I got out today with the GS-911 attached and a PC in the Top Case for a 100 mph run up a section of posted 50 mph highway that runs through a flat swamp nearby. I didn't get past fifth gear before running out of highway. I continue to operate at 52 psi fuel pressure and a mixture of 13.8:1 no BoosterPlug or any other modification to my '04 RT.
The idea was to see when and where the Motronic runs the Closed Loop program. I've got some charts coming but here are a few observations. Keep in mind that the max 95HP is at 7250 RPM.
--Closed Loop was operational at 100 mph (The engine seemed very smooth here)
--Closed Loop was operational in 2nd, 3rd, 4th gears at nearly 6500 RPM.
--Closed Loop was operational at 48 degrees throttle (80 degrees is wide open) going 100 mph
--In 3rd gear, while accelerating to 70 mph the Motronic was Closed Loop a lot of the time. Same in 4th gear to 90 mph.
--In 5th gear, WOT Motronic stayed mostly Open Loop from 65 mph to 100 mph. But as soon as I "relaxed" the throttle to about 3/4 open at 6400 RPM, Closed Loop kicked in. Amazing!
Given the amount of time and operating areas where the Motronic will enforce lean Closed Loop, I think it gets easier to see the advantages of mixture richening by using a Wideband O2 to shift Lambda from 1 to something less--0.94 in my case.
--At 6000 RPM & WOT the injector was on for 7.2 milliseconds. One revolution of the engine only takes 10 milliseconds at that RPM. At 7250 RPM (max horsepower) each revolution is only 8.3 mS. The injectors would be open 90% of the time!
(The air temperature was 90F today; had it been 20F the 7.2 mS injector pulse would lengthen to 8.1 mS. Were I to boost my fuel output using a -20C air-temp shifter on a 20F day, that pulse would lengthen to almost 8.6 mS. More than 100% on-time! Fuel pressure is a better method for boosting injector output (compared to IAT shifting or PCs or Techs) since it doesn't require the injector pulse to be lengthened.)
That's the raw data. I'll try and post a chart tomorrow after I've thought about it further.
I thought some might like to see the chart but I don't have time to provide the detailed annotation yet. Briefly, the Green line has two states: Closed Loop program running is the HIGH state but forget the label on the right side of the graph, it's just used to shift the 1/0 to the top of the chart. The red and blue curves use the left axis labels.
There are 6 RPM peaks. They are gears: 1st/2nd, 2nd, 3rd/4th/5th. I'll note them on the photo later when I get time for further detail but for now the comments in the prior post apply to this chart.
In first gear, Closed Loop seems to stop at 4000 RPM. In Neutral (not on the chart) Closed Loop ends around 3000 RPM, or maybe lower.
As I mentioned in the prior post, note that in 5th gear, 6350 RPM and 45+ degrees of throttle, the Motronic goes Close Loop!
Last edited by Roger 04 RT; 09-18-2012 at 05:15 PM.
How the Motronic handles spark advance has been something of interest. When the data two posts back was collected, I also collected ignition timing data, plotted below, for reference and for those who are interested. This data is for the Motronic MA 2.4, Pink Coding Plug.
Unlike fueling which can be modified externally, spark advance is under the control of the Motronic's internal program so can't be modified without an ECU chip replacement.
The charts below show spark advance compared to RPM and to throttle angle. In the RPM chart you can see that advance is increased with RPM, reaching a maximum of about 43 degrees above 4000 RPM.
In the TPS chart you can see that the maximum advance is only for throttle angles below 18 degrees (80 degrees is WOT), and is then reduced for wider throttle angles. From 50 degrees to wide open throttle the advance is limited to 20 degrees.
The other thing worth noting is that while the spark is advanced with RPM up to certain throttle angles, there are a lot of points scattered well off the curve. This shows that there are other factors that the Motronic uses in its timing calculations.
Last edited by Roger 04 RT; 10-01-2012 at 01:19 AM.
