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Discussion Starter · #1 ·
I need some large-minded help with a small driveability issue. In my tune, I seem to have a bug that is causing a Throttle Position dropout. I've attached a short log that clearly shows the problem when comparing PEDAL POS REL to TP ABSOLUTE. (I know there is a lot of other junk in the log...I was trying to find any correlating data that might help lead to a cause).

This happens every time I start from a stop with the engine warm and light-moderate Pedal. The Pedal position is either constant or increasing. The TP mirrors it just fine...except for a pair of dropouts that cause a huge lag in acceleration (twice). It feels like I've let off on the throttle on purpose (twice)...but I haven't. The dropouts from the start to finish are almost .5 sec long.

I feel that this is a Drive-By-Wire problem...and I have SCT Advantage 3.3 with Calibrator access. Problem is...I have NO IDEA what to try. Any ideas to help me?
 

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Discussion Starter · #3 ·
Thanks for looking at it Eric.
 

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Discussion Starter · #4 ·
Another log....

I did some more logs of the problem today. I changed many of the parameters I was logging looking for something else that might lead to a clue. Still no clues for me :cry:
 

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Discussion Starter · #5 ·
Bump....no one?
 

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Discussion Starter · #7 ·
Eric, I have logged this problem many times. When the engine is warm, this problem with the TP will occur twice every time light->moderate acceleration from stop or low speed occurs. Here are some logged events. In every case listed here, the TP dropped DRASTICALLY on the very next logging cycle while the Pedal Position (PP) was constantly increasing. The TP then recovers about .5 sec later.

TP PP RPM
253 104 2850
221 116 3015
278 106 3340
276 127 2967
339 177 3600
225 80 2475
293 123 3240
270 113 2980
341 157 3521

Thanks

Read more at: http://www.modularfords.com/threads/196953-Pedal-Position-vs-Throttle-Position-Drive-By-Wire-problem
 

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Discussion Starter · #8 ·
Example Log of the dropouts

Eric, here is a screenshot of one of the worst (best) examples of the Pedal Pos -vs- TP problem. In this log, the TP actually spikes UPWARD once at the beginning and DOWNWARD several times. Generally, there are only two downward spikes.

TP Dropout.jpg
 

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That's table is messed up. The table show increase going up and decrease going from left to right. Fix that blue area on the higher part of the table. See if that helps. That's what stands out right now.
 

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Discussion Starter · #10 ·
Alfie, The trends you mention in my table match the trends in the Stock table. I agree that it looks odd to have decreasing values as the table goes to the right...but that's how the stock is also. My table is highly modified from the stock table...but the trends are the same. I don't know how to "fix" it?

As far as the "blue" areas on the right side...they are all outside the area of concern. I don't think they would be affect a solution since they are above the RPM area where the problems occur.

If you can give me specific advise on what you think needs modification in the table....I'm willing to try. Can you show me a table that you feel is correct?

Thanks
 

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Ok. Sorry man. Just looked at a stock table and have u tried loading the stock table and see if it does it still? What drive by wire tables ?scalars have u messed with ?
 

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Discussion Starter · #12 ·
I have a Kenne Bell Big Oval Throttle Body. The only Drive By Wire tables that have been modified are per the data that KB provided. I don't think that running the stock tables would be good...it seems that this Driver Demand Engine table was fairly significantly changed per their data as well as the Effective Throttle Area table.
 

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U can still run the stock driver demand table. The effective throttle area table is a model of the flow of the TB.

The driver demand works with other tables. The thing that can get u in trouble in the driver demand table is do NOT make the negative numbers positive. The way it's set up is to simulate a cable feel. That's what as u can see at some point the numbers from left to right decrease. The PCM uses these numbers to determine the how much throttle angle you are requesting. (Simple and fast explanation) now if these are the only table u changed and did nothing with the predicted throttle angle table than I would assume your Allowable wheel torque error is raised. The predicted ff table is one of the important table that should be done correctly to have the PCM property determine if you have a run away condition. So if you didn't do this and you have raised your IPC allowable error. Than it's really pointless to mess with the driver demand table since all it does is improve the feel of the throttle. (At this point ) so I suggest to use the factory table and see if the conditions still happen. If it fixes it. Let me know. I can help u make changes to this table.
 

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Discussion Starter · #15 ·
Alfie, thanks for the help. Here are other tables that have been changed in the Drive By Wire.

- Indicated Engine Torque Inverse - All rows except bottom two have been significantly increased
- Max Scheduled Torque - All values set to 900 for all RPMs
- Max Throttle at RPM - All values set to 82 for all RPMs
- Open Loop Ff TA Prediction - All values reduced in all cells (except column 1 which remain at 0.00)
- Tip In Rate Change Multiplier Sr Nov - All values in all cells set to 10000
- Ynorm Drive By Wire 07 - Only one cell changed, Inferred TP Vacuum bottom cell changed from .200 to .300
- Ynorm Drive By Wire 17 - Torque Column rescaled to max at 800

- - - Updated - - -

Here's my current Open Loop Ff TA Prediction table with the stock values in the compare below it.

Open Loop Ff TA Prediction.jpg
 

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U may have to start from scratch. But just for **** and giggle change that DD table use the stock table. See if it still does it.
 

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Discussion Starter · #17 ·
Ok...I'll guess I can see what happens. I don't understand what I should expect though...would you expect it to still actually go WOT? The values in the table are HUGELY different than the stock table....and far lower on the left upper.
 

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Discussion Starter · #19 ·
It appears that this problem has been resolved...thankfully! I'll be "playing" with it more in the days to come to make certain there are not still "drops" in the TP. Eric gave me some input that not only makes sense...but works. My DBW Scalar ***=WOT Start was set way too low. It was at 50. He suggested a value of 200 as a start. This naturally did affect the "feel" of the Pedal...and I'll be working on that some in the future in the DD table. But...thankfully...no TP dropouts occurred in multiple tests this evening. Thanks Alfie for your inputs and education also on the DD table.
 
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