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  #1  
Old 02-19-2010, 02:32 AM
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Warlock_440 Warlock_440 is offline
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Question 14 psi at idle??

Ok guys I need some help. After lurking in the shadows (and learnig alot in the process) its my turn.

I picked up an 02 Ram 2500 Cummins 4x4 6spd back in October. Its a total loss vehicle that has been all fixed up. You'd never be able to tell from looking at it that it was a roll over.

Anyways, I had the scanner hooked up the other day to check out a couple ABS related codes and i started poking around everywhere else just checking things out.

And i noticed that with the truck just idling, the data on our Snap On Modis scanner was showing 14lbs of boost. Then I shut the truck off... Still showing 14lbs. WTF!?! Also showing boost at 1.0V

I took it for a drive and it shows 34 psi at WOT.

So I disconnected the charge air sensor (aka MAP sensor), checked the scanner, 0 psi 0.0Volts, checked for the 5V reference = good, ground = good, jumped the 5V wire to the signal wire and scanner showed 5.0.

So this leads me to believe that the wiring to the pcm is good. I ordered a new MAP sensor and put it in today with great expectaions and...the same damn thing.

Just wondering it anyone can shed some light on this. Its not a big deal, the truck runs fine. I was just thinking that this might have something to do with my poor mileage situation. Doing about 18mpg

Thanks in advance, Devin
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  #2  
Old 02-19-2010, 11:11 AM
peg leg peg leg is offline
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Default 18mpg

That's good average mileage. I'm asuming you mean highway mileage. City runs around 14-17 on average.
Is there a fueling box on the truck? If so, what brand name is the box? Some have built in boost foolers, some don't. Changing the MAP sensor should have cured the issue, unless the box is lying to your gauge.
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  #3  
Old 02-19-2010, 01:42 PM
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Warlock_440 Warlock_440 is offline
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No fueling box. You can tell there was one there at one time by the tell-tale velcro strips on the fuse box but its gone now.

Yes thats highway mileage, a friend has the identical truck and its making more around 23 - 25 mpg.
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  #4  
Old 02-19-2010, 06:05 PM
peg leg peg leg is offline
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Default Sounds like

Your ECU needs an update to remove any damage caused by the fueling box. I cannot think of any other cause for your readings.
Your friend's mileage is a bit on the embellished side. Unless he's driving 45 MPH with no load and a heavy tailwind, that is not realistically achieveable mileage. My best ever, summer temps, full fuel load, 484 mile trip, few hills and no wind was 21. Interestingly, my mileage went from 18 to 20.3 after installing a fueling box, 4 inch exhaust, boost fooler and boost orifice, same trip.
If your friend is relying on his overhead monitor for his figures, that would explain the figures. The monitor is not accurate on any vehicle.
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  #5  
Old 02-19-2010, 07:45 PM
mopartec mopartec is offline
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there is nothing wrong.14psi relates to atampheric preasure. 14.7psi. at wot you said 34psi. that would a total of 20psi boost.i believe it was 2002 chrysler changed the way they read boost. i and several other teches have been burned in 02 when we saw that too.
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  #6  
Old 02-19-2010, 07:55 PM
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Warlock_440 Warlock_440 is offline
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The mileage thing could be somewhat embelished. I just thought these trucks were getting better mileage than what I'm seeing. I know that the overhead reading is just a ball-park figure.

I would have thought that in the whole design of the sensors and computers that they would have compensated for atmospheric pressure. But if they haven't then yeah that makes perfect sense.

I guess I should have posted this before I went and bought a new sensor.. Oh well.

Thanks for the help guys!!
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  #7  
Old 02-20-2010, 10:41 AM
peg leg peg leg is offline
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Default Aha!

It occured to me that you are not reading boost pressure, but some analysing device.
Mopartech has it right.
If you add a fueling module to your truck, you should pick up 2 mpg.It's almost guaranteed. Remember, these aren't lightweights. Mine is a long box, camper shell, and with full fuel and two aboard weighed 7680 on a certified scale.
By the way, I also have the 275HP injectors, which did nothing to my mileage.
So my total engine work includes injectors, VanAaken box, boost orifice reducer, boost fooler module, 4 inch exhaust and triple clutch converter. Axle ratios are 3.55 (4X4).
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  #8  
Old 02-20-2010, 12:34 PM
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ehostler ehostler is offline
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With my daily driving (lots of stop and go, and an average speed of less than 30MPH), I get around 15 MPG on my 2006 quad cab, 4X4. I have seen 19 MPG on a trip. If I go by the OHC, I get 20+ MPG on a regular basis.