Although I'm no authority on spark advance, I did receive my early introduction to it from a Model A fire truck. This print out looks to me like a bit of Monday morning programming and could contribute to the surging and backfire issues. I believe it would be counter productive to decrease the advance as the throttle angle increases. What's your take?
Wait...The charts don't match. When you try to use degrees advance to correlate the two charts, the results don't make sense. Are these two different runs under different conditions?
It's very interesting data to me and the charts are indeed from the same run. If you go back to the post with the closed loop data you can see that WOT happens before peak RPM. So the sequence is open the throttle aggressively, get RPM to start building, relax the throttle some, reach peak RPM, stabilize the throttle.
It turns out that it is the norm in a spark table for advance to increase with RPM but on the TPS axis of the table the advance initially grows to about 1/3 to 1/2 throttle and then the advance is reduced. One reason is that at WOT the mixture is pretty rich and the flame front velocity is faster in richer mixtures, leading to less advance required.
Here is a link to a good description and a table: Spark Timing Table
Last edited by Roger 04 RT; 10-01-2012 at 12:46 AM.
This brings up a whole host of questions. I think the graphs would be easier to interpret if you did a few one-gear-runs...say 2nd gear at a gentle throttle and WOT. And for graphs, show open-closed loop, superimposed on the timing advance vs rpm, vs tps angle and also mixture.
The reason I say 2nd gear is that you can do a takeoff to redline all in the same gear. I wonder if the advance curves and advance transitions as the mixtures richen would be more apparent.
Since the GS-911 takes data sequentially, what I'd really like to find is a 3D Scatter Plot function for Excel. That would make my life much easier. For now these plots are the best I can come up with and they do open a window into the Motronic's spark timing world. Hopefully I'll find a 3D scatter tool.
Originally Posted by JHGilbert
10-01-2012, 05:16 PM
Is it just me or does anyone else see the possibility of getting more power at using 5/8 throttle if RPMs are low, versus WOT?
10-06-2012, 03:23 PM
Here is the final mounting of the Aeromotive 13301 adjustable fuel pressure regulator that I used to richen Open Loop fueling 10% (20% increase in pressure to 53.5 psi).
It is mounted to the frame using an included mounting bracket, on the right hand frame near the alternator. (I misread the torque value and broke the bolt which led to having to drill it and back it out.)
The mounting bracket is soft steel and was easy to twist with a vise and adjustable wrench. You can see the fuel line routing in the photo below. After taking the photo I realized that I could attach the battery vent hose (no longer needed with the Odyssey battery) to the regulator atmospheric vent.
10-09-2012, 09:47 PM
In the spirit of a picture is worth a thousand words, I've added a block diagram of the Motronic MA 2.4. This is my interpretation from research, the data I've taken throughout this thread and some deduction. I believe it to be a good-fit, functional representation of how the Motronic does it's job as a fueling and spark computer. As I find errors, I'll correct the diagram. (e.g. I don't know if there is a cold oil temperature, spark timing adjustment.)
Next I plan to post other diagrams showing how the Wideband O2 mods of this thread affect the system, as well as diagrams of how the PowerCommander and Techlusion interact with the Motronic MA 2.4. Eventually I'll add all four diagrams with a PDF link.
10-10-2012, 02:12 PM
Before going to the diagrams of the Wideband modication, here is a view of the differences between the Open Loop and Closed Loop fueling.
Open Loop fueling starts with the TPS and HES signals and proceeds through adjustments for air temperature, barometric pressure, etc., proceeding to a fuel pulse being injected into the engine (ignoring the Adapt box for a minute).
Closed Loop fueling is a software program that begins with an Open Loop fuel pulse but then quickly uses measured Oxygen from the exhaust (the O2 sensor) to determine whether the mixture is richer or leaner than the target set by the O2 Sensor (switch). With a bit of trial and error, it locks into a range of fuel pulses that alternate between being a bit rich and a bit lean. The Closed Loop program is an aggressive "enforcer" of the mixture specifed by the O2 sensor. In a stock system that mixture is a lean 14.7:1 (for gasoline).
