Question about how turbos work

[5amp5on]

During a couple of launch control WOT runs yesterday, I noticed that the highest boost I got was 18-19lbs.

The thing I also noticed is that the boost would drop from 18-19 down to 15 lbs of boost after 5,500 RPM up to redline of 7,000. This happens in all gears.

Why does the boost drop like that when the RPMs go over that level? I'm not saying it's a bad thing I'm just wondering why?

Here are few pics to illustrate:

 

[Modfather]

During a couple of launch control WOT runs yesterday, I noticed that the highest boost I got was 18-19lbs.

The thing I also noticed is that the boost would drop from 18-19 down to 15 lbs of boost after 5,500 RPM up to redline of 7,000. This happens in all gears.

Why does the boost drop like that when the RPMs go over that level? I'm not saying it's a bad thing I'm just wondering why?

Here are few pics to illustrate:

Turbos have a certain efficiency range that they work within, on a stock car they are typically sized so that boost comes in quickly so you don't get a lag when you put your foot down, the knock on effect of that is they run out of puff at the top of the rev range. when you go to bigger turbos they might take a bit longer to get to full boost but will pull all the way to the rev limiter

 

[5amp5on]

@Modfather thank you for that concise clear explanation. Much appreciated and good to know this is normal.

 

[Will-Stillen]

Want some added HP?? Check out our Trucontrol tuner!

https://stillen.com/collections/ele...ntrol-by-stillen-inline-power-module-tc101001

 

[RobotAZ]

Turbos have a certain efficiency range that they work within, on a stock car they are typically sized so that boost comes in quickly so you don't get a lag when you put your foot down, the knock on effect of that is they run out of puff at the top of the rev range. when you go to bigger turbos they might take a bit longer to get to full boost but will pull all the way to the rev limiter

Do our turbos actually get in the way at highest revs?