Nameless Downpipe: Official 5th Gen GT Install Thread

[jojorios]

Not sure on the stock turbo but I know in the case of my old turbo (a BNR 20G), it was ported and successfully eliminated my overboost issue but on Sm00veM00ve's setup, he still had an issue. The effectiveness of the porting is a bit subjective as some jobs may be done 'better' than others.

 

And yours had to be ported on top of the port that BNR already does correct?

[jackal8788]

And yours had to be ported on top of the port that BNR already does correct?

 

That's correct - it was in addition to what BNR does already.

[FLlegacy]

The 20g also is a larger compressor wheel right? So more flow in the same housing...

 

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[fahr_side]

I don't have a simple answer for you guys but I do have a couple of comments.

 

Wastegate flapper interference. The stock flange is completely flat and the port out to the cat is (by looking at the photos) smaller than that on the Nameless item. I don't see how the flange is preventing the WG flapper opening all the way and don't think this is the problem. EDIT: The flapper had hit the extended turbine dump pipe in some cases.

 

Relative pressures. Someone mentioned that the gas coming out of the WG should be at higher pressure than the flow from the turbine. I agree with that idea, but note that if the dump area in the exhaust housing is open, and the production J-pipe doesn't close off the turbine area, the pressures in here will equalize almost immediately the gas reaches the open flapper. What you're left with is gas exiting the turbine in a swirling turbulence and that from the WG port has just made a 90* turn from the throat of the housing and then hits the flapper which is at most about 45* open. Of course the gas can and does change direction and flow around the flapper, but it is partially shrouded and some of the gas is deflected in the direction of the opening in the flange for the cat pipe. EDIT: The turbine dump does extend toward the housing and does prevent much of the merging in the housing but does not close it off completely so pressure should be almost the same on both turbine and wastegate sides.

 

Relative pressure drop. The demonstration with the leaf blower shows that the velocity of air passing through the cat will indeed create a pressure drop at the wastegate dump pipe, but in the test all the flow is directed into the cat pipe and that is sealed. Of course there should be more pressure drop over the cat than there is over the length of the WG dump pipe but if both are open to the back of the exhaust housing much of the pressure differential is lost in comparison to the test. FWIW the wastegate dump tube would draw more of a pressure differential if it was merged into the cat pipe at a less obtuse angle. EDIT: The angle at which the the wastegate dump pipe joins the turbine dump is important.

 

Turbulence and flow merging. On the original part the cat pipe extends past the flange and toward the port for the turbine, which likely all but closes the turbine flow off from the rest of the dump cavity in the housing. On the one hand that forces all the gas from the WG port to flow around the sides of the flapper into the dump pipe which is placed slightly further into the upper rear corner of that space (as installed on the car). That is asking the gas to turn in the opposite direction it is going after being deflected off the flapper. OTOH doing this prevents the tendency of the gas inertia to push the gas coming out the wastegate off the open flapper at the turbine flow. Note that the turbine flow is very turbulent at that point, is at lower pressure and lower temperature than that in the wastegate port. Gases at different pressures and temperatures don't mix spontaneously, although you would think strong turbulence might help overcome their shyness. I am guessing that in operation the wastegate flow is not sufficiently incentivized to turn at almost 90* again around the flapper, then out it's dump pipe. Much of the gas will take the easier path of deflecting roughly 45* off the flapper and at the turbine stream, trying to push into that flow, but having to kind of take a number and wait before it can get out through the cat pipe hole. EDIT: The turbine dump does extend almost to the housing which prevents some turbulent mixing.

 

This is a TiAL design which results in the minimum number of direction changes possible for the wastegate gas flow, nice smooth curves to flow around, and introduces the two gas flows while they're already going in the same direction for minimal interference:

 

http://ep.yimg.com/ca/I/titanmotorsports_2269_721424418

 

I'm not going to get into what Nameless ought to do about this since it's none of my business. If I owned one of these I'd either be asking Nameless to tack a deflector on there or a short length of tube with the same ID as the cat pipe, like the original design, or doing that myself before install. EDIT: It's more likely the merge angle after the cat is to blame.

 

http://legacygt.com/forums/attachment.php?attachmentid=229409&stc=1&thumb=1&d=1462114335

 

Maybe some of you remember this old Grimmspeed design for the oldskool turbo location:

 

http://builtnotboughtauto.com/wp-content/uploads/2012/12/photo-2-4.jpg

 

Those still having issues have the options of replacing some of the original exhaust parts to increase overall back pressure enough to stop boost creep, or pull the turbo and port the wastegate. I think I've mentioned in a couple of places that porting solved all the boost creep issues I've run into so far but then we don't have cold winters to deal with.

 

All standard disclaimers apply!

Edited May 24, 2016 by fahr_side

[BBPeik]

Well that about sums it up then doesn't it. As always Fahr_side amazing work. I have to say that old Grimmspeed design looks very well engineered. Quite a bit of thought went into that one.

[GTEASER]

Thanks fahr_side, I'm going to have to read that several times so everything you're discussing sinks into the brain properly.

