jackal8788

So I've been talking with a local guy who does a lot of custom exhaust fabrication and we are looking at options for a custom EWG header. I wondered if the flanges for the header (the two which connect to the engine exhaust ports and the one which the turbo connects to) can be purchased anywhere? My gut feel was no and that those who have had custom headers made also had the flanges cut by their fabricators. Is this correct? He has a laser table so I know we can cut the flanges. Just don't want to do it if they can be purchased. Second question - does anyone know the tubing sizes that are have been successfully used? I'm talking for individual runners and size once the runners merge. Thanks in advance all! Sent from my iPhone using Tapatalk

Well, I made a new plate today with 1.375" diameter hole because as noted, the other plate helped but wasn't enough. Annnnnnnnnnnnnnd....................IT WORKED!! I maxed out at about 10.5 PSI which is just what I was seeing the wastegate actuator move at last weekend when I tested it. This was the happiest I've ever been to only see 10 PSI on my boost gauge I don't see this as being my final solution but it does get the car back to a safe and fun status and I can finally stop spending money on chasing ghosts. Long term I am leaning most toward getting an EWG at which point I simply drop out my restrictor plate and enjoy. What a ride this one has been! Edit: I should point out (in case it is not clear to some) that I was running a 0 WGDC map when I did this pull - that's why only seeing ~10 PSI was a good thing

I was going to ask how, but then I saw your location. Thinking that may have something to do with it...

Well the plate helped but it wasn't enough. There were not any abnormal noises that I noticed with it and it has decreased the severity of the overboosting but I was still able to get to 25+ PSI, though this time it was at closer to 70% throttle than the previous ~40%.

Have you done any of your dyno pulls in higher gears? It might help generate an overboost scenario.

Having them right now.

I would agree with this. I think I've seen a few posts where people ran 0 WGDC and still had overboost so in that scenario, even an EBCS won't bail you out.

I'll be putting the plate in shortly but my confidence in it completely solving the issue has dropped a bit. I agree with the statements about a longer section at reduced diameter. The plate will still create a pressure drop / backpressure, but maybe not quite enough as would be needed. I know cww15 made a half-joke about a potato in the exhaust but I may actually try plugging a tip, even with snow, as a temporary means of creating further restriction since my exhaust drops to 2.25" diameter pipes at the 'Y'. Should know more in a couple hours.

Not to worry fellas - I can make up a bunch more these bad boys and I'll have a group buy!

Maybe add 'Boost target' and the turbo dynamics parameters? Your WGDC is mighty high for only hitting 13 PSI. Edit: Your A/F correction 1 is very high so it's adding fuel when in Closed Loop. This could be a leak on inlet side. Making 13 PSI might be close to what your BOV spring is so there is a possibility you blew the signal line off the BOV and when in vacuum, you're drawing air in, thus creating the high A/F corrections to compensate and when you try to boost, you have no pressure signal to keep the BOV shut beyond it's own spring pressure. Maybe check that BOV signal line...

^Truth

Yeah, I have been questioning that as well if I should have gone even smaller just based on the how insanely the car is overboosting. It is currently cut to 2". If it doesn't provide enough backpressure though, I can either tack a washer to this plate to further reduce the flow area or else just crank out a new one as this is a pretty quick thing to change out. Honestly, even though the concept makes sense, I'm still pretty skeptical. In all the reading I've done on here (and it has been copious), I haven't really stumbled upon any other stories of such severe overboost. Lots of folks missing by maybe 5 or 6 PSI, but I don't even know what the ceiling would be for me right now. I've had it sneak to beyond 25 and based on how fast that happened, I would not be surprised it if could hit 30. Just seems hard to believe that everything else in my setup is working right and all the overboost is coming purely from such a free-flowing exhaust. Good point on the potential sound impact this will have. I'm seeing this plate (if it works) as a short-term solution to give me a safely driveable car while I weigh out my more long-term plan (vaguely formed ideas right now include a billet 18G and EWG).

I ended up just plasma cutting this thing yesterday from some 304 stainless so we'll see how well it works...

Would something like this work? I don't know what the hole spacing is of our bolts but if it is 4 1/4", I think this would be right.....

Appreciate the feedback (and your name got a good laugh from me as well!) - I don't know of anyone local who would have a stock DP unfortunately. There aren't many 5th gen GT's in my area that I'm aware of.

I can't recall what the pipe connections look like off the top of my head and I'd like to make the plate today if possible. Does anyone have a picture or better yet, suggested OD for the disk that I could sandwich in one of these joints?

