Ideal Runner & Outlet Size for Turbo Application?
 

Apologies if this is the wrong subforum for this topic, but I figured it's on the subject of turbocharging so, yeah... Anyway, I've seen a few differing opinions thrown around concerning the ideal OD for the exhaust primaries, ranging from 1 1/4" to 2". I was looking at 3-into-1 turbo collectors on Burn's Stainless and which are offered in various sizes. Edit: Looks like the runner size is going to be 1 7/8" which also matches the Racing Beat flange, nice... Now my only concern is the outlet/V-Band size. According to the following diagram, the turbo I'm looking at uses a 3" V-Band but also states a 2" inlet. Edit2: It looks like the turbo inlet is actually 2 1/8" so I'm guessing that's what I should specify for the collector outlet. I guess that means these are the V-Band flange & clamp I need?
https://cimg4.ibsrv.net/gimg/www.rx8...285ea5224d.jpg
https://cimg1.ibsrv.net/gimg/www.rx8...eee9cbc023.png

P.S. Btw, where can this flange be obtained? I don't see it listed on Racing Beat's website and a couple of other places that have it listed show it is out of stock...
https://www.atkinsrotary.com/store/w...6168Detail.jpg

maybe you should back up to state your goal first and then list the specific turbo model and turbine housing you think is going to meet that goal.

the flange is likely out of stock due to the covid hysteria, you’d probably have to call them to confirm if it will be offered again in the future.

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I guess the pandemic really has screwed up many businesses... Man, I'm so glad I already got my 2nd shot lol.

Dang, I just noticed the Racing Beat header that utilizes that flange is on backorder until 9/15/21! If I had to guess, the flange would most likely be out of stock until then as well...

Regarding which turbo and housing I have in mind:
XR 6564S X2C - Xona Rotor
Housing will be a TiAl 0.82 V-Band unless someone thinks the 1.03 would be a better choice.
As for HP goals... I'd be content w/ somewhere around the mid 300's.

Edit: If anyone's wondering why I've selected this turbo. It's mainly due to the design of the turbine blades, which I suspect would work well on a Renesis.

Having a similar problem; a vendor told me yesterday that Garrett updated the release of the G25-660 w/divided T4 0.92 turbine housing from “end of March” to “between now and June” 🤬.

I would generally try to steer you away from a brand that can’t produce flow maps. Yeah, “ultra high flow turbine wheel” sounds impressive, but what does it actually mean wrt mass flow and Pr? With most turbos oriented for use on reciprocating engines the choice for the Wankel rotary engine is a bit more critical. Your choice though. It will take roughly 47 - 50 lb/hr compressor flow to achieve ~350 whp.

The RB flange is designed more for an NA header. It has socket slip-fit joints for 1.75” OD tubing, but imo that’s a bit too small for a turbo on this engine once you get the wall thickness enough for the heat and weight strength needed. Most people are going to use at least 1.5” Sch. 10 stainless steel pipe & fittings instead, which has a 1.900” OD x 1.682” ID. However, this pipe OD closely matches the OD of the port extension on the RB flange. So I’d recommend grinding the socket slip-fit lip down until it’s flush and then butt weld the 1.5” Sch 10 pipe fittings to it that way. A die grinder can then be used to match up the ID between the two and with good welds should be plenty strong. I was looking at doing it that way and decided to go in a different direction. Unfortunately I let someone else have the RB flange about 6 months ago.

V-band flanges are a bit tricky because they’re not all the same mating face type and they usually size them by the large OD end of the flange rather than the connecting pipe/tube size. Which you can see in the flange picture below for that turbo. The 2.13” ID is a pretty good match for 2” Sch. 10 pipe which is 2.375” OD x 2.157” ID. I’m fairly confident that the v-band flange for that is going to have a socket slip fit for that same 2.375” OD pipe size. So if you were to use Sch. 10 pipe & fittings you’d want a merge with 1.5” Sch. 10 inlets merging into a single 2” Sch. 10 outlet. If you use OD tubing instead it probably needs to be around 10 Ga thickness (0.105”) which is roughly the same thickness for the 1.5” & 2” Sch. 10 pipe/fittings. You’re probably looking at a custom merge any way you cut it since most of them are thin-wall type for NA headers.

