TurboXS Dump Pipe and Recode Tuning for Golf R

[Lazarus7]

Great vid, thanks mate.

Interesting the part about the splitter, makes me wonder about the effectiveness of the APR design. However as stated above the type of turbo and its turbulence characteristics will play a fair part in how well or otherwise a design is.

[fuzion]

With all this talk of downpipes. Recently have seen 3 downpipes made for golf r from Liverpool exhausts who have extensive experience in exhaust making even though the name is a deterrent. The quality and design was top marks.

Cost wise was considerably less than most branded ones out there.

Funnily enough on my mk4 which had a custom made downpipe (elsewhere made locally) made more power than any other mk4 with same mods.

Not raining on the parade as I do have a milltek but the turboxs or other custom could and will do the same as a branded one as they also have experience. And let's be honest. They all somewhat copy one another somehow due to it's a simple design as such.

[Fab_R]

Very interesting this thread....

I seem to remember APR before releasing their unit conducted tests using both designs, and found the divorced set up superior.?

[Corey_R]

This is a image of the Borg KKK K04 64 which is what is in our Golf R's and Audi S3's etc.




This was the best image I could find which actually shows the turbine outlet and internal wastegate flapper valve in the turbo.
You can see clearly see from this picture that the APR downpipe's exhaust opening should not cause a restriction as it's still larger than the turbine outlet. You can also see that there is still room to "split" the two outlets effectively.

CarbonVW posted a video from MRT Performance who are a well respected local Subaru and Mitsubishi specialists. In fact, they often compete with (against?) APR in MOTOR Magazine round-ups. This is what they had to say in their video in relation to what they feel is an often overlooked aspect of improving throttle response with aftermarket exhausts, discussing the difference between divorced, split bellmouths, and bellmouth exhausts.

What you need to do is have a splitter plate which directs into the back of the turbo to keep the wastegate outlet and turbo outlet separate because the aim is to when the wastegate comes on boost you want the exhaust gases coming out of the wastegate to go through in the same direction as what the exhaust outlet is going so that when the two flows of gas merge together in the same direction and then go down out through the exhaust. If you don't have this plate here then what happens is when it comes on boost, the exhaust gases come across the back of the turbo outlet and obviously form a high pressure zone which causes a little bit of lag because of course that's where all the gases are coming out of the main stream of the exhaust outlet on the back of the turbine housing itself. But if it's going down that hole there, then obviously you've got two effective areas for the two lots of gases to follow one direction and then merge correctly in a short path down here. Now it doesn't need to be a pipe on its own separately. Those exhausts systems with two separate pipes have no mechanical advantage at all, they just look good, because effectively they don't have the splitter...."

Now obviously, the APR exhaust is a divorced downpipe, but importantly (in MRT's opinion) it also has the splitter.


Anyway, I'm not a fluid dynamics engineer so I'm in really no position to say whether one is better than the other. I just thought we needed to see a clearer picture of what is actually in the turbine housing of the K04 Turbo we've all got, so you can actually see the turbine outlet and the wastegate outlet, and thought that the explanation from MRT on the purpose of the splitter was rather interesting.

[Lazarus7]

Oops missed the splitter on the APR one...well perhaps it is the goods. Nice pictures there Corey, quite helpful.

[dave_r]

I seem to remember APR before releasing their unit conducted tests using both designs, and found the divorced set up superior.?

I think you need to do your own testing. You like to change wheels and intakes more than socks, why not DP's as well

[parso_rex]

Trying not to start a s@#tfight . That MRT article really applies to the TD04 and VF series turbochargers used on the rexies both of which have a pretty ordinary wastegate flapper position relative to the turbine outlet flow. The problem with these is that the wastegate flap opens up in the direction of the turbine outlet. It forces the gasses from the wastegate directly into the gasses exiting the turbine and its not good at all.

This isn't the case for the K04's, as you can see from the pics above it opens in opposite direction. It will never be an issue.

The problem with many divorced setups (and no I don't mean this one think the Subaru once again seeing as that's what is being mentioned atm) is that when the wastegate flap opens the exhaust gasses hit the wall of the tube which hurts flow badly leading to boost control issues as the now less effective wastegate tries to get things back under control. You have to modify the tuned file to make the wastegate flap open to a much larger angle than it was previously usually by reducing values in boost solenoid duty cycle tables.
The K04 though is a bit different, its recessed slightly and the splitter is forcing it down the tube to some extent and it seems to work otherwise they wouldn't be selling them, of course the tuned file would have different wastegate duty cycles to accommodate this - and it is too !!. Superior - no chance but that's just my opinion I have to tune a number of cars so If I don't have to radically modify one bunch of maps then the old Keep it simple rule works for me. All these options including custom are better than the stock one, lets leave it at that.
The TXS dump offering is pretty good so I'll l be using them for now but I still need to find the best option for a mid and rear section so
I'm still looking.
I have another R coming in the next week or two with some nice non-rice mods APR pump, Big FMIC etc so we'll see how we go with that too. I believe Zbeast will be getting a pump soon too so we can finally get some decent boost happening down low

[Corey_R]

Thanks for the feedback parso_rex. For what it's worth, I wasn't trying to start a "s@#tfight" either. Neither am I saying that the Turbo XS is bad - you already know that I defended it previously against some people attacking its credibility. I really only started posting on this line of discussion as I believed the "mouse drawn red marks" on the photos which were indicating that the turbine exhaust flow of the K04 is blocked by the exhaust flange on the APR DP to be incorrect and misleading - but that is no reflecting on you or Turbo XS

[parso_rex]

Hi Corey,no I didn't take it that way at all and I know your fairly balanced about all this stuff its just that usually a few people get upset if I post anything that different to what they have assumed to be normal practice.

[zbeasty]

I wasn't trying to start a s@#tfight either so sorry if that was the impression. If you have a look at the divider on the MRT video it is very thin. Given the heat that a turbo is subjected to I would actually be concerned with the splitter disintegrating over time with heat cycling. There is only a very small gap between the turbine outlet and the wastegate on the K04. To put a splitter in would mean that you would again have to use very thin material which would not stand up over time and end up destroying your cat converter. One thing that you can't really see in the photo is that the diameter of the turbo where the turbine is is actually larger than at the flange. The red circle on the photo that I loaded indicates where the pipe would be if you could get a straight run. If someone is up for modifying the casting of the outlet they could get the full benefit of the divorced DP because you could fully isolated the wastegate from the turbine flow. The only other option is the external wastegate which means another turbo because it would be cheaper than modifying the K04.