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Ok, I have seen alot of guys asking, "How can I get more boost out of my truck?". So I am doing this little post to help out. Mods, feel free to sticky it if you feel necessary.
Down to business:
How to get more boost. The answer is more fuel.
These trucks have MAP sensors in the intake manifold. MAP = Manifold Absolute Pressure, in other words, a sensor that reads boost in the intake. SO (standard output) trucks have programming in the ECM that cuts back on the fueling (defuels) when a set amount of boost is seen at the map sensor. This happens at about 20-21 psi. ( a bit higher on the HO-high output trucks).
So, if you put a boost gauge on your stock truck, you will see maximum boost somewhere in the neighborhood of 20 psi.
Besides the stock ECM fueling parameters that keep you from exceeding around 20 psi of boost, there is a wastegate on your turbo. The function of any wastegate is to bleed of excess boost from the turbo. The wastegate has a spring and diaphram inside it that physically moves a rod and plunger in the exhaust housing of the turbo at around 20 psi.
So to get more boost out of your truck you:
A) go buy a "chip". This gives you more fuel. Practically everything on the market these days has a "Boost Fooler" built into it. The "boost fooler" tricks the ECM into thinking that the boost is not exceeding stock limits, so that the ECM won't DEFUEL to try and keep you below 20 psi.
Now, you got your chip with boost fooler, and you crank her up hoping for high boost, but you only get around 24-25 psi. How are all these guys getting 30, 35, 40, 45 psi??? Well, Even though you added more fuel the WASTEGATE on the turbo is still doing its job! Its bleeding off that extra psi you are making to keep things around 20 psi. Which brings us to :
B) You need to get control of the wastegate. This can be done in a few different ways, all achieving the same results. I will focus on the most common. First We need to know what stock turbo you have. The options are HX35 and HY35. If you have an 01 or 02 model automatic trans truck, You have an HY35 turbo. To increase the boost on this turbo you need a "J-hook". This is a hook with a spring that effectively holds your wastegate closed to a certain point, allowing you to make higher boost with that fancy fueling box you bought!
If you have an 98.5-02 manual trans truck, or a 98.5-00 auto trans truck, you will have an HX35 turbo. To increase the boost on these turbos, you need a "Boost Elbow". This replaces the stock elbow coming out of the compressor housing with one with a smaller orfice, OR an adjustable orfice, so you can set the boost level you want. Now you are capable of higher boost on your HX35!
Couple of things to remember:
1) Your boost won't go any higher if you aren't adding more fuel.
2) If you add a "boost elbow" or "j-hook" to your truck, without adding an electronic boost fooling device, you will cause the ECM to DEFUEL! , Giving you the same or less power than before. You will also be throwing P0237 codes (turbo overboost condition).
3) You can run a fueling box without running a boost elbow / j-hook on your turbo. It will work. You just wont be taking full advantage of the extra fuel you are adding, and your EGTs will likely be a little higher than if you had the extra boost.
http://www.tstproducts.com/pdffiles/PMInstr6.pdf Page 3, halfway down page, pics of (left to right) boost elbow on HX35, stock metal boost line on HY35, and HY35 with J hook installed. Also, installation intsructions for boost elbows and J hooks above and below pics!
Boost pressure is not indicative of cooling performance or power. Turbochargers have what is called a map. This states the efficiency of it's design. There is a finite amount of flow a turbocharger can produce without causing "hot air". Hot air is the excessive heating of the charge air. Once a turbocharger begins to exceed it's efficiency map, it increases the hot air. Hot air actually will begin to impede performance. Another portion of the map is the drive pressure and ratios. You may be able to fuel an HX35 into overspin to 50+ psi. But the hot air produced coupled with the extreme drive pressures tax the engine. Simply put, more pressure isn't "good". It needs to be done in moderation.
Generally accepted safe numbers for the HY/HX-35's are as follows:
HY35's are good to 32psi, and will begin to overspin at 35psi.
HX35's are good to 35psi, and will begin to overspin at 37psi.
heres a question, hope this is a good place to ask.
if say my stock turbo produces 35 pounds of boost with what is in my sig. and i went and bought an aftermarket turbo and set it to 35 pounds of boost would it be any better, or is 35 pounds 35 pounds nomatter what turbo produces it?
white 02 quadcab 4x4 5sp/ ind. inj. hrvp/ rv275's/ airdog 150/ isspro gauges: pyro, fuel, boost/ valair kevlar-ceramic clutch/ silencer ring mia./ BHAF/ straight piped/ boost elbow/ custom shifter/edge comp hot/ 2-stroke oil SOLD ITnow have a 98 1500
Yes the 35lbs of boost from the "upgraded" turbo would be moving a higher volume of air. And Air volume, not boost, is what makes you more power. You will also benefit from an extended map range, that way you aren't pushing the turbo out of its map and making it unefficient.
35 psi from one turbo is a different volume of air vs. 35 psi from another turbo.
Clear as mud? LOL
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