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

[xkrexplorer]

AJP turbo,

Some thoughts, what do you think?...

I do not think the wastegate is opening under such low throttle and load.  I think Ford has set the wastegates to remain closed at lower load to keep the tiny turbo's spinning and avoid lag.  I don't know what the wastegates are set to open at under such low loads, but maybe they are programmed to open at a higher throttle/load/pressure.  For me this all occurs at 1/4 throttle or less.  Maybe they are not opening and that is the problem.  They are not opening by design, but there is too much boost in the intake for the engine to use at such a smaller load, and instead of the bypass valves being opened when throttle closes to dissipate boost, they are opening to dump too much boost for the engine to use.  Is that possible?
Maybe a tuner can jump in?

 

[John Miller]

I data logged it and sent in the Unleashed.  He is going to compensate by making the car gear down to 5th faster.  I suspect they'll be some tweaking necessary to get that exactly right, but I'll let everyone know how it goes.  He got the tune to me already, but it will be tomorrow (at least) before I can get the thermostat, plugs, and tune into the car.

In the meantime, the data log config I used (per Torrie) had 36 PIDs.  For the tuner types out there, if there are specific ones you want to see, list them out.  I'll single them out within Livelink during the time the flutter is occurring, take a screen shot, and post up for the group.

 

[John Miller]

Wastegate in maroon, boost in orange, actual throttle angle in purple, RPM in light green.

Stating the obvious:  Boost and Wastegate Percentage keep dropping and bouncing back up.

 

[xkrexplorer]

Wastegate in maroon, boost in orange, actual throttle angle in purple, RPM in light green.

Stating the obvious:  Boost and Wastegate Percentage keep dropping and bouncing back up.

That is great work.  The wastegate is dumping. I know for sure that in my explorer, the bypass valves are dumping as well (very clear if you vent to atmosphere as a test), and I wonder if that is because in your logging, the throttle position seems to increase and then decrease as the waste gate dumps and this opens the bypass valves.  Again, I wonder if this is all because of Ford trying to prevent turbo lag and they keeping the turboes spinning at such low rpm's and part throttles but its too much boost for the amount of load the engine is under.  I have started using the paddles to downshift at any point where I have found this to occur.

 

[ajpturbo]

Did you log desired tip? Post the log if u can

And see if the bypass valve pid is in the config. I dont usually look at the pid but i think the bypass valve is on/off so see if it pulses with the wastegate

This is strange but i would lean to a hole in the tune rather than hardware..the stock tune can have holes also

Torque converter speed ratio pid will help you see if its going in and out of lock...but i. 6th gear it locks fairly early for fuel economy...around 1400 rpm i think but need to look

What rpm and load is it

 

[John Miller]

Okay, I don't have my laptop with me, so I'll look at the logs tonight and see if those PIDs are there


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[ajpturbo]

What is the boost/load rpm ?

 

[John Miller]

Not sure what you are asking.

Btw, retread your first post - I can tell you from memory that desired and actual throttle position are nearly identical.


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[ajpturbo]

Curious of the load when its happening?...and desired tip is turbo inlet pressure

 

[John Miller]

Gotcha - will look tonight.


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[ajpturbo]

Desired tip is basically desired boost....so if that is flat and tip is rising then its attempting to maintain boost but it doesnt have to be that abrubt...the wastegates should operate smoothly.....that seems like a hole in the tune..wastegate duty should be smooth and sweeping and cruise and while steady on the gas pedal

Also want to log desired intake cam timing and actual intake cam timing and see if the cam is rolling...shouldnt be but if you are at an rom where its transitioning that that can affect load which would show as pulsing...the cam should roll smoothly

 

[xkrexplorer]

AJP turbo,

I see you have downpipes like I do, and I am presuming you don't have the same issues with the partial throttle mild surging.  If that is the case, can I ask you, are you running a custom sct tune and who did the tuning or a canned tune, since I would like to try the tune you are using and see if it makes a difference. Thanks.

 

[ajpturbo]

I havent noticed this issue but id like to see the exact operating conditions and see if i can replicate

I am running my own tune now....in the past i had an unleashed tune and didnt notice it either

The closest tune you could get to me now would be to contact matt at gearhead automotive performance....my tune is becoming vastly different lately though

 

[ZSHO]

AJP turbo,

I see you have downpipes like I do, and I am presuming you don't have the same issues with the partial throttle mild surging.  If that is the case, can I ask you, are you running a custom sct tune and who did the tuning or a canned tune, since I would like to try the tune you are using and see if it makes a difference. Thanks.

xkrexplorerer if you would be kind enough to setup a signature,thanks.  Z

 

[John Miller]

AJP turbo,

I see you have downpipes like I do, and I am presuming you don't have the same issues with the partial throttle mild surging.  If that is the case, can I ask you, are you running a custom sct tune and who did the tuning or a canned tune, since I would like to try the tune you are using and see if it makes a difference. Thanks.

I suspect the issue is very common, but not throughout. Perhaps strategy driven? Especially since everyone I have found complaining about it said that it was worse with a tune, presumably since the boost jumps are exacerbated.

I bet many probably have it and don't know it, since the conditions have to be so specific. If you drive entirely in the city, or have a heavy foot that forces a downshift at every hill, you my never notice it.

 

[xkrexplorer]

I agree with John Miller, its there.  If you drive the thing like you stole it, you won't notice.  If you are on a rough and non smooth rode or an older highway, you may think its just motion from the highway. For me, on the drive home from work, I have a very gradual incline on the highway.  Maybe rises 300 feet over three miles.  Cruising at 65 mph on this incline, my explorer will buck ever so slightly as long as gas pedal is depressed 1/4 or less.  Give it gas and accelerate or downshift and its gone. You can feel it in the wheel and slightly in seat.  Passengers may not notice it.  Radio off, and I can hear the bypass valve dumping if I concentrate.  So I vented my front bypass valve to air and went for a ride.  Sure enough, dumps boost, cycling every second or so as long as I am under those conditions. Worse when temp is colder for me.  Does not occur in open loop (wot or when engine warming to operating temp).  I can also replicate it pretty much on demand on shorter country rode hills if I give 1/4 or less pedal and don't let the car downshift.  I am guessing in the city, no issue really or if you have a heavy foot, you won't notice.

 

[John Miller]

Agree 100% - except I never noticed it being worse in colder weather. The rough roads thing is the reason my dealer couldn't replicate -- all the highways around them are rough as hell.

I thought the steering wheel feel was my imagination - glad to see I'm not crazy

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[John Miller]

TIP Boost is orange, Tip Boost desired is bold green.

Load is the thinner lined green. 

 

[John Miller]

Check this out.  It is a small piece of a different run under similar conditions.  It shows boost (orange) and boost desired (green) in 6th gear, then a downshift to 5th (blue).  Look how much it smooths out with the downshift.



Again, this is a different run than the rest of the data logs I posted both before and after this post, so don't try to match it up against the other logs.  This run was specifically to log the 6th to 5th results.

 

[John Miller]

AJP, I did find "Intake Cam Position Desired."  Not sure if this is what you were looking for.