So, you are stating; a wastegate, that gets it's signal from the compressor side of the turbo, will still come into play, or as quickly (if at all), even though less compressor pressure would be generated, via, a less restrictive intake side, in this case, freer flowing heads? I was discounting, the turbo having the 'reserve', to be capable of the necessary, extra flow needed to regain boost to previous level. I am thus incorrect, for not considering, that the turbo could/would be capable of generating the extra needed boost, set up in it's present form.

 

If boost is below the spring setting of the wastegate, the gate is closed and all available exhaust will be directed thru the turbo. If your running a turbo that cannot compensate for a few more cfm due to head work, your running the wrong turbo. The wastegate doesn't care how many cfm the motor is flowing, it will continue to spin the turbo way out of efficiency if it has to. Not great for making power, but it will happen if the turbo is to small.

 

yes, which will cause very high IATs...

I dont think i'm going to loose 2-3psi from these heads though... we will see... if thats the case then I will upgrade...

 

thx man!

its the medium spiral grey the c5s had... the gunmetal basically i love it

 

That's where i'm confused on your understanding.... you don't "lose" boost with a turbo when the engine's airflow properties are changed. It doesn't matter if you have a t88 on a stock 350 or a 427, if the wastegate is set to maintian 6psi, it will bleed off enough exhaust gases (when neccessary) to maintain 6psi of intake manifold boost and stay there (albeit in a completely different time frame and rpm). You have to consider the turbo and the engine kinda in a seperate manner. The only connection between the two is exhaust gases. And they spin the turbo directly based on how much exhaust pressure is present and the design of the turbine wheel. The turbine (exhaust) and the compressor (to the engine's intake) spin at the same speed. There's a complicated emperical equation MEs use to calculate the effective force on a turbine when air or water flows accross it. This force creates a moment (or torque) on the shaft, which causes it to turn. So as long as enough exhaust gases (pressure) are present, the turbo's shaft assembly will accelerate and will continue to do so until the wastegate bleeds off exhaust pressure. Air is a fluid, and so exhaust gases are too. Think of the exhaust gases as the "motor" that spins or operates the turbo. So to manipulate the turbo's spool characteristics, you must manupulate the motor, or gases in this case.

i hope this helps?

 

Yea i left out many of the ideosyncracies involved concerning turbo size, A/R ratio, engine size, etc. The point was just to describe the wastegate's role in the process and how it is the regulating factor on the turbo's rpm. As long as the turbo's compressor wheel and housing are capable of moving the extra air, it will still create the amount and "quality" of boost. Quality refers to the temperature of the air. The more temp, the less the intake charge density. The cooler, the more density which means more oxygen molecules per unit volume. A T49 wouldn't work too well on a 383 much above 6 or 7psi i suppose as they are only effecient up to 600cfm of flow (i can't remember what the exact specs are right now), which a healthy 383 will eat that much air pretty easily.