Best way to plumb a WG

milldog

milldog

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May 9, 2009
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I am new to external wastegates and would like to know the best way to hook up the boost lines. I am running a HE351/S475 set with a Tial 38mm WG. The wg came with a .9bar spring and I am using that for a starting point. I have overall boost going into the side port of the wg adjusted by a boost elbow. Is this the best way and change springs if I have to? Or should I run it into the top and let drive pressure open it up by pushing on the seat(guessing it would open when DP becomes greater than overall+13.05psi). I am thinking the second way would over speed my secondary. Not to sure which way would be best to save the stocker from the excessive DP"s. Open for all suggestions. Thanks guys!
 
We plumb ours with drive pressure to the top combined with the spring to offset the opposing drive force on the valve face, keeping the gate closed as you build boost. Then in the bottom side we regulate in enough boost to overcome the spring/drive holding it closed to lift it at your desired point.
 
cool Im going to try that. Anyone have a different way they are running it?
 
I run regulated drive to the top, regulated boost to the bottom. I suspect you could run regulated boost to the top and top only. I haven't tried it. Maybe some others have. What you have to watch for is before the charger is spooled, you will see some pretty high backpressure, with not much boost. That might be enough to overcome the spring.
I also suspect you could try just regulated drive to the top. If I recall I think it takes 30 psi to move the piston with both springs. SO if you measure the piston diameter that will give you the force it takes to move it.
Then measure the diameter of the valve, and you can figure out what drive will open it. Then measure the diameter of the top side of the gate, figure out what drive you want the gate to open. Say that is 50 psi of drive and that equals 150 lbs of force. Your springs say provide 100 lbs of force, so you then need to make up the other 50 lbs with pressure to the top.
 
Like Zstroken's set up, We have had to run a regulator to the top in cases where drive was heavy enough that we need to put a ceiling to the system after a certain point in the run to allow the gate to open fully and relieve the excess pressure. Its a good idea to plan a second regulator in if you are running an overly tight turbine housing since they dont add much to the cost of the system. We use Parker 14R regulators, its a couple bucks more (still under $20ea) but they are rock solid in their operation.
 
At what point is your drive pressure to total boost getting out of hand. I know 1:1 is ideal but how high is still safe? Right now I am 1:1.18 (55boost,65DP) I would like to dial it in to get about 65psi of boost so what should be the highest I see for DP?
 
I would want to keep it below 80 but without knowing your fuel capability you may be able to exceed that by a long ways.
 
Thanks for the info. Im only running 90's so I doubt I would be able to get it over 80. I was thinking 70-75 at the most so it sounds like it should be pretty good.
 
You're welcome and I would think you wont be that high with those injectors either.
 
ok im confused which air is plumbed to the top and which to the bottom. this is on a single setup. and how do i know my gate is only opening when boost hits 50 psi.
 
The way I am running, thanke to the guys that helped me out on this thread, is drive pressure to the top and regulated boost to the bottom. I havent needed a regulator on the top yet. The DP to the top will help keep the wg closed against the pressures in the manifold trying to open it prematurely. And the boost in the bottom will control the opening.
 
Kenny, give me a call when you have yours in front of you and I will walk you through the set up. Chris
 
that is the plan chris thanks, i was just wondering if theres anyway of knowing your not loosing drive pressure befor your desired boost, aside from temperaly running the WG exhaust where you can see it for tuning.
 
Did you get drive pressure in the top of the wastegate, and intake boost in the bottom? Is`nt the hot exhaust hurt the diaphragm. Regards
 
If the wastegate is functioning properly you won't have exhaust gasses traveling at a significant volume to heat it up. It is basically a trapped system, plus you should coil some copper tubing up to let the heat dissipate.
 
When you plumb it that way, the waste gate only dictate the ratio between the drive pressure and intake pressure, not the maximum pressure or?? Have it been plumbing that way on a original stock setup on some engine? The pressure from the exhaust on upper side of the Diaphragm and the spring will give the force to hold close, and the intake pressure and the and the pressure on the valve in the exhaust will open it or? Is it just to try to get it right, or did you calculate with areas on Diaphragm, spring pressure, area on valve?
Best regards from Sweden
 
I have an E.D. wastegate, running regulated boost to the bottom port with unregulated drive pressure to the top port. I assumed that the drive pressure pushing up on the bottom of the valve and the pressure pushing down on the top of the actuator would be the same? Then it was just the boost vs. the spring pressure to determine when it opened up. But I have a 50mm wastegate and the valve size is probably closer to the actuator piston size.

Milldog, how do you like that setup? I was going to run the same setup eventually, but I wasn't sure about what specs to get on the S400.
 
Curious question: Why use drive pressure at all? I realize that I have only set two of these up on my truck but I have yet to use drive pressure and have yet to have an issue, boost seems to work just fine.

Educate me!

Jim
 
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