building boost

[whitetsi95]

I have a question. Why does my boost build faster when I am in a higher gear? Like when I'm in first or second gear second, and running about 1500-200 rpms, then slam on the gas it takes longer to build up boost. But when im running about 1500-200 rpms in 4th gear then slam on the gas my boost builds up alot faster. Just wondering why it does that?

 

[Mr Peepers]

I've actually experienced the exact opposite since it takes less time to get the rpms up to the boost threshold in lower gears. You will reach the same psi at a slightly lower rpm in a higher gear since it has more time to spool the turbo.

Load also has an effect on spool. In higher gears there will be more engine load, leading to a quicker spool. I'm not sure if there is a limit to this though.

 

[whitetsi95]

Thanks for the reply. I just couldn't fig. it out.

 

[Defiant]

If you are a turbocharger, pushing against the pistons with air, "boost" is how hard you have to push against them. It's the same as you pushing your kid sister in her wagon versus pushing a loaded city bus up a hill. Less load, less boost.
If the either is moving ten miles an hour, you'd have to run like hell to build any "boost" against them.

 

[Mr Peepers]

Boost is technically air loading up in front of the intake valve, if that makes anything clearer.