What can be done to help this motor build boost a little quicker?? seems my truck is always running with little to no boost ??? Anyone else noticing that?

Engine needs RPM's to get the boost. If off the line performance is what you are after you can double foot it to get the revs going (and destroy your tranny in the process) or get a tuner that will increase low boost fueling. At 600 rpm (not exact idle speed, but makes math easy) turbine only has about 70 cfm. No boost.
402c.i. X 600 rpm= x 1/2x (4 stroke engine) /1728 (cubic inches in cubic foot)= CFM My formula stops working once the turbo starts making boost, but shows why you dont get any at idle. Also showswhy (variable geometry aside) the turbo won't build boost linearly.

I have a tuner and it still seems to make little to no boost at road speeds. if I stand on it, it will make plenty of boost. ???

I have a tuner and it still seems to make little to no boost at road speeds. if I stand on it, it will make plenty of boost. ???
I make about 4lbs at 60mph.

I run close to 6 psi on the highway and when travelling at a brisk speed (about 95) I have seen it at 25 psi. I would guess that it has something to do with the variable geometry.

that is about what I see.. and my EGTs suck. My dodge made more boost at the same speed with an HX40.

If you don't need the air, why generate the drag of back pressure just to make unneeded boost? You only need us much air as you are burning fuel.

If you don't need the air, why generate the drag of back pressure just to make unneeded boost? You only need us much air as you are burning fuel.
So you like driving around at 900-1000 degrees unloaded? and never mind pulling a large trailer with even the 40hp predator tune in. I have a buddy with the same setup I have and on the 40hp tune pulling a 25' gooseneck with an 04 dodge cummins on it he would run right around 1200 constant (in tow/haul) and when hitting some slight inclines... 1400-1500. Boost we still very low compaired to what either of us would see on a cummins with a hx40 sized charger. Maybe there is something wrong with both of our trucks???

Turbo lcc,

I drive around with twins at 600-700 degrees at 70mph on the 100hp setting on the predator.:ro)

Now thats what I'm talkin about :D

Turbo lcc,

I drive around with twins at 600-700 degrees at 70mph on the 100hp setting on the predator.:ro)
Have fun convincing the wife you need this modification, Lynn.....):h

no kidding.. that one might take some talking

on the lb7 at 74 mph on cruise, on a level road not pulling, i see my boost from 4 to 6lbs and egt in the 5 to 800degrees, pre turbo, at about 2000, to 2100rpm, when pulling these numbers increase to about 12 to 19lbs and temps about 300 degrees, what i have seen once you go over the 26lbs of boost is when the egt seam to go over the safe point

From what I understand....could be wrong.....you don't need nearly as much boost with a larger displacement engine. If you have 10psi of boost in a 6.6L motor and 10psi of boost in a 5.9L engine, you are moving a heck of alot more air with the 6.6L as opposed to the 5.9L. If you tried taking the same amount of air generated with 10psi boost in a 6.6L motor, it would equal (math formula minded people can help me out here) 10+++++++psi in a 5.9L motor. This is ASSuming equal RPM's. If this is wrong/incorrect. Somebody please correct me.


So you like driving around at 900-1000 degrees unloaded? and never mind pulling a large trailer with even the 40hp predator tune in. I have a buddy with the same setup I have and on the 40hp tune pulling a 25' gooseneck with an 04 dodge cummins on it he would run right around 1200 constant (in tow/haul) and when hitting some slight inclines... 1400-1500. Boost we still very low compaired to what either of us would see on a cummins with a hx40 sized charger. Maybe there is something wrong with both of our trucks???

Just got back from an extended trip. I have a backpressure guage as well as a boost and EGT.

On the highway, 70 MPH cruise up and down hill going across PA mountains. Truck only, light load.

Backpressure varied little. Always 7-10 PSI regardless of load.
EGTs 400-900. Very steep downhills would drop it into the high 200's, but not often.
Boost is usually 0 till moderate hill and would climb to at most 4-5 psi. Never ever over 5 while in cruise.

I found in my 05 that my offline boost dropped when I installed the down pipe. It set a low boost code and egr codes what a dog. Installed the finger stick and the boost is back and she rips. I guess with the engine setting those codes it bypass boost. So if you don't have a finger stick get one