Although some people might not think it's so thought provoking (IE: Todd ) -- I was thinking about what to do to achieve over 10psi on the 745i wastegate. As some of you may know, the 745i wastegate automatically opens at 10psi due to the pressure in the exhaust manifold overcoming the spring force of the wastegate, thus opening it and controlling boost to 10psi max.
So the wastegate is controlled by boost -- when a certain amount of boost is made the wastegate opens. And the 745i wastegate will open at 10psi reguardless.
What if I were to use my boost controller on a VACUUM line(anything pre-turbo) and control the max vacuum seen by the wastegate. Would that infact force the wastegate shut until the manifold pressure overcomes it? Would that also force the wastegate shut eliminating the problem of it being slightly creeped open during the first two gears, reducing the amount of boost built --- thus allowing me to make better boost in low gears??
Vacuum would open it since you are pulling on the reverse side(top) of the diaphragm, and it would open it more efficiently since once the air is gone on the top side of the wastegate it will start pulling the kevlar diaphragm loosening the spring tension.
This is why they place bolts on the top of the wastegates so that it adds spring tension and holds it closed longer. Not sure if adding boost through a check valve to the top chamber of the wastegate would add tension or just blow the diaphragm.
Honestly either the 745i fix or the aftermarket wastegate are the only logical ways to go.
and crack the cast iron fins in the process? There is no real way to support the wastegate for this type of mod. It sucks using 20 year old technology.
Feed boost pressure via a pressure regulator to the back side of the wastegate diaphram. You want a small regulator that has fair reolution down to a couple of psi. We did this on the TCD 325 "Buzzbomb". You want more boost, add a little more pressure to the back of the wastegate. You could cockpit mount the regulator too.
Run one signal line from the intake manifold to a "T" fitting. Off the "T" a main line to the wastegate actuator (to open the WG) the other line off the "T" goes to the regulator, from the regulator to the "back" side to the WG to keep it closed.
I will do the MS and possibly the TCD kit before I even consider a different wastegate. 480 is just for the 48mm gate they already have. It is an extra 250.00 for them to R&D the adapter. And this is U.S. Dollars not OZ Bucks. At this rate I would rather save my pennies for the TCD kit, finish building the B35 engine, and sell the M106 block/turbo if it has not blown up by then.
) -- I was thinking about what to do to achieve over 10psi on the 745i wastegate. As some of you may know, the 745i wastegate automatically opens at 10psi due to the pressure in the exhaust manifold overcoming the spring force of the wastegate, thus opening it and controlling boost to 10psi max.
Just looking at any possible situations.