The Closed Loop program also has another activity which is to compare (the Compare box) the Closed Loop result with the Open Loop calculation. Over time, if these fuel pulses are different, the Closed Loop program "teaches" the Open Loop program some adjustments (the Adapt box). This means the Open Loop program gets corrections that can take into account: fuel type (e.g. E10 or gasoline), fuel pressure, air filter restrictions, fuel injector contamination, and throttle body, valve & cylinder accumulations. A weakness of the 1150 Motronic is that it treats both cylinders equally, which means we have to manually balance (left and right cylinders) the air (TB and valves) and fuel (injector cleaning and matching).
The diagram below can give an idea of which engine modifications will have a long-term effect on engine performance and which will be "learned out" by the Motronic's Closed Loop program.
My objective with the Wideband O2 project was to leave the many functions of the Motronic intact even while richening the overall mixture.
10-11-2012, 09:19 PM
Before posting the next few diagrams, I spotted a function that I'd originally left off the Motronic that is relevant to any fueling modifications that disable the Motronic's Closed Loop operation (1150 Motronic MA 2.4). If you look back at the previous two charts, they have a "Limp" function in the final fueling decision box.
The Limp box is the final step in Open Loop fueling, just after Adapt values have been applied. The Limp function as I have measured it (plot below) expands the variation of Open Loop fueling to a 10% variation. That is twice the amount of mixture variation that occurs in Closed Loop. The full post was here, Open Loop fueling variation. Although there is speculation that the Limp-Home function uses is a rich mixture, the measurements say that it runs 5% richer than and 5% leaner than the fuel table cruising target of 14.7:1.
What that means on an 1150 is that if you disconnect the O2 sensor and run a Powercommander, Techlusion, 3.5 Bar pressure regulator or BoosterPlug as an Open Loop fueling enhancement you can count on the Motronic to vary the fueling in a 10% range, like the plot below.
The next post will be a block diagram of the Wideband O2 system.
Last edited by Roger 04 RT; 10-13-2012 at 04:00 PM.
10-12-2012, 12:51 PM
Here is the block diagram showing how I've installed the Innovate Motorsports LC-1. The stock Narrowband O2 sensor has been removed, and in its place the LC-1 is installed. With months of measurements under my belt, I'm now confident that the Motronic functions the same with this sensor as it does with the stock sensor, it just programs and enforces a richer mixture.
Looking at the diagram you can also see that I've boosted the fuel pressure. This is an optional enhancement. When you shift the O2 setting from Lambda = 1 (stock) to Lambda = 0.94 as I've done, if you do nothing else the ADAPT box in the diagram will learn, over time, how much it needs to adjust the fueling to get the L=0.94 result. It takes time to adapt but eventually it does. Every pulse it sends out would become several percent longer.
The other option is to give the Motronic a headstart. One way is to add something like a BoosterPlug. It tells the Motronic the air is 20C colder and that results in a 6% richer mixture. The Motronic then has less adapting to do and gets to the final result faster.
The option I choose was to boost the fuel pressure by an amount that was equal to the shift in Lambda (plus an amount for E10 fuel) so that the Motronic would have almost no Adaptation work. (Fuel Pressure balances Lambda shift.) That means two practical things: as soon as you fire up the Motronic it's in the right ballpark; and every cell of the fueling table has been corrected (every pulse is affected by the increased fuel pressure), versus the coarser correction of the Adaptation process.
It seems like I've made a lot of measurements and tests to arrive at a simple solution for mixture enrichening but a side benefit is that a lot was learned about how the Motronic does its job and I've got a good confidence that the LC-1 implementation is compatible and that the Motronic is fully functional and operating as intended by the designers, just richer.
Tomorrow I'll add a block diagram for a Powercommander and Techlusion implementation.
Last edited by Roger 04 RT; 10-14-2012 at 03:43 PM.