Low RPM Knock Retard

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mituc
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Re: Low RPM Knock Retard

Post by mituc »

zaclaw wrote: November 9th, 2020, 3:03 am With LTFTs reset, using stock CX-7 partition breakpoints, the STFTs are around 10-12% at idle and they increase from there, maxing out up to 25% even under light acceleration.
Well, that is one reason why we use different fuel trims partitions, because the stock calibration assumes that a correction will be the same in both vacuum and boost (see the last partition). Which is totally wrong.
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
zaclaw
Posts: 42
Joined: June 9th, 2017, 9:29 pm
Location: South Carolina, United States

Re: Low RPM Knock Retard

Post by zaclaw »

mituc wrote:
zaclaw wrote: November 9th, 2020, 3:03 am With LTFTs reset, using stock CX-7 partition breakpoints, the STFTs are around 10-12% at idle and they increase from there, maxing out up to 25% even under light acceleration.
Well, that is one reason why we use different fuel trims partitions, because the stock calibration assumes that a correction will be the same in both vacuum and boost (see the last partition). Which is totally wrong.
What are the recommended partitions then? STFTs are still crazy even without learned LTFTs.


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2007 Mazda CX-7 AWD Grand Touring - Electric Blue Mica
CST4 turbo, CS 3.5bar MAP, CS Stage II SRI w/ TIP, dual port BOV/BPV, 3 port EBCS, 3" TBE w/ Magnaflow muffler, KYB Excel-G shocks, deleted catalytic converters
Disabled EGR, 2nd O2, VTCS
mituc
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Joined: December 17th, 2011, 2:47 pm
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Re: Low RPM Knock Retard

Post by mituc »

At this point it's a lot easier and practical to simply pressure test all the tubing, including exhaust, rather than trying to spend hours to make a tune around the current defect.
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
zaclaw
Posts: 42
Joined: June 9th, 2017, 9:29 pm
Location: South Carolina, United States

Re: Low RPM Knock Retard

Post by zaclaw »

Found a significant leak at the turbo going to the manifold. Didn’t see the leak last time I smoke tested exhaust. Ordered new hardware kit from Corksport.
2007 Mazda CX-7 AWD Grand Touring - Electric Blue Mica
CST4 turbo, CS 3.5bar MAP, CS Stage II SRI w/ TIP, dual port BOV/BPV, 3 port EBCS, 3" TBE w/ Magnaflow muffler, KYB Excel-G shocks, deleted catalytic converters
Disabled EGR, 2nd O2, VTCS
mituc
VersaTuner guru
Posts: 1324
Joined: December 17th, 2011, 2:47 pm
Location: Iasi/Romania

Re: Low RPM Knock Retard

Post by mituc »

You can get them from a lot of places, no need to wait for these from CS... I'd go with the OEM ones to be honest if the ones currently there cannot be tightened properly.
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
zaclaw
Posts: 42
Joined: June 9th, 2017, 9:29 pm
Location: South Carolina, United States

Re: Low RPM Knock Retard

Post by zaclaw »

Well, replaced the turbo gaskets and that fixed the exhaust leak. Engine still runs terribly though. It misfires almost all the time now. Before it was only really bad when engine was cold. Severe hesitation/lack of power at low RPMs, smooths out above 3k. Backfires a lot and engine vibrates. Fuel economy is trash.

Misfire moved to cylinder 1, seemingly after replacing cylinder 2 injector. Before it would alternate between cylinders 1 and 4. SP63 said my core’s inner filter had collapsed, preventing testing and refurbishing, and possibly clogging the nozzle. I suppose the next thing to do is replace the other 3 injectors but it’s a pain and ETA is 1-2 weeks. Cannot test fuel injectors with scan tool by commanding them to turn off when engine is running. It worked with the same scan tool on a gen2 MS3 the other day. I also tried to do it with FORScan, didn’t work. So without being able to test it, I’m stuck waiting for more parts to take another shot in the dark.
2007 Mazda CX-7 AWD Grand Touring - Electric Blue Mica
CST4 turbo, CS 3.5bar MAP, CS Stage II SRI w/ TIP, dual port BOV/BPV, 3 port EBCS, 3" TBE w/ Magnaflow muffler, KYB Excel-G shocks, deleted catalytic converters
Disabled EGR, 2nd O2, VTCS
mituc
VersaTuner guru
Posts: 1324
Joined: December 17th, 2011, 2:47 pm
Location: Iasi/Romania

Re: Low RPM Knock Retard

Post by mituc »

Ideally you should send all the injectors for servicing, and when you put them back in replace all the o-rings between the injectors and fuel rail as well as the injector seals if they are not reusable (the brass ones can be reused just fine as long as you do not damage them when you remove the injectors from the head or the seals themselves from the injectors).
Cause for random misfires was also the coil pack wiring. So since you take everything apart in that area just take a look at the harness and inspect it visually.
Also try to move the coils between cylinders and see if the misfire code migrates with the coil. The coils from these engines do not fail often but when they do the behavior is quite misleading.
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
zaclaw
Posts: 42
Joined: June 9th, 2017, 9:29 pm
Location: South Carolina, United States

Re: Low RPM Knock Retard

Post by zaclaw »

I’ve moved coils around, no change. Replaced plugs. I’ll inspect the wiring again.
2007 Mazda CX-7 AWD Grand Touring - Electric Blue Mica
CST4 turbo, CS 3.5bar MAP, CS Stage II SRI w/ TIP, dual port BOV/BPV, 3 port EBCS, 3" TBE w/ Magnaflow muffler, KYB Excel-G shocks, deleted catalytic converters
Disabled EGR, 2nd O2, VTCS
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