know there's fuel in the tank, there is a good chance fuel is OK... but there are plenty of banana peels under our feet on this one. Problems that arise here are likelier due to the age of the truck more than anything else. Hence... the add-on fuel pressure gauge.
The electrical signal to the injector is a two-stage process. The Powertrain Control Module (PCM) is the brains of the operation, but the Injector Driver Module (IDM) is the *** (you know... the donkey-looking horse). Ta-daaah. What goes on inside the PCM is uber-complex, but we have zero need to understand it for the purpose of starting the truck. We just need the appropriate sensors to tell the PCM it's party time, the PCM then needs to grab the ol' whip and crack the ***, the *** then needs to get off same... and start haulin' same.
I mentioned sensors need to tell the PCM that the keg and the lunkheads are are ready before it's party time. What sensors? What are they supposed to say to the PCM? Before we get into that, we need:
Let's start with the injector, because everything in starting is all about getting fuel into the cylinders. Once we have rotation (the starter doing its part) and compression (the engine doing its part), we just need some fuel please, thankyouverymuch (at the right timing). Think of it as a frat party... waiting for beer. As soon as the beer shows up, 8 lunkheads make a racket. If nobody gets beer, no party. If only some of them get beer, there's a fight, which involves a lot of bucking and kicking. If the tap on the keg just dribbles, the party stalls.
In order to get those pesky HEUI injectors to cough up some “beer”, we need:
- High oil pressure in the top half of the injector (pump up the tap)
- Fuel in the bottom half of the injector (beer in tap)
- An electrical signal to the solenoid on the very top of the injector. (thumb on the tap lever)
Believe it or not, fuel pressure is not so critical for firing... but enough fuel flow to refill each injector before it gets fired again is paramount. The closest we can get to seeing if there's enough flow is to look at the pressure, so the pressure gauge is a proxy for a flow gauge. Think about it, if a specific pressure value was so critical (on this truck), where's the fuel pressure sensor? Do you think they just overlooked it... after they went into convulsions on sensors for the oil? You're probably thinking “The fuel part of the truck must have been engineered in a different department and those guys are idiots.” Well... while this has some merit, the fuel system is pretty basic: If you hear the pump and you know there's fuel in the tank, there is a good chance fuel is OK... but there are plenty of banana peels under our feet on this one. Problems that arise here are likelier due to the age of the truck more than anything else. Hence... the add-on fuel pressure gauge.
The electrical signal to the injector is a two-stage process. The Powertrain Control Module (PCM) is the brains of the operation, but the Injector Driver Module (IDM) is the *** (you know... the donkey-looking horse). Ta-daaah. What goes on inside the PCM is uber-complex, but we have zero need to understand it for the purpose of starting the truck. We just need the appropriate sensors to tell the PCM it's party time, the PCM then needs to grab the ol' whip and crack the ***, the *** then needs to get off same... and start haulin' same.
I mentioned sensors need to tell the PCM that the keg and the lunkheads are are ready before it's party time. What sensors? What are they supposed to say to the PCM? Before we get into that, we need:
- Sufficient oil level and pressure (the low oil pressure on the dash gauge)
- Acceptable quality fuel
- Sufficient fuel pressure
- Sufficient air supply
- Proper glow plug operation (on a cold truck)
- Proper injector timing (PCM controlled with input from Cam Position Sensor – CPS)
- Vehicle Power: At least 10.5 volts with glow plugs on (but that low number is marginal... I have at least 11.5 on my truck)
- RPM Signal: 100 RPM minimum (from the CPS)
- Injector Control Pressure (that ICP you burned into your thinking... like pumping up the keg tap): 500 PSI, or about 0.85 volts on the ICP sensor
- Fuel Injector Pulse Width (FIPW): Between 1 and 6 milliseconds (0.001 to 0.006 seconds) on the 7.3L .........Between 0.5 ms and 2 ms (with FICM SYNC and SYNC achieved) on the 6.0L
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Joined: Jan 2011
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From: Puget Sound
Thread Starter
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Hotshot
Joined: Jan 2011
Posts: 18,849
Likes: 179
From: Puget Sound
I wish... it would make the class a lot easier. That's a good question. Basically, it needs to be connected to a vehicle system so it knows what to provide on the list of PIDs. If we just tried to select from all possible Ford PIDs [LIST] on all possible vehicles and individual systems, the list would overwhelm us. Now... for playback, we can tinker with the ranges.... but we can only graph 4 PIDs at a time in record or playback. If we want more PIDs on the graph at the same time, one needs to get good at graphing in spreadsheets... or maybe a graphing software.
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Joined: Jan 2011
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From: Puget Sound
Three No-Starts
I have some graphs here of trucks cranking but not starting. I put color-coded arrows at the minimums needed for each sensor reading. They all have different problems... two are easy and one is difficult.
I have some graphs here of trucks cranking but not starting. I put color-coded arrows at the minimums needed for each sensor reading. They all have different problems... two are easy and one is difficult.