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After more than a year of collecting dust, my Calum daughterboard ECU is now actually IN the car. I drove for a week with the Innovate! AFR as my copilot to assess the fuel mixture and general behavior of the ECU. I am using Calum's SR20DE tune version 4 on my 1991 Classic with AEM CAI, TopSpeed Header and fuel pressure set a 44 psi (with the vacuum hose removed and plugged).
Here is what I have found:
1. The car drives well -- no roughness (after I changed timing from 19*BTDC to 15* BTDC and opened the IAV screw by a quarter turn to restore the idle).
2. The car feels peppier -- pulls nice from mid to high RPM. Can't wait to get it on the dyno.
3. Idle AFR is rich -- 12.5 after full warm up.
4. WOT AFR is rich -- 12.5 on a long pull in 3rd, drifting up toward 12.7 at 7000RPM.
5. Light throttle AFR is rich -- 13.5 at steady speed, light throttle.
6. The car still got 33 MPG in mixed driving even though it is running a little rich.
I do not think that the feedback loop is working to maintain 14.7 at idle and light throttle. Can anyone explain whether the feedback loop has been removed from this tune, or is it just that I have to get the AFR closer to the right value by tuning?
I ran an Active Test with Nissan DataScan with the fuel delivery cut to 90% of what the ECU was trying to deliver. This accomplished the following:
1. Idle AFR increased from 12.5 to 14
2. WOT AFR increase from 12.5 to 13.5-13.7
How should I proceed?
Should I reduce the K value by about 15% to try and adjust the idle mixture to 14.7? This will make other areas of the fuel map too lean and so then I would have to go back and increase individual cells.
OR
Should I reduce the K value (about 7%) to tune in the WOT AFR to 13.3-13.5 and live with the idle?
OR
Some other approach?
Is adjusting K the only way we know to adjust the idle mixture?
Thanks -- I'm new to this stuff, been trying to learn from past posts, so please be gentle.
OK, so Ive been reading and experimenting and making some progress. Maybe it will help some others who are just starting out to hear about what Ive been doing. My progress has been slow because I have been out of town on business and deprived of my cars, but Ive gained some fundamental understanding and successfully corrected my AFR at idle.
First, I got the Nissan Datascan Map Trace Function working. I set it for the fuel map, rather than the timing map, because thats what I need to be working with. I used the inputs that Calum provided here for the B13:
OK, so the Map Trace showed me that when the car is idling, it is pulling the fuel correction factor from fuel map cell 1000 RPMx20 on the load scale. For this bin file, the location is the top row, third column from the left. I also got a good idea of where the ECU reads from for light throttle application (upper few rows left of center) and WOT (totally in the far right column).
For the idle cell (1000x20), the value on the map is 3. I found a posting on another forum that explained what this means. The value is a correction factor that is applied to the basic pulse width calculated for an AFR of 14.7 (which is called stoich -- the correct ratio for complete combustion of gasoline based on the chemistry of the fuel). To calculate the basic injector pulse for stoich the ECU uses K a parameter that is entered into the bin based on injector flow, and the MAF voltage converted into a flow quotient estimate using the VQ map for the MAF that is being used. The VQ map relates the MAF voltage to the air flow to generate the column headings that we see in ROM Editor (i.e., 8,16,20, 24 80 it works for me to think of these as % flow based on the actual MAF voltage reading and the maximum MAF voltage reading possible).
OK, so I said the value in the fuel map was 3 for the idle cell. What does this mean? If I reduce it to 1 do I cut the fuel by two thirds? What about if I enter 0, will I get any fuel at all? The posting that I mentioned above from the other forum gave me a way to noodle through these questions. Here is how to calculate the injector pulse duration correction factor (multiplier) based on the value in the fuel map:
If the MAP VALUE is less than 128, then MULTIPLIER = (DATA + 128)/128
If the MAP VALUE is greater than 128, then MULTIPLIER = (DATA 64)/128
I set up an excel spreadsheet to calculate the MULTIPLIERS for me based on the MAP VALUES. For a map value of 0 we can calculate that the multiplier would be 1. For a map value of 3 we see that the multiplier is 1.02. To get multipliers less than 1 we need to enter values greater than 128. For example, a value of 160 gives a multiplier of 0.75, and for 192, the multiplier is 1 again. Values higher than 192 have multipliers greater than 1. Kind of weird, but workable.
