2011 speed 3 underboosting

Nick1150

Nick1150

Greenie N00B Member
Year/Make/Model: 2011 Mazdaspeed 3

Mileage: 106700

Location: Wheaton, MD

Concern: Underboosting after exhaust leak repair

DTC's: N/A

Modifications: forge bpv, aftermarket turbo inlet (just inlet, not intake), unknown muffler

ECU/Tuning Software: N/A, though I don't know if previous owner tuned the car (stock ECU)

Tuner: N/A

Is the concern intermittent? No

Can you duplicate the concern? Yes

Recent Repairs: over the year I replaced gasket between upper cat and turbo, new oem boost control solenoid from edge autosports, new aftermarket turbo inlet (couldn't afford OE), new OEM upper catalytic converter, rebuilt turbocharger from cwturbochargers (sent me a k04-881), new OE wastegate actuator.

Correction: not sure what to write here but summary of all diagnosis throughout the year: first was finding exhaust leak which was between the turbo and upper cat, pressure tested tmic, forge bpv, and tubes (plugged off at throttle body) and it all held from what I remember 14-15psi till the bpv opened, smoke tested intake and no leaks found (did plug off right before throttle body), inspected downpipe under the idea it is clogged restricting spool up to find previous owner had busted it up and it was in pieces in front of the secondary cat and found the cat mount was missing, checked vac lines at wastegate actuator and BCS to find the barbs the secure the vac lines broke off on the BCS and turbo inlet, and the original turbo had a fair amount of radial play but no axle play (still have it if needed to post photos).


Extra note, car to my knowledge isn't tuned and i don't have a AP. i do have a Bluetooth scanner and car scanner elm obd 2 app. Also I'm more of a diyer, not a car guy too. So some words and acronyms might be wrong, just let me know. Here to learn :)


so the journey continues, bit of a copy paste from my reddit account, tbh I didn't know about this forum till someone told me yesterday :sweatsmile:


Bought a 2011 speed 3 back on September 2021. Car was great but with an exhaust leak coming from between the downpipe and turbo. so it gets fixed but is now under boosting. Used to say 15 psi at 3k rpm wot on the gauge, but now says between 5-7psi at 3k rpm wot. It doesn't hit 15 until around 4500-5000 rpms.

Started going through diagnosis.

Pressure test tmic and rubber pipes, held pressure. Found the boost control solenoid and turbo inlet had broken vac barbs so I replaced it, OE BCS and aftermarket inlet as OE is too expensive (not intake, just inlet).

Still under boosting, so check the catalytic converter thinking it's possibly clogged restricting turbo spool up. Come to find out that it was busted and in pieces In front of the secondary cat. the previous owner did this. I bought an OEM cat and cleaned the secondary one. Still under boosting.

Eventually get a Bluetooth scantool to check everything. I find the boost gauge on the dash is reading accurately. Also my afr when trying to boost at 3k rpm drops to 10-9.5 afr which I think is pretty rich.

After that inspected the wastegate actuator and it seems to be working. Also did a smoke test instead of pressure test on intake; confirmed it's still ok.

cleaned up and relubed the bypass valve. it is a forge bpv. Also did a compression test and got these results
5/10/22
C1 155psi
C2 155psi
C3 157psi
C4 153psi

I gave up for about 7 months and recently bought a rebuilt turbo from cwturbochargers and just swapped it today alongside a new OE wastegate actuator just in case. It is still under boosting, but while attempting to boost at 3k rpm AFR is reading closer to 13, maybe related to having the ECU unplugged for a day? Also the climate control fan makes a weird sound now. I did burp the coolant with hot air on max so not sure if it just went bad or is related to turbo swap.

I can't figure this out. intake, tmic, wastegate and actuator, BCS, inlet, downpipe, turbo... Everything should be fine. what else am I missing? Why did it work fine with the exhaust leak, but now doesn't? Loved the car when I test drove it, still love it now, but it's just bringing me down. I feel like I've done everything to find the issue, but I still haven't found the problem.

https://photos.app.goo.gl/hgjah3pYJxVaRH5x5

Also a collection of photos/videos. The video of the "pull" was with the old turbo WOT once I hit 3k rpm, the honeycomb is the broken cat from before, oily turbo is old, and graph is a recent snippet from after I replaced the turbo yesterday. And most recent video is the weird fan issue after burping the coolant. Anything you need, photos just let me know, i just want to go back to the day I got it and have my full boost
 
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StreetSpeed6 said:
Just curious why you had the ecu unplugged? No codes?
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The ECU is the computer next to the battery right? I had to remove it for a lot of the work. Unless I'm mixing it up and it's the box under the passenger seat. Never actually checked under there or know if there's anything, just remember my '02 civic had something under there back then. If it's the battery box computer it's OEM. I never had any codes minus when there was the broken cat causing p0420.
 
