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There’s a reason this thread is 76 pages long. Great first hand, honest information
You know, I was thinking about that right after my last post. 2020 is the 10 year anniversary of this thread, which is crazy. Shit, 2 days from now. ~1500 comments and 408k views. I might be biased, but it's my favorite thread on the whole internet. :D Thank you everyone for contributing over the years. Lots of good discussion and good ideas came from this thread over the years.
 

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I do. All of my gates leak some actuation air down the valve stem, so on a recirced gate, it will make the AFR read leaner. My downstream O2 reads about 0.5 gas scale AFR leaner than the average of the 4 pre-turbo O2 sensors. I've thought about operating the WGs with exhaust pressure rather than boost pressure (which I often do on small turbo stuff), but there's some risk of plugging up the WG's valve stem/guide with combustion shit or overheating the diaphragm. CO2 would probably work better but I'm not looking to go there yet. In the meantime I trust the pre-turbo O2s and only use the downstream gauge for a visual going down the track.
Obviously every setup is different, but at least that gives me a rough idea. One method of combating this that I though of was running the WB in an extended bung on the downpipe (the long 90* ones people use to fool post-cat o2's) and then running a -3an nicop line from the header collector to the side of the extended WB bung. This way the WB is fed pre-gate exhaust gas but doesn't see any more pressure than the downpipe. Obviously there will be a little bit of response lag, but I can't imagine it being that large at full load. The WB is already reporting past events no matter where you put it.

You know, I was thinking about that right after my last post. 2020 is the 10 year anniversary of this thread, which is crazy. Shit, 2 days from now. ~1500 comments and 408k views. I might be biased, but it's my favorite thread on the whole internet. :D Thank you everyone for contributing over the years. Lots of good discussion and good ideas came from this thread over the years.
Definitely one of my favorite threads as well. I've pointed several people this direction for the sake of learning.
 

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If you're having O2 contamination from your recirculated valves, you could do what I do: machine the ewg exhaust v-band flange faces .020 and run a 16oz copper gasket. I also use them on my normal v-band flanges as well. The copper heats up and crushes when you tighten the v-band flanges together. I originally started using them on male/female exhaust v-bands where you can't machine the flanges flat after welding despite using heatsinks during welding to control warpage, and it's super annoying having customers come back and say "Hey my brand new v-band is leaking". On exhaust flanges I don't machine the flange face, the copper is slim enough to fit between the flanges and still have the OD clamp compress properly.
 

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Discussion Starter #1,524
Obviously every setup is different, but at least that gives me a rough idea. One method of combating this that I though of was running the WB in an extended bung on the downpipe (the long 90* ones people use to fool post-cat o2's) and then running a -3an nicop line from the header collector to the side of the extended WB bung. This way the WB is fed pre-gate exhaust gas but doesn't see any more pressure than the downpipe. Obviously there will be a little bit of response lag, but I can't imagine it being that large at full load. The WB is already reporting past events no matter where you put it.
That's definitely an interesting idea.

One way I get around a super short exhaust on my car (it's 1 inch long), for my downstream WB, I put it in the WB dump tube. Works great, but only when at full boost. :) Side benefit, I know roughly when the WG opens by that sensor starting to read. I'm sure there's some delay there, but it's fun to watch. This WB I really just use going down the track so I can lift if it goes really lean for any reason (never happens, but I still watch for it).
 

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If you're having O2 contamination from your recirculated valves, you could do what I do: machine the ewg exhaust v-band flange faces .020 and run a 16oz copper gasket.
To be clear, the issue here isn't the flanges leaking, it's actuation air leaking down the valve stem (from the lower/side port). Since that's usually boost, it has oxygen in it and leans out the reading. The changes can be 100% sealed and this issue still exists. Without upstream O2 sensors I may never have caught this. Well, I know what my AFR should be based on mass airflow and fuel flow, and an error of half to 1 full AFR would have been obvious, but I probably would never have pinpointed the cause and just dicked up my tune to make it work. :)
 

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Ah got you. I tend to tie ewg in after the primary O2 on non-compound cars, so actuation air bleeding around the stem is not something that I've run in to. Ewg discharge tubes leaking on recirculated street cars, however, that's a problem. :)
 

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Kevin, have u considered using a BW EFR turbo or one of Garrett's newer G series turbos perhaps? I can't imagine what you'd be able to achieve w/ a considerable budget. Maybe we should all pitch in or do a crowdfund thing for ya lol.
 

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Lol! I definitely consider all turbos at all times, but FP/XR is the only choice for me on my own stuff. I just feel they are at the cutting edge of new tech consistently, and having dealt with them for like 18 years now it's just a no brainer for me. The dream setup for me right now is is a Xona Rotor version of my small turbo to take advantage of the split UHF turbine wheel (7164S, or for an upgrade 7864S or 7869S), and one of their larger frame turbos, which are based on BW S400s, and available with 80/84/88mm compressors. I expect this would spool just as easily as what I have now but have less back pressure and more power. It would be a fair bit of work to converter everything over to Tial turbine housings, but there are benefits to that as well. Some day! In the meantime I get to be involved in testing all of the other turbo brands on other people's cars that I help out with, so I can still stay up to speed on them. :)

To be fair, I'm still pretty happy with my current turbo setup. Back pressure could be a little lower but at 1.4:1 I can live with it. I've got much bigger issues at this point. Once I can get the car to keep up with the turbos I know this setup will go low-mid 7s. I think I know the path to achieve this now, I just need the time and the money to make it happen. Hopefully this season.
 

