Super excited because it's been about a month since I dropped it off. It's an 05 gt, and is making 347 rwhp with 4lbs of boost. I'll post pics later. My question is this, if I make 347 at 4lbs of boost, how much boost will I likely have to run to get to ~425-450? Is it a linear function, exponential, etc? Right now I don't have a boost controller on it, but I plan on adding guages and a controller around Christmas.

Anyway, just wanted to share my excitement and ask a little question too,
Thanks!
Pete

 

why not change the spring on the waste gate and see what it does?

 

That was my original plan. I think turbosmarts usually come with 3 lb springs, but I had them add a 7 lb spring to mine (so it should have been 10lbs). Anyway, it didn't work so I'll just do the boost controller over Christmas or something. I went and picked it up today and it was fun to drive - but raining most of the time because of the hurricane that's breaking up over the midwest.

I did have a few dry spots and it seemed fast, but not like I was hoping. I'll drive it again tomorrow to see if my thoughts on this change any. I guess it spools fast enough, it just doesn't pull me back or anything. I also wasn't launching at 2500 rpms or anything either.

 

You can ball park an estimate for the boost you will need to get the 450 hp using the pressure ratio method. Since you already know you make 347 hp with 4 psi of boost, the expected hp can be calculated. First, your n/a power is found by dividing the current hp (347) by the current pressure ratio (14.5+4)/14.5= 1.27

So n/a power is 347/1.27 = 272 hp


Now, you know you want 450 hp, so divide by n/a power (272) and you get a new pressure ratio of 1.65 which means you need (1.65 x 14.5) - 14.5 = 9.5 psi boost to make 450 hp

This is only theoretical of course , and assumes the numbers you gave are accurate, but its in the ball park.

 

Thanks TurboLou, that's a great explanation.

 

That has me more confused now. LOL Where does the 1.65 come from? Or is that the standard number?

 

1.65 is the required pressure ratio. 450 / 272 = 1.65

 

What's your set up?

 

If you have a 7psi spring and are only making 4psi then you have an issue that needs to be addressed. Just make sure that once you fine out where you problem is you check the tune and make sure you are still safe (timing and fuel).

 

Hi Guys,
Sorry for the delay, I've been super busy. I will try to put pics up tomorrow