Engine/Transmission (1998.5 - 2002) "Normal" boost and idle readings?

[Troubleshooter]

Gents:

Got into a discussion today regarding the "normal" readings for boost and idle for an '01 CTD with AT. Can't seem to find any references in my Haynes manual. Appreciate some help with the three questions below.

1. What is considered "normal" idle in Neutral?
2. What is considered "normal" idle in Drive?
3. What is considered a "normal" boost reading?

All these were taken with the Smarty set to "stock" mode. We got 14psi boost today, but it continued to read 14psi after shutdown as well. Not sure whether this is correct. Appreciate the benefit of your experience.

 

[JR]

How are you reading your boost? 14 Psi at idle is way out of wack, my boost gauge barely even reads 1-2 pounds at idle.
Just for reference, I hauled an 8k pound truck on my 3800 pound trailer today. I was running 10-12 pounds of boost maintaining 65 mph on the freeway.Running empty at the same speed would normally net around 5-7 pounds of boost.

 

[BarryG]

Idle on my 01 is approx 750 rpm neutral or drive. Boost is pretty variable depends on fueling and load. At idle mine is zero. However the 14 psi you are seeing might very well be psi while actual gauge readings are psig the g stands for gauge which most gauges are which means they have been calibrated to sea level which is 14.7 psi. So some scanners and I think our truck ecms are psi not psig so if reading 14ish that in reality is zero psig. Not sure that makes sense but psi at sea level is 14.7so most gauges are calibrated to read zero at sea level

 

[Troubleshooter]

Thanks for the info on idle speed, I'll let him know about that.

He's reading the boost from a scanner.

 

[RustyJC]

Ask him if the scanner's readout is psig (pounds per square inch gauge) or psia (pounds per square inch absolute). If it's psia, then a reading of 14 psia at idle would be fine, depending on your altitude.

Maximum stock boost on my 2002 HO/6 speed was about 20.5 psig, or 35.2 psia at sea level. Your SO engine might be slightly lower.

Rusty

 

[wcjp]

My 06' analog gauge has zero boost at idle. My Bluetooth Scantool MX reads the computer calculated Boost at 1-2psi of boost at idle

 

[Bob4x4]

Your scanner is reading atmospheric pressure Deduct that number from what ever you see while driving to know the boost pressure

 

[Troubleshooter]

His scanner was indeed reading the actual pressure with atmospheric pressure included. Thanks for the replies!

 

[WalterJ]

Hmmm, I never thought about the fact that our ECM's MUST utilize absolute pressure (psia) calibration or it would not be able to compensate for traveling mountains & valleys, as the atmospheric pressures change with altitude! Cool. Thanks for the education.

 

[SnoKing]

Stock HY-35 makes 18-22 lbs of boost when pulling hard. SNOKING

 

[Troubleshooter]

Much obliged, Snoking!