Low RPM Knock Retard

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zaclaw
Posts: 35
Joined: June 9th, 2017, 9:29 pm
Location: South Carolina, United States

Low RPM Knock Retard

Post by zaclaw »

Recently experiencing an intermittent lack of power in the 1500-2500 RPM band, mostly around 2000 RPM, especially while cruising in 5th gear. No CEL. Just in case, I replaced the (original?) air fuel ratio sensor. No change. High KR >8 reported in logs using a known stable and modest tune that only dissipates after letting completely off accelerator. There is not much else that looks alarming to me in the log. This seems to be happening during every drive cycle, sometimes the KR isn't quite as high. No problems observed at higher loads/higher RPMs. I've got fairly new NGK Ruthenium HX spark plugs (factory heat range) gapped to about 0.029. I checked them and they look okay. I have a knock-off Turbosmart Konnect Dual Port BOV/BPV that is set up 50/50 during this log. All other mods in sig. The spring is tightened all the way. I had tried full recirc and it didn't seem to make a difference in driveability. Here are 2 logs from 2 different days and the current tune. I cannot remember if the first log was taken with this map but the second one was.

Logs:
https://www.dropbox.com/s/944fcg7gwni7b ... 3.csv?dl=0
https://www.dropbox.com/s/tfg0hjsqoqmpu ... 0.csv?dl=0

Tune:
https://www.dropbox.com/s/us9u0tijiy2hk ... vtune?dl=0
2007 Mazda CX-7 AWD Grand Touring - Electric Blue Mica
CS turbo, CS 3.5bar MAP, CorkSport Stage II SRI w/ TIP, dual port BOV/BPV, 3" TBE w/ Magnaflow muffler, KYB Excel-G shocks, deleted catalytic converters
Disabled EGR, 2nd O2, VTCS

mituc
VersaTuner guru
Posts: 910
Joined: December 17th, 2011, 2:47 pm
Location: Iasi/Romania

Re: Low RPM Knock Retard

Post by mituc »

What intake are you actually using? Is it the one from the signature?
Also, can you check the oil and make sure it is not full of gas? You are getting AFRs of 10 even when the commanded is 14.7. And you're getting AFRs of 10.something as well as 15.x when the commanded is 14.7 at the same MAF voltage. Something is definitely wrong there. that's the reason for your loss of power, that small knock at partial throttle/low load is not causing this even though I've never seen this occur at so low RPM.
2008 Cosmic Blue Mazda 3MPS
Build engine + WMI + GTX3071, ~476WHP @31-32PSI
2008 Icy Blue Mazda CX7
Stock engine and exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 320-ish BHP

zaclaw
Posts: 35
Joined: June 9th, 2017, 9:29 pm
Location: South Carolina, United States

Re: Low RPM Knock Retard

Post by zaclaw »

mituc wrote:
May 18th, 2020, 10:15 am
What intake are you actually using? Is it the one from the signature?
Also, can you check the oil and make sure it is not full of gas? You are getting AFRs of 10 even when the commanded is 14.7. And you're getting AFRs of 10.something as well as 15.x when the commanded is 14.7 at the same MAF voltage. Something is definitely wrong there. that's the reason for your loss of power, that small knock at partial throttle/low load is not causing this even though I've never seen this occur at so low RPM.
Yeah I'm using the CorkSport Stage II SRI w/ TIP. I checked the oil and it does smell like gasoline.
2007 Mazda CX-7 AWD Grand Touring - Electric Blue Mica
CS turbo, CS 3.5bar MAP, CorkSport Stage II SRI w/ TIP, dual port BOV/BPV, 3" TBE w/ Magnaflow muffler, KYB Excel-G shocks, deleted catalytic converters
Disabled EGR, 2nd O2, VTCS

mituc
VersaTuner guru
Posts: 910
Joined: December 17th, 2011, 2:47 pm
Location: Iasi/Romania

