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

[AJP turbo]

What is the rpm in 6th?...im sure you didnt log this but it would be nice to see torque converter speed ratio....i bet the converter is going in and out of lock....thats easily adjusted and makes sense that when u downshift you get into a part of the converter map where you are staying in or out of complete lock instead of maybe cycling between the two quickly...maybe...

And you logged intake cam desired...which is good but then u want to view intake cam actual to see if its actually doing what is being commanded

[John Miller]

Went out today and got a short run on smaller hill, using the new PIDs.

Boost vs wastegate.  Obviously, the spikes are when I'm feeling the flutter:



Boost versus torque converter slip and speed ratio.  I'm new to this, but I don't see correlation:



And the Cam stuff up against the boost dip.  Neither side matches desired (light blue line) but it is consistent from side to side:

[AJP turbo]

That first pic is really good....the bypass valve is the blow off valve not the wastegate

The bypass valve is off/on..a value of 1 is on and 0 is off....see when it comes on boost dips as you said...there are scalars for bypass valve actuation i think...your strategy may have a value close to the load you are at while cruising maybe causing it to occilate..im not sure at this point though...post you log...maybe see what the load is and later tonight ,like really late, i can poke around and see what the bypass scalars show...mine are all stock and i would suspect yours are as well...maybe the explorers have something different

[xkrexplorer]

John Miller,

That is great work.  That log of the bypass valve opening an closing is exactly what my explorer sport does.  You and I have the exact same issue.  I do think it may be present in all these vehicles but some are aware more than others, probably because of our driving habits and the roads we drive on bring it out more.

[John Miller]

So, got the tune in from Unleashed. He made it downshift  to 5th earlier. Seems much, much better, but let me play for a week and report back.  I want to make sure it is downshifting soon enough as well as not hanging in 5th so long that gas mileage begins to suffer substantially. He already sent me one revision, and it might be good enough.

Also, we're not positive that the cruise control is following the same shifting tables. I use cruise a lot, so I need it to fix there also.

More to follow ....


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[John Miller]

The tune is impressive from a power standpoint. Anyone else have some serious wheel hop during the 1-2 shift at WOT? I'm still on the stock, non-PP, Michelins ...

Should have seen the look on the wife's face when it banged second gear and wheel hopped. She's all "What the hell was that?!?!"


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[AJP turbo]

The sound was most likely your tranny binding and not accepting the gear change......i believe the percieved wheel hop is a mis diagnosis ....ask your tuner to lower the shift pressure

[FoMoCoSHO]

He already sent me one revision, and it might be good enough.

Also, we're not positive that the cruise control is following the same shifting tables. I use cruise a lot, so I need it to fix there also.


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I'm not sure its a problem with cruise. I was watching mine yesterday and the car wasn't in boost it was advancing timing when accelerating.

[AJP turbo]

Fomo was that odd to you?....typically if load is constant the spark curve should advance as rpms increase...more spark can be tolerated because of faster piston speed

[John Miller]

The sound was most likely your tranny binding and not accepting the gear change......i believe the percieved wheel hop is a mis diagnosis ....ask your tuner to lower the shift pressure

He put the torque management back to stock and it still does it.

[FoMoCoSHO]

Fomo was that odd to you?....typically if load is constant the spark curve should advance as rpms increase...more spark can be tolerated because of faster piston speed

I'm not sure what you mean by odd, the car felt normal but as the car was transitioning through hills etc, it was well into vacuum and timing was advanced, sometimes +5 (on the KR gauge)to maintain speed. I suspect it is like that for fuel economy.

I haven't driven that route for a while so I have no idea if anything has changed. I doubt it cause I don't think Torrie messes with non-wot unless there's a specific issue to address.

[AJP turbo]

The sound was most likely your tranny binding and not accepting the gear change......i believe the percieved wheel hop is a mis diagnosis ....ask your tuner to lower the shift pressure

He put the torque management back to stock and it still does it.

Torque management is different than shift pressures and slip times for shifting...you can heavily add torque reductions for power and also make the shifts happen faster or slower

[AJP turbo]

Fomo was that odd to you?....typically if load is constant the spark curve should advance as rpms increase...more spark can be tolerated because of faster piston speed

I'm not sure what you mean by odd, the car felt normal but as the car was transitioning through hills etc, it was well into vacuum and timing was advanced, sometimes +5 (on the KR gauge)to maintain speed. I suspect it is like that for fuel economy.

I haven't driven that route for a while so I have no idea if anything has changed. I doubt it cause I don't think Torrie messes with non-wot unless there's a specific issue to address.

I mean you made it sound like it was odd to see spark advancing while engine speed was increasing.....the engine can handle a ton of spark in vac and the spark tables in the stock tune is conservative i think so the advance from the knock sensor makes sense to me

[John Miller]

Okay, the next revision fixed the "wheel hop" issue.  Now, it "bangs" into 2nd from 1st at WOT, as you would expect it to, but no violent shaking feeling.  And, a cursory internet read reveals that the WOT shifts are usually hard after a tune until the car adapts.  I take that with a grain of salt, but it is satisfactory now anyways.

As for the cruise thing, I need to drive it for a week or so and feel it out.  It is unclear to both me and Torrie whether the altered shift points (that mitigate the flutter) apply when the car is operating in cruise control.  Torrie reports there are a total of 10 shift tables, so it could be that the car operates under different tables, presumably still in stock configuration, when the cruise control is engaged.

I will report back for the greater good.

[AJP turbo]

Idont think cruise control uses a different shift table...the shift tables are for the different drive modes...like 4x4 , tow, sand, snow, warmup...they are simply output speed shaft speed bs pedal position