boost adjustment

[davidb]

How do I adjust the turbo boost? What numbers am I looking for? What are the effects on performance and mileage. I just installed a boost guage.

 

[Dieselnerd]

Are you stock? Normal stock boost with the 12 valve 180HP auto is about 18-19, I'm not sure with the 5 speed but I believe it's around 21-23 with the 215HP engine. Boost is not adjustable unless you add something like a TST kit with an adjustable elbow that changes the pressure signal that goes to the wastegate. If you are stock, there is nothing to be gained by increasing boost. More air without more fuel actually can reduce power. Read the excellent posts on "Wastegates" that are very recent threads. You will learn a lot. I actually reduced my WOT boost by 4 pounds after reading the posts and my egt's are reduced without adding smoke and the engine should now be more efficient.

 

[SLang]

With a given turbo configuration, say your HX-35 with 12 cm housing, you can not get more boost with out more fuel or without changing wastegate settings. You can not actually get more air without more fuel. This is a nice thing about a turbe diesel... you can not lean the engine out!



Also more boost should decrease EGT for a given power level. This is a big factor. If you can get more boost at a given RPM without adding more fuel then your engine will run cooler. This is done through changing the turbo not the fuel level. That is why high performance trucks spend countless hours developing maps for the turbos.



If you keep the same turbo and add fuel then you can get more boost at a given RPM. For the same turbo it takes the same amount of fuel to get the same PSI of boost. So for stock fueling it takes so much fuel to get 20 PSI of boost. With a TST plate and the same turbo it take the same amount of fuel to get 20 PSI of boost. The use of the plate is 20 PSI of boost is at 3/4 pedal and not full pedal.



Now if you remove your waste gate line your truck willonly get as much boost as it has fuel for. I believe this is around 25-30 PSI. This will really not help you any. And you will also not beable to achieve this unless you turn your AFC spring up so you get fueling earlier.