Boost pressure

I'm going to ask what I'm sure some will consider a dumb question so I'm prepared for the smart ass answers but hoping for a legit answer or 2. This is my first turbo vehicle so I'm still trying to figure out some things related to that. What factors lead to max boost being created? I always just assumed that wot = max boost but I've learned that isn't necessarily true. I've seen some people say that the truck needs to be "under load" to create boost but I'm not sure exactly what that means.

It is correct that boost is directly correlated to load. This is because load determines the airflow and fueling needs of the engine.

If you accelerate lightly and keep the engine in a low gear, you’ll notice that it won’t build boost regardless of RPM. This is because the throttle plate is barely open, so there is not a lot of airflow through the engine. Turbos spool on the principle of exhaust flow and the expansion of hot exhaust gas, so the turbines will be spinning but the compressor is not proving any airflow/pressure above what the engine requires, which is what it’s drawing in on its own.

When you put a load on the engine, such as hard acceleration or pulling a hill, the throttle plate angle is much greater (open). More air flows through the engine, and therefore more fuel is injected to keep the air/fuel ratio in the desired range. This means more exhaust flow, which spools the turbochargers up to speed, which can be as high as 200,000 RPM.,With the additional exhaust flow, the turbochargers pressurize the air in the intake system, since the turbos are able to provide more airflow than the engine can draw in on it’s own. The pressure between the turbo and intake valves is boost; as the intake valves open, air is forced into each cylinder as opposed to being drawn in my vacuum.

Great explanation ford tech , When i sold my tuned 2014 tremor . The new owner said he is only getting 15 PSi max , I said it should peak at 20 to 21 and avg 17-18 WOT . I told him to send me a video of SCT display . Shoots back a video of a launch and I can hear is tires roasting 2wd . I replied back, launch in 4 hi all that tire spin = less load = low boost PSI .

FordTechOne said:

It is correct that boost is directly correlated to load. This is because load determines the airflow and fueling needs of the engine.

If you accelerate lightly and keep the engine in a low gear, you’ll notice that it won’t build boost regardless of RPM. This is because the throttle plate is barely open, so there is not a lot of airflow through the engine. Turbos spool on the principle of exhaust flow and the expansion of hot exhaust gas, so the turbines will be spinning but the compressor is not proving any airflow/pressure above what the engine requires, which is what it’s drawing in on its own.

When you put a load on the engine, such as hard acceleration or pulling a hill, the throttle plate angle is much greater (open). More air flows through the engine, and therefore more fuel is injected to keep the air/fuel ratio in the desired range. This means more exhaust flow, which spools the turbochargers up to speed, which can be as high as 200,000 RPM.,With the additional exhaust flow, the turbochargers pressurize the air in the intake system, since the turbos are able to provide more airflow than the engine can draw in on it’s own. The pressure between the turbo and intake valves is boost; as the intake valves open, air is forced into each cylinder as opposed to being drawn in my vacuum.

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Ditto on the excellent explanation to give a new guy! Your very patience with a lot of the people on the forum and that makes me wonder if you have kids. Me, no kids no patience lol

My question is about increasing boost and how it's done correctly, I come from the world of using a supercharger and that was an easy mod by swapping pulleys
When I watch these car/truck shows and I have heard them say " I did that pass with 22 pounds of boost and i'm going to dial it up to 26 psi" because they were getting zero or very little spinning the tires. I know it's not easy to get a car dialed in, too much power and all you have is wheel spin, and curious about it and they make it sound so easy

I am also curious how you would increase it and how much you can increase the boost on a stock Raptor. I have heard something about different colored springs, is it each being different wire thickness and spring weight like a coil spring?

Different color spring are referring to a manual waste gate which the ecoboost raptors do not have. We have electronic waste gates which open and close to bleed off boost pressure by bypassing the hot side of the turbo. That is how tuners control how and when the boost is applied. So by adjusting spark timing, fuel delivery and boost pressure they can tune the power output.

richnot said:

Ditto on the excellent explanation to give a new guy! Your very patience with a lot of the people on the forum and that makes me wonder if you have kids. Me, no kids no patience lol

My question is about increasing boost and how it's done correctly, I come from the world of using a supercharger and that was an easy mod by swapping pulleys
When I watch these car/truck shows and I have heard them say " I did that pass with 22 pounds of boost and i'm going to dial it up to 26 psi" because they were getting zero or very little spinning the tires. I know it's not easy to get a car dialed in, too much power and all you have is wheel spin, and curious about it and they make it sound so easy

I am also curious how you would increase it and how much you can increase the boost on a stock Raptor. I have heard something about different colored springs, is it each being different wire thickness and spring weight like a coil spring?

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Tune the ECU. It’s in charge of everything, including boost. Until you run out of air, fuel or charge cooling, there’s no point in changing hardware.

And remember the more you spoil up the Nagasaki Noisy Bois, the worse off your fuel economy will be. It helps to keep an eye on your gauge and downshift or lock out higher gears at low speed, because of the transmissions desire to be in the highest gear possible. That shift strategy will hurt more than it helps sometimes because the top gears require a lot of boost to overcome small grade changes and the PCM is reluctant to downshift.

Intake temp, and driving mode determine the max boost and timing curve, on hot summer days you will build all the boost, but the timing tables will be off.