New to tuning, chasing a stutter/hesitation

Discussion of tuning specific to MAZDASPEED6/MAZDASPEED Atenza/Mazda 6 MPS vehicles
BrownDog185
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Joined: September 28th, 2020, 5:08 pm

Re: New to tuning, chasing a stutter/hesitation

Post by BrownDog185 »

ok so ive managed to log the problem with your preset

on the second pull in this log approaching the 3000rpm mark you can see the hesitation in the RPM line
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Ugnius @ VersaTune
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Re: New to tuning, chasing a stutter/hesitation

Post by Ugnius @ VersaTune »

mituc wrote: September 30th, 2020, 9:17 pm Convert to .csv before posting the logs on the forum. Those who can help you don't necessarily have the MS6/6MPS specific version of versatuner and will not be able to import these logs.
BTW all editions of VersaTuner (including free) can now open logs from any supported car.
mituc
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Re: New to tuning, chasing a stutter/hesitation

Post by mituc »

Ugnius @ VersaTune wrote: October 1st, 2020, 10:28 pm BTW all editions of VersaTuner (including free) can now open logs from any supported car.
Awesome news! I did not try this lately and I probably missed this info in the release notes!
2008 Cosmic Blue Mazda 3MPS
Built engine + WMI + GTX3071 gen2, ~509BHP @34PSI
2008 Icy Blue Mazda CX7
Stock engine and exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 330-ish BHP
mituc
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Joined: December 17th, 2011, 2:47 pm
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Re: New to tuning, chasing a stutter/hesitation

Post by mituc »

BrownDog185 wrote: October 1st, 2020, 3:57 pm ok so ive managed to log the problem with your preset

on the second pull in this log approaching the 3000rpm mark you can see the hesitation in the RPM line
Yeah. So this happens because you are reaching the throttle reduction boost limit (31PSI MAP). Common causes for this:
- disconnected or cracked EBCS-to-wastegate actuator hose;
- disconnected or cracked EBCS-to-turbo inlet pipe hose;
- corroded or blocked wastegate actuator arm;
- cracked wastegate actuator membrane.

If it's not one of the most common causes which are the first two, the last two can be diagnosed by hooking up an air compressor to the wastegate nipple, pressurize to 0.8-1BAR and see if the arm moves. At about 0.8BAR/12PSI the wastegate should be fully open which from outside can be seen as full travel of the wastegate actuator arm.
2008 Cosmic Blue Mazda 3MPS
Built engine + WMI + GTX3071 gen2, ~509BHP @34PSI
2008 Icy Blue Mazda CX7
Stock engine and exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 330-ish BHP
BrownDog185
Posts: 10
Joined: September 28th, 2020, 5:08 pm

Re: New to tuning, chasing a stutter/hesitation

Post by BrownDog185 »

ok awesome, this would make sense as why the high load maps are worse and why my previous flash tune works without issue

the tuner that did the flash said he had to reduce boost to 15psi to keep it happy, he assumed it was due to the owner using 91 fuel

ill sus out the lines tomorrow and post an update, cheers
BrownDog185
Posts: 10
Joined: September 28th, 2020, 5:08 pm

Re: New to tuning, chasing a stutter/hesitation

Post by BrownDog185 »

any ideas as to why there is a miss as the throttle is opened after coasting
mituc
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Re: New to tuning, chasing a stutter/hesitation

Post by mituc »

Throttle body may need cleaning. Also it may be related to sparkplugs wear or fueling. Log it!
2008 Cosmic Blue Mazda 3MPS
Built engine + WMI + GTX3071 gen2, ~509BHP @34PSI
2008 Icy Blue Mazda CX7
Stock engine and exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 330-ish BHP
BrownDog185
Posts: 10
Joined: September 28th, 2020, 5:08 pm

Re: New to tuning, chasing a stutter/hesitation

Post by BrownDog185 »

i actually managed to log it in the posted log
its not an instant miss but is shortly after the throttle is opened

log shows the desired AFR dips where the miss happens
BrownDog185
Posts: 10
Joined: September 28th, 2020, 5:08 pm

Re: New to tuning, chasing a stutter/hesitation

Post by BrownDog185 »

1
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mituc
VersaTuner guru
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Joined: December 17th, 2011, 2:47 pm
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Re: New to tuning, chasing a stutter/hesitation

Post by mituc »

I would rather look at some values than a picture. If you have the actual log please post that.
2008 Cosmic Blue Mazda 3MPS
Built engine + WMI + GTX3071 gen2, ~509BHP @34PSI
2008 Icy Blue Mazda CX7
Stock engine and exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 330-ish BHP
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