with my dashpot tune - I'm fighting IPC and surge under moderate acceleration, worse until the car warms up.
I'd been thinking, the dashpot tune is adding requested air (dashpot, preposition etc) that predicted throttle isn't accounting for, so I disabled all dashpot by lowering dashpot parameters, raising enable flow and vss. the last thing I did was enable oscillation switch, and desired air mass logic, the IPC at part throttle is still there.
What else could be contributing to this?
Last edited by GapRider; 03-16-2019 at 12:56 PM.
2019 C7 Stingray M7 - long tube headers, 6.30/6.22 226/238 cam, supporting stuff, DOD and VVT delete.
Stock everything else
Do you have Torque Based Decel enabled? Are you attempting to tune dashpot?
IPC Wheel Torque Error would be your Torque/Inverse tables. Your torque values do not match the airflow values of the inverse table or your airflow values do not match the torque values in the torque table. However you put it, these tables have an inverse relationship, not being inverse usually results in torque errors.
Disable the oscillation switch will help. I haven't looked at your files so its something you can overlook.
Just before determining the desired MAF for the throttle control the ECU selects the higher value for the airflow from the idle speed controller or the TTL to ensure that the final requested airflow does not decrease below the idle speed control setting due to any modeling errors in the torque-to-load table. Using the low values for idle airflow as you have makes it use the TTL value as its minimum, the one prone to errors. This is both true for no pedal input or part throttle. The pedal position(app) gives the MUX a value of 0,1, or -1. -1 meaning use idle/ dashpot, 0 being part throttle, and 1 being WOT. Hopefully the highlights in the attached image helps explain the flow.
US6279531-drawings-page-5.png
Increase your Idle airflow values in the higher RPM cells to prevent desired airflow from dropping lower than it should, closing the throttle when it shouldn't.
thanks for the help (murfie too), I thought I was gonna be on my own on thisOriginally Posted by Thatwhite5.0
I'll turn the oscillation switch back off
2019 C7 Stingray M7 - long tube headers, 6.30/6.22 226/238 cam, supporting stuff, DOD and VVT delete.
Stock everything else
thank you, the explanation and drawing do help.
If I understand correctly, my low idle airflow values at higher RPM's are causing the ECU to default to TTL (which is likely to be incorrect/error prone) to request ETC air - in my case, Actual MAF is exceeding Desired MAF.
I don't see this with Torque decel enabled - is it because this dashpot algorithm is no longer providing input to ETC opening?
I will increase the idle air flows at higher RPM and log to see what happens. Hope to have good news, I've been messing with this thing for a while.
2019 C7 Stingray M7 - long tube headers, 6.30/6.22 226/238 cam, supporting stuff, DOD and VVT delete.
Stock everything else
You're purposely trying to use dashpot instead of torque based decel?
torquedecel.JPG
Try increasing your driver demand torque. S197's have a little bit more play with driver demand than an S550. Your car is making more torque than requested, sometimes increasing torque request to more than what the ECM's calculation will help get rid of errors. A torque request is a request for more air. Actual MAF is exceeding Desired MAF or your Engine Brake Torque is exceeding Torque Request.
Your distance tables can also be playing apart of the error since most of your errors are happening during a blend between the mapped points. You can increase Best Drivability min and Fuel Economy Max and clean up the distance tables a little bit.
distancesss.JPG
With torque decel enabled, the idle desired MAF is coming from a torque value and isn't coming out as low as your airflow tables are making them. So when TTL drops below this threshold, it's not closing the throttle too much. You can also see the desired airflow for idle also makes its way into a trim for determining engine brake torque, which should be the same as driver demand. This allows Idle to be targeting 0 torque.
Also keep in mind idle is targeting an RPM ultimately, not an airflow and is actually more spark controlled once at idle. Dash pot wouldn't be something added unless the throttle goes from open to a closed position, meaning idle is desired. It's basically too slow the throttle closing and slow the RPMs from dropping to fast, and overshooting idle essentially stalling. If the RPMs do not drop to idle then engine breaking is desired, dash pot should decay fast enough to prevent the cruise control feeling and get engine breaking. This is why you had regular dash pot and 4th gear dash pot.
lots of good info, thank you both!
First, yes I want snappy RPM decel on gear changes, like a carb, it makes driving the car a lot more enjoyable as I shift gears. (I don't care for the rev hang in modern cars)
I couldn't get that snappiness with torque based decel so I began playing with dashpot, I got the rapid decel I love but needed to fix IPC surging.
I tried the suggestion of increasing the higher RPM idle flows but didn't see a change in IPC.