[fahr_side]

Haha. Sorry, if that was a bit too much the tl;dr would go:

 

If they'd made the production items like the samples it probably would've worked okay, but if they'd done it more like TiAL did it would have been even better.

[blklgt05]

This is why if you have boost creep and you want to keep your stock turbo setup, you have to port the wg. I've done quite a bit of reading and decided not to join the GB, Invidia's catted dp's blank plate design may be a cheaper design, but the extra restriction should help with boost creep. I've read that some people even add extra resonators in the exhaust as a cheaper alternative to help.

[fahr_side]

This is why if you have boost creep and you want to keep your stock turbo setup, you have to port the wg. I've done quite a bit of reading and decided not to join the GB, Invidia's catted dp's blank plate design may be a cheaper design, but the extra restriction should help with boost creep. I've read that some people even add extra resonators in the exhaust as a cheaper alternative to help.

 

Please understand it is not that simple. The flat plate design is horrible, because it makes the wastegate flow make a few more turns than are necessary and also there's the problem of the wastegate's flow trying to merge into the flow from the turbine and pass out the same hole. The smoother and less restrictive the flow out of the wastegate, the more authority the boost control system has and the less spiking and creep you will see. Where you run into trouble is increasing total flow without paying attention to wastegate flow in particular. The turbine spins because of the pressure drop across it, so yes, adding restriction to the midpipe or cans for examples will lower boost for a given WGDC or for example with the WG held wide open. Nameless' original design is very clever in that while flow out the turbine is increased due to the more open metal cat, they also took care to avoid funneling the WG gas flow into the turbine dump by giving it a bypass path around the (still restrictive) cat and on into the main dump pipe. Therefore while turbine dump flow is increased, WG flow (in theory) is increased even more. Too bad the production one undid most of that good work.

 

I've used the Invidia part to good effect on many stage 2 cars with no boost creep whatsoever, which I put down to the slight bellmouth they give going from the flange into the cat. It's not just a straight 76mm pipe. On stage 3 cars we do see creeping with the Invidia if the CBE is very open, which I could only cure by porting the wastegate. In that case the owner did not want more resonators, he wanted more noise!

[Ellesedil]

Nameless' original design is very clever in that while flow out the turbine is increased due to the more open metal cat, they also took care to avoid funneling the WG gas flow into the turbine dump by giving it a bypass path around the (still restrictive) cat and on into the main dump pipe. Therefore while turbine dump flow is increased, WG flow (in theory) is increased even more. Too bad the production one undid most of that good work.

 

[FLlegacy]

I think I see what fahr_side is saying with respect to how the gases flow from the two ports of the turbo. I don't see the difference in the flange of the original and GB ones though, the flange looks identical. The angled junction after the cat is obviously different and probably creates less pull from the turbine side.

 

Couldn't a small piece of pipe be welded in to shield the wastegate flow after the cat from the divorced pipe to smooth the transition into the main exhaust and reduce that turbulence? It would probably create a little more backpressure, which could be a win-win.

 

The interference with the flapper that has been noted has been from it hitting the pipe that extends to the turbine outlet not from hitting the flange. That was where I suggested flattening it out to keep it from being a potential issue.

 

Edit-So if I am thinking correctly, the oversized pipe for the turbine outlet is doing 2 bad things: 1.Taking away space for the gases to flow out and around the flapper and 2. Blocking the flow of gases from the wastegate port since the flapper opens right into the pipe...hmmmm was the original pipe smaller?

Edited May 24, 2016 by FLlegacy

[fahr_side]

Would someone identify this as the original or GB version please? http://legacygt.com/forums/attachment.php?attachmentid=219856&d=1447723242

 

 

Sent from a device using some software.

[ripstik]

Would someone identify this as the original or GB version please? http://legacygt.com/forums/attachment.php?attachmentid=219856&d=1447723242

 

 

Sent from a device using some software.

 

can't tell from that angle, but if there is bend on the wastegate pipe where is meets with the turbine flow than its the original. if it just goes straight into it it's the group buy

[Starks]

That's pretty much right. Fischbach was the original car the DP was designed on. Someone else bought one, and then Swannee too, so those are the 3 original design downpipe that I know of. Then 22 or 23 sold with the GB of the revised simplified design.

 

I am now officially in possession of Swannee's DP. And our boy is now officially a married man.

Good thing you got a hold of an original as well. What do you need to do before you test the two out?

 

If it would take some donations to get you going I'd be down to help. It seems we put most of the picture to this puzzle together. I'm about ready to put this issue to rest and get a resolution.

 

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[eckseleven]

Would someone identify this as the original or GB version please? http://legacygt.com/forums/attachment.php?attachmentid=219856&d=1447723242

 

can't tell from that angle, but if there is bend on the wastegate pipe where is meets with the turbine flow than its the original. if it just goes straight into it it's the group buy

 

That is the GB version. That picture is of my DP that the shop took when troubleshooting the flapper interference problem.

