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Overboost with Tial 38 install. What am I doing wrong
Yesterday I finally replaced the original WG unit with a used Tial 38 I got from a fellow forum member quite a while ago.
The Tial came with adaptor plates pre installed so installation was quite easy.
I hooked the original boost line coming from the CV to the Tial middle port (instead of the top port which I understand is for boost control).
I left the top port open for now.
I checked the WG and it had a red spring in it (see photo below), which I though will give me 0.8 bar boost, but when I test drove it, it felt much more and the boost gauge went way beyond 2 which probably means I was way over 1 bar.
Does anyone have an idea what is wrong here? I do not have another spring to test with, but if it is the spring rate, I will order a new spring.
Just to add one thing, I recently installed VEMS and I think that with VEMS the CV is not used.
Can that cause the issue? Do you think that hooking the boost line directly from the Intercooler hard pipe will help?
BTW, by design, the factory wastegate's valve orientation allows it to open because oncoming exhaust flow/pressure act upon the backside of the valve face and actually force it to open.
The Tial, oncoming exhaust flow actually keeps it shut.
That's why the Tial hits harder compared to an old factory one that creeps in.
The valve on the Tial has to open in the face of exhaust pressure keeping it closed.
The factory design has a bit of a safety built in to it.
If you have an air pressure source, apply 20psi to the ports with a finger lever controllable hand blower with a rubber tip.
Hook your boost line to the one that opens the valve.
Sounds like you should: 1) check to make sure the wastegate isn't installed backwards, and 2) route your own control lines (and manual boost controller or VEMS solenoid) rather than using something that is/was from the factory cycling valve. Lots of threads here -- here's a sampling showing both the right and wrong orientation.
Thanks for the info.
I plan on adding a solenoid (MAC) to have and EBC controlled by VEMS.
If I understand correctly it will allow me to increase pressure beyond the 0.8 bar of the spring when I need to.
After exchanging messages with Peep, I am pretty sure I need to connect the boost line directly to the charge pipe (to IC) instead of using the old cyclic valve.
I am not sure if this is the only thing wrong, but I will start there
Just to add one thing, I recently installed VEMS and I think that with VEMS the CV is not used.
Can that cause the issue? Do you think that hooking the boost line directly from the Intercooler hard pipe will help?
This is correct. If you are not using an aftermarket boost control solenoid, bypass the CV and run the boost hose straight to the lower port of the Tial and leave the upper port open. This way it should operate from spring pressure only.
You can add electronic boost control at a later date if you wish. Peep's VEMS config uses the factory CV wires to connect to an aftermarket boost control solenoid, but mine was configured incorrectly in the setting and I got overboost. Peep changed my config and it works great. Here is a bad screenshot of how to plumb a dual-port aftermarket wastegate and boost control solenoid (I highly recommend the HP Academy courses to anyone, by the way):
11-24-2018, 05:29 AM
Overboost with Tial 38 install. What am I doing wrong
