Mid 20s boost IDI !

[jimraelee]

Guys lets put it simpler... take a air compressor for your shop with small single pump... it will put out 100psi, but only at a smaller CFM of lets say 8cfm. Now you get a bigger air compressor maybe a twin, and it will put out 100psi but with a greater 10.0cfm. Now it will also run less (ie more efficient and less heat) than the smaller one... The bigger unit will run for 2 min to build up tank pressure, and the smaller unit will take 20minutes...

 

[Jake S.]

Pressure is caused by a restriction of flow. No matter what turbo is on our trucks, the restriction is the same. So if a small turbo and a large turbo are making the same pressure(boost psi) on our motor, the flow(cfm) is the same. More cfm will net more boost. But like fordguy said before, more boost doesn't make more power if the air is superheated. Hence an intercooler. But there is a pressure drop associated with them. It is the same amount of air through the intake but the colder air takes up less space so the pressure drops. Which makes a cold 9 psi better than a hot 12 psi.

 

[streaker]

Jake S your last sentence explains what I have been saying. The higher flowing turbo is better, because it flows equal amounts of air at lower psi. The bigger turbo packs more punch per psi.

 

[hahn_rossman]

Further comments on the combined gas law

I think you are fooling yourself with the way you are solving that equation. Using the online version here:http://www.1728.com/combined.htm
If you solve for volume and enter your 15psi/100c/5l for #1 you get 1.5l as your
volume for #2.
On the other hand if you enter your 15psi/30c/5l for #1 and again solve for volume you get 16.667!
Clearly temperature has a huge impact on volume (intercooler anyone?)

There is a good explanation of properly selecting a turbo herehttp://www.automotivearticles.com/Turbo_Selection.shtml

Part of the challenge is too remember that any selection is a compromise. At least we have a smaller rpm range then the gassers.

Hope this helps.

 

[FordGuy100]

I think you are fooling yourself with the way you are solving that equation. Using the online version here:http://www.1728.com/combined.htm
If you solve for volume and enter your 15psi/100c/5l for #1 you get 1.5l as your
volume for #2.
On the other hand if you enter your 15psi/30c/5l for #1 and again solve for volume you get 16.667!
Clearly temperature has a huge impact on volume (intercooler anyone?)

There is a good explanation of properly selecting a turbo herehttp://www.automotivearticles.com/Turbo_Selection.shtml

Part of the challenge is too remember that any selection is a compromise. At least we have a smaller rpm range then the gassers.

Hope this helps.

For the pressure, did you add 14.7 to 15psi? Otherwise, your calculating for basically just above atmospheric pressures. Or if you want to use torrs just multiply the psi by 760 (or it also stands for mm of Hg).