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Old 11-29-2021, 11:08 PM   #1
Bluebieru
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Member#: 520461
Join Date: Nov 2020
Location: Toronto
Vehicle:
2004 WRX
Silver

Default MAF volage low+Overboost? [LOGS]

2001 wrx
jdm ej205 engine (avcs disabled)
k&n short ram intake
3inch catless downpipe
3RD GEAR WOT LOG: https://drive.google.com/file/d/102R...ew?usp=sharing

Im getting an etune and my tuner has noticed a few things wrong with my car. 1. My maf voltage is reading ~3.7v at 6000 rpm wot (lower than expected)
2. Im overboosting to 18psi
I LIVE IN TORONTO ~100M ABOVE SEA LEVEL

Ive verified my turbo is a stock td04 by the serial number and bought a brand new MAF sensor to make sure the old one wasnt failing. I also did a vacumm leak test and it was fine, i idle at around 19hg/in.

Ive been trying to find the solution for a while but it isnt making sense to me. if im overboosting by so much shouldnt my maf voltage be near maximum too?
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Old 11-30-2021, 10:54 AM   #2
86Dreams
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Member#: 385256
Join Date: Mar 2014
Chapter/Region: NESIC
Vehicle:
'18 Giulia QV
'21 Giulia Q4

Default

Who is your tuner?

First, try putting the stock intake on and see if that corrects the problem.

If it doesnt then you need to get a wide band O2 sensor and gauge and check that the MAF Voltage is correct by comparing the commanded fueling to the supplied fueling. If they are about the same then you can conclude that the MAF Reading (and there fore sensor) is OK.

If the readings are different then there is a problem with the airflow metering. First step is to put the stock intake on and confirm thats not the problem. If that doesnt work, clean the MAF sensor and recheck readings. If that doesnt work then get a known working MAF sensor or a new one from Subaru (it CANNOT be a cheap off brand MAF sensor because it will not produce the correct readings). If the MAF checks out then start looking for an issue with the ECU or the intake.

regarding this
Quote:
Originally Posted by Bluebieru View Post
Ive been trying to find the solution for a while but it isnt making sense to me. if im overboosting by so much shouldnt my maf voltage be near maximum too?
the answer is no, not necessarily, boost and air flow are separate properties, here is a compressor map for the stock turbo.
https://www.miataturbo.net/engine-pe.../#&gid=1&pid=2

18PSI is about 2.2 pressure ratio. and your maf rate is about 125g/s which is roughly .10 m3/s. The turbo is operating slightly outside of its efficiency range, but its not a part of the compressor map that doesnt make sense.

So in other words, its entirely possible its producing that MAF rate at that boost level

Last edited by 86Dreams; 11-30-2021 at 03:34 PM.
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Old 11-30-2021, 04:54 PM   #3
benflynn
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Td04 @18psi, can’t be more than 23lb/min? Shouldn’t need too much MAF voltage for that. Pro tune with a td04 may be a bit much tho
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Old 01-06-2022, 11:18 AM   #4
jon7009
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Member#: 394646
Join Date: Jun 2014
Chapter/Region: NWIC
Location: Oregon
Vehicle:
2003 WRX Flex Fuel
Pv=nRT

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check your turbo inlet/intake charge system for boost leak/smoke test.

a leak between the maf and turbo would provide plenty of unmetered air.
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Old 01-06-2022, 11:19 AM   #5
jon7009
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Quote:
Originally Posted by benflynn View Post
Td04 @18psi, can't be more than 23lb/min? Shouldn't need too much MAF voltage for that. Pro tune with a td04 may be a bit much tho
0.185 to 0.19 m^3/s is about 30lb/min at sea level
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Old 01-30-2022, 10:31 AM   #6
CharlieSti
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Vehicle:
2004 Wrx Sti
Red

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I have a TD04HL-15t. If you hold down the throttle on a long pull it’ll reach 18 or like 18.5. It’s on a stage 2 tune, off the shelf tune.
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Old 01-30-2022, 10:33 AM   #7
CharlieSti
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Red

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I have a TD04HL-15t, on my jdm ej205. Was on the car when I bought it. It will boost to 18 or 18.5 on a long (3K-7.5K rpm) pull. It’s on an off the shelf stage 2 tune. Maybe you just have the same thing? I haven’t had too many issues with it
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