legacycentral bbs

how much of a horse power gain will i get if i get a boost controller and run 11psi, i have everything stock except the exhaust and intake.

15-20 hp maybe.

Mark

A lot of people say 15hp for every 2psi, but who knows?

I believe that is a rough estimate, dependent on the type of turbo. As long as you stay within 70% of the turbo's efficiency range, and the inlet temps don't rise to dramtically (considering you don't have an intercooler), you'll see an increase.

I would honestly open up the exhaust before you go with more boost, considering that's probably a huge restriction.

boostjunkie wrote:I believe that is a rough estimate, dependent on the type of turbo. As long as you stay within 70% of the turbo's efficiency range, and the inlet temps don't rise to dramtically (considering you don't have an intercooler), you'll see an increase.

I would honestly open up the exhaust before you go with more boost, considering that's probably a huge restriction.

Speaking of the efficency range. What is the PSI that the VF-11 is most efficent at?

Speaking of the efficency range. What is the PSI that the VF-11 is most efficent at

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Most likely 8.9 psi, hence the Subaru engineers chose that number four our cars.

Mark,

I think that is incorrect. The optimum pressure at 14.7 PSI atmospheric pressure is +14.5 manifold pressure.

Once you reach 10 thousand feet the turbo is only efficient to 10.4 PSI.

You have to take elevation into consideration. Subaru chose a pressure that could be compatible for the entire range of operating enviroment.

14.7 psi, you sure. That little thing will be burning up by then.

Mark,

There is a thread about it on here where someone did the calculations. At sea level (14.7 psi) the turbo is happiest at 29.2psi total pressure.

Here's the topic you're thinking about ciper
http://bbs.legacycentral.org/viewtopic.php?t=14816

my turbo didnt burn up yet and i ran 21psi mileg on the turbo was 500thousand ks and it still works.

but you did blow up your motor a few times and you have a truck front mount IC right??

Mark,

touche!

So 13 psi is 76% on a car flowing more air, in my rough calculation a stock car with the turbo still under 80% would be about 14.

truck intercooler yes and the motor just blew up at 500thosuand ks i got it with 179ks the best motor subaru makes, it can with stand a beatting its a real rally motor.

I bought a Turbo XS standard MBC. with bypassing the controll solenoid and taking the bleeder valve out (thats how the standard ones work. no restrictian) All I could get the car to run was about 11 to 12 psi at full throttle. If you are on it with just partial throttle than it can raise to about 15 psi. so a boost gauge would be helpful. But if you get a standard controller from them, and back off the valve all the way, you should get the boost you want. those 2 psi make a big difference. one more psi makes an even bigger difference. My car runs great with 13 psi.

the reason you only get 12 PSI at full throttle and 15 PSI at full throttle is because of your boost controller.

You are bleeding off too much pressure, and the Wastegate actuator does not have enough pressure holding it closed. So what's happening is the exhaust gases are blowing the wastegate open at full throttle.

You can do a couple things...you can throw some springs on to hold the wastegate rod closed, or figure out another Boost Controller method

i agree turbo xs does not make good boost controlers. i have the dual stage one and the single one and i could not get past 15psi and it was to hard to set. get hks products the best u can bye