Boost oscillation- on external gate!
 

I have a TIAL external wastegate with a 15psi spring inside it.

The gate signal is plugged directly into my compressor housing port.

My boost is oscillating between 6psi and 18psi.

See attached plot:

Attachment 241518

What do you think would cause this?

Every car Ive tuned or ridden in with a TiAL had rock solid boost and no issues.
I would start checking your vacuum source/routing.

It sounds (from the many times you keep finding new issues) like you really should take more time with and put more effort into routing everything properly and without leaks.

Tell us about how you're using a large hose, so large that it will barely grip the barbs.

Are you using a boost controller? (I had this problem)

Are you sure the turbo inlet and outlet are sealed-up tight?

Are all couplers right?

Did you install the spring or open it up?

Are the plugs tight in the gate, and do you have one port open on the top of the gate?

see ^

are you positive the spring in there is for 15psi?
does the gate go to atmo or routed back in?

This was actually a problem at first- the nice tight fuel injector hose got brittle and started to leak. Put a fresh silicone hose on and still had the same issue though.

No, directly routed with 1 hose compressor to gate.

Everything should be but I will check it again.

Everything should be but I will check it again.


Yes I installed the spring and yes I opened it up.

Can't be more than 15psi unless you stack springs. See here. (pdf)

http://www.tialmedia.com/documents/w3_tial_38_sp.pdf

post a screenshot of the log showing the oscilation

Are you absolutely certain you did not pinch the diaphragm, by starting the bolts then checking visually for clearance?

Are you certain the spring is seated in the grooves?

've heard of people twisting the spring (it grips at the housing) and causing problems like this. You should take it apart and inspect the diaphragm.

That is what I am thinking too. There's not much else to go wrong.

Unfortunately I think I will have to take off my turbo to do so. sigh

^^ what he said. you're showing us power oscillation which could be caused by things other than boost oscillation.

needs more BOOST log.


http://www.boostedmiata.com/gallery2/d/4830-1/lean.JPG

http://www.boostedmiata.com/gallery2/d/4839-1/noise.jpg

http://www.boostedmiata.com/gallery2...e_olderguy.jpg

OK Here's a log when it was doing it's thing.

hydra have an over boost? are you setup for spark cut only? I'd look into that...
the first dyno i posted was a car trying to run 14psi with a 12psi overboost.

won't boost cut stop him from making a complete pull all the way past redline?

or are we talking about some sort of "soft cut" that will dumb down the boost without completely cock blocking him?

not if you keep on throttle. try it on your MS...stay on it, youll just bounce on/off limiter.

Yes overboost was set to 20psi and it hard cuts fuel for 1/4 of a second. It's very noticeable.

That first dyno chart of yours really does look similar though.

My new license plate will be:

VOMTCMT

I just went for a drive and my girlfriend datalogged. She was not impressed by my car's unconventional power delivery. Boosted part of log is attached. I am not hitting boost cut.

So it is probably a stupid mechanical issue.

Update.

I figured out the problem.

Attachment 241513

What's wrong with the circled item in this picture? Those of you who have worked with an external gate before should be able to figure it out.

This really is worthy of much facepalm. If I had a sense of shame I would not post this. At least I was not the only one who missed this though. Yesterday all of http://www.amstuning.com/ and element tuning were staring at the thing and did not notice despite them installing hundreds of external gates.