Bad wastegate?
 

So, I am beginning to think the BNIB wastegate I bought earlier this month is a lemon, and would like some input.

The main issue is it is very inconsistent as to what boost pressure it is going to hold. It always overshoots, which I understand to mean the wastegate hole on the turbo needs some porting. However when it falls back down, it holds different boost pressures. Some pulls it will hold 7, some pulls it will hold 9.

When I referenced post-TB, it did the same thing, but held somewhere between 10 and 12. When i moved the wastegate reference to the compressor housing, it fell and held between 7 and 9 as I said above. I added an MBC to get things back up to where I had them tuned before, and now it holds somewhere between 12 and 15.

Are there any other likely causes to behavior like this aside from just a bad wastegate?

Just out of curiosity, what are you using to measure the boost pressure? (Please don't say an autometer gauge...)

Mechanical autometer gauge. Reads pretty much the same as megasquirt. This issue has been confirmed via both the gauge and tunerstudio.

Ok, well as long as you are logging it in the Megasquirt to make sure. I have found the autometer gauges are not really accurate enough to say if something is 7, 8, or 9. Is it possible the arm on the wastegate is binding at all?

Visually inspecting it not in motion, I would say it is unlikely. However I plan on hooking it up to a compressor tomorrow to see what pressure it opens at, and will be observing any binding issues both in the actuator and the flapper.

On checking its cracking pressure, you will get a false number. You can certainly read the pressure applied to the diaphragm at which point the actuator begins to move. But, that's only about 60% of it. Exhaust gas pressure applied to the wastegate valve is the other %age. That you cannot easily duplicate.

Your test will reveal any binding, so continue by all means.

corky

I discovered a wastegate binding issue on the efr last weekend. Somehow my arm bent, I'm assuming its from when I was trying to slam the engine into the bay at 1am before a race. Just remember your compressor chuck is probably going to hold air pressure so you need to pull the hose off or something to get the wastegate to go back quickly. That means it may not be going back slow because of the binding.

A valid point I had not considered.

10-4. I can just pop off the quick release instead of releasing the trigger. Interested to see if we uncover a binding issue now, though I won't cross my fingers.

Also doing the first compression test since the car has been boosted. Fingers are definitely crossed here.

Results of all the above tonight.

So as it turns out, the wastegate setup that "looked right", is far from okay. The actuator is unable to open the wastegate anywhere close to 90deg. I suspect I am going to have to fabricate a whole new wastegate bracket and re-position things. Appreciate all the input! Video below, along with compression numbers. I am a little disappointed by the compression numbers when compared to my results from 11 months ago. The rings seem to be wearing quickly...


https://cimg7.ibsrv.net/gimg/www.mia...e3cabcb007.jpg

That is some serious binding! Well that was easy, now to solve it!

Those numbers are at least even!

Admittedly, when you guys kept saying binding, I had a completely different image in my head. I was thinking like: The rod extends, hits the flange or something and can't move any further. The rod simply not being able to push out far enough makes much more sense. FYI, it took ~16psi to get it to move, as you can see in the video.

I guess the initial plan is going to be trying to modify the existing bracket that I have. Probably cutting a section out, bending it to close the gap, and welding it back to get rid of the angle it has now. Then re-positioning and tapping new holes where it needs to be.