Now I was ready to change the fuel map to fix my rich idle. After warm up, my idle was about 12.5 AFR with a map value of 3. (multiplier of 1.02). I wanted to move it to 14.7, or 2.2 ratio units. To figure out how much to reduce the fuel flow multiplier, I divided 2.2 by 12.5 to get a 17% decrease in fuel delivery, or 83% of the original multiplier. 0.83 x 1.02 = 0.85, the new multiplier that I would want to use for this cell. Using the formula above, a map value of 173 gives us a multiplier of 0.85.
So I entered 173 in the idle cell. I also entered the same value in adjacent cells to smooth things out, and then 0 in the next rank of cells to transition back to the value of 3.
I burned my first 2 chips with the new program and installed them in the ECU. The ZIF sockets are really nice I just pulled the ECU over near the accelerator pedal, removed the top, and swapped the chips, making sure to put them in the correct orientation.
Now, the moment of truth: Turn the ignition key. The fuel pump hummed, the car started and ran fine. After warm up, the idle was corrected to a nice oscillation around 14.7. Just changing these cells and increasing the Feedback Control in the Global Map from FO (240dec) to F5 (245dec) not only corrected the idle, but also put the light throttle AFR under 3000 RPM into the closed loop area and it is no longer rich, but running at 14.7. After a week of driving, I have experienced no drivabilty issues and still got 30 MPH in a lot of stop-and-go rush hour driving.
I plan to use Map Tracer to determine how many more cells to give this treatment to get a more complete resolution of the light throttle richness. And finally, I will address the richness at WOT and high RPM. Then I will be ready for the dyno. I plan to play with the timing map a little and then do a back to back comparison of the OEM tune with the Calum tune.
Any advice that you can give me will be appreciated.
I’m glad to hear that someone is interested in seeing this stuff.
Here’s more of my long story, but let me remind you that this is the first time that I’ve done anything like this. What you see here is just my description of how I am proceeding – not in any way a recommendation on the best way to get it done. I’m still looking for input on how to do this. With that in mind, here is some more of my story.
OK, so after successfully getting the idle in closed loop, I wanted to work on the light throttle portions of the fuel map. I was running rich here, and found that Calum’s NA B13 v.4 tune eliminates the O2 feedback or closed loop feature of the normal factory tune. The factory ECU provides a tune in which a large part of the fuel map – lower RPMs and air flows – uses the O2 sensor to richen or lean out the mixture to maintain an AFR of 14.7 (this is the stoichiometric ratio, or the perfect mix based on the chemical makeup of the fuel for gasoline to burn with nothing left over,).
In ROM Editor, the closed loop values are the “higher” set of values. That is, using the formulas that I provided in my last post, the fuel map gives a pulse width correction factor of “1.00” for an entry of either “0” or “192.” If you enter “0” the ECU will be in open loop when it is reading that cell, and if you enter “192” the ECU will be in closed loop mode when it is reading that cell. According to Calum’s postings, as long as your “high” range value is “close to” stoich, the closed loop will be able to dial it in to 14.7 – you can watch your AFR data cycle around 14.7 when you are in closed loop. I’m not really sure how close it needs to be. The high range (closed loop) values in the fuel map are easily identified because they turn the cell blue, the lower values are shades of red.
So, my first task was to identify which cells of the fuel map I wanted to put in closed loop mode. To do this, I used ROM Editor to look at the factory tune BIN file that I had pulled from my own 1991 SE-R using DataScan. I found that the following cells are in closed loop from the factory: 600-1600 RPM and 8-48 flow quotient; 2000 to 3600 RPM and 8-56 flow quotient; 4000 RPM and 8-48 flow quotient; 4400 RPM and 8-40 flow quotient; 4800 RPM and 8-32 flow quotient; and 5200 RPM and 8-24 flow quotient.
