It is an 91 turbo motor in an 88 SE body. Stock turbo running purely off the wastegate spring(direct vacuum line from compressor housing to WG) with a medium streetport. Now I know that stock boost should be around 8 or so on an S5 but is that wastegate spring pressure or with a solenoid connected?

This was measured with an aftermarket boost gauge and only a pull in 2nd gear til redline and part way through 3rd.

 

Thats with the solenoid connected. Wastegate spring pressure is only about 5psi. Curious, is it creeping at all in 4th/5th?

 

As mentioned, the S4 & S5 turbos share the same wastegate spring (5.5psi). If you intend to run more than stock S5 boost (7.5psi), forget the solenoid and go with an aftermarket boost controller. The S5 turbo duty solenoid is a bleed type boost controller anyway, which will allow the wastegate to crack open before 7.5psi is reached. A ball and spring MBC or an EBC will give a much quicker spool.

 

Thank you for your responses!

I really haven't taken it into 4th or 5th at WOT yet. The motor only has 250miles on it since I rebuilt it. Though it shouldn't too much, it just has a gutted exhaust and the wastegate is supposedly ported already. He had an ebay MBC installed when I first bought the car but since it had a blown motor I took it off and figured I would just run straight wastegate, but after seeing this I think I will put it back on and shoot for stock boost for now.

 

You should put some more miles on it before bringing the boost up. I know a lot of people even like to run 0 boost during an engine's break in period to play it safe.

 

What solenoid are ya guys talkin about? the pressure sensor on the strut tower?

 

^^^^^^ The pressure sensor isn't a solenoid. The turbo duty solenoid is with all of the emissions solenoids.