Tial 38mm WG question

[Kdouglas89]

Hey guys,

I purchased a tial F38 38mm wastegate during the off season. I installed it off of my o2 housing with my ported flapper hotside. I noticed that off just wastegate I was running 22lbs~ of boost, which was fine for the off season, and didnt hook up my Hallman MBC.

The problem : My buddy mentioned to me that I was using the wrong Vacuum ports on the tial. The tial came with the line running off the top, and the bottom port being vented. He said I should be running from the bottom, and venting the top. I just tried to swap the fitting, and it seems the bottom port thread is smaller.

I checked this diagram on install instructions, but it doesn't seem to help much.
http://www.turbomaster.info/eng/applications/instalation_w3_tial.php?wg=F38

Any help would be appreciated.

 

[Smilinjay]

Your friend is right. The bottom port will push up on the diaphragm to open the wastegate at lower boost, and the top port will assist the spring in keeping the wastegate closed at boost higher than what the spring is rated at. For instance, if you have a 10 psi, spring it will open at 20 psi with no boost signal on either ports. If you attach the boost signal to the bottom port, it will open at 10 psi. If you attach the boost signal to the top port, it will open somewhere above 30 psi.

I just checked my tial f38 and both fittings were the same size and thread.

 

[Kdouglas89]

I just checked my tial f38 and both fittings were the same size and thread.

Thanks for checking that, makes me wonder if I accidently bought a ebay tial. The diaphragm is orange though

 

[Mello]

For instance, if you have a 10 psi, spring it will open at 20 psi with no boost signal on either ports. If you attach the boost signal to the bottom port, it will open at 10 psi. If you attach the boost signal to the top port, it will open somewhere above 30 psi.

I don't think I understand this correctly. I was under the impression that with a 10lb spring no vacuum line connected would be limited to only the 10lb of the spring and most boost would be is 10psi. Connect the line to the top port could at best boost to double the spring rate or 20psi in this example & with a boost controller of some type would let you adjust to between the these two min/max limits, again in this example between 10 - 20 psi. Where's the extra 10psi coming from?

 

[enriquez2000]

You can always make a gate open later by bleeding air out with a mbc if you want more boost

 

[Smilinjay]

I don't think I understand this correctly. I was under the impression that with a 10lb spring no vacuum line connected would be limited to only the 10lb of the spring and most boost would be is 10psi. Connect the line to the top port could at best boost to double the spring rate or 20psi in this example & with a boost controller of some type would let you adjust to between the these two min/max limits, again in this example between 10 - 20 psi. Where's the extra 10psi coming from?

External wastegates work more or less in the reverse of internal wastegates. So while what you said would be true for an internal wg, it is pretty much the opposite for ewg. Inside an ewg there is a diaphragm, with one boost port on the top and one on the bottom. I have a 1 bar spring in my wastegate and it opens at ~14psi with the boost signal to the bottom port (with no boost controller). With no line hooked up it would open at 28psi. I have never really played around with the top port but it is more commonly used with electronic and dual stage boost controllers.