Then I went to Calum’s BIN file for the v.4 tune to locate the comparable cells in his fuel map. The first thing I noticed was that Calum changed the RPM scale to extend it to higher RPMs and give finer resolution to the tune at higher RPMs. Smart fellow! To do this, he had to sacrifice the fineness of the tune at lower RPMs. So, where the factory tune has a row for 600, 800, 1200, 1600 and 2000 RPM, Calum’s map has rows at 1000 and 2000. But the factory tune stops at 6400 and Calum’s extends to 6800, 7200, and 7600 RPM. Since Calum’s map has the lower RPM rows scrunched together, there are a lot fewer closed loop cells to deal with. Here are the ones I decided to target for closed loop: 1000 RPM with flow quotients of 8-48; 2000-4000 RPM with flow quotients of 8-56; 4600 RPM at 8-32; and 5200 RPM at 8-24. I made up an excel spreadsheet with these cells laid out and printed a copy big enough so that I could put it on a clip board and take it out on the road with Map Tracer and note the AFRs that I would get in each cell. Using this information I could calculate the “blue” numbers needed to get me close to 14.7 and into the closed loop cycle.
So out on the road I went with my clipboard and laptop set up for Map Trace in Nissan DataScan. I cruised up and down the interstate dialing in the appropriate cells with throttle application and noting the AFR on the clipboard. I noticed that the AFR would change within the cell range depending on RPM – that is to say it was different at 2100 RPM than at 2900 RPM, even though the ECU was reading from the same cell in the fuel map. Once I noticed this, I started to read the AFRs in the middle of the RPM range for a given cell and this gave me much more consistency. I used lower gears to access the higher RPM cells and found that this worked fine. The range of cells that I identified would allow you to cruise in closed loop up to 75 mph – plenty for most driving conditions.
A word of caution: I was able to do this without running into the rear of another car, or off the road, but it sure would be safer and easier to do it with a helper. There is a lot going on with watching the Map Tracer, modulating the throttle, watching the tach, reading the AFR and writing it on the clipboard! You could also do this on a dyno.
Most of the AFR readings that I read from Calum’s NA v.4 tune for my car under these conditions were in the high 12s or low to mid 13s. So, I took this information back to ROM Editor and individually leaned out each cell an appropriate amount and entered the “high” or “blue” number into the fuel map. Then I saved my new tune and burned new chips and swapped them into the daughterboard as before.
Amazingly, the car started and ran again! Driving it around, I was pleased to find that my new chips were keeping the car in closed loop, showing AFR vacillating around 14.7 under all light throttle conditions. This was leaner than I was seeing with the original Calum tune, which was giving me 13-13.5 under these same conditions. I also noticed the ECU learning the new tune – as I drove more, the AFR became steadier under closed loop. My first tank of gas with this tune gave me 34.7 mpg in mixed driving, but this seems almost too good to be true, and I will check it again to confirm.
I want to mention one more thing. I have developed an EXCEL spreadsheet that calculates the fuel correction factor from the map data value using the equations in my last post. You plug in the map value and it gives you the correction factor to the pulse width and the equivalent closed loop value (blue cell value). This makes it easy to figure out what numbers to enter into the fuel map. I also made a hex-dec converter in an EXCEL spreadsheet. I do not know how to (or whether I can) post these files here, but will be happy to send them to you via email if you just ask for them through pm or email.
Next I will move on to the high flow quotient columns (far right side of the map) which are also running a little rich at this point.
Also, I plan to run my VE up to 9K. I currently have the VE bin, but I haven't even gotten the motor installed yet so I'm just doing the recon right now. How much work would it take to get the map extended to 10K just in case?
I noticed you have yet to play with the timing map. Do you plan to do any tweaking on that? Have you decoded that yet?
