Half because this board needs to be livened up... Other half because I don't know, but would like to...
Gassers use o2 sensors to track lambda and trim fuel accordingly.. you want it to cross zero as often as possible... Zero is perfect but impossible to peg for any amount of time.. engine temperature, ambient air temperature, load, rpm, manifold pressure or mass of air flow, ect..., are used to write short term fuel trims, which turn into long term fuel trims and are scripted into tables on a gassers pcm in order to customize it to its purpose and environment.. It's adaptive... Always learning... And remembering..
My rig starts acting stupid after about 6k miles... Lag starts becoming more pronounced (not transmission reaction time, but revving speed/throttle response)... Temps both oil and coolant find a rut and never vary but a degree or so at any given time/place.. example- halfway to work, no matter ambeient temp, I can guess my temps and I'm dead on more than I'm one degree off... Its like the truck knows what's happening... It knows where fuel stations and whichwhichs are too, bit that's another story... Anyhow...
Around the 6k mile Mark, I'll get a little surge while taking foot off brake and getting ready to apply throttle... That's when I know it's time to freshen tune the thing. I'll fresh tune it (as I did tonight), using the precise tune file and settings, and it's like driving a new rig... A new rig that slowly but methodically lames down until I can't bare it anymore... And, lo and behold is about 6k miles later- every time. The only explanation I have is adaptive learning and environmental tables being applied... But what and where would it get such information? These aren't gassers.. they don't sniff air/fuel ratio as a reconciliation of sensor adjustments... So... What's going on here?
You don't have o2 sensors but you do have a frp sensor that we all know is known to cause some screwy calculations (lie-o-meter coming to mind as one of many). That combined with maf, ebp, iat(that is NEVER right...) , etc... I really wouldn't be surprised if you are right drew. It would be interesting to actually be able to interpret what the pcm is calculating.
Once again drew, you find another annoyingly complicated topic that I want/need answered now lol.
Those are the players on the field, crazy, I just don't know what game they're playing.
Ran 40 miles this morning, topped off fuel (108 total gallons so there is some weight) and everything is crisp again (on a fresh tune) where it seemed lazy and sleepy before, for lack of better description.
I aint talkin transmission, now.. gotta be clear about that.. I'm talkin turbo bitin' in, and throttle response as indicated by rpm's.
I tend to re-tune from the 210TP (pulling toys) to the 300 (daily driver) rather frequently, but when I have a gap in time that I sit on the 300 tune for too long, I experience the same thing.
I always attributed it to the ECU 'learning', and over time it's accumulated so much data, that's it's veered away from Spartans settings...but honestly I have no idea. I just now how to remedy it.
Gassers use o2 sensors to track lambda and trim fuel accordingly.. you want it to cross zero as often as possible... Zero is perfect but impossible to peg for any amount of time.. engine temperature, ambient air temperature, load, rpm, manifold pressure or mass of air flow, ect..., are used to write short term fuel trims, which turn into long term fuel trims and are scripted into tables on a gassers pcm in order to customize it to its purpose and environment.. It's adaptive... Always learning... And remembering
This reminded me, for whatever reason, of sitting through one of my Ford Tech classes. Before they started using MAF sensors on everything and were just using MAP/Baro sensors. The example of someone driving to Tahoe and there car would start running terrible until they either stopped and restarted the car or floored the gas pedal. Either of which would allow the MAP/Baro sensor and PCM to read the barometric pressure and adjust for the altitude and trim the fuel properly according whatever table the PCM would then use.
Now there are so many things happening I sometimes wonder which comes first the chicken or the egg.
MAP/Baro/Boost sensor
MAF sensor reading the amount and density of the air
Throttle position, load, EBP, IAT, along with the above sensors controlling injector pulse width.
MAF accounting for EGR flow (if you have one still)
And everything, of course, is run through different strategy maps within the PCM and adjusted accordingly to your driving style (adaptive learning strategy).
And I know I'm forgetting some things and this is an overly simplified version of what's actually taking place but I haven't been up long and caffeine is still kicking in (late night) :dunno:
That's really not over simplified, that's pretty close.
