I ran my 3 port that way. Was VERY sensitive. I didn't like it.

 

That's odd, I've done this several times on 4-5 different cars with no issues. Thinking a lot of that has to do with gate placement and size. I can run 9-30+ and everything in between very easily with 2 properly placed 38mm gates. I do run a small pin hole in the top line to ensure it can vent properly.

 

I was wondering how it vented.

 

the top chamber has the valve going down through it. So it generally vents ok without the hole depending on the design of the gate. Some "top sides" are tighter than others.

 

I run two 46 gates on my twin turbo. Placement is very good. With 4 1/2lb springs, I can run 4 1/2 -30+lbs with no issues controlling boost with just boost pressure on the mac valve. No need to reinvent the wheel imo.

 

I was simply stating 4 ports don’t give you any more range than a 3 port. The best they can do is block the signal 100% to the lower port and open it 100% to the top. Both can easily do that. So your min/max numbers are the same with a 3 port or a 4 port.

In my experience 4lb springs won’t ever make 30+ (without onboard air). At least with every setup I’ve done. I always use the supplied 10lb spring. Makes roughly 10lbs at the manifold with the lower port open 100% and nothing going to the top.

With no boost reference going to top or bottom (spring alone). You should get roughly double spring pressure. I saw about 20lbs on spring alone with no ports connected. Then adding 100% to the top of the gate and no signal to the bottom it should double again… so around 40lbs.

That assumes 1:1 Back pressure and reasonable valve surface areas etc. So numbers will very a few psi. But I don’t see how a 4lb spring nets 30psi+ Usually only see 4x the spring (less once you factor in back pressure) You are claiming over 7x spring pressure. Not sure how that works. Not saying it doesn’t, or that I don’t believe you… Just don’t follow how you get 7x spring pressure.

 

I guess my setup never talked to you?

 

Indeed it did not.

But ditch the 4 port and run a line straight from the turbo to the top port. That's the most boost you're gonna get using manifold pressure to the gate.

A 4 lb spring doesn't net 7.5 times the spring pressure in any world I know. No matter how ya figure it.

I mean this is straight from Tial. They probably know a little about wastegates...

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I have asked for 15# and getting it with a 3.5# spring (that's what it makes with the boost controller off)

 

Boost Controller OFF or all the lines disconnected from the WG to the top and bottom of the WG is open to fresh air?

ks

 

With no power to the 4 port BC, feed from the cover, lines to top and bottom.

 

Maybe I'm wrong but if I'm following the system correctly then when the WG valve is trying to open it needs to draw in air through the tubing on the bottom of the WG port and push air out the top port. But the solenoid is closed so the WG valve cannot open due to no air being drawn in.. if I follow the system correctly then it won't open at spring pressure.

When I test boost using only WG springs I disconnect the tubing from the WG's completely so I'm taking out the entire solenoid "system" from the equation.

With the key ON disconnect the top and bottom tubing from the WG and blow through each tube. If there is a restriction and you can't blow through the tubing then this can affect when the WG opens.

If disconnecting the tubing still produces that much boost over the springs then those springs may not be rated correctly. One thing I could never find out is are the advertised spring #'s the actual spring rate (15 lbs/in) or an estimated boost psi (15psi)...

You could calculate the spring rate yourself of those springs, just measure how much they are being compressed in the WG when they are installed and since you know what PSI they actually open at and the WG valve diameter..


ks

 

Spring rate isn't the only factor, which might be why it's not published. Heat on a spring changes it's effective rate as well, so depending on where you place the gates and how long the vehicle runs the rate can be lower or higher.

Pre-load matters too, a longer spring of the same rate will crack later, a very heavy spring with little pre-load could crack sooner than a light one, but take more pressure to go wide open. Depending on the rest of the system the gate just cracking could be enough to stop boost from rising. I think the people designing the systems an specifying springs do their best to put the rate and length in a sweet spot, but they can't control the rest of the install.

 

I may not be doing it correctly. The WG is a cheap eBay unit. My neighbor let me have the lightest spring he had left over from his precision turbo WG.

My understanding (which could be wrong). When there is no power to the WG, or 0% duty cycle the boost from the cover flows through the Mav valve to the bottom of the gate. The top of the gate goes back to the Mac value and out the vent.

At 100% duty cycle all boost goes to the top and the bottom out the vent.

Not really sure what happens at say 50% duty cycle I assume some to the top and some to the bottom.

I did a bunch of fiddling with the spring that came in my second gate when I had boost creep.

(Might could have been resolved by un pinching the diaphragm on the original gate. It may have been limiting value travel?)

I bought a digital scale and measured the install height of the spring in the gate, and how much lift the valve had. Put it in the press to find out how many pounds the spring put on the scale at the install height. Measure the size of the valve and estimate how many pounds per square inch the spring is worth.

Don't remember what I came up with, but decided the spring that came in the second gate was good enough to use. I think of it as an overflow gate with a much stiffer spring with good priority on one bank.

 

Edit: I reread my thread. I put a different spring in the gate, one from the original gate.

I need to get it back to the track to test.

 

I'm not sure why you don't believe what I'm saying?

Attached is a screenshot of a log. 4.5lb wg springs installed. GPC1 is mac valve duty cycle. As you can see, it is way over 2x or even 4x. There is more boost left in mac valve duty cycle.

I didn't feel like digging for a 4.5lb pull log. I'm sure you wouldn't believe it anyway.

Now before you come up with some excuses like; WG's are to big, WG's are to small, WG don't have good flow to them, WG have priority flow, etc., that's what my setup will do running a 3 port Mac valve. Manifold pressure goes to the bottom of the gates (full time) and mac valve output goes to top of gates.

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Not sure why you think I don’t believe you, I do. I’m only saying I don’t understand why it seems to work for you. The most I’ve seen is a tad over 4x spring pressure. That is pretty standard from the 10-20+setups I’ve done. And usually, more than enough range.

I used manual ball valves on one of my cars to switch between "street" and "track". Basically open to lower port only for street. Then I'd use a ball valve to close the lower port and open the top. S0 100% to the top port, zero to the bottom. 6lb spring net me about 6lbs on the street and would creep to a little over 26lbs at the track. Your setup seems to be making 7.5x spring, which isn't common.

What I’m saying is what you are doing is not what is not optimal or even recommended. That is straight form the manufacturer of the top WG’s in the industry. So when giving basic advice to others trying to setup a basic system, it is often confusing to throw out a scenario that isn’t “Standard”.

 

Drove the mustang today with no power to the mac valve and the light spring it drives stockish and turbo spool is pretty slow. 1,2,3 gears making a left hand turn.

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With the power going to the mac valve (Holley is controlling with custom MAP based boost control, I am targeting a rising boost trying to keep it reasonable though peak torque, But in reality on the street the turbo might be on the large side so its still spooling. This is 2nd and 3rd gear from a roll.
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4.1 PSI with the power off, 15.8 with it on targeting 15#, 35% on the mac valve.