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I suggest drilling a tiny little bleed hole in the line going from the top of the gate to the Mac valve. You may not need to do this, but the jgs gates are high quality and I expect little leakage with their design. The bleed hole will give the boost in the line somewhere to vent when the Mac diverts to the bottom port.
Mac valve is just a flow diverter valve that you can pulse to get a desired amount of flow between the ports.
I have it routed exactly like this diagram, at 0% duty cycle all the pressure goes to the bottom port, at 100% DC all the pressure goes to the top . Even bench tested it to verify I have the ports correct before I installed it . Having said that I'll double check the lines again lol.
I finally recieved my boost controller couple of days ago . Hooked it up last night and was playing with it today . Still having issues controlling boost . Have the solenoid hooked up as mentioned in one of the above post . 0% DC makes 5-7 psi , going from 10% to 88%DC I only see it going from 9 psi to 13 psi respectively. Which only leaves me with a very narrow window of resolution to play with .Is that usually the case ? Should I try putting in stiffer springs and see if that works better . If I command 100% DC it will make over 26 psi ( which is where I have the boost cut set ).
And as said before...without the bleed hole, it will be difficult for many controllers to achieve stable control in the mid-ranges
Or just use this for a higher range but easy control.
I'm sure I've said it plenty of times....unless you absolutely need to use that method...do not.
Re-plumb it for the most simple method first to prove it all works.
As mentioned in my first post , its really hard for me to keep the wastegate shut( inefficient setup ? High back pressure? ) . Using two springs and spacers the max I can achieve having both ports vented or pressurized, no boost controller hooked up straight lines to compressor was 20 lbs tapering off to 14psi by redline . Hence my need to put pressure just on the dome to achieve more boost .
Going to try this setup, see if I can get a better range . I did try this setup before I had an electronic controller and just used a plastic barb with a hole drilled into to make a stable 18 lbs tapering off to 14 lbs near redline with a relatively light spring
Ok I tried the above method only to have no control over boost basically spring pressure of 12 lbs didn't matter what DC I commanded unless it was 100% which gave me infinite boost lol .
So I tried switching the hoses around and viola I have full boost control .
So my guess is as above mentioned by stevie turbo is that the wastegate being a quality piece seals very well and needs a vent . If I were to make a small vent at the hose going to the bottom on the wastegate and I'm pretty sure the very first method mentioned in this thread would work very well as well. The problem is the pressure between the top bottom of the dome is always equalized hence it doesn't matter what I do with duty cycle .
The bottom chamber will always leak, the valve stem is never sealed.
The top chamber may be sealed...so drilling a hole for the bottom chamber will be pointless.
My theory is that the bottom chamber is sealed pretty good as well .If it was leaking why would flipping the hoses give me control of the wastegate with the method mentioned in my last post ?
Now with the first method if the lower chamber was leaking putting dome pressure would give me more boost , which it did not . Because there was always pressure at the bottom chamber pushing back on the dome pressure .
But this all theory, I'll try both methods vent the top first and vent the bottom to see what results I get.
This may not be applicable but I had a Huron V1 T4 setup with a 7875 on a 5.7 with a single 44mm WG that I was unable to run a soft spring on to control boost.
I had a 3-4 lb. spring with my EBC to dump boost in the event of a lean spike but (and I'm assuming) the back pressure in the system would cause the gate to open prematurely in the lower gears causing me to not see any boost until top of 3rd and 4th gear.
After installing a higher base springing in the 7-8 lb range I could then control boost with the EBC.
My guess was there was too much BP in the hotside, again this may not be applicable to what the OP is dealing with but I thought I'd share it anyways.
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