I know this has been talked about (trust me, I have done a search), but now that many members are opting for the Procharger, I think this may be important to have its own thread. Anyhow.....Maybe I am misunderstanding something....I have the Procharger and would like to buy a Crawford Plenum. Now, if I increase airflow with the plenum but lose a little boost does this mean I can get a smaller pulley to make up for the boost and still SAFELY (And I DO MEAN SAFELY if thats possible) put 7 psi to the motor? Is it the psi that I am putting to the motor that can be harmful, or the overall power? ATI says 7 psi is safe on our motor, so I take it I can get the Plenum and a smaller pulley to make 7 psi and be safe? Am I crazy? I understand that I will be putting more power into the motor but since our rear cylinders flow less than the power delivery with the Plenum would be more equal, therefore safer for the engine even with the increase in power? Any suggestions or insight is appreciated.

Dan

 

I don't see why the plenum would drop the amount of boost.

 

It would be total horespower, not psi. It would effect PSI, sense the increased flow provided by the plenum would require more air flow from the supercharger in order to maintain the overall psi.

 

Glad you asked, Here is how it works. The important thing to remember is that boost does not equal power. AIR MASS equals power. Example if it takes 10psi to move 10lbs of air though a straw in a mintue and 2 psi to move 10lbs of air through a 1 inch diameter pipe you still move 10lbs of air. Follow? So if you have to burn 10lb of air every minute to make 1 hp then in both examples you make 1hp, even though one is running 10psi of boost and one runs 2psi.

Those numbers are just made up but show you how it works. So for the Z with a "plenum" you lower the boost by making the "pipe " bigger but still move the same AIR MASS. When you get a small pulley and get back to 7 psi you are moving the same air mass as a higher boost. So the effective cylinder press will go up and cause more thermal stress which is more likely to cause knock or detonation. Now there is Much more to this as the compressor efficiency changes with boost levels and air mass flow but it's the basic answer your looking for.
Gary

 

Thanks for the insight!

 

Thanks 7 eleven. That needed to be said. It's a common misconception.

 

My understanding is that with the SC you do not need the new plenum because with the added pressure you are making up for the low flow to the front cylinders.

 

Also, what must be remembered at this point is you void the warranty for the procharger if you use a different pulley to get more boost to the engine. I would love to see a dyno with a before and after for the plenum with FI. Truefully, boost pressure should make up a lot for the bad flow characteristics of the stock plenum. And, if I went FI, I would prefer my intake be as stock as possible so that if something goes wrong, I can look directly at the FI manufactor. Don't want them to be able to blame something else, UNLESS that something else (ie plenum) makes alot of power and makes me want it real bad.