[turtle1hp]

I have been searching for information on here, and the Interweb, about what changes can be made and their effects on exhaust/drive pressures.
 There are the few obvious "physical" changes that effect the exhaust pressure. 
Exhaust housing size
Engine RPM
Intake boost pressure
 Then there are the "tuning" changes that can effect the exhaust pressure.
Ignition timing
Fuel mixture
 But one "tuning" item that I have been searching for, that I only find LIMITED information about, is advancing and retarding the Cam Timing.

 I have seen where a few people say that advancing the cam timing will increase exhaust pressure at lower RPM to help spool up time. I have a couple of questions regarding this information. 
Does this increase the exhaust pressure only at lower RPM, or all the way through the RPM range? 
If it does increase it all the way through the RPM range, is it a linear change across the RPM range?

I can add some more questions about the cam timing effect on the exhaust pressure, but I think this is enough to get the conversation started.

[dan_xr4]

I think advancing the camshaft timing should increase the exhaust pressure at lower engine speeds and reduce the exhaust pressure at higher engine speeds. This guess, of exhaust pressure change, is based on increasing the air flow at lower engine speeds and reducing the air flow at higher engine speeds.

I assume you want to make improvements to how your vehicle drives in specific situations. You want to improve how your vehicle feels to you when you ask it to do certain things. I don't think that looking at exhaust pressure is the best way to accomplish your goal. You can measure exhaust pressure and you can make changes to exhaust pressure. How do exhaust pressure changes affect how your vehicle drives ? You are probably looking to help the turbocharger spool faster. Will advancing the camshaft timing make the vehicle feel better ? I say try different camshaft timings and see what you think. If you are driving a turbocharged vehicle with an automatic transmission, then the transmission gear selection has a huge effect on how your vehicle drives. If you are driving around in the higher gears at lower engine speeds and you want more torque, then advancing the camshaft timing should help the situation at the expense of hurting the performance in lower gears and at higher engine speeds.

[turtle1hp]

Thanks for the reply, and I agree 100% that advancing the camshaft on a Naturally Aspirated engine will change the given RPM range of the engine up or down when retarding/advancing the camshaft.
 However, I am trying to look at the entire system for tuning on pump gas. (everything)
  I want to reliably increase my boost pressure, which would mean that I would need to control the combustion temperatures to help reduce the threshold for detonation.  The entire system is a balancing act to achieve this. If something is not complimenting the combination, then you start to limit  it's full potential. Getting everything working together will make for a happy engine. 
  So far from what I have read and understand, increases in pressure in the exhaust can/will also increase the combustion temperature. This will increase the possibility of detonation.

 If I increase the boost pressure, the exhaust pressure will also increase. 
 So if advancing the cam opens the exhaust valve sooner, prematurely allowing (still expanding) cylinder pressure into the exhaust, it will increase the exhaust pressure.  This is what helps some combinations to spool up quicker. 
  So if I retard the camshaft, will exhaust pressure decrease as a result?  

As of right now with a Reground Range Roller cam installed straight up, (no advance) my exhaust pressure entering the turbo is 22 PSI, as compared to the Intake boost of 18 PSI at 6,000 RPM. This is a 1.22:1  Ex. to Int. pressure ratio. 
2:1 is more like a quick spooling street application, while 1:1 is close to a racing application. 

Right now I have no issue getting it to spool and I am still early on in the total tuning process.  I still have wiggle room with the ignition timing, fuel mixture and cam timing moving forward from this point.  

 I have several more details involved with this given combination, to help control detonation,  but I am just trying to see if anyone has details or experience with testing exhaust pressure and cam timing.