PRESSURE RATIO & MAP/BOOST SENSOR OBD-2?

[FellowTraveler]

While looking at BOOST sensors a question came to me, it appears when using a 2 BAR sensor and running a higher pressure ratio than 2 BAR it seems there would be a de-fueling issue, or am I thinking too far into it?

 

[Nick Gustafson]

I run a 3 BAR Map sensor, and so does pacificdrumma. It's prevented defueling on both of our trucks, and i've had no issues. I don't think he's had any either

 

[FellowTraveler]

While reading through this thread http://www.thetruckstop.us/forum/threads/boost-baro-sensor.36050/ I notice the voltage/psi scale on a link FREM included.

2 BAR @ 22.9 PSI voltage is 3.75 on a 3 BAR @ 23.1 PSI the voltage is 2.50 so am I right using a 3 BAR will reduce fuel delivery across the rpm range or?

 

[THEFERMANATOR]

No, the ECM uses the boost sensor to control boost and make sure it doesn't overboost. If in an overboost it will defuel, but if it thinks boost is in a normal range it will still fuel normally. The 6.5L ECM is pretty dumb by all accounts.

 

[Nick Gustafson]

I'm not sure if it decreases fuel delivery, but my truck did feel less peppy than it did before. Iirc, it'll tell the ecm to push more fuel because it's reading less boost than the motor is actually receiving. Not too sure though

 

[FellowTraveler]

No, the ECM uses the boost sensor to control boost and make sure it doesn't overboost. If in an overboost it will defuel, but if it thinks boost is in a normal range it will still fuel normally. The 6.5L ECM is pretty dumb by all accounts.

FERM, so the difference in voltage @ any given boost between the 2 bar and 3 bar is a moot issue, or?

What brought this topic up is I have my mechanical boost controller with very little adjustment and I get just over 2.5 BAR when I stand on it and it runs good and wonder if it would run better w/3 BAR boost sensor.

 

[FellowTraveler]

I'm not sure if it decreases fuel delivery, but my truck did feel less peppy than it did before. Iirc, it'll tell the ecm to push more fuel because it's reading less boost than the motor is actually receiving. Not too sure though

FERM'S reply points out how dumb the OBD-2 6.5td computer is so it maybe a moot issue.

 

[THEFERMANATOR]

If your not defieling, then why mess with it. Once tuned, theres no reason to mess with it. The switch to a 3 bar map was to prevent defueling or coding when running higher boost on tunes not set up for it.

 

[FellowTraveler]

If your not defieling, then why mess with it. Once tuned, theres no reason to mess with it. The switch to a 3 bar map was to prevent defueling or coding when running higher boost on tunes not set up for it.

Got it, thanks!