Air is monitored for volume and density incoming and in the manifold... Fuel is added as catalyst based on volume... Throttle position is mapped.. load is determined (closed loop, open loop or when person goes wot, that's out the window), operating temperature is monitored, and the computer adjusts the duty cycle of the injectors... What the computer can't adjust is fuel sync, or when the injector fires.. just how long it's open. The timing for the event to start is based off of the cam and shaft sensors...
The upwind o2 sensors sniff the lambda (stiochometric) which basically grades the performance of the other sensors, and having the final say, adjusts fuel trim to attempt to reach zero.. this is tricky: the o2 read either positive or negative and report to the pcm. The pcm displays to a scan tool/monitor either positive or negative, bit it's not the condition the o2 sensors are reading, but instead what they're doing about it.. so, a negative reading demonstrates a rich mid and the pcm trimming back that percentage in order to achieve zero. A positive number is a lean condition and the pcm adding fuel to attempt to arrive at zero. Crossing zero is a good thing, as this means the computer is close to maintaining perfect trim. Now take what I just said and flip it when working with a gm vehicle. Grrrr..
The downwind o2 sensor just tattles on the catalytic converter, primarily, expecting the exhaust to be cleaner. It does have a minor role in trim, but not near as much as the upwind..
I used to hate efi but now I love it.. there is a whole new dimension opened where things can be closely monitored instead of ballpark, and can adapt based on temperature, humidity, elevation, driving conditions... All of it. Those ol 426 hemis, for instance, pumped out 450ish ponies... Through carbs.. of the same rig would have been built like the current 392 hemis, you'd be looking at well over six if not seven hundred ponies.
One of my favorite tricks on a mopar is to adjust the fuel sync. It's done by hooking up a scan tool and unbracing the dizzy... Just like adjusting timing of old..
Mopar used the back of a hot valve to atomized fuel better, which works for that and also cooling the valves off. What we discovered was replacing the single hole (pencil) injectors with four hole injectors made by Ford motor sports relieved the need to atomized the fuel, and meant the timing of the injection could be held back (retarded) a few degrees.. -2 degrees was the sweet spot, up from -6... Better throttle response and bump in power down low, but a measurable difference in economy, picking up as much as two mpg's.
Try tracking that down with a carbed engine. It just ingested what was available already mixed in the manifold, which made for sloppy fuel delivery and gummy valve backs, leaking valve guides, and snotty exhaust (due to cam overlap and the exhaust pressing unburnt fuel into and through the exhaust, killing cats and stinking up the joint)...
Now these oil squeezers... If I could just figure out what adaptive tables are collecting... I'm lost with these things.
And to just touch, ever so slightly, on at least some of what you're talking about.
Emissions and fuel economy are so much better, especially when compared to a carbureted motor. If you're off the throttle, coasting as it were, the injectors are not injecting any fuel (why you see 99 or 999 mpg on the lie-o-meter going down a grade with 0% from the TPS).
And especially now that so many parameters are monitored by the PCM, grams of air per second, density of the air, temp of the air, elevation, barometric pressure (which is of course relative to MAF and MAP), O2 before and after the CAT or CAT's, etc. You add all of these to the enormous amount of mapping and 'learning' that the PCM does and things get super precise, saving on fuel and lowering emissions.
All of this also allows for some incredible power from some tiny motors. The Focus ST comes to mind with 252 hp? from a 2.0L motor. Remember the old 5.0 Mustangs and the 225 hp that seemed, at the time, fairly high.
And Drew I know what you mean about hating it all at first. For me, after going to so many manufacturer's classes. My shop became one where people were sent when others had thrown so much money and parts at cars, without fixing anything, because they were guessing at the problems. But I digress
EDIT: I realize this is a lot of rambling now that I read it back a few times :dunno:
Have you contacted any of the guys that write tunes for them? It might be worth calling Matt over at gearhead and see if it is possible to write something into a tuner to actually log this stuff...
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