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Map vs boost pressure

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4 years 2 weeks ago #38148 by Jalvrzjn
Hey Im looking for some direction here. I have a 2010 Acura rdx with a p0234 overboost code. I have checked the wastegate actuator by applying compressed air and it seems to be working. Also tested the wastegate actuator solenoid with a flowchart I found and it passed. I monitored my MAP sensor and Turbo Boost sensor and they are different. map is about .8V near 5psi. Boost is about 2V near 14.6 psi at idle. Not familiar with turbo systems. Wondering if this is normal or not.

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4 years 2 weeks ago - 4 years 2 weeks ago #38152 by Andy.MacFadyen
What are the readings at key on engine off ? MAP pressure is absolute but although they measure the same pressure Boost Pressure is expressed as gauge pressure.

Boost pressure = MAP - Atmospheric Pressure.

Map at key on engine off should be atmospheric pressure roughly 101,325 pascals = 14.65 psi ---- lower at altitude or in bad weather

Boost pressure at key on engine off should be zero.

" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)



Last edit: 4 years 2 weeks ago by Andy.MacFadyen.

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4 years 2 weeks ago #38160 by Jalvrzjn
Replied by Jalvrzjn on topic Map vs boost pressure
Hey I appreciate your response. I believe map pressure did read about 14.5 psi koeo and 0 psi was boost pressure koeo. Now my scan tool reads map and boost at psi. They differ about 10psi at idle but once I drive and and accelerate they both read close to each other. For example they would be roughly at 28 psi. Do you think this is normal? Why would it differ at idle but be similar under load.

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4 years 2 weeks ago #38185 by tech25
Replied by tech25 on topic Map vs boost pressure
hey there, what kind of scan tool are you using?? does it have bi-directional controls?? if so, can you activate the waste gate control solenoid ( hear it click )

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4 years 2 weeks ago #38188 by Jalvrzjn
Replied by Jalvrzjn on topic Map vs boost pressure
Hey. I have an Autel Mx808 I believe. I dont have bidirectional controls but was able to energize the solenoid. It is power side switched. I realized today there are 2 actuators. One for boost control and one for wastegate operation. I checked the boost control and not wastegate actuator being unfamiliar with turbos and especially this one. But I am getting pretty familiar now. Im betting I will see no action from the wastegate when I insert compressed air. But I will see.

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3 years 6 months ago #42783 by JDoyle88
Replied by JDoyle88 on topic Map vs boost pressure
Did you solve your issue?
My ‘07 RDX is giving me the same p0234 code. Both of the actuators seemed to work fine when I used compressed air. I also did a smoke test and didn’t have any leaks. I’m not sure how to go about testing the Solenoids since I just have a cheap scanner..
JD

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3 years 6 months ago #42786 by Jalvrzjn
Replied by Jalvrzjn on topic Map vs boost pressure
Hi yes. With the over boost code I thought I would find a faulty waste gate actuator or faulty waste gate actuator solenoid. But found both to be ok. I ended up replacing the turbo unit itself witch was a pita but everything is working fine now. If your scan tool doesnt read the solenoid pids or have bidirectional you can at least remove them and apply power and ground. Or you can figure out if its ground side switched or power side switched and actuate them where they live. I can get you more info on vacuum testing them. Its been awhile now.

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