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(overspooled)
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Discussion Starter #1
I posted a similar question a while back, but here goes...
I finally got off my lazy a$$ and got my zeitronix stuff installed.
There boost sensor at sea level with the engine off reads 0
Here in NM at 5700' it reads -4.9inhg which I believe = 0.48977038 x -4.9 (~-2.3psi)

So...My boost controller shows around 13.7 where my zeitronix unit shows around 12.5+- my question being what should I go by? Should the boost controller display be the gospel? do I just add ambient to the zeitronix reading?

Iam in the process of making a few tweaks to a/f (safcII)and I want to add a little more boost; no interest in blowing my motor because I was running 2.3extra psi on shitty NM Gas
 

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(overspooled)
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2,836 Posts
Discussion Starter #2
Response:

Yes,
your engine creates 12.5 + 2.3 PSI= 14.8PSI over the ambient atmospheric pressure.

----- Original Message -----
To: Zeitronix

I’ll try to quit bugging you with this…. So if absolute “positive” pressure is 12.5 under this scenario, does that mean I am only running 12.5lbs of boost?

I was under the impression that boost was anything greater than ambient, which in my case is -4.9mmHg.

-----Original Message-----
Reply From Zeitronix:

The MAP sensor (Manifold Absolute Sensor) reads absolute pressure. -4.9 inHg is correct at your altitude, and your engine is making 12.5 PSI absolute positive manifold pressure. This is how a good boost gauge works. Once you drive down to near a sea level it will read 0.

----- Original Message -----

To Zeitronix:

Subject: boost sensor readings



Hello,

I received and installed my boost sensor. I have one question. I have done some logging…

At peak it reads 12.5psi, it feels like I may be running a little bit more. When I turn my ignition on, before I start the engine. The sensor reads -4.9. I am assuming this is inHg. That would equate to about

2.3 psi (.489x). At altitude (5700’) is it normal to start in the negative thus making 12.5psi=14.8 absolute? Any help on this would be appreciated. If I really am only at 12.5 I’m going to add another 5lbs right away!
 

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(overspooled)
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Discussion Starter #3
So in summary, If you use the Zeitronix unit; which I'd highly recommend to everyone;
Turn your ignition on and let the sensors com online to see what ambient is. Convert mmhg to psi and add that to your boost reading. The conversion tables can be found online, they vary with temperature but are around .48
 
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