edit: 2.13” below is the mating slip connection. so it most likely is a true 2” ID inlet. That’s what I was referring to about them being different/tricky. You’ll just have to inquire with them about what size tube/pipe the manifold adapter is intended for.


https://cimg0.ibsrv.net/gimg/www.rx8...97d7d2f42.jpeg

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Yea, I am put off by the lack of compressor maps tbh. But I'm okay with being a guinea pig for once if it results in providing more data points for others to make more informed purchasing decisions in the future. Worst case scenario, I leave a bit of performance on the table. Best case scenario, I see reduced EMAP compared to other turbo choices and the Renny breathes happier as a result. Either way, it would be significantly faster than a N/A Renny lol. Not gonna lie though, a G-series Garrett or EFR turbo both sound very tempting. Anyway, thanks for the insight regarding OD sizing. I will reconsider my options and perhaps forgo the RB flange, especially considering its unavailability. Also, I'd really like to get the manifold made in Inconel if it's not too cost-prohibitive (ah screw it, might as well even if it is lol).:yelrotflm

I just marked out my own manifold flange using a gasket and had it profile cut. You don't need that fancy Rb one. Most just squash the tube ends to mate with the rectangular ports. That turbo looks the part but I agree you will be somewhat of a guinea pig in selecting it. If there was a significant price advantage I'd be tempted as well , but it looks like they are right up there with tried and tested turbos so ... yeah , good luck :).
As far as tube size goes .... anything bigger than the outer port area is pointless and will be a negative on spoolup.

It’s a bit more troublesome transitioning from the rectangular opening to round pipe is the reason to use it. Less prone to warping too, but then has more heat mass retention. There are other reasons not to transition it to round pipe, but I’ll reserve that for another day.

So I was looking at the RX8Performance turbo kit, and was wondering what size runners do they use for their manifold? Their kit utilizes a PT6266 turbo, which is a slightly larger turbo than the XR6564S, so I'd expect the Xona to perform similarly albeit w/ a bit less power and an earlier spool.

Precision Turbo is a rival company of Forced Performance in the sense that they are both smaller firms targeting the performance aftermarket segment. This is in contrast to mega-corporations like Garret & BorgWarner, which also serve the OEM segment. That's the main reason why Precision Turbo and Forced Performance don't provide compressor maps. I don't believe it's because they are purposefully withholding information, but simply that the equipment necessary to produce those maps is very expensive. They either don't have the capital to purchase the test cells or if they do, then they've probably done a cost analysis and determined it wasn't worth the expenditure. Xona Rotor is a partnership between Forced Performance and TiAl Sports for those that don't know. That's why I basically see Xona turbos as being HTZ compressors paired w/ their newly designed "UHF" turbines and fitted w/ TiAl housings. The Xona units are also manufactured in TiAl's facilities (in Michigan?) so the workmanship/build quality is what you'd expect from TiAl. Definitely a step up from the FP units. Lol, I must sound like a fanboy right now, but this is just some of the info I've dug up in my research lately. Anyway, I know that both PT and FP turbos are often used in the 4-banger communities (the Subi/Evo/DSM crowd) and are considered comparable to each other, despite the lack of compressor maps.

Edit: So going through Curt's build thread (which uses a PT6266) and seeing the impressive results he's achieved has put me more at ease wrt my turbo selection. However, I noticed that the plumbing geometry differs somewhat between what's depicted on the product page and the photos in Curt's thread. What are people's thoughts on the manifold design of the RX8Performance kit overall? The angle of the rear-most runner looks like it's almost perpendicular to the turbine inlet.

Team, I read your Header Theory thread and agree with the points you made there. Since that was mostly under the context of a N/A setup, I was wondering what your thoughts are regarding a turbo setup. Basically, don't bother with equal-length runners or anything of that sort and simply reduce restriction as much as possible, right? Are there any nuances I should be aware of?

not relevant

This is a rough sketch I made a while ago back when I was considering doing a Rotrex (centrifugal s/c) build. This was before I stumbled upon your thread btw. Relevant or not, I just felt reassured that I came to a similar conclusion as you regarding header design. But I guess none of that matters anyway since I doubt a log-style manifold would fit for a low-mount turbo setup. I was simply curious if (theoretically) it would be better/worse compared to a bundle of snakes for a turbo Renesis.
https://cimg6.ibsrv.net/gimg/www.rx8...b5e8a7eb7b.png

hard to believe you commented on my turbo thread and then say that ! Didn’t you look at it ?

