?? For seasoned tuners (re; hesitation)

VoodooJef

VoodooJef

My friends call me Captain Zen
Greenie N00B Member
Greenie Member
I`ll forego the qualifiers. We are adults here.

Self tuned w/ VT and the car runs really great, makes tons of power, and has so far been reliable as I could have asked since built motor. One odd thing it does, and I can`t recall when it started, is it seems to stutter or hesitate if I just mat it. Not a misfire type situation at all, rather it starts to accelerate, hesitates, then rips my face off like it`s supposed to. Almost feels like it`s caught in the CL/OL transition. Nothing particularly noteworthy in the logs. The tune isn`t specifically aggressive as far as timing goes. It seems to only do it at lower engine speeds (lower being 2500-3K)...if I floor it at 4K in 4th, for instance, it just hauls ass but if I`m in 2nd or 3rd and I`m scooting away from a stop sign it`ll do it.

I`ll dig into it once the weather warms up and eventually figure it out but anyone have any ideas to cut my troubleshooting time down?
 
This sounds exactly like a symptom I used to have. Do you have a check engine light involving cam/crank position correlation, or timing over or under retarded? My issue turned out to be an improperly timed intake cam, just a few degrees off. It ran great up top, but if I entered boost at 3000 rpm, it would bog and pull ignition timing back until 3700ish and then pull hard. Retimed just the cams, and all was good. Maybe timing slipped a touch? I'm just going off what I've personally experienced. Those friction washers are kind of scary to think about.
 
VoodooJef said:
I`ll forego the qualifiers. We are adults here.

Self tuned w/ VT and the car runs really great, makes tons of power, and has so far been reliable as I could have asked since built motor. One odd thing it does, and I can`t recall when it started, is it seems to stutter or hesitate if I just mat it. Not a misfire type situation at all, rather it starts to accelerate, hesitates, then rips my face off like it`s supposed to. Almost feels like it`s caught in the CL/OL transition. Nothing particularly noteworthy in the logs. The tune isn`t specifically aggressive as far as timing goes. It seems to only do it at lower engine speeds (lower being 2500-3K)...if I floor it at 4K in 4th, for instance, it just hauls ass but if I`m in 2nd or 3rd and I`m scooting away from a stop sign it`ll do it.

I`ll dig into it once the weather warms up and eventually figure it out but anyone have any ideas to cut my troubleshooting time down?
Click to expand...

More details are needed. "Nothing noteworthy in logs" - The type of activity you are referring to would surely be visible in logs. You should log the behavior with the following parameters and report back:

APP
Calculated Load
IAT
BAT
Vehicle speed
MAF Volts
Boost pressure
Throttle position
Actual AFR
Engine RPM
HPFP Actual pressure
IDC
WGDC
KR
Intake valve advance
Spark advance

Please also post the following details:
- Year and model of car
- Disposition of any SWAS defeat measures in place
- Air bypass valve make/model
- Turbo make/model and compressor housing used if it's a Garrett or precision unit

This is as likely to be a hardware problem as a software problem.
 
no CEL at all, all good there. Not saying it couldn`t be, just no evidence.

Also, it very well may be SWAS influenced. It seems to only do it if I have SWAS enabled (though not enough digging at this point to see a true consistency), and the car has shown previously to be very sensitive to swas input.
 
My car is doing the same thing thing. I am thinking it is in my gear 1&2 load tables. It behaves just like SWAS, but I was under the impression VT disabled those characteristics if you checked the box. Almost feels like the car is hitting high load and the ECU is doing everything it can to reduce it.


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I can say from true tested experience that even VT doesn`t completely disable SWAS. Steve has gone on record saying they (as well as everyone else tuning the platform) didn`t want the responsibility of disabling a factory safety feature. Once I hit about 400ft/lbs swas was a constant nuisance, and with it disabled in VT it came back around 425ish ft/lbs. I do have a switch wired in for it but it`s blatant when I forget to turn it off if I`m getting on it hard.
 
Damnit. I can understand as to why VT would be hesitant. I guess I will be making a cool “Go Baby Go” switch. Thank you for the good info @VoodooJef hope this fixes my issue.

Regarding your issue, have you been able to confirm that SWAS was the cause in your case?


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Littleloogy said:
Damnit. I can understand as to why VT would be hesitant. I guess I will be making a cool “Go Baby Go” switch. Thank you for the good info @VoodooJef hope this fixes my issue.

Regarding your issue, have you been able to confirm that SWAS was the cause in your case?


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Click to expand...
No, I haven`t gotten to A/B for these symptoms yet. I can tell you definitively that swas interferes and what to look for, just haven`t gotten to log these particular symptoms yet. I am 100% sure that at least in my case it`s not a load cap thing. Maybe I`ll take the long way to work today and see if I can catch it in a log.
 
70 degrees out today and no hesitating. I`m guessing there is a load table that`s set close to its headroom limit being affected by the cold weather.
 
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