Nick1150 said:
The ECU is the computer next to the battery right? I had to remove it for a lot of the work. Unless I'm mixing it up and it's the box under the passenger seat. Never actually checked under there or know if there's anything, just remember my '02 civic had something under there back then. If it's the battery box computer it's OEM. I never had any codes minus when there was the broken cat causing p0420.
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Ok yeah was the ecu then. I forget it is located there as I have a speed 6 which is in a different location under the driver's side dash. Have you double checked the vac lines are hooked up properly from your ebcs to the turbo? I know you mentioned working on that area a lot and a messed up/ wrong routed vac line could cause boost issues obviously. I feel like having an accessport would make this much easier to diagnose.
 
StreetSpeed6 said:
Ok yeah was the ecu then. I forget it is located there as I have a speed 6 which is in a different location under the driver's side dash. Have you double checked the vac lines are hooked up properly from your ebcs to the turbo? I know you mentioned working on that area a lot and a messed up/ wrong routed vac line could cause boost issues obviously. I feel like having an accessport would make this much easier to diagnose.
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I believe I have the vac lines on correctly, from wastegate to ebcs the vac line is connected closest to the connector, and the further is connected to the turbo inlet. I think this photo should help.
 

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U made it here from Reddit lol, welcome.
Id do what easter bunny said and unbolt the second cat and go for a drive and see what happens.
When you say its not boosting, like no boost at all or just not a lot of it?
 
Nick1150 said:
I believe I have the vac lines on correctly, from wastegate to ebcs the vac line is connected closest to the connector, and the further is connected to the turbo inlet. I think this photo should help.
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Looks good to me man :-) Seems odd but definitely could be the cat issue mentioned above.
 
Really interested in what ur problem is. Im also having the same issue in my speed 6 but i mostly hear its about the tune.
 
chris' speed 3 said:
U made it here from Reddit lol, welcome.
Id do what easter bunny said and unbolt the second cat and go for a drive and see what happens.
When you say its not boosting, like no boost at all or just not a lot of it?
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Not a lot of boost, generally around 5-7psi around 3k rpm at wot. I need to hit around 5k rpm wot till i hit 15psi which wasn't necessary when it had the exhaust leak. at first i thought it was a wastegate issue, but given theres a rebuilt turbo in and i still have the issue that doesn't seem to be the case. Going to try the exhaust thing Wednesday when I have off :)
 
Nick1150 said:
Not a lot of boost, generally around 5-7psi around 3k rpm at wot. I need to hit around 5k rpm wot till i hit 15psi which wasn't necessary when it had the exhaust leak. at first i thought it was a wastegate issue, but given theres a rebuilt turbo in and i still have the issue that doesn't seem to be the case. Going to try the exhaust thing Wednesday when I have off :)
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Where was the exhaust leak?
If it was making more boost when u had an exhaust leak but now that you fixed it its harder to make boost, somethings clogged up. I wouldn't try anything else besides disconnecting the second cat, because you changed the first one already. I bet you its clogged up and the turbos not getting enough airflow to make more boost.
 
chris' speed 3 said:
Where was the exhaust leak?
If it was making more boost when u had an exhaust leak but now that you fixed it its harder to make boost, somethings clogged up. I wouldn't try anything else besides disconnecting the second cat, because you changed the first one already. I bet you its clogged up and the turbos not getting enough airflow to make more boost.
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Hey so I just tried no second cat and i think that was the problem. Old me didn't do a good job cleaning (or maybe it just wasn't salvageable) and with it off it felt like how it's meant to be :) now I'm trying to figure out next steps. Really happy it's this; can still pass emissions without it. i had no cel lol

I am trying to find just a catless midpipe (? Not sure if that's the right name) but no one sells it as a single piece. Might go to my local exhaust shop and get something custom made if they can do that. I'll make an update after, but thank you again you and everyone for nudging me to double check :)

Jeffry said:
Really interested in what ur problem is. Im also having the same issue in my speed 6 but i mostly hear its about the tune.
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Given my test today i think it's a clogged secondary cat. Just popped it off and went for a drive and it felt great minus the noise (tbh really liked the sound, but I don't want to subject my neighbors to my 1am arrivals lol). I'll update the post if when I get a catless midpipe it works :)
 

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Usually people who just remove the second cat run a resonator there as it looks similar to a cat and help the exhaust sound good.
 
StreetSpeed6 said:
Usually people who just remove the second cat run a resonator there as it looks similar to a cat and help the exhaust sound good.
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I'd disagree, most folks I know of just run the test pipe, no resonator especially if you don't need to worry about passing visual inspection. Sounds just fine without a res, no different than running a long DP with highflow cat (still quieter than that with oem primary cat).

Even a full catless DP with stock cat back sounds good and isn't too loud imo
 
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