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Discussion Starter #1
Hello everyone I am having some partial throttle issues and would like to offer my datazap logs, can someone provide some insigiht as to what exactly is happening to my car while I am driving?

Anytime I have my foot partially on the gas my turbo will boost to whatever target it is trying to hit and then proceed to climb down and them up and down and up almost as if the turbo is "breathing".

The car pulls very strong at wide open throttle and the torque is great on the bottom end but I am just having this one particular issue that I can't nail down. Any help would be appreciated!

(I can't post links so I had to break the link below)

h-ttps://datazap.me/u/rscar/2017-rs-3rd-gear?log=0&data=5-9

current mods
fmic, mountune uprated bpv (w/BRA), and an intake
 

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Wow...very interesting. I'm no expert, but I do enjoy looking at logs, so I'll just give some of my observations and ask questions:

-Does this anomaly only happen during partial throttle? Do you have a data log of a full throttle pull to compare it to?

-Are you tuned or is this just just a Cobb OTS? If so, which OTS tune? If tuned, have you brought this up to your tuner? They might have a better idea of whats going on

-You mentioned that it "pulls strong on wide open throttle". Were you able to reach peak boost? (typically ~23psi, depending on conditions) Since you have an aftermarket intercooler, have you checked for any boost leaks?

-Working through your data, I see you are on map slot #2. Do you know what type of "tune" is on that slot? Could it be a non standard tune?

-Taking a look at the throttle (ETC angle) it looks like it too is oscillating, which directly correlates to your boost oscillation. I know on a standard 3rd gear redline pull (with your foot planted on the throttle) the ETC can momentarily close between 4.2k to 4.8k rpm. Not sure if this is what's happening here or there is something funky going on with the ETC control. Have you checked to make sure your MAP sensor is installed correctly?

-I notice all your turbo control signals are oscillating similarly. The "turbo mfract des fraction" and WGDC control table (ie "base x" and "base y") all flip-flop around, telling me that the control isn't "happy". They typically should flatten out once the desired boost pressure is attained. Perhaps you can try to record "TIP Actual" and "TIP Des" to see if the ECU is seeing the pressure difference and is reacting as expected?

-Only other thing I can think of to check is if the "Requested Torque". Typically, the ECU takes the desired torque and tries to target that by controlling the ETC.

Again, no expert here, just a curious guy on the internet lol
 

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Welcome to my world. I get this with my mountune tune (but not stock) that randy was never able to fully get rid of, but also at WOT in higher gears. I think it only doesn't happen in lower gears because the engine rpms are climbing too fast to oscillate. No hardware mods.

Sadly I have no thoughts.
 

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Discussion Starter #4
Wow...very interesting. I'm no expert, but I do enjoy looking at logs, so I'll just give some of my observations and ask questions:

-Does this anomaly only happen during partial throttle? Do you have a data log of a full throttle pull to compare it to?

-Are you tuned or is this just just a Cobb OTS? If so, which OTS tune? If tuned, have you brought this up to your tuner? They might have a better idea of whats going on

-You mentioned that it "pulls strong on wide open throttle". Were you able to reach peak boost? (typically ~23psi, depending on conditions) Since you have an aftermarket intercooler, have you checked for any boost leaks?

-Working through your data, I see you are on map slot #2. Do you know what type of "tune" is on that slot? Could it be a non standard tune?

-Taking a look at the throttle (ETC angle) it looks like it too is oscillating, which directly correlates to your boost oscillation. I know on a standard 3rd gear redline pull (with your foot planted on the throttle) the ETC can momentarily close between 4.2k to 4.8k rpm. Not sure if this is what's happening here or there is something funky going on with the ETC control. Have you checked to make sure your MAP sensor is installed correctly?

-I notice all your turbo control signals are oscillating similarly. The "turbo mfract des fraction" and WGDC control table (ie "base x" and "base y") all flip-flop around, telling me that the control isn't "happy". They typically should flatten out once the desired boost pressure is attained. Perhaps you can try to record "TIP Actual" and "TIP Des" to see if the ECU is seeing the pressure difference and is reacting as expected?

-Only other thing I can think of to check is if the "Requested Torque". Typically, the ECU takes the desired torque and tries to target that by controlling the ETC.

Again, no expert here, just a curious guy on the internet lol
Thank you for your interest and your time!

I will try and answer your questions as best as I can in order.

1. This only occurs during partial throttle and I can absolutely get another log but it would require changing tunes again at this point =) please read on in a moment
2. Peak boost is 23-24psi at wide open throttle - no leaks!
3. I believe slot 2 is no lift shift or flat foot shift (I do not understand the difference in terminology) per this tunes calibration
4. I am not entirely sure - where is the MAP located? Is it the sensor that plugs in directly above the intake?
5. I will keep this in mind if it continues to happen in the future!
6. I think that this is exactly what is happening -I believe this is the ecu using torque limiting to control etc and that is causing partial throttle blade closures at this particular speed.
Given that the car also has 1-1/2" spacer for the gas pedal I wonder if that in any way relates to this or at least being able to reproduce the symptoms....thinking out loud here.


