I am having a slight issue with my Tru-boost not “holding” the set boost. Right now I have ‘a’ set to 25psi (what the car was originally tuned for) and ‘b’ set to 15psi. Even on setting ‘b’ I am still showing a peak of around 23-24psi.
One of the problems it could be is that I am unsure of my wastegate spring size. As far as I know, it is just the standard spring that was included with the Tial 38mm which from what I’ve found is around 7-8psi. However even setting that, it didn’t change anything. Can I safely (and temporarily) run the turbo pressure line directly to the lower port on the EWG to see where it opens and that should give me my spring rate…correct? Then from there I should be able to set it properly on the tru-boost.
I did notice that even before the FMIC, tru-boost, etc. that it would over-boost with the Perrin MBC on a heavy pull… so that makes me unsure if it is even a controller issue or of the EWG spring is too small or the EWG in general is too small and not able to keep up with the turbo.
For those that don’t know, its an 04 STi with a FP Green, equal length headers, no cat., borla exhaust, and a K&N filter on the crappy FMIC intake pipe connected to a Samco silicone turbo inlet.
Thanks for the help!
Yes you should be able to disconnect the ebc and run just the wg spring. Then check where your peak is and that will yell you the spring rate in it. The ebc will only divert pressure to hold the wg closed. So running just the wg shouldn’t peak over your spring rating even if you set the ebc lower then 7psi.
So if I just set the ebc to say 3psi that would essentially be the same as diverting the vac lines correct? I thought about that (since its a hell of a lot easier than changing the vac lines… which I made nice and tight) but wasn’t sure if that would work in anything other than theory.
And on that note, if I am still seeing over-boosting, (more than what the spring should be) then does that mean the EWG is too small?
Correct, you can leave it hooked up and you shouldn’t max out more then the spring. If you still peak after that, you may have a bad solinoid on the ebc and its staying closed. Unhooking the vac lines for the ebc will tell you if the solinoid is bad or if you have a issue with the wg spring. Basically isolating the ebc from the car.
The ebc won’t run lower then your spring rate. So you would need a smaller one.
The lowest the tru-boost would go was 10psi but there is also an ‘off’ option. I tried both settings and I was still getting up around 26-28psi boost. So when I got home from work I disconnected and plugged the line going into the solenoid from the turbo pressure and lower EWG port (essentially just connecting the turbo pressure directly to the EWG) and even then I was still getting to 26-28psi on a pull. I can physically hear the wastegate opening and dumping… but it doesn’t seem to be holding the boost pressure.
Any ideas?
Is the vent open on the wastegate
With the tru-boost connected, it is not vented, but when I tested the wastegate (line connected from turbo directly to the wastegate), it was vented.
U have four ports all together two on top and two on the bottom right
There is only one port in the center of the cap and then 2 ports on the side… one is plugged .
Ok so the port on top leave it open as a vent and plug one the side and the other to the turbo c if u get your 7psi
A picture is worth a thousand words. It is currently connected so that the top center port is vented, one side port is run to the turbo pressure, and the other side port is blocked.
The only thing I notice is that my turbo pressure line is not on the ‘horn’ of the turbo, but instead it seems to be on the casing itself (still in the housing so it should still see the same pressure I would think)
so all of this was working correctly at one point? what has changed between it working like it should, to working shitty?
ur wastegate diaphram is probably ripped or torn a tad buddy
I never really got on it hard when I first got it, so I didn’t really notice it until a month ago or so. It was over-boosting before any of the recent changes (FMIC, BOV, etc). I had originally assumed it was because I was pushing too much boost through the factory TMIC and BPV but apparently that was not the case. There is a distinct sound when the wastegate is opening and I do not hear anything that would resemble an exhaust leak during normal driving… wouldn’t a ripped diaphram sound similar to an exhaust leak??? I was also wondering if maybe the 38mm was too small for the FP Green at the set pressure… especially mixed with the completely free flowing exhaust (no cat).
the diaphram inside the WG would not sound like a leak, it will cause your pston to not open properly and thats why you prob hear it opening, but its not open as much as it should be.
take the wg off, take off the top where the spring is located, and inspect the insides. if your wg is hooked up without a boost controller and its not limiting your boost to your spring pressure, you are either creeping like a motherucker OR your wg isnt functioning properly.
Well i was thinking about changing out the spring anyways since it is probably only a 7psi spring, but what would be a good spring to go with? I would like to be able to run down to 15psi for daily driving and only turn it up when “needed”. So would a 1bar (14.7psi) spring be good? Or should I just stick with the 7psi?
I beleave that the top port shouldn’t be connected to anything
well imo if you want 15 psi, do the closest spring to that. then run what you want to run full tilt on your EBC. then when you want to go down to 15 psi, just turn off your EBC
if he is running it off the spring, then you are correct