Jackal's 20g to 18g e85 Soap Opera

From what I've read it looks like all the dp's are prone to the over boosting. Nvidia catted/catless and the nameless. I'm not sure the cost of having an exhaust shop make a dp for you, but since you had your 20g ported previously by your builder, might it be a cheaper option to just have the stock turbo you just go ported?

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?

I seem to remember one member having a hi Flo cat welded into his dp.

 

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

Wouldn't adding a hi flo cat to a catless dp be similar to just buying a catted dp which would most likely still have a big chance of the overboost issue?

 

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Wouldn't adding a hi flo cat to a catless dp be similar to just buying a catted dp which would most likely still have a big chance of the overboost issue?

 

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Only if the cat matched the one used in the catted dp from the manufacturer. I would suppose that the number of cats that could fit on the dp is limited by the space/location available to add one.

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

 

I really don't know if it was even an overboosting issue or just a desire to look legal/reduce noise.

Stuff a potato in one of the cans and see if the added back pressure helps?

 

Only partly joking, as I'm sure there's something better than a potato that you could use, but if you induce a little more back pressure and the issue goes away, a catted downpipe may help. Chances are you'd need to restrict both cans, having one open is probably all we need anyway.

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.

Why tack weld it in when you could just make a plate and sandwich it between the DP and intermediate pipe flanges? Edited January 3, 2016 by GTEASER

Why tack weld it in when you could just make a plate and sandwich it between the DP and intermediate pipe flanges?

 

 

Because that never occurred to me and now I have an even simpler and better plan. My thanks!!

 

 

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Might not have been said but I have heard the stock EBCS can cause boost spikes. Maybe try a 3 port EBCS?

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!

 

 

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I just finished this thread from begining to end and man jackal8788 i hope you figure this out soon. That having been said is there some you know that can let you borrow a stock DP for a couple days so you can figure out if a catted DP would help? Just my 2 cents.

Wouldn't adding a hi flo cat to a catless dp be similar to just buying a catted dp which would most likely still have a big chance of the overboost issue?

Good idea! The cat doesn't necessarily have to be where the stock one is. Just be aware that welding it after the 90* bend might require you to extend or reroute the wiring to the rear O2 sensor. I like the idea of having the cat out from under the engine bay and further back. Recommend a 200 cell cat. 400 is too restrictive and 100 does nothing. Our 403whp BR9 runs a 200 cell cat.

 

Why tack weld it in when you could just make a plate and sandwich it between the DP and intermediate pipe flanges?

Great idea for proof of concept!

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?

I just finished this thread from begining to end and man jackal8788 i hope you figure this out soon. That having been said is there some you know that can let you borrow a stock DP for a couple days so you can figure out if a catted DP would help? Just my 2 cents.

 

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?

 

 

Just find a 3" exhaust flange gasket with a smaller hole in it, like 2".

 

 

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Just find a 3" exhaust flange gasket with a smaller hole in it, like 2".

 

 

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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.....

You might have to knock the edges flat to use it as a 'gasket' but it should work. Just check the bolt spacing on the flange.

 

 

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

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

 

Dang dude, that looks pretty nice for just knocking it out. What's the inside diameter? By the looks, think I would have started a little smaller, just to be sure.

 

Don't be surprised if that sharp edge adds an all new hum or shriek to your exhaust sound profile. Might even find an rpm range where the metal resonates and "sings". I've forgotten most of what I know about that stuff from when I did speaker port tube velocity modelling for work, so just making an educated guess based on a hunch, so you don't freak out if it sounds crazy bizness. Just a tiny edge would show up as harmonic distortion, and there's going to be some insane turbulence going through that.

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).

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.

 

I had no issues until I went from a CBE to a TBE using the Nameless DP. My tune is set to 0% WGDC and when it gets cold enough boost will shoot right up to 21 psi and then Christmas tree the dash. It happens extremely quickly, within 1k RPM of going WOT in a 3rd gear pull.

 

The warmest temps I've tested in are about 65 and even then boost will hover around 16.5-17; still far above waste gate spring pressure. Everything I've tested/tried points to the exhaust being too free flowing. When I get time and it warms up a bit I'm going to put the stock mid pipe back on and see what happens.

 

As for you being able to hit 25 psi, I'm guessing it can be configured in the tune where boost cut is triggered.

As for you being able to hit 25 psi, I'm guessing it can be configured in the tune where boost cut is triggered.

 

Pretty sure he has a rescaled MAF and a 3bar MAP sensor which will get him 30psi + without throwing a code like you do on the stock 2bar MAP at around 21psi.