[Zee199969]

How difficult would it be for a shop to cut off the existing wastegate dump tube and re-pipe it with a bend that is similar to the original 1st run DPs? I realize what I'm saying is overly simplistic and likely there are issues with engineering and physics that I am not taking into account.

[fahr_side]

That is the GB version. That picture is of my DP that the shop took when troubleshooting the flapper interference problem.

Thanks. Then I take back some of the points I made above. It looked to me like the GB items had the main dump tube truncated at the flange. Any efforts made to stop the flow out of the wastegate merging straight into the whirling tornado coming out of the turbine are worthwhile. I can't tell if they shortened the pipe extending from the flange toward the turbine but as long as it comes close to the housing itself you're doing well. If you can set it up so the dump pipe actually encloses the turbine outlet and seals it off that would be best as then you're truly divorced. In that case you'd have much lower pressure in the wastegate side and it would flow better toward the merge downstream of the cat.

 

If the big change is the angle at which the wastegate dump pipe merges into the main pipe the difference between the two would be smaller, but then it would show you just how critical the whole system is. It's been shown before that very obtuse merges (like 90*) are very bad for flow.

[Starks]

How difficult would it be for a shop to cut off the existing wastegate dump tube and re-pipe it with a bend that is similar to the original 1st run DPs? I realize what I'm saying is overly simplistic and likely there are issues with engineering and physics that I am not taking into account.

Wait wait wait...you want a shop to do custom work on an already custom exhaust? Maybe you're more lenient then I am but it's product description says...

 

"We are pleased to release our 5th Gen Legacy GT true divorced twin circuit downpipe! Utilizing this design, we are able to remove all turbulence created by the internal wastegate on the OEM turbocharger and route it smoothly in to a single 3" outlet. This grants better spool, a more consistent boost curve, and no boost creep. This parts does require a tune to operate effectively, and bundles with the Cobb AccessPort V3 and/or our CBE are available upon request."

 

I don't think it's acceptable that people have to modify the DP to that extent. Especially if Nameless is pushing to sell a full exhaust with it as well which would cause more creep.

 

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Edited May 24, 2016 by Starks

[Zee199969]

 

I don't think it's acceptable that people have to modify the DP to that extent. Especially if they are pushing a full exhaust with it as well which would cause more creep.

 

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Disclaimer: I don't own a nameless divorced waste gate dp as of yet.

 

I was just brainstorming to see if that would be an option for the ones who do own it. I would hope that if something like that could "easily" fix the DP, that nameless would step up and take care of it. But for those who don't want to wait for something like that, I was just asking if something like redoing the waste gate dump was feasible.

[FLlegacy]

Wait wait wait...you want a shop to do custom work on an already custom exhaust? Maybe you're more lenient then I am but it's product description says...

 

"We are pleased to release our 5th Gen Legacy GT true divorced twin circuit downpipe! Utilizing this design, we are able to remove all turbulence created by the internal wastegate on the OEM turbocharger and route it smoothly in to a single 3" outlet. This grants better spool, a more consistent boost curve, and no boost creep. This parts does require a tune to operate effectively, and bundles with the Cobb AccessPort V3 and/or our CBE are available upon request."

 

I don't think it's acceptable that people have to modify the DP to that extent. Especially if they are pushing a full exhaust with it as well which would cause more creep.

 

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I can respect and understand what you are saying, on the other hand, we would most likely have to foot the bill for shipping back to nameless at the very least. If a shop can make a small adjustment for very little money it would be worthwhile to try, vs sending it across the country and playing the waiting game some more.

 

Maybe it is time to get Nameless on this thread...

[Starks]

Ahh, I see. Yeah, if I had a local buddy who welds, I'd buy him some beer and lunch and have him give it a go. As far as paying a shop another $100 to modify a $800 part that doesn't work as intended? Good luck, but that isn't acceptable to me.

 

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[Apexofthevortex]

So just to recap, Sarang, Driezhen, and I are the only ones who are currently running the DP successfully right?

[eckseleven]

IMO if these issues stem from Nameless's revision to the original design, it should be up to them to fix it. That would mean them footing the bill for shipping both ways. The end customer shouldn't have to pay anymore when the product doesn't function as promised. Alternatively, if they offered reimbursement for having some modifications done locally, I'd probably be ok with that.

[FLlegacy]

IMO if these issues stem from Nameless's revision to the original design, it should be up to them to fix it. That would mean them footing the bill for shipping both ways. The end customer shouldn't have to pay anymore when the product doesn't function as promised. Alternatively, if they offered reimbursement for having some modifications done locally, I'd probably be ok with that.

 

Not too many retailers do that anymore, even purchasing on ebay, if you are sent a fake part the seller has no obligation to refund you shipping, only the purchase price. And there is no recourse other than a negative review.

 

If the shop steps up and determines the issue was design flaw and does take care of it all both ways, then that would be awesome.

[eckseleven]

^ Yeah I know. Hopefully they'd want to protect their reputation and make it right. Seems like they are a decent company.