did you copy and paste that out of my book? hehnever2muchboost said:heres what i wrote so maybe it will help someone else
the ltft is time based and takes a while for all the cells to update if you go in under monitors and watch the fuel trims you will notice most of the cells will be a higher negative value.stft is how it tunes itself in closed loop but it is based off of the ltft number.the emanage is a 2d map rpm x load if you have it map based.the biggest problem is that the pcm has more variables such as baro,ambient temp,load,throttle angle etc.one cell in the pcm could cover 10 different cells in the emanage.the bigger injectors change the phasing bigtime.the algorythms are factory tuned at a specific flow and pressure so if you change ve and flow rate the pcm gets very confused.there isnt much that you can do about it which is the downfall of piggybacks.its pretty much a double edge sword.at wide open throttle the pcm goes into open loop and relies more on ltft and map voltage.the sacrifice is driveability though.
a couple things you can do to remedy the stumbles though are by doing a bottleneck fix on the pump.this will mechanically increase the volume of fuel making it more stable.if you have your fpr set to vac/boost as soon as you touch the throttle fuel pressure increases and becomes unstable because of the high pressure low volume and begins to scavenge.you can either put a check valve in the vac line going to the regulator so that it only sees boost and wont increase with vacuum or run the line from the uppipe.it will work on a 1/1 basis.the stumble will also decrease with a higher fuel pressure.
if you drive the car with the drb on it watching the ltft in monitors so that you can see the switchpoints on the pcm map.turn the trace on the emanage and compare the cell breakpoints to the drb and you will see its eratic.focus on a particular cell on the pcm and hold it there.if that cell on the pcm is for example at -21 go into the active cell on the emanage and take out around the same percentage or until that ltft number drops down to near zero it will take a few moments to respond.when that number is close to zero you will see the stft will usually switch back and forth from aroun -4 to +4.that means that the upstream o2 is switching efficiently and it will respond quicker.the fucked up thing about it like i said though is the pcm looks at alot more data than the emanage so if you have one cell that is a zero ltft and short term is responding efficiently if the coolant temp,ambient temp and baro change the pcm will go to a different cell and need more or less fuel but the emanage is still making the same correction for the different temps.
i understand your frustration...i have a very extensive background with chryslers ngc controllers and i was one of the first people trying to conquer what you are trying to do.when you have two completely different systems working against each other most often it will lead you into banging your head on the wall like you are doing now.
as far as aem ems is concerned it is a VERY popular misconception that it is loaded with bugs.truth of the matter is there are not any bugs in the ems.dont take me wrong there have been issues in the past but majority of them are due to tuning errors.the aem is extremely efficient and the driveability is amazing when it is tuned and setup correctly.i see peoples ems maps everyday and find major errors in almost all of them.tuning one is not that hard but it does require a very in depth knowledge of what a pcm should do and when it should do it.there is enough support for the ems and resources are abundant.i have customers that have cars running giant turbos and injectors that if you drive them normally you cant tell what is under the hood.thats the way it should be.yes ems is pricy but its worth more than its weight in gold.even other standalones that i tune like fast,megasquirt etc they dont have the power that ems has.you have access to all of your multiplierswith the click of a mouse.
there are tons of other drawbacks with the piggybacks that are more complicated and difficult to explain.for example if you are clamping map voltage very low in order to lean it out and make power the lower you clamp it the higher the negative value goes in the pcm.the closer you approach the maximum threshold for ltft the more aggressive it will be with timing until it reaches a point where it will begin knock retarding and reducing the timing.the problem is with bigger turbos and higher cylinder pressures it requires less ignition advance and if you have too much timing other problems arise such as oil detonation above the top ring land.this is why you will see alot of guys cracking pistons.oil has its own octane rating and as cyl pressure and temps rise it will detonate.that detonation is strong enough to rattle even the best built motor you can buy.
hopefully it helps you out