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Ooh, I just looked into those Xona Rotor turbos you mentioned and I really like wut I see! I'm really just looking for the turbo w/ the best turbine design, and their split UHF turbine looks really promising (I want as much flow thru the hot side as possible). Are there any compressor maps for the XR turbos? I couldn't find it on their website. I'm looking at the 7869S specifically.
 

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Lol! I definitely consider all turbos at all times, but FP/XR is the only choice for me on my own stuff. I just feel they are at the cutting edge of new tech consistently, and having dealt with them for like 18 years now it's just a no brainer for me. The dream setup for me right now is is a Xona Rotor version of my small turbo to take advantage of the split UHF turbine wheel (7164S, or for an upgrade 7864S or 7869S), and one of their larger frame turbos, which are based on BW S400s, and available with 80/84/88mm compressors. I expect this would spool just as easily as what I have now but have less back pressure and more power. It would be a fair bit of work to converter everything over to Tial turbine housings, but there are benefits to that as well. Some day! In the meantime I get to be involved in testing all of the other turbo brands on other people's cars that I help out with, so I can still stay up to speed on them. :)

To be fair, I'm still pretty happy with my current turbo setup. Back pressure could be a little lower but at 1.4:1 I can live with it. I've got much bigger issues at this point. Once I can get the car to keep up with the turbos I know this setup will go low-mid 7s. I think I know the path to achieve this now, I just need the time and the money to make it happen. Hopefully this season.
Last week I hade the opportunity to go to Xona/TiAL for the morning. Seeing everything they do there up close was amazing. I have been a hardcore BW fanboy for years, but if/when the time comes, I would absolutely switch to xona. The results we've seen on our shop slingshot are astounding. The Xona we're running there is externally almost the exact same footprint at a gt2860, but has made over 550whp with boost in the high 20's.

If i do make the swithc on my car someday, I conveniently already have tial vband flanged housings on both turbos ;)
 

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FP does not release compressor maps for their compressors, unfortunately. They only have a couple people answering phones and compressor maps generate too many questions for them to answer. Small turbo company problems. :) Hopefully someday they can release them.

Last week I hade the opportunity to go to Xona/TiAL for the morning. Seeing everything they do there up close was amazing. I have been a hardcore BW fanboy for years, but if/when the time comes, I would absolutely switch to xona. The results we've seen on our shop slingshot are astounding. The Xona we're running there is externally almost the exact same footprint at a gt2860, but has made over 550whp with boost in the high 20's.

If i do make the swithc on my car someday, I conveniently already have tial vband flanged housings on both turbos ;)
That's awesome. I need to get a tour myself someday. I'm gonna bust Robert's balls when here's here in May for our DSM/EVO race.

I was sold on XR turbos as soon as I put one on my truck back in 2015 I think. I have an early 6156 on that. The turbo is tiny compared to the T3/T4 50 trim it replaced, spools much quicker, and made 100 more whp. That was a win all around.
 

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I think I've officially been converted to the Xona side lol. Back to the topic of compounding...would a 78 lb/min and a 112 lb/min compressor go well together? I recall it was mentioned that the primary & secondary shouldn't be too close in size.
 

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That's starting to push the limits of the ratio I like to see, but I wouldn't afraid to try that. If you can spool that small turbo, the big one will come up immediately behind it even with a big turbine side.
 

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Lol! I definitely consider all turbos at all times, but FP/XR is the only choice for me on my own stuff. I just feel they are at the cutting edge of new tech consistently, and having dealt with them for like 18 years now it's just a no brainer for me. The dream setup for me right now is is a Xona Rotor version of my small turbo to take advantage of the split UHF turbine wheel (7164S, or for an upgrade 7864S or 7869S), and one of their larger frame turbos, which are based on BW S400s, and available with 80/84/88mm compressors. I expect this would spool just as easily as what I have now but have less back pressure and more power. It would be a fair bit of work to converter everything over to Tial turbine housings, but there are benefits to that as well. Some day! In the meantime I get to be involved in testing all of the other turbo brands on other people's cars that I help out with, so I can still stay up to speed on them. :)

To be fair, I'm still pretty happy with my current turbo setup. Back pressure could be a little lower but at 1.4:1 I can live with it. I've got much bigger issues at this point. Once I can get the car to keep up with the turbos I know this setup will go low-mid 7s. I think I know the path to achieve this now, I just need the time and the money to make it happen. Hopefully this season.
91mm from FP coming soon. :D Better turbine wheel also.

Edit: looks like I need to update my avatar.
 
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