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I have a 745i turbo setup. I believe the boost is set at 8 psi. on the stock application. I have heard that it can be changed with a new spring inside the wastegate. I have also heard it can be changed with a standard boost controller. Can anybody with experience in this tell me how it can be done. I realize that with changing boost level I will need fuel upgrades. thanks for your help

I chopped off the cap on my wastegate and made it adjustable with the stock spring. Welded it back together and it has run at 10PSI without issues.

You could use a grainger valve for further fine tuning.

I thought the ECU stock has a fuel cut if you go over 9psi? Check over at the 745i.com

RussC

russc wrote:I thought the ECU stock has a fuel cut if you go over 9psi? Check over at the 745i.com

RussC

If you are using the 745i ECU.

what about the ecu out of an 86 535i 3.4l manual car? I have heard its around 10 psi but you can do more with an fmu and a chip that retards timing without getting a full standalone system for fuel and spark..??????

Yeah - the 745i ecu only causes troubles...

I'm running 10psi flat right now, but my wastegate has begun to wear a little. I tapped the top chamber, sealed it off, and now I blow boost into there -- it keeps my boost right at 10psi. I'm pretty sure I can bump it to whatever I want... but I'd rather have a more "mechanical" way of adjusting it.

jimbixjr wrote:what about the ecu out of an 86 535i 3.4l manual car? I have heard its around 10 psi but you can do more with an fmu and a chip that retards timing without getting a full standalone system for fuel and spark..??????

Look at my website, the 059 DME is scalable to 1000hp. But it doesn't monitor boost like the m106 system.

RussC

I haven't seen a 745i wastegate but if it's activated via a pressure hose, you can use an "adjustable check valve" as a cheap manual boost controller. I used it with great success on my turbo dsm!

http://www.gusmahon.org/html/boostcontrol.htm

Take a moment to visit the site; it's about the old turbo Mopars!

Monotalonawd wrote:I haven't seen a 745i wastegate but if it's activated via a pressure hose, you can use an "adjustable check valve" as a cheap manual boost controller. I used it with great success on my turbo dsm!

http://www.gusmahon.org/html/boostcontrol.htm

Take a moment to visit the site; it's about the old turbo Mopars!

The 745i wastegate acts quite different from other wastegates...

@ 10 psi it will open and no boost controller will change that.

More than some might know, its a pulsed design, the valve is pulsed a 10 or 12hz which sets up resonace in the exhaust system to enhance flow, and made more low end torque. In much the same way N/A cars tune intakes and exhausts.

RussC

RussC, what is your website address?

I just updated my profile again. It seems it keeps getting lost!

My page is in the profile now.

I really need to make some updates, especially to the tuning pages.

RussC

i have a stock 745 wastegate plus a " home depot" boost control, i've run anywhere from 8 psi to 15 psi,
every turn past 8psi is 2 more psi
totally shut is 15+ psi

Do you have any pics of your setup?

I wouldnt mind running my setup at around 15-17 psi.