overspeeding/overboosting turbo

Discussion of tuning specific to CX-7 vehicles
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sirocco44
Posts: 4
Joined: September 13th, 2020, 1:04 pm

overspeeding/overboosting turbo

Post by sirocco44 »

2007 Cx-7 FWD
No mods
Stock except for gutted cat (cat was melted after a faulty o2 sensor and removed)
Currently on stock tune.

Hello all, My cx-7 is over boosting. Looking to build a custom tune to fix my issue if that's possible. The psi hits 21.5 and the ecu triggers a fuel cut. I am assuming this is because of the fuel cut for the manifold is around 32psi.
So i have two questions
Would the gutted cat be responsible for an overboost condition on the stock tune considering there's more flow in the downpipe?
and if that is the issue..
Rather than change the load targets, what are the proper values to adjust to account for the extra exhaust flow?

mituc
VersaTuner guru
Posts: 1020
Joined: December 17th, 2011, 2:47 pm
Location: Iasi/Romania

Re: overspeeding/overboosting turbo

Post by mituc »

No, the removed cat would not cause overboost. It would help/cause the turbo to spool faster and produce boost suner, but not fast enough for the boost control system not to react properly.
You should check for issue in the boost control system (disconnected lines from the EBCS, stuck wastegate arm, broken wastegate actuator membrane, and so on).
Also, take and post a log which we can review.
2008 Cosmic Blue Mazda 3MPS
Built 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

sirocco44
Posts: 4
Joined: September 13th, 2020, 1:04 pm

Re: overspeeding/overboosting turbo

Post by sirocco44 »

mituc wrote:
October 20th, 2020, 7:36 am
No, the removed cat would not cause overboost. It would help/cause the turbo to spool faster and produce boost suner, but not fast enough for the boost control system not to react properly.
You should check for issue in the boost control system (disconnected lines from the EBCS, stuck wastegate arm, broken wastegate actuator membrane, and so on).
Also, take and post a log which we can review.
What parameters should I log to get the best diagnosis?

mituc
VersaTuner guru
Posts: 1020
Joined: December 17th, 2011, 2:47 pm
Location: Iasi/Romania

Re: overspeeding/overboosting turbo

Post by mituc »

You will have to log at least RPM, Load, MAP, MAF g/s, throttle position, WGDC duty, fiel rail pressure, injector duty cycle and actual AFR to see the overboosting issue and now it's mitigated, but no parameter will tell you what is causing it.
2008 Cosmic Blue Mazda 3MPS
Built 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

sirocco44
Posts: 4
Joined: September 13th, 2020, 1:04 pm

Re: overspeeding/overboosting turbo

Post by sirocco44 »

mituc wrote:
November 8th, 2020, 6:21 pm
You will have to log at least RPM, Load, MAP, MAF g/s, throttle position, WGDC duty, fiel rail pressure, injector duty cycle and actual AFR to see the overboosting issue and now it's mitigated, but no parameter will tell you what is causing it.
Thanks for all the insight. I captured a log that i think would illustrate the issue I'm having. I think at one point my boost pressure hits 22psi and initiates an abrupt fuel cut. Almost like a hiccup. Here is the csv if you (or anyone interested) has the time to look at it and give me some pointers.
Data log - 2020-11-21 20.43.04.csv
(331.77 KiB) Downloaded 13 times

mituc
VersaTuner guru
Posts: 1020
Joined: December 17th, 2011, 2:47 pm
Location: Iasi/Romania

Re: overspeeding/overboosting turbo

Post by mituc »

When you capture an event in a log, please log just that event. If you capture it several times make several logs. These are events that last a few lines, while looking for them in 5000 lines is not really easy.

So from how this looks it seems that there is no boost control. WGDC is 0 and the load/boost keeps creeping up despite de moderate throttle input. So you need to check the EBCS, the lines going to it, the wastegate actuator, wastegate actuator arm, the hose in between the secondary WG actuator nipple and turbo, everything in that area.

Also, the relative throttle position values seem a bit low for the load we see in the logs. Was there any work done on the throttle body?
2008 Cosmic Blue Mazda 3MPS
Built 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

sirocco44
Posts: 4
Joined: September 13th, 2020, 1:04 pm

Re: overspeeding/overboosting turbo

Post by sirocco44 »

mituc wrote:
November 21st, 2020, 9:04 pm
When you capture an event in a log, please log just that event. If you capture it several times make several logs. These are events that last a few lines, while looking for them in 5000 lines is not really easy.

So from how this looks it seems that there is no boost control. WGDC is 0 and the load/boost keeps creeping up despite de moderate throttle input. So you need to check the EBCS, the lines going to it, the wastegate actuator, wastegate actuator arm, the hose in between the secondary WG actuator nipple and turbo, everything in that area.

Also, the relative throttle position values seem a bit low for the load we see in the logs. Was there any work done on the throttle body?
My apologies. I'll make sure to log it like that from now on. Thanks for the tip.

As for any modifications to the throttle body, there's none as far as I know. The person I got the car from was not aware that this car shared an engine with the Mazdaspeed platform so I assume he didn't mess with anything. What could be done that could affect that value? Is it possible the throttle body is going out?

With the EBCS, what could I look at to test its function or to make sure it's doing it's job? And the secondary actuator is the one on the turbo housing correct? Or the one leading to the inlet pipe?

Again thanks for all the help in figuring this out.

mituc
VersaTuner guru
Posts: 1020
Joined: December 17th, 2011, 2:47 pm
Location: Iasi/Romania

Re: overspeeding/overboosting turbo

Post by mituc »

To be honest I've never seen any of the 2.3DISI-T throttle bodies going bad. However I've seen people ending up replacing them because of hectic behavior due to improper service. the throttle calibrates only when you connect the battery on the car. If someone pulls the TB out for servicing and puts it back in without disconnecting the negative terminal of the battery, at the next start the car can behave quite weird. It can also be your case (incorrectly reported throttle position) so if you didn't already try disconnecting the battery for a minute or two and connect it back, see if anything changes.

As for what I see in the logs is this: the ECU is trying to mitigate the increase of boost by reducing the EBCS duty cycle. And it reduces it down to 0 and boost is still maintained and actually slowly increasing which led me to the list of issues I already told you about in more or less detail:
- EBCS (stuck closed, not letting air go through and command the WG);
- EBCS lines (cracked or hooked up backwards);
- wastegate arm (jammed);
- disconnected wastegate flap inside the turbo (that would be bad);
- wastegate actuator (broken mebrane, broken spring);
- throttle body (jammed, damaged position sensor, or just improperly serviced/reconnected).

I know it's not the MAF because the AFRs are on par with the load and boost levels from a factory-ish tune. I know it's not the MAP because the load values are on par with the manifold pressure values.
2008 Cosmic Blue Mazda 3MPS
Built 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

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