stupid boost question

[NA2ndgen]

Hope you guys don't mind me asking this. I have always wondered what a pound of boost is. It it one pound of air pressure over atmospheric pressure at seal level or what?

My other question is this. What would 1 pound of boost get ya?

Thanks in advance.

[m90daytona]

psi=pounds per square inch so 1 psi is 1 pound force applied to 1 square inch. how much h/p you get out of 1 psi has alot of variables like altitude,intake temp,compression,ignition timing,fuel delivery,bore,stroke etc...but a good rule of thumb is 10-15 hp per 1 psi.

[c2xejk]

A good rule of thumb is NA hp/14.7 psi. Atmospheric pressure is 14.7 psi and at that pressure the engine makes it's NA hp.

For the 3L V6, NA hp (stock) is 141hp (crank.) So 1 psi will buy you 141hp/14.7psi or 9.6hp/psi.

However, that is a rule of thumb since NA engines can not bring the plenum to atmospheric pressure without something like a "ram air" setup...

For another reference point, Atmospheric pressure is about 28-30" Hg. So 1psi is roughly 2" Hg.

[NA2ndgen]

Thanks you guys. Now I have a better idea about it.

Appreciate it.

[c2xejk]

This is one of the reasons I recommended a vacuum guage... With it, you could tell if you are loosing hp because the plenum pressure is dropping as RPMs climb.

According my scantool, my van has this problem. Going to a 60mm Jeep 4L TB helped, but not as much as I had hoped... I may look at stepping up to a bored out (62mm) TB. At ~5K RPM, the vacuum is in the 2-3" range...

That said, I should probably get a differential pressure guage to make sure it is the drop across the TB that is causing the problem...

[NA2ndgen]

Quote:

Originally Posted by c2xejk This is one of the reasons I recommended a vacuum guage... With it, you could tell if you are loosing hp because the plenum pressure is dropping as RPMs climb. According my scantool, my van has this problem. Going to a 60mm Jeep 4L TB helped, but not as much as I had hoped... I may look at stepping up to a bored out (62mm) TB. At ~5K RPM, the vacuum is in the 2-3" range... That said, I should probably get a differential pressure guage to make sure it is the drop across the TB that is causing the problem...

Now I see why. Sadly I really didn't get it before. As soon as I can I will get one. That will help me to recalibrate my butt dyno. I swear my ram air made a noticeable difference, but the vac gauge will be the final authority on it.

Thanks Ed.