Re: Low RPM Knock Retard

Post by mituc »

zaclaw wrote:
May 18th, 2020, 11:09 am
Yeah I'm using the CorkSport Stage II SRI w/ TIP. I checked the oil and it does smell like gasoline.
It is expected to smell like gasoline, but is it way above the max level?
Basically what I'm trying to get you figure out is if you have a fuel pump issue (pinched or failed o-rings may cause gas to be pushed into the oil) or if you have some sort of weird exhaust leak or or a stuck open injector whatever can throw your fuel trims that far.
2008 Cosmic Blue Mazda 3MPS
Build engine + WMI + GTX3071, ~476WHP @31-32PSI
2008 Icy Blue Mazda CX7
Stock engine and exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 320-ish BHP

zaclaw
Posts: 35
Joined: June 9th, 2017, 9:29 pm
Location: South Carolina, United States

Re: Low RPM Knock Retard

Post by zaclaw »

Ok I’ll check the level after it has sat for a bit. As far as I know the HPFP seals are original with the car, 216k miles, so seems likely. Wouldn’t a stuck injector cause a CEL or misfire? The idle AFR seems stable. For an exhaust leak to cause excessive richness, the leak would have to be before the primary sensor, right? I’ve heard of a faulty purge valve causing rich issues but should also set a code. It does seem very strange that the AFRs go so lean too but maybe that’s a result of the PCM compensation for rich condition.

The KR seems to be a different issue. The last log I posted with this tune had KR no greater than 1. Power loss is the most severe when the KR occurs, usually 2+ degrees, up to about 8 degrees, around 2000 RPM.


Sent from my iPhone using Tapatalk
2007 Mazda CX-7 AWD Grand Touring - Electric Blue Mica
CS turbo, CS 3.5bar MAP, CorkSport Stage II SRI w/ TIP, dual port BOV/BPV, 3" TBE w/ Magnaflow muffler, KYB Excel-G shocks, deleted catalytic converters
Disabled EGR, 2nd O2, VTCS

zaclaw
Posts: 35
Joined: June 9th, 2017, 9:29 pm
Location: South Carolina, United States

Re: Low RPM Knock Retard

Post by zaclaw »

The problem appears to be caused by a sticky purge valve. I unplugged it. Then I disconnected the canister-side hose to make sure there was no vacuum from the nipple with the engine running to make sure the valve wasn’t leaking internally and that it wasn’t stuck open. No vacuum felt at idle. Test drove and no more hesitation. I haven’t checked the PIDs or logged yet but I’m fairly certain this was the culprit. It holds vacuum and circuitry seems okay with no CEL so I’m going to attempt to clean it out this weekend. The conditions under which the problem was occurring definitely make sense, especially with stable AFR at idle when the valve is closed.
2007 Mazda CX-7 AWD Grand Touring - Electric Blue Mica
CS turbo, CS 3.5bar MAP, CorkSport Stage II SRI w/ TIP, dual port BOV/BPV, 3" TBE w/ Magnaflow muffler, KYB Excel-G shocks, deleted catalytic converters
Disabled EGR, 2nd O2, VTCS

zaclaw
Posts: 35
Joined: June 9th, 2017, 9:29 pm
Location: South Carolina, United States

Re: Low RPM Knock Retard

Post by zaclaw »

It seems that unplugging the purge valve only made the rich AFRs slightly better. AFRs are still oscillating, mostly on the rich side. Hitting down to 9.4 when minimum allowed is 10.29. Oil does smell of gasoline but the level is on point. Still no CEL. All other readings appear normal. What should I check?


Sent from my iPhone using Tapatalk
2007 Mazda CX-7 AWD Grand Touring - Electric Blue Mica
CS turbo, CS 3.5bar MAP, CorkSport Stage II SRI w/ TIP, dual port BOV/BPV, 3" TBE w/ Magnaflow muffler, KYB Excel-G shocks, deleted catalytic converters
Disabled EGR, 2nd O2, VTCS

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