For sanity check, I logged the torque based decel tune I had been running and it also has IPC surging, less noticeable but there. Actual MAF is greater than Desired MAF.
Now I'm wondering. I compared to the bone stock Ford tune and there are no changes to speed density, torque tables or mapped points stuff. I did see that I'd played with idle spark timing.
If I could get the snaopy rev decel from the torque based decel I'd do it.
Now that I see that it also has the IPC issue, I know I need to fix that no matter which decel mode I use.
My car is totally stock except for after market catback so I'm puzzled that stock torque and ETC values would be giving me issues with IPC.
Do you guys suggest I go ahead and try to tune the torque tables to get rid of the IPC as rcmikey and you guys have described?
Last edited by GapRider; 03-19-2019 at 05:45 PM.
2019 C7 Stingray M7 - long tube headers, 6.30/6.22 226/238 cam, supporting stuff, DOD and VVT delete.
Stock everything else
I also dislike the decel of modern cars and wanted mine to be quicker however I only adjusted the 'decel torque' tables to get it done. Works great.
What I would like to know is how to get rid of the idle staying high during coasting (like 1100-1200) until I come to a complete stop. This is a stock built in thing I've seen on many Fords - autos or manuals.
I saw your tune was basically stock, and didn't really look too much at your log.
Your Long term fuel trims are not working at all, and your short term fuel trims are all over the place for a stock tune. Rich to the point they cant maintain AFR, thats not good. I would figure out what you have physically wrong and correct that before you start putting all this error into your calibration where it doesnt belong.
Out of control fuel.PNG
I wonder if, by making it based on airflow and not torque, your stock MAF transfer covers the low airflow values well enough to do what you want it to.
Last edited by murfie; 03-20-2019 at 12:34 AM.
That's what I'll do, I saw the trims off a while back after I'd installed the TREMEC transmission I thought maybe I got an O2 sensor dirty during the swap out and it'll burn clean after running for awhile. You pointing it out being still a problem means I gotta fix it. Thanks murfie.
Could an exhaust leak where x pipe attaches to cat pipe affect that since it's downstream of the o2 sensors?
2019 C7 Stingray M7 - long tube headers, 6.30/6.22 226/238 cam, supporting stuff, DOD and VVT delete.
Stock everything else
Exhaust leaks show as lean. This is rich, and usually just before it should be going into dfco.
You may just need to work on your driver demand. Log the pedal ADC, I think its transmission pedal or something like that, and histogram it. The driver demand torque gets modified by vehicle speed and baro, so its the torque at the driven wheels. Its logic then works backwards. The different gear ratios will require you to change this demand.
I will check into that also, I think I do have DFCO effectively disabled (I'm at work, I'll have to check when I get home). I did update every gear ratio parameter I could find when I installed the TREMEC (so everything's correct).
Can you explain more about the histogram, am I logging pedal against DD? What do I look for to signal a need for change and what do I change? Sorry, I just don't know enough to follow.
2019 C7 Stingray M7 - long tube headers, 6.30/6.22 226/238 cam, supporting stuff, DOD and VVT delete.
Stock everything else
Torque ratio = "engine brake torque / scheduled torque"
First you need to understand ICP error and torque ratio. Many IPC error happens when torque ratio is above 1. From the attached image you can see the worst of your IPC error is when torque ratio goes over 1, I lined up 0 IPC error with a reference line of 1 torque ratio. The ECU is thinking the engine is making too much/ more torque than it should be. You can see it tries to fix it with the throttle, when compared to your pedal. This situation happens when the throttle closes, so you see torque ratio spike but no IPC error. You can also get IPC error at less than 1 torque ratio, again the ECU is thinking the engine is making too much torque to satisfy the drivers demand.
IPC and TQ ratio.PNG
If there is nothing wrong with fuel delivery, and because of your particular situation, you would possibly fix this in the driver demand. You basically have a stock engine so the stock calibration for engine parameters can be relied on as good.
The Graph/histogram would be setup just as you see your driver demand table. engine speed for x axis, pedal position for y axis. For your pedal position being ADC, you can use voltage and convert it to ADC, but error in your math could be putting you in the wrong spot of the driver demand table. Just log trans pedal position and be comfortable in knowing you are in the same cell as the ECU. You would then filter the input by IPC error greater than 0. The input would be a user math of scheduled torque x .85 or what ever you think you torque ratio should be for the particular section of log you are looking at. This gives you the values to put into your driver demand table. A good part of what your torque ratio should be is dependent on how far your final spark advance is from MBT spark advance. I attached a graph file, you would just need to select trans pedal position, and create a user math for scheduled torque x desired torque ratio.
