Tial 38mm Wastegate Plumbing

[NCGermerican]

Hi Folks. 87 Turbo. I currently have a Tial 38mm dual port wastegate installed along with an LR manual boost controller (mounted in engine bay). I'm not a fan of the manual controller and would honestly rather have my foot determine my boost PSI. This is not a race or drag car - my goal is to have around 300 reliable HP to keep up with modern cars on the street.

After speaking with Charlie at Evergreen (I have a Raptor X), his was very insistent on just using WG spring(s) to determine max boost pressure. His recommendation is to use 1.1 bar spring(s) to get to about 16 consistent pounds of boost at max throttle.

Because there are no 1.1 bar springs available, I will use a large yellow (0.7 bar) and a small red (0.4 bar) to get to 1.1 bar.

My question is about the vacuum line plumbing. Charlie said that I would run the boost source line from the factory location (banjo bolt on pipe before the IC) to the LOWER port on the Tial. He said I should leave the Upper port open (vent to atmosphere).

Can I get some thoughts and/or confirmations on this?

Thanks!

[944m3]

This video really helped me understand how a dual port wastegate works.

[whalenlg]

For what it's worth...
My 86 turbo came with a Huntley Stage 1 Cheater turbo and a LR Dual Port Wastegate + LR Manual Boost controller.
Stock cycling valve had been removed.
I could never get it to predictably control the boost. Tried replacing the MBC when I figured out its seals were blown. No difference. Boost would spike to 20+ PSI, so my foot ended up as the boost controller like you mentioned.

After I failed CA smog for mods, I installed a used cycling valve and put all the vacuum lines back to stock. That meant leaving the secondary port on the LR Wastegate open and the primary connected to the intercooler banjo fitting.
Everything just worked. I happily max out at 16 PSI now no matter how much throttle I give it.

[NCGermerican]

For what it's worth...
My 86 turbo came with a Huntley Stage 1 Cheater turbo and a LR Dual Port Wastegate + LR Manual Boost controller.
Stock cycling valve had been removed.
I could never get it to predictably control the boost. Tried replacing the MBC when I figured out its seals were blown. No difference. Boost would spike to 20+ PSI, so my foot ended up as the boost controller like you mentioned.

After I failed CA smog for mods, I installed a used cycling valve and put all the vacuum lines back to stock. That meant leaving the secondary port on the LR Wastegate open and the primary connected to the intercooler banjo fitting.
Everything just worked. I happily max out at 16 PSI now no matter how much throttle I give it.

I think the vacuum lines may actually be reversed on a LR vs. a Tial. The LR pushes outward while the Tial moves inward. I believe that swaps the line routing, but that's what I wanted to confirm.

[four0four]

My question is about the vacuum line plumbing. Charlie said that I would run the boost source line from the factory location (banjo bolt on pipe before the IC) to the LOWER port on the Tial. He said I should leave the Upper port open (vent to atmosphere).

Can I get some thoughts and/or confirmations on this?

Thanks!

Yes, this is correct. The factory wastegate valve moves outward (into the crossover) and the Tial inward (pulls into the wg body).

You can justify this for yourself with a vacuum pump on the top port of the Tial (pulling a vacuum here means the bottom power is under pressure relative to the top chamber)...Or very careful application of low pressure air to the bottom port.

[NCGermerican]

My question is about the vacuum line plumbing. Charlie said that I would run the boost source line from the factory location (banjo bolt on pipe before the IC) to the LOWER port on the Tial. He said I should leave the Upper port open (vent to atmosphere).

Can I get some thoughts and/or confirmations on this?

Thanks!

Yes, this is correct. The factory wastegate valve moves outward (into the crossover) and the Tial inward (pulls into the wg body).

You can justify this for yourself with a vacuum pump on the top port of the Tial (pulling a vacuum here means the bottom power is under pressure relative to the top chamber)...Or very careful application of low pressure air to the bottom port.

So if I understand this correctly, if I put vacuum to the top port of the tial, it should remain closed until 1.1 bar (16 pounds) of vacuum pressure is achieved and at that point, the valve should open?

[four0four]

Perfect vacuum in the top chamber would only result in 14.7 psi against the spring - so no, but if you installed a weaker spring for arguments' sake, then yes. You miiiight see it begin to move. Sorry, I hope that's not confusing!

[944m3]

This might be semantics or I’m missing your point. But I would not think of it as vacuum.

This is how i understand it, please someone correct me if I’m wrong

If you put the pressure from the intake via the banjo bolt to the top of the Tial wg, you are adding pressure which helps to keep the wastage closed. Notice I say help. If your spring is 1 bar, and you produce 1 bar boost, the heat or gas pressure in the crossover pipe will need to be 2 bar to open the wastegate. The pressure at the top bar assists the spring. This a very simplistic explanation but both work together to keep the wastegate closed so the engine gets as much boost as possible. Note, this not a good thing in most situations.

If you put the pressure on the side port you are helping the spring “open”. You can control how much you “help” the spring with a boost controller.

The point of a dual port wastegate is that it allows you to more accurately fine tune the opening of the wastegate using a boost controller because you can control the pressure helping the spring or countering the spring. It’s a balancing act. The video I linked does a good job at explaining this

[NCGermerican]

This might be semantics or I’m missing your point. But I would not think of it as vacuum.

This is how i understand it, please someone correct me if I’m wrong

If you put the pressure from the intake via the banjo bolt to the top of the Tial wg, you are adding pressure which helps to keep the wastage closed. Notice I say help. If your spring is 1 bar, and you produce 1 bar boost, the heat or gas pressure in the crossover pipe will need to be 2 bar to open the wastegate. The pressure at the top bar assists the spring. This a very simplistic explanation but both work together to keep the wastegate closed so the engine gets as much boost as possible. Note, this not a good thing in most situations.

If you put the pressure on the side port you are helping the spring “open”. You can control how much you “help” the spring with a boost controller.

The point of a dual port wastegate is that it allows you to more accurately fine tune the opening of the wastegate using a boost controller because you can control the pressure helping the spring or countering the spring. It’s a balancing act. The video I linked does a good job at explaining this

Applying vacuum to the top port would only be for testing purposes (verify spring pressure) with the wastegate off the car. While on the car, the boost source would attach to the side port and the top port would vent to atmosphere.

My goal is to have the accelerator and the spring be the boost controller since the manual boost controller isn’t very reliable and only accessible in the engine bay.

This gets confusing which is why I posted up for some advice.

[Tom]

Curious advice from Charlie at Evergreen. Legions of 951 folks have used a cabin-mounted manual boost controller and dual port wastegate over the last 2 or 3 decades, with good reliability and control. Much easier to dial in to your desired boost level too. You might need some trial and error with springs alone to get to an optimal boost level. I'm sure Charlie has his reasons, but sitting here I can't think of an advantage of eliminating the boost controller?