I do not know how to quote multiple people in one post so Jumperalex I believe I may have found the solution with the most recent revision...please stand by for logs..
 

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I too am experiencing this problem. It is definitely the electric throttle opening and closing of it's own accord in an attempt to achieve some goal - boost pressure? perceived torque?
 

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Reviving this thread with my own log as it's more relevant here than on the datazap thread.


My wastegate duty cycle looks like it's going up as it should, then slamming shut to 0%, then recovers and keeps climbing etc etc. While that's going on, it looks like the throttle is trying to do something to recover and the entire car is just rocking back and forth as the power comes and goes. This also only happens on part-throttle, the car pulls to redline on WOT effortlessly.

Did anyone come to a definitive conclusion why this happens? Or have any new info the can share to try to troubleshoot?
 

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Reviving this thread with my own log as it's more relevant here than on the datazap thread.


My wastegate duty cycle looks like it's going up as it should, then slamming shut to 0%, then recovers and keeps climbing etc etc. While that's going on, it looks like the throttle is trying to do something to recover and the entire car is just rocking back and forth as the power comes and goes. This also only happens on part-throttle, the car pulls to redline on WOT effortlessly.

Did anyone come to a definitive conclusion why this happens? Or have any new info the can share to try to troubleshoot?
Have you tried poking around the thread where it was discovered that the accelerator pedals would go bad? That or spark plugs perhaps?
 

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Have you tried poking around the thread where it was discovered that the accelerator pedals would go bad? That or spark plugs perhaps?
The thing that's confusing about that is that the accel pedal position is consistent with the throttle inputs I'm giving it. I also thought it might be the spark plugs, so I had them replaced prior to taking that log.
 

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Reviving this thread with my own log as it's more relevant here than on the datazap thread.
Did anyone come to a definitive conclusion why this happens? Or have any new info the can share to try to troubleshoot?
Taking a look at this again out of curiosity... Yours seems to be a much larger oscillation compared to the OP's, with the boost swinging ~4-6psi, which is pretty crazy (vs the OP's more frequent 2-4psi).

That wastegate actuation is weird AF... that curve is definitely not normal imho. It looks to be behaving similar as OPs (fluctuating between two extreme states), which is not typical. Looking at all my logs from different tuners, it should be pretty wide open during spool-up, but then reach a steady state (or close to it) ~50-60% and hold steady or slowly rise with the rpms. I would check the wastegate function first, along with any leaks on the hose, etc.

Have you tried poking around the thread where it was discovered that the accelerator pedals would go bad? That or spark plugs perhaps?
Probably not the same issue since the throttle signal (accel pedal pos %) looks steady. The throttle plate is definitely fluctuating, but it looks to be due to chasing the boost (trying to keep up with the surges).
 

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Looking at all my logs from different tuners, it should be pretty wide open during spool-up, but then reach a steady state (or close to it) ~50-60% and hold steady or slowly rise with the rpms. I would check the wastegate function first, along with any leaks on the hose, etc.
Thanks for taking the time to check it out. The wastegate holds and rises from 45%-70% steadily with RPMs on WOT runs, the issues are only in part throttle. I'll take another log with a different tuner's map to verify my wastegate is working.
 

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Thanks for taking the time to check it out. The wastegate holds and rises from 45%-70% steadily with RPMs on WOT runs, the issues are only in part throttle. I'll take another log with a different tuner's map to verify my wastegate is working.
Ah, that's true, I forgot we are looking at a partial throttle condition. Now that I think of it, I think my JST and Stratified tune did something similar. Nothing that I can feel, but I can certainly hear the surging from the intake noise (specially if I don't have the hood lining on). Maybe I'll try to take some partial throttle logs to look at for ****s n giggles...
 

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After going back to my Stratified tune, the problem has been resolved. It's definitely a tune issue. That said, I do feel it on that tune as well, but it's very very VERY subtle and I really have to be looking for it to notice.
 

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After going back to my Stratified tune, the problem has been resolved. It's definitely a tune issue. That said, I do feel it on that tune as well, but it's very very VERY subtle and I really have to be looking for it to notice.
Would be good to try to get a log of it on your Stratified tune to compare. It would actually be more interesting/definitive to see if you get the same from the stock tune.
 

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Done. Setting it private is a habit.
Good habit to have ;)

Looks like this latest log (stratified?) looks much closer to normal. The waste gate actuation appears to be looking normal as well, which suggests its the way the tune is controlling it that is causing this weird behavior.

I've been told by a tuner friend that part throttle tuning can be very tricky. That's why it's so important to do some street tuning after doing dyno tuning. It's easy enough to just keep "bumping up" the table when at full throttle, but it takes some finesse to make it handle well in the street.
 

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Looks like this latest log (stratified?) looks much closer to normal. The waste gate actuation appears to be looking normal as well, which suggests its the way the tune is controlling it that is causing this weird behavior.
It is indeed Stratified. Only tuner I've never had an issue with.

Thank you for confirming the actuation and taking the time to check out the logs. :)

I guess I can blame my part throttle funkiness on the tune. Others in this thread or finding it on a Google search might want to switch between the OTS/stock/other custom tunes to troubleshoot.
 
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