Boost/Fuel Cut & Overboost Code

Discussion of tuning specific to MAZDASPEED3/MAZDASPEED Axela/Mazda 3 MPS vehicles
Post Reply
YenR33T
Posts: 1
Joined: January 2nd, 2023, 5:31 am

Boost/Fuel Cut & Overboost Code

Post by YenR33T »

Hello everyone.

I'm new to these forums so hopefully posting in the correct place. I've had an overboost and fuel/boost cut issue for the last while.

I am consistently getting fuel/boost cut with a P0234 overboost code. Every single time I go WOT, high in the rev range it will hit a wall. It feels jerky and not smooth either. Normal driving seems fine, it isn't until WOT that it breaks up. I have noticed that the "power" doesn't increase gradually with the throttle, it's like once I press the pedal around 70% It all comes at once and I can hear the turbo a lot louder.

I have rechecked all hose clamps multiple times and they are all definitely tight.

I'm currently running the OTS Versatune High Load Map, and the overboost seems to have started after that even before upgrading the intake. I'm really hoping that this issue is tune related, and a pro tune could fix this. I'm also wondering if the MAF housing is slightly larger than stock and it's messing with readings? Bearing in mind the weather is cold here too, was around 2°c during these logs.


Only mods I have currently is the Corksport Stage 2 TIP + Intake. I have triple checked all hose clamps.

Thanks in advance!
Attachments
10m Normal Drive w 2min idle.csv
Normal driving with 2 min idle at end
(356.6 KiB) Downloaded 50 times
4th Gear Wot Fuel boost cut - YH09 NYB.csv
WOT Log
(8.47 KiB) Downloaded 67 times
Dolfius
Posts: 64
Joined: May 31st, 2017, 2:54 am

Re: Boost/Fuel Cut & Overboost Code

Post by Dolfius »

It could be an over load condition. Please share the map here if you're comfortable to do so.

Alternatively you're welcome to mail it to me to have a look

[email protected]
mituc
VersaTuner guru
Posts: 1324
Joined: December 17th, 2011, 2:47 pm
Location: Iasi/Romania

Re: Boost/Fuel Cut & Overboost Code

Post by mituc »

YenR33T wrote: January 2nd, 2023, 5:48 am I am consistently getting fuel/boost cut with a P0234 overboost code.
Hey!

I remember seeing these logs on FAILbook but I don't remember you mentioning the overboost code. Also the normal driving log is extremely useful.
So to sum it up now that we have more insight: it looks like you have a vacuum leak, that would be between the MAF sensor and the turbo somewhere. The fuel trims in your normal driving log are high positive (sometimes go quite well above 10), meaning that the engine is getting sometimes more than 10% unmeasured air.
Also in the WOT log while the ECU is trying to achieve the target load it ends up overboosting because the air getting into the engine is not measured, therefore the calculated load is quite far down from the target, and because of that the load compensation WGDC value is significantly higher than the overboost compensation WGCS value, so the load targeting wins which eventually leads to overboost.

As far as I remember from the picture you posted on FAILbook when I asked you to confirm the EBCS routing your intake has quite a lot of couplers and clamps, so one of them may not be as tight as it looks on a simple visual inspection. So I'd inspect them all starting with the MAF o-ring, MAF screws and eventually confirm that the MAF is not dirty.
Dolfius wrote: January 2nd, 2023, 11:22 pm It could be an over load condition. Please share the map here if you're comfortable to do so.
Alternatively you're welcome to mail it to me to have a look
Well, he shared two relevant well taken logs and stated that he is using the high load OTS map. That's quite significant and enough to work with and draw a conclusion.
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
Post Reply