I was referring to Team's Header Theory thread (which I only got around to yesterday) when I said "This was before I stumbled upon your thread btw." Your threads ("Ultimate Renesis Turbo", "450 Theory", & "G30-660") were some of the 1st ones I read on the forum. Sry for the confusion. I've been spending the past few weeks trying to absorb everything I can on the forum lol.

Edit: Ah, I see...looks like I overlooked the current manifold design you're using (log-style). I was under the assumption you were still using the manifold design discussed in your Ultimate Renesis thread. The one where the wastegate is hooked up to the siamese runner. Are you content with the one you're currently using? Or is there anything you'd want to change wrt its design? It looks a tad restrictive as you've mentioned, but apparently, it works and I bet the smaller volume aids in response/spool. But I'm going to defer to your opinion since you've got the actual data/experience w/ it. :p:

Edit2: Was thinking more about your manifold design. Since TiAl housings don't come in twin-scroll configurations...how well would a single-scroll variant work in your opinion?

My current g30-660 is single scroll and it's working great. Some :suspect: have said the manifold is a restrictive design , but they don't seem to be getting it. I think it's the LEAST restrictive turbo manifold that's ever been built for a Renesis.
I'm so happy with it that I'm having some stainless cast versions made up to sell.

the problem here is I can’t express my view without it becoming a bickerfest. I don’t agree with the way some things have been done in the past or even some of the comments being made in this thread. I will agree about the G-Series turbo being probably the best choice out there now, but again am in a position where I have to start explaining why your entire approach is wrong and is likely going to end up with you either blowing up and/or me just talking to the wall again.

So on all those points; no thanks.
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I agree ...no point in starting a bickerfest . You think what you think and I'll just continue enjoying what is proven and working great.

You are the one with something to prove on this subject. Stop messing about and go do it. You might actually have something worthwhile to say then.

I was looking for some actual numbers regarding that and was able to find some more details about it in the following video. At around 7:50 into the video, Robert states the UHF turbine wheel has ~40% less MOI compared to a full-bladed design. At around 11:25 he states that a UHF turbine flows equivalent to a traditional turbine ~4 mm larger. EMAP-wise, the Porsche mentioned in the earlier Dsport video saw ~100KPa (14.5PSI) less backpressure by switching just the turbine wheel. Same size, same setup except for the UHF wheel; mentioned around 25:40 in the video. They were able to make an additional +100HP as a result (1200HP -> 1300HP).

I wasn't trying to imply the Xona turbo to have a lesser MOI than the G-series turbo. I'm perfectly aware of how awesome Garrett's newest turbos are and the Xona turbo is clearly inferior in almost every regard except perhaps the turbine. But yes, I'd basically be doing it to be different, although not simply for the sake of being different. Like I've said, I'm really curious what effects the turbine's splitter-blade design will have on a rotary application. Just by looking at it, you can clearly see it's a significant departure from blade designs used in other turbines. And no worries, no offense taken...I know you're just looking out.

Staf00 I wouldn't say it's inferior , just relatively new and untested on our platform. There are some really good features. Def worth a try if you don't mind being the first. Although , if it were me, I'd probably try and reach out to someone who was already using one in a harsh environment IE race car.

I did give data... and that's exactly what they did. They tested it on a Porsche 997 w/ a twin-turbo setup that originally used a pair of XR6564 turbos then did a direct comparison with a pair of XR6564S turbos. Same setup, with the only difference being the turbines (same compressor as well). The Porsche saw ~100kPa less EMAP, which is ~14.5psi to achieve the same power (watch the 1st video @ video 2:55 & the 2nd video @ 25:30). As a result, they were able to push the new setup further and gain +100whp (1200 -> 1300whp) because it was able to breathe so much easier.

Edit: As far as the turbine wheel size being larger...well, I'd say that's a good thing. Most Garrett turbos are optimized for piston engines (which can get away w/ a more restrictive hot side compared to the Renny) while the XR6564S, in particular, seems to have a much better compressor to turbine ratio. Now, I never claimed that the Xona turbo was better than a G-Series turbo. It's clear that the compressors on the G-Series turbos are superior both in terms of flow and efficiency. Imo, a hypothetical turbo that utilized a G-Series "660" compressor wheel paired with a Xona UHF "64S" turbine wheel would be my ideal configuration.

frustