I'm installing the STS kit and am trying to decide whether to hook up the boost reference line for the wastegate to the reference port on the compressor, or to the intake manifold.

The install manual states to hook it up to the manifold (but they already do other things wrong so I can't trust them), and the STS guys (athenG et. al.) said to hook it up to the manifold - so I'm sure things will be fine that way.

However, Julian had said in a post that if you hook up the reference line post throttle-body you can run the risk of tearing the WG diaphragm from going in and out (that's what she said ) of boost - since the vacuum will be harshly sucking the thing closed. Is that true?

The downside to running it off the compressor housing is that boost will read higher there than in the manifold (due to piping, FMIC, etc.) - resulting in the WG opening earlier, and that there might be a delay in closing the wastegate since the boost won't bleed off as much there as it would near the BOV?? Is that right?

I searched, but as usual couldn't find much of anything.

 

get your boost source at the plenum.

 

I dont think this is an STS thing and pretty sure most ST or TT uses the manifold for boost reference... By the way Julian himself used the manifold for both me and goosegoose install.

 

Aarrgh! Why did he have to confuse me

Well, this thread can be deleted now, haha. Thanks again athen.

 

I'm pretty sure that's a bad idea for the reason you mentioned. My boost reference source for the wastegate is in the compressor outlet pipe (JWT kit).

Here is a quote from the Garrett website (link here):

 

That quote is referring to a internal wastegate as opposed to an external...

Does the STS kit use an internal wastegate?

 

I thought I recall reading something from Tial about vacuum damaging their wastegates also, but I'm not really sure... (I have internal so someone else gets to research that )

 

Considering the extreme temperature environment external wastegate diaphragms have to work in, they are extremely durable things. I doubt the vacuum an engine produces is much to worry about.

My w/g I think references both. I would have to check, but top port sees compressor pressure and bottom port sees plenum pressure via the boost controller solenoid. Or vice versa. I don't know, all I do know is my **** works.

 

Yeah, it's an external WG. Since I haven't seen anyone post up about problems with theirs being setup that way, I'm sure I'll be just fine running it off of the manifold. It would have been nice to not have run tubing all of the way back there though

EDIT: Hmm...Tial's install directions specifically show it getting a boost source pre throttle body.

 

Actually, just doing some random searching on the interwebs it seems as though pre-throttle body is the way to go. However, when the turbo is putting out 7 psi, the motor might only be seeing 6 psi. Post-TB reference will be less reactive (might get some spike), and pre-TB reference will be more reactive (most likely won't hit your target boost).

Well, after some searching, it seems as though people have had no problems with a post-TB setup - their wastegate has lasted many miles. The best setup is probably to run it off of the intake tube just before the throttle body (like the instructions show), which would work well with the STS since it's already tapped there. For now though, I might as well give referencing it off the compressor housing a shot.

 

Your pressure in the plenum will always be a bit less than at the compressor due to pressure drop in the intercooler, piping, across the TB etc. Therefore (if you are running just off of the wastegate spring) your car will actually be making a bit more HP if you reference it at the plenum.


Both will work though....... especially if you have a boost controller. I personally use the port on the compressor.

 

Let me know how you make out... I might do the same. The only time I get some spike is when I'm doing some hard shifting but it only last for a couple of hundred RPM. It is not a big deal coz it very short live but if this help solve that then I might try it. Also I'm not sure if you'll have the same problem but I have a .5 bar WS spring and when using just the spring I only see 6psi. Not sure if its the BCS doing it but I can set Utec Boost Map to all 0 and couldn't go past 6psi with my .5 bar WS spring My worry is that if I use the Turbo as the reference then I might just see 4psi

 

Will do. I was thinking the same thing last night: maybe the problem you guys were/are having with the TXS BCS not reacting fast enough causing a spike has something to do with this. I guess we'll see.

I plan on just running off the WG spring just to get started (everything to 0 in the boost map). But like you said, coming from the compressor I probably won't be hitting much boost. The bright side is that I won't have to run a vacuum hose the length of the car

EDIT: And thanks SP for chiming in to add some credibility to this question.

 

lol.. this will also give you an idea how much pressure you loser from the piping and FMIC... What spring do you have? Please dont be the 4.5psi spring..lol

 

Haha, I don't even know. I'll check it when I get home. 3 psi here we come!

 

I would be interested to see what kind of pressure drop you see. Since you are referencing before all of the pressure drops through the piping, it will change based on rpm and flow rate. Maybe the change in flow rate won't effect anything but please post the logs when you do it!!!

I am going home on leave this weekend, I can get you a starter map if you haven't already gotten one.

 

I was able to get a hold of one - thanks though. Another one couldn't hurt I guess

I bought the JeffSoftware LogAnalyzer as well, so I should be able to post up some sweet as screenshots *sarcasm*. I'm HOPING to get this thing going by the weekend, but you never know what could go horribly wrong.

 

Haha this obviously isn't your first rodeo so I wouldn't expect anything to go wrong.

Your build is inspiring me to work on my car