Also, I plan to run my VE up to 9K. I currently have the VE bin, but I haven't even gotten the motor installed yet so I'm just doing the recon right now. How much work would it take to get the map extended to 10K just in case?
I noticed you have yet to play with the timing map. Do you plan to do any tweaking on that? Have you decoded that yet?
_SHig
Whatever settings in the fuel and timing maps are in the bottom row (highest RPM) will be read and used by the engine when you exceed that RPM level. So, if your map goes to 7600 RPM, those fuel correction factors and timing advance instructions will be used at all engine speeds above 7600. As a result, if these values provide a good tune, there is no need to expand the map. If you want to expand the map, there is really no need to go beyond your fuel cut. To accomplish this should be pretty straightforward. In ROM Editor, you just double click on the RPM cell in the map and you can change the specification (RPM) for the row. But you only have 16 rows in the map to work with, so you will need to make the rows available at the high end by reducing the number or rows that you expend elsewhere in the map. After setting up your row structure, then you would have to adjust the fuel correction factors and timing advance instruction to make sense on the "landscape" of you new map (that is reconcile the data in the cells with the new RPM specs for the row).
Calum already tweaked the timing map on the BIN file that I am using. Until I get to a dyno, I do not plan to make any changes to the timing.
Have you tried using TP yet? You should be able to replicate the same excel stuff inside TP, its pretty easy to use.
__________________
All posts by Calum in this thread are copyrighted by Calum, and cannot be edited, deleted, or copied without his express permission. calum@calumsult.com
I too wanted to say THANK YOU for posting this information (and thanks to Erich for pointing this thread out to me!)
My VE IS installed in my P10, but I don't have the Calum Realtime unit just yet. Jon (another local VE'd P10 owner) will be getting the Calum ECU before I will and we'll work on tuning his car together (because we'll have the same exact mods).
We've got access to a Innovative Automotive wideband (thanks again to Erich for selling it to me!) that we'll use for checking the mixture.
I feel like after reading this, I'm actually ready to start playing around with a BIN file.. so I'll have to bug Jon to get his Calum soon!
Keep the info coming Bill... Even though mine is turbo, this will help me smooth out the closed loop cells on my pig rich eye watering gas infested garage turbo car from killing me...
I'm glad that you guys are finding this somewhat useful. I will continue my story after a brief interlude for clutch replacement (including Fidanza flywheel) and work-related travel which separates me from my SR20s.
Sorry, I have been too busy to get back on this. The clutch and flywheel replacement went well. The car still pulls strong and I am getting fabulous gas mileage -- 32-38 mpg in mixed driving.
I will eventually get back to tuning in the mixture at WOT and then I plan a dyno session to compare the final tune with Calum's version 4 (where I started) and the OEM tune from the factory. Naturally, I will post the results here.
Sorry, I have been too busy to get back on this. The clutch and flywheel replacement went well. The car still pulls strong and I am getting fabulous gas mileage -- 32-38 mpg in mixed driving.
Bill
DAMN YOU!!!! Jealous if not a bit incredulous. Are you running tiny 13" tires/wheels and throwing your ODO off! :^) That's amazing for MIXED driving, let alone freeway only.
What mods do you have? I found a CAI/Intake KILLS fuel mileage.
DAMN YOU!!!! Jealous if not a bit incredulous. Are you running tiny 13" tires/wheels and throwing your ODO off! :^) That's amazing for MIXED driving, let alone freeway only.
What mods do you have? I found a CAI/Intake KILLS fuel mileage.
_SHig
My mods are: Topspeed header, HKS exhaust, AEM CAI, and the Fidanza flywheel. Before the flywheel, and with the factory ECU, I would get 30-32 mpg on the same commuting routes (timing set at 19*). I think that the advanced timing as well as the leaner mixture both contribute to increased mpg with the Calum ECU.
My wheels are NX 2000 standard OEM issue with Bridgestone Potenza RE960AS Pole Position tires in 186/60x14. No funny stuff going on there.
I pinch myself every time I fill the tank, just to make sure I'm not dreaming.
