How to read boost properly
Thread Starter
Senior Member
Joined: Oct 2005
Posts: 365
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From: San Jose
CL65 AMG , white S550 Sport w/ white Giovanna 22s, wild custom chopper
How to read boost properly
I see the following on my freeze frame data:
: Intake Manifold Absolute Pressure : 53.8 inHg :
That's around 26 psi. I'm running stock K24 turbos, but I have the lighter aluminum impellers - Speedriven upgrade. I'm supposed to be boosting max 21psi.
Is my boost too high or is that intake manifold absolute pressure parameter output means something else?
: Intake Manifold Absolute Pressure : 53.8 inHg :
That's around 26 psi. I'm running stock K24 turbos, but I have the lighter aluminum impellers - Speedriven upgrade. I'm supposed to be boosting max 21psi.
Is my boost too high or is that intake manifold absolute pressure parameter output means something else?
Member
Joined: Apr 2011
Posts: 130
Likes: 53
From: NC
'15 GLK350, '05 CL65 AMG, '04 C320 4matic
I see the following on my freeze frame data:
: Intake Manifold Absolute Pressure : 53.8 inHg :
That's around 26 psi. I'm running stock K24 turbos, but I have the lighter aluminum impellers - Speedriven upgrade. I'm supposed to be boosting max 21psi.
Is my boost too high or is that intake manifold absolute pressure parameter output means something else?
: Intake Manifold Absolute Pressure : 53.8 inHg :
That's around 26 psi. I'm running stock K24 turbos, but I have the lighter aluminum impellers - Speedriven upgrade. I'm supposed to be boosting max 21psi.
Is my boost too high or is that intake manifold absolute pressure parameter output means something else?
Thread Starter
Senior Member
Joined: Oct 2005
Posts: 365
Likes: 0
From: San Jose
CL65 AMG , white S550 Sport w/ white Giovanna 22s, wild custom chopper
Member
Joined: Apr 2011
Posts: 130
Likes: 53
From: NC
'15 GLK350, '05 CL65 AMG, '04 C320 4matic
So I checked up on this further and I believe your boost pressure actually converts to about 11.5 psi if you were to measure it on a boost gauge. When you convert from MAP to boost you need to subtract 1 Bar. The difference is PSIA (Absolute) vs PSIG (Gauge).
Last edited by Geraldius; Aug 19, 2017 at 11:54 PM.
Thread Starter
Senior Member
Joined: Oct 2005
Posts: 365
Likes: 0
From: San Jose
CL65 AMG , white S550 Sport w/ white Giovanna 22s, wild custom chopper
Thanks, that helps. From doing simple math from the freeze frame data, I think I understand it now.
It's 67.6 inhg (intake manifold absolute pressure) - 29 inhg (barometric pressure) = 38.6 inhg which converts to 18.95855 PSI.
So I was boosting around 19PSI when I tripped the computer with the misfire code. Am I doing the math right?
It's 67.6 inhg (intake manifold absolute pressure) - 29 inhg (barometric pressure) = 38.6 inhg which converts to 18.95855 PSI.
So I was boosting around 19PSI when I tripped the computer with the misfire code. Am I doing the math right?
