Yeti wrote:
OOOOOO .....glad to speak with someone that know more about me and to learn from , I need to learn more , and I'm happy to do this , the map you asked is simply the torque requested at the position pedal , increase this , increase the response of the gas pedal , for the question about the 12 map , I think....and not sure .......one map correspond at one time for open and close .....but I do not know if the injector open 3 or 5 time , and for what you say about the EGR , now I know why the different sound come with egr disabled and when is cold or hot , I need to know what map are correlated with EGR function , all 12 at low range ? or one in particular ?
I have see the negative timing valley in the 1800 to 2800 range, at certain rpms especially at partial throttle , but I haven't the necessary experience to touch it , I hope we can adjust the time of injection and the angle to decrease fuel consumption and pairing the advance with EGR Off , you think we can do it ?
Marco
Well... How about this... Does anyone have a way to read the actual injection timing while the engine's running? I don't have anything that can. Chrysler has sort of hobbled these things by using the European computer and protocols for the engine, but everything else uses Chrysler's own network, at least for 2005, if I understand correctly.
By your comments, I take it that there's a torque reduction that happens when you put the rig in low range or 4wd?
Also, I thought someone said there's one for lockup condition. I don't need any reduction, because I have a Suncoast.
If we could figure out which map is in use under what conditions, I think it would be relatively easy to get a pretty good economy tune.
The theory behind common rail injection has these parameters:
1. Degrees before TDC to start of injection
2. Degrees of rotation "during which injection occurs"
3. Combustion speed (how long does it take for the fuel to burn and reach maximum power?)
4. How long it takes for the required amount of fuel to get through the injector.
To obtain maximum economy: The greatest amount of force down on the piston must occur during the period just AFTER the crank pin crosses the dead center line, and last as long as possible while the piston has good leverage against the crank (hasn't gone down too far).
Things that work against you are: As the piston starts down the hole, it accelerates rapidly. If your timing is too late, the explosion of the fuel burning doesn't catch the piston with great force. If it takes many degrees of rotation to get the fuel into the cylinder, and then catch fire and burn, the fuel at the end will not help you much.
If it's a long rod engine, with moderate stroke, the piston accelerates away from the explosion slower - so you want to inject the fuel slower and sustain the "explosion" (or burn time) longer, so as to achieve maximum force against the piston. If you inject too fast, the explosion happens when the piston hasn't much leverage on the crank and heat is absorbed into the head and piston and cylinder walls, rather than spinning the crank.
So, CRD's use pressure to determine how fast the fuel gets into the cylinder... And period of time to determine how much. Of course, changing pressure changes time required to get the same fuel.
As you know, raising pressure raises temperature. About 2800 degrees F (1500C) is when Oxides of Nitrogen form (NOx). So, when you raise combustion pressure, the temperature also climbs. So, to mitigate this, the fuel is injected later, and slower, to decrease the peaks in both pressure and temperature. Also, EGR slows down the burn rate - because it decreases the oxygen molecule density -which decreases both temperature AND peak pressures.
Raising boost RAISES the density of oxygen (air) in the combustion chamber, which speeds up combustion... but it also dilutes the air/fuel ratio, which absorbs some of the heat of combustion.
Why is there retarded timing at 1800 to 2800? Well, to reduce engine drag, you don't raise the boost a lot at those speeds, since you're not using a lot of throttle and the turbo isn't spinning hard at low rpm and small amount of fuel burned. This low quantity of air tends to result in high combustion temperatures. So, to reduce them, you delay injection. Besides, when you hit the pedal, increases in fuel happen before the turbo speeds up. Once the turbo speeds up, you don't need quite as much timing advance, since the boost increases burn speed. And, you need the burn to be slightly later in the crank cycle to obtain maximum use of the fuel. Since the turbo's not boosting, and the EGR doesn't have much back pressure (and the intake doesn't have a lot of vacuum), the part throttle EGR is going to be low. Thus, NOx production has to be prevented by delaying the injection (ignition) event and keeping maximum pressures down.
So, to recap (and I hope I haven't confused everyone)
These are timed at some speeds to reduce efficiency for emissions reasons - that appears to be mostly from 1800 to about 2400 at almost every load position (some more than others).
More boost requires less advance
More boost reduces emissions, but decreases economy.
EGR appears to be used to cause a broad, more flat topped curve in cylinder pressure and temperature to prevent NOx formation above about 3000 - 3300 or so. By decreasing EGR and advance a little, you should be able to add a little fuel and a LOT more horsepower. By smoothing the light load advance curves and dropping the deep timing valey (on the 3D map) I'd guess we could get anywhere from 10 to 30% economy gains, assuming you keep your danged foot out of it
Our experimenting show us that when we disabled EGR, we needed about 15-25% less advance (depending on motor) to achieve proper performance at high speed. And that a small increase in advance at the 'cruising' speeds usually resulted in dramatic economy improvements - unless the motor had a lot of EGR at light load and it was disabled. These don't seem to have that, so I don't see any need for that trough in the timing. It should be a rather smooth curve.
Also, I cannot imagine any reason for having radical changes in timing from 3000 up. It should be a relatively smooth upward curve.
Please understand, that these maps were developed by engineers running the motor in a laboratory, adjusting egr, timing, and fuel quantity while observing the exhaust emissions and fuel consumption. Their first priority was emissions. That had to happen, no matter what. And, they had just these parameters to adjust. To stay comfortably below emissions requirements, they often went well beyond "just enough", so that it would never fail under testing. They used what they had to work with. And we're not as constrained as they are. Nor are we going to spew out massive amounts of pollution by making small changes to the maps. The only one you're likely to violate at all would be NOx, and unless you get crazy changing things, it will happen rarely and in small amounts - you're still being kind the world you live in.
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Thanks Yeti
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