Turbo 'flutter' during low rpm / high gear acceleration...

John Miller · April 21, 2016, 07:34:21 PM

Good info - I will certainly find out

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AJP turbo · April 21, 2016, 07:42:45 PM

Quote from: John Miller on April 21, 2016, 07:34:21 PM
Good info - I will certainly find out

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I dont think you will be able to....scalar descriptions are hard to come by...im telling you what is in the tune...there is a seperate section for cruise control...no shift tables there

John Miller · April 21, 2016, 07:45:02 PM

I meant I will use the cruise control and find out if the updated shift parameters, already experienced during normal driving, also apply with the cruise on

.

Torrie did mention that there are two shift tables labeled CR2 and CR3.

John Miller · April 22, 2016, 07:57:27 PM

I know I said I would report in a week, but my first commute impression:

The last revision got the 1-2 shift from the "wheel hop" feel down to a hard "bang" shift. After one commute in, the adaptive leaning has done the rest ... all shifts are now smooth and just firm enough. Not even the bang feel. Perfect.

As for the flutter at hand, the quicker downshift seems to be an answer. Under almost all the conditions I could previously replicate the flutter, the car will go to 5th before it can happen.

I say "almost" cause, if I try really, really hard on just the right incline, I can ease into the throttle just enough around 65 mph to get it fluttering. But, I really have to get it perfect and I don't think it is something that would happen during normal driving. Probably will end up 95% fixed and a good compromise, as I would hate it to gear down too quick. And, I think I've worn out my revision grace with Torrie

Didn't try cruise today, as I still want to get a feel for the car in its new state.

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SHOdded · April 22, 2016, 09:34:35 PM

Nice detective work, John

SHOnUup · April 23, 2016, 07:40:33 AM

Glad to hear the situation is solved...by the way, I know guys that are on over 50 revisions with Torrie...quite a few actually. You have plenty of those revisions left just so you know.

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John Miller · April 23, 2016, 08:35:03 AM

Thanks. I don't know it is "solved," but will know more after 5 or 10 more commutes.

I think it is possible that it is downshifting perfectly at most speeds but that there is a small window where it just needs to downshift a hair faster. I'm not married to that idea though - I need to drive it more.

According to Torrie, the downshift calculation is a function of output shaft speed to throttle position. So, if I do find a window in MPH that needs adjustment, I'll need to data log to find the OSS and actual throttle angle for him.

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SHOdded · April 23, 2016, 09:08:31 AM

Quote from: John Miller on April 23, 2016, 08:35:03 AM
Thanks. I don't know it is "solved," but will know more after 5 or 10 more commutes.

I think it is possible that it is downshifting perfectly at most speeds but that there is a small window where it just needs to downshift a hair faster. I'm not married to that idea though - I need to drive it more.

According to Torrie, the downshift calculation is a function of output shaft speed to throttle position. So, if I do find a window in MPH that needs adjustment, I'll need to data log to find the OSS and actual throttle angle for him

Keeping in mind that much as we like accuracy, electromechanical interaction means there will be a range you'd need to work with, rather than a fixed point set in stone. For example, you may be seeing a decay in sensor function over time that forces periodic tune adjustment. May not be in the best interests of longevity either

That said, def looking forward to seeing how much fine control we have over the SHO

ZSHO · April 23, 2016, 09:29:43 AM

Glad to see some progress in the right Direction. Z

Excalibur · April 23, 2016, 06:54:06 PM

It's been a week with my final revision from my tune from Torrie and I have noticed mine doing the same thing. checked all the hardware checks stated earlier, so I'm guessing I'm going to have to email Torrie as well and see if it will fix mine. I'll report back after I find out something. great thread btw.

John Miller · April 23, 2016, 07:37:15 PM

It's going to take some trial and error.

I confirmed this afternoon that it must use different shift tables when you activate the cruise control - my early downshift disappears with cruise activated.

I'm still going to give it some time - I want to confirm whether there are any speeds that I still need a little earlier downshift (to avoid the flutter) and do the OSS logs. Once that is done, I'm hoping Torrie can figure out which table(s) are for cruise and mirror the "perfected" shift parameters there.

Just gonna take time and patience. Thanks, Ford. After all, the car was so cheap, we should expect to have to find our own answers, right?

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SHOdded · April 23, 2016, 08:16:31 PM

Quote from: John Miller on April 23, 2016, 07:37:15 PM
Just gonna take time and patience. Thanks, Ford. After all, the car was so cheap, we should expect to have to find our own answers, right?

Fix Or Repair Daily

FoMoCoSHO · April 23, 2016, 09:28:53 PM

http://www.focusst.org/forum/focus-st-performance/10369-turbo-flutter.html

"This is from Braden over at Cobb:

Normal, completely. The design of the wastegate, and the low pressure spring in use make it difficult to control during high load, low rpm conditions. There is a LOT of VCT in action to create exhaust flow along with the boost control solenoid being driven at high duty cycle to allow for nearly instant spool on this engine. The factory tune delays the turbo response in these conditions partially to eliminate excessive load, but also to work around a poorly suited set of hardware. The noises you are hearing are a combination of valve overlap and aggressive wastegate dynamics coupled with a soft wastegate spring opening and closing the flapper as it is overloaded. Once exhaust flow is stabilized the system works extremely well and uses dynamics to keep boost levels near their targets.

As many have stated, downshifting is the best way to avoid these conditions. Generally, anything above 2500-3000rpm is OK in all gears, but starting lower than 2000rpm in 4-6th will net some interesting harmonics. None of which are caused by the bypass valve.

Cheers,
-Braden @ COBB"

John Miller · April 23, 2016, 09:38:24 PM

Interesting. But .... Is the "flutter" he refers to about a sound, and not about how the vehicle is actually running as described in this thread?

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ZSHO · April 24, 2016, 08:05:08 AM

Quote from: Excalibur on April 23, 2016, 06:54:06 PM
It's been a week with my final revision from my tune from Torrie and I have noticed mine doing the same thing. checked all the hardware checks stated earlier, so I'm guessing I'm going to have to email Torrie as well and see if it will fix mine. I'll report back after I find out something. great thread btw.

Excalibur please add your signature,thanks. Z