Possible. At this point though I am running a 0 wgdc map so I should only be making the mechanical spring pressure of the wastegate and I'm easily able to push 25+ PSI at less that 50% throttle. Totally agree that 3 port is a more reliable solution to accurate boost control though. I'm just not even in the ballpark of reasonable at this point! Sent from my iPhone using Tapatalk

Because that never occurred to me and now I have an even simpler and better plan. My thanks!! Sent from my iPhone using Tapatalk

I've been thinking about this still more and what I think I'll try is making an orifice plate. I've used them very frequently in different pump designs and hydraulic circuits to create a desired pressure drop or upstream pressure. I'm not able to calculate the size as neatly as I can for hydraulic applications, but regardless, it wouldn't take much to tack weld a stainless disc inside the midpipe starting with an ID of maybe 2". That's likely too small especially considering the high turbulence created by the sharp edges of a plate as opposed to a smooth reducer-style fitting, but enlarging a hole is easy to do. I could start with my 2" orifice, take a few runs and see what I'm getting for peak boost and if it's still well below what I'll be targeting, the hole can always be enlarged. Unless someone has a convincing reason that this is a bad idea, I think that's the route I'll take. It's cheap, simple, and if it doesn't have the desired results, I can take it out.

Was that sufficient to eliminate his overboost issues? If so, any details on what he used?

Appreciate the feedback everyone. jojorios, good point on the porting as that was successful for my 20G in conjunction with more tuning. My only concern is that I never ran that configuration in very cool weather so while it seemed to work okay this summer, I don't know for a fact that I wouldn't have had issues in winter. Honestly, I'm just concerned that I'll drop another $300 to port it and maybe it will be close but still not quite enough. At this point, I am leaning toward increasing exhaust restriction. I no longer have my stock CBE, but if memory serves, I thought I have seen notes about people putting an actual muffler or similar in the midpipe to increase restriction? My other thought is that I could remove the current 3" pass-through resonator and neck down to a 2". That will certainly add some resistance and will be significantly cheaper than porting or pursuing a custom downpipe (and of course, any EWG options). Any thoughts on this?

So it sounds like what I've got here is 'typical' and there is nothing malfunctioning - true statement? It also sounds like there are people on both sides of the fence, those who have had issues and those who have not with a similar setup. Not surprisingly, I have landed on the 'issues' side of that fence, territory I know quite well. At this point, I wondering if my best course is to look into a downpipe that offers either a bellmouth or divorced collector for improved flow from the wastegate? I've already spoken to a guy in the area who's done quite a bit of custom exhaust work for others and has said the he could definitely do whatever I wanted for a downpipe design but I wanted to see what everyone thought before unlimbering my wallet again.

Okay now I am completely stumped. I pulled the downpipe off today and re-tested the wastegate to see if it was truly opening at a much higher pressure. Turns out it is working normally and it began to open at ~10 PSI. I did see that it doesn't really open very far. I don't have a pic, but the flapper angle is nowhere near 90 degrees when the actuator stopped moving. I would guess it to be no more than 45 degrees, which seems surprising. I could not see any mechanical obstructions that would have caused it to stop prematurely though. Does anyone else know if this is about right for the stock flapper? The other thing I noticed was that the Invidia downpipe design really isn't very good. You can see in the picture all the area circled in red is area right behind the wastegate. I have to believe this generates some good potential for overboosting as well. In conclusion though, things do seem to be working correctly (unless someone can tell me that my downpipe is not consistent with what others have or that my flapper door is not opening as far as it should) and I know there are plenty of forum members running a stock turbo, non stock CBE and a catless DP who don't have issues like this. I am currently running a 0 WGDC map from my tuner so the tune shouldn't be a factor here. Any thoughts?? PS - I know Nameless makes a DP that has a divorced wastegate passage on it which I'm sure they did because the Invidia design really looks like pure garbage, but I feel like there have to be some other members here running a similar setup to what I now have that aren't overboosting. Truth??

Yeah, you said it.... I was thinking that as a means to prevent a major boost spike until I have the wastegate fixed, I could disconnect the signal line from the top of the BOV and plug it. This way, there is no leakage or added air since it will be plugged and the maximum boost I could make would be whatever the spring pressure is in the BOV. Any issues with doing this as a temporary safety measure to keep things under control?

Is this type of failure common, or at least something you've seen before? Sent from my iPhone using Tapatalk