Build Thread Want To Blow 5 Years And $50k On A Foxbody? Step By Step Instructions Inside!

[hoopty5.0]

Pardon my dumb questions, but the logic doesn't add up to me. I understand how a WG works in theory - Once you hit a certain pressure, the WG diaphragm is pushed open and any excess pressure bleeds off over the set pressure. I also understand that running on a spring isn't going to net you the exact rating of the spring. But how did you make 15 lb on a 3 lb spring?

 

[FoxMustangLvr]

@RacEoHolic330
Doesn't look like it but do you have the ability to adjust spring preload?

 

[RacEoHolic330]

To answer both your questions, that's what the electronic boost controller does. The bottom of the wastegate sees manifold pressure (from compressor outlet) and the top of the gate sees an input from the boost controller. The manifold pressure forces the diaphragm open diverting exhaust gas to limit boost. The pressure from the boost controller acts against the manifold pressure and tries to keep the diaphragm shut (basically making the spring stronger), which makes the turbo produce more boost than that gate spring would allow by itself. The problem with a tiny spring is that the exhaust backpressure has enough force to push on the wastegate valve and inadvertently compress the spring, which reduces boost. The boost controller then has to fight the pressure from the exhaust to try to keep the gate shut so boost can build. It can only do that to a certain extent, especially without CO2 control. From what I understand, the wastegate spring should rated for about half of what you want your max boost to be. I went with what I thought was a 10psi spring because I wanted around 20psi of max pressure. It's actually surprising that I was able to even make 15psi on a 3psi spring.

I bought a large red (10.1psi) spring, so that will give me 13psi when I use both springs.

 

[RacEoHolic330]

Screw it. Just drive the damned thing until something pops and you have to replace it. hehe

So long as you're making in the neighborhood of 400 HP before 2800 rpm? Win! ...and a ton of fun on the street. lol

That's generally the plan! I do want to see how the car spools up with the correct size spring in it now. I would have to guess that it should spool up much faster.

 

[FoxMustangLvr]

That's generally the plan! I do want to see how the car spools up with the correct size spring in it now. I would have to guess that it should spool up much faster.

Should spool faster. I would assume the valve was cracking open way before you even reached 15psi causing a slower and longer spool.

 

[RacEoHolic330]

Exactly, and then it was only closing as the boost controller started to kick in. I did think my torque curve wasn't steep enough for a turbo car.

 

[RacEoHolic330]

My other concern is that there is no gasket or seal between the top and bottom part of the spring housing. This area sees pressure from the boost controller, so I'm guessing this should be sealed so it can hold the pressure. Is there usually a gasket there? @90lxcoupe @GroverDill, what do you guys think?

 

[hoopty5.0]

How does the boost controller produce the pressure to offset the boost? Is it an air pump of sorts, that can have CO2 assistance?

 

[FoxMustangLvr]

My other concern is that there is no gasket or seal between the top and bottom part of the spring housing. This area sees pressure from the boost controller, so I'm guessing this should be sealed so it can hold the pressure. Is there usually a gasket there? @90lxcoupe @GroverDill, what do you guys think?

Looks like the diaphragm assembly could act as a seal. Check out this exploded view from Tials website
http://www.tialsport.com/documents/explodedmvr.pdf

I know it's not the exact same model as yours but should be similar. You have the V44, right?

 

[RacEoHolic330]

Mine is an older model than that, but I was thinking the outer edge of the diaphragm might do the sealing. I'll have to take a closer look at mine to verify.

 

[RacEoHolic330]

How does the boost controller produce the pressure to offset the boost? Is it an air pump of sorts, that can have CO2 assistance?

The electronic boost controller uses 2 solenoids to control the pressure at the top of the wastegate. It uses manifold pressure. Nothing but vacuum lines. It adds pressure to effectively increase the resistance of the spring. If you have a 10psi spring, but you want to make 14 psi you would set the boost controller to 4psi. It adds that pressure on the top of the spring until the controller sees 14psi and then it backs off. The solenoids (one increase, one decrease) keep constantly working to maintain that pressure on the top of the gate.

The benefit of CO2 is that it provides a constant pressure to the solenoids at all times, which will create more stable boost levels. Important for drag racing, but not as necessary on the street. You can also run a smaller spring with CO2 and still get larger boost numbers because the solenoids will always have something like 40 psi on them all the time.

 

[Noobz347]

It's actually surprising that I was able to even make 15psi on a 3psi spring.

Probably because the waste-gate is too small to bypass all exhaust volume. It only has to be large enough to bleed excess pressure and not a ton of actual volume.

 

[RacEoHolic330]

Ah, good point noobz. That's why we keep you around here.

 

[90lxcoupe]

No idea on the wastegate gasket, sorry im no help.

 

[hoopty5.0]

I can feel my mind expanding!

 

[RacEoHolic330]

Looks like the diaphragm assembly could act as a seal. Check out this exploded view from Tials website
http://www.tialsport.com/documents/explodedmvr.pdf

I know it's not the exact same model as yours but should be similar. You have the V44, right?

I looked closer at mine and the outer edge of the diaphragm sure does seal the housing. That should be good to go. I'm just waiting on my other spring and then I can see how she rips with the gate operating properly.

 

[FoxMustangLvr]

I looked closer at mine and the outer edge of the diaphragm sure does seal the housing. That should be good to go. I'm just waiting on my other spring and then I can see how she rips with the gate operating properly.

Good to know! Did you get some miles on the car yesterday?

 

[RacEoHolic330]

I can feel my mind expanding!

Hurts, doesn't it?

 

[RacEoHolic330]

Good to know! Did you get some miles on the car yesterday?

Unfortunately no. Hectic day. I'll hopefully get some windshield time this weekend.

 

[RacEoHolic330]

I put about 100 miles on the car this weekend. For a car that isn't making boost like it apparently should, this thing friggen rips. Aside from a squeaky left front caliper, it has been perfect so far. It was in the high 80's all weekend and the car had no trouble keeping cool in traffic.

I am going to wire up the relays for the fan and water pump so I can manually turn them on without the ignition needing to be on. When the engine is at about 200 degrees and I shut it off in weather like this, the water temp rises another 20 degrees before starting to cool back down. When I let the fan and pump run with the engine off for about 3-4 minutes, it comes right back down to 165 degrees. Once I wire in my alarm system I can set an output on the remote to turn the pump and fan on or off as I choose. I just prefer to get the engine temps down so the engine bay doesn't bake itself in a parking lot. I can't exactly leave it with the hood open when I go into a restaurant to eat dinner.

It's weird driving a fox with 3.27 gears. 5th is of no use until at least 60 mph. I cruise at 70mph at less than 2000rpm. The sound of the turbo spooling is just heavenly, so I have a hard time keeping my foot out of it. I'm excited to get that other spring in the gate to see if it acts much differently.

Oh, she handles real well too, even with the drag radials in the back. I'm excited to get some some seat time. There are a couple of interior rattles I need to hunt down, but it's a fox, so whatever.