The volt to ADC conversion instead of the actual logged value is throwing the cell off, but you can see from this pic what you should end up with.
Graph vs table.PNG
You may notice theres some small IPC error in spots you are at constant RPM and pedal, This is when TR is low, and ECU thinks the engine isn't making enough torque for DD.
Last edited by murfie; 03-21-2019 at 12:39 AM.
Im sorry, in my post I have it mixed up. The schedule torque X desired torque ratio would be for when the TR is too low.
To raise schedule torque, to lower and correct the TR when its too high, you would use engine brake torque/ desired torque ratio. Which is more of what you need to do to get rid of the IPC error.
You'll find you are aiming for a inbetween, basically when the ECU thinks the desired torque and engine torque are equal IPC will be happy.
Last edited by murfie; 03-21-2019 at 01:27 AM.
thanks so much murfie, you've given me new insight. let me set this up and dig into it.
looking back through some old logs, I see there's always been a little IPC around half throttle @ ~3000RPM, I think these recent dashpot tunes have amplified the IPC condition.
Last edited by GapRider; 03-21-2019 at 05:47 AM.
2019 C7 Stingray M7 - long tube headers, 6.30/6.22 226/238 cam, supporting stuff, DOD and VVT delete.
Stock everything else
Here's from my view.
First pic in the log is torque error free, second pic has a torque error.
noerror1.JPG
error1.JPG
You're getting torque errors most over the ratio of 1.0. Engine Brake Torque is higher than ETC Request and Scheduled Torque.
A lot of people increase their torque tables to try and fix their problems. When I adjusted my Torque Tables for N/A Cobra Jet, I actually decreased from stock values to lower my Engine Brake Torque. You can also recalibrate your throttle body to achieve results similar. You can only increase ETC Request/Driver Demand by so much. Calibrating the throttle body essentially allows you to increase driver demand so you're able to request the amount of torque needed to get rid of the errors.
I see what you mean, during IPC, the EBT has jumped over ETC & SchTq (due to MAF or ETC flow I guess). It seems like adjusting one pair of tables (ETC) would be 'easier' than adjusting many pairs of torque tables.
Laymen thought - throttle opening exceeds requested flow>load>torque, ECU gets mad and cuts throttle. I want to adjust the ETC tables to reduce the directed throttle opening through these ranges so actual MAF is a little less than DesMAF.
I set up a histogram for this but I don't think it will get me all the way there. The column and row headers are from the ETC Pred Table and the plotted value is user math DesMAF/ActMAF. Is there a better user math I could use there?
ETC MAF error.JPG
Also, ETC Throttle error looks valuable but I don't know what that PID is a calculation of?
ETC Eff Angle Error.JPG
Just changed this histogram to plot ETC angle errors. I used it to adjust angles in the ETC Pred tables. I'll log next and see what happens
Last edited by GapRider; 03-23-2019 at 08:55 AM.
2019 C7 Stingray M7 - long tube headers, 6.30/6.22 226/238 cam, supporting stuff, DOD and VVT delete.
Stock everything else
I wouldn't say ones easier than the other adjusting the two throttle body model tables or adjusting the torque/inverse tables. Both of them coincide with each other.
If you study either sets of tables, you'll notice that the axis of one table are in the cells of the opposing table. In the opposing table the axis are in the cells of the one table.. you want to actually increase the airflow to the amount of air required for the engine brake torque you're reaching.
On the torque table side. There are more tables but an excel spreadsheet can calculate very quick.
You have airload vs torque and torque vs airload. In the .1 airload row are the torque values for .1 load. In .2 are the torque values for .2 load.
The inverse table works the same. In the row with axis 37ft lbs, you'll have the airload that equals 37 ft lbs. So the axis values show what each are.
.1 = 0ft lbs which is not a real calculation. I change the first column to 7 ft lbs.
.2 = 37 ft lbs
.3 = 72 ftlbs
If you have 37 ft lbs in any of your torque cells, then inverse table must have .2 in the same cell location. I'll post a formula once I get to my laptop
Thanks so much for that good info. I?m just learning so I chose the ETC tables cuz there?s only one pair.
I did get rid of all the IPC error I had but now I get some when the car?s in the two highest vacuum rows, I?ll change those rows back to stock (where I had no IPC error to begin with), then smooth and try that in the morning. I started by logging ETC throttle error but then switched to MAF/DesMAF because I?d have areas where there was no throttle error but there was still IPC error and coinciding MAF>DesMAF. I used that to show me where to adjust ETC Pred. I?ll let you know how it works out. I guessed at the ratio of MAF error to ETC angle. Again, thanks so much for the help.
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