Boost Trick part of Edge box???

[Firewalker]

I have read many times here that the existing Edge box for the 2003 will not let the truck through an over bost code????



Here is what i found out and i am questioning what the ECM is actually reading. .



Aftermarket guage reads 34 pounds of boost



When i plug in my wonderfull OBD-II pc link



I get a reading on the map sensor of 69. 591 hg MAX



converted into PSI = 34. 183099 PSI



Well lookie here the ECM actually reads and sees the full boost numbers>...



What is up with that?/ Why am i not getting an overboost code???

Thought edge was suspose to block the high boost numbers???



ken

 

[KLockliear]

What software are you using? Are you reading MAP pressure?

 

[CLAYTON]

I thought the ez just gave the computer a code of 9psi constant. . is that not the case?

 

[Firewalker]

I am using the software from www.obd2.com



And yes it reads map pressue



I also thought from reading past posts that the edge gave a flat 9psi reading, well guss what --- that is not the case??



Any more input???

ken

 

[Firewalker]

bump

 

[KLockliear]

The EZ/TTPM relays MAP pressure to the stock ECM until it hits 20-22psi. At that point, it continues to feed that reading (20-22) back to the stock ECM regardless of the continued increase in boost pressure.



Fire, my guess is that your software is showing you MAP = Manifold ABSOLUTE Pressure. This means that at idle, it would show your absolute atmospheric pressure reading (14. 7 at sea level). So if that is correct, 34psi - atmospheric of 14 = 20psi of boost.

 

[Firewalker]

KLockliear



yep your correct, i forgot how to cifer!!!



69. 591"hg max = 34. 1831 psi



at idel 29. 317"hg = 14. 40psi



max boost the ecm sees is 19. 7831 psi



MAX boost = 34. 1831 PSI





forgot about that sea level thing



at idel i was reading 30. 5"Hg which = 14. 9psi atmospheric pressure

so you are correct is saying that the ecm only sees 20psi rise in boost.

ken

 

[curatchko]

I'm thinking boost is boost. Regardless of atmospheric conditions. What the map reads is what the map reads. It's an isolated system.



Can someone convince me I'm wrong?

 

[KLockliear]

MAP = Manifold ABSOLUTE Pressure.



Barometric pressure is absolute pressure corrected for elevation above sea level.

 

[DieselB59]

The Powerstroke's MAP is 14 at idle at sea level. The MGP, which is manifold gauge pressure reads zero at idle at sea level. And that reading (of 14 psi) in data stream is Manifold Absolute Pressure.

 

[CFollett]

PSIG : Pounds Per Square Inch Gauge, This is the gauge pressure , the gauge reads zero at atmospheic pressure.

PSIA : Pounds Per Square Inch Abslolute: Is the true pressure. The pressure that has the barometric pressure added too, which is 14. 73 at sea level, or as the elevation increases the pressure is less, At 200 feet it is 14. 53 and so on. This is the pressure of the air around us.



So a PSIG gauge at sea level will read zero with nothing on it ,. A PSIA gauge will read 14. 73, with no pressure on it at sea level. The 200 foot increase as above is now really 14. 53. The elevation change didnot change the zero of the gauge but it really a different pressure. Less atmospheic pressure pushing on it .



The trick is to know if the pressures you are talking about are PSIG or PSIA. A boost gauge is a PSIG reading . Most computors are reading PSIA, That way the atmospheic pressure is taken care of and a more accurate reading is taken.