I see no reason why a 6 Speed couldn't get a true 23 MPG on the highway.
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  #9  
Old 02-20-2010, 02:26 PM
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Warlock_440 Warlock_440 is offline
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Yes that's reading boost pressure off of our scanner at work. I was thrown off when I saw 14psi not running. Didn't realize it read absolute pressure. Glad nothing is wrong.


So basically I'm getting the proper mileage for my stock truck yes? With exhaust, fuel box, etc etc. It should get up there huh?

Peg Leg, whats this boost orifice reducer you speak of?
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  #10  
Old 02-20-2010, 04:54 PM
peg leg peg leg is offline
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Default Orifice

The boost orifice is a brass button with a hole in it, smaller than the boost pressure hose that operates the waste gate. It reduces the volume/pressure to the waste gate, keeping the gate open longer, and thereby raising maximum boost. They look like a carburetor jet, and install in the rubber gate pressure line fitting on the turbo pressure side. You need to add a boost fooler piece to prevent the ECU from coding when you raise boost. Both should be available from genosgarage.com. Genos is a good reliable source for most things Cummins/Dodge, and much better priced. Don't forget to look into a pyrometer gauge setup for EGT, too.
My max pressure went from 16 to 35 PSI.
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  #11  
Old 02-20-2010, 05:05 PM
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Or you could get and Edge Juice with Attitude. It will resolve the low boost fueling issue (turbo lag) and allows you to set max boost. It will give you more power and better fuel economy.
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  #12  
Old 02-21-2010, 01:49 PM
mopartec mopartec is offline
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a word of caution. starting Jan 2010 we now smog Diesels in California. all the tuners,modules and cold air intakes, big turbos. etc are now ILEGAL unless they have a C.A.R.B label.welcome to California. JOY oh JOY.you know others will follow
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  #13  
Old 02-21-2010, 04:57 PM
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And people wonder why I don't live in CA anymore. Right now, diesels are sill emissions testing exempt, in the state of Virginia.
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  #14  
Old 02-25-2010, 02:15 PM
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Come to Saskatchewan... No emissions testing on anything! (Yet)
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  #15  
Old 06-08-2010, 04:06 PM
BlackSkyRacing BlackSkyRacing is offline
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Quote:
Originally Posted by mopartec View Post
a word of caution. starting Jan 2010 we now smog Diesels in California. all the tuners,modules and cold air intakes, big turbos. etc are now ILEGAL unless they have a C.A.R.B label.welcome to California. JOY oh JOY.you know others will follow
They'd love me then... I actually updated my old 12 valve to a VGT Holset Granted the pump is tweaked pretty good, and the 5x.014 injectors are pretty clean for what they are, I'm pretty sure I'd fail any smog test in my current state of tune. I suppose if they ever bring emissions to Wisconsin I'll just have to move my plate and AFC housing back

Oh and to the OP, I was fooled by an 05 Ford F550 that was doing the same thing. Or at least I thought it was a cause for surging under load. I was thinking the ECM was seeing an over boost and opening up the vanes on the VNT to lower boost, over correcting and then closing them back up causing an over boost all over again. Turned out the spring that holds the EGR valve shut was getting weak allowing the EGR to open prematurely leaking too much exhaust pressure into the intake making boost surge and choking out the engine all at the same time...
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  #16  
Old 06-10-2010, 01:10 AM
mopartec mopartec is offline
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so far in calif its only 98 and newer diesels that get smogged.
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  #17  
Old 06-12-2010, 12:14 AM
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So far in VA, it's no diesels that get smogged...
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  #18  
Old 06-14-2010, 03:03 PM
BlackSkyRacing BlackSkyRacing is offline
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Quote:
Originally Posted by mopartec View Post
so far in calif its only 98 and newer diesels that get smogged.
Guess I'd be fine then

Quote:
Originally Posted by ehostler View Post
So far in VA, it's no diesels that get smogged...
I was wrong, they do smog test vehicles in Wisconsin... Just not in the rural areas in the northern part of the state. I swear, Milwaukee, Chicago and all the surrounding metro areas should just form their own state. They're so far out of line with the views and needs of the rest of the state that it's not even funny.
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  #19  
Old 07-30-2010, 08:39 PM
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bulldog426 bulldog426 is offline
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our ford f550 with the 6.0 has a boost gauge on it, and it idles around 12-14 psi, and open throttle around 35 psi pulling a kubota 91-3 mini ex on a gooseneck with a crapload of tools with a toolbin on the truck, and toolbins on the trailer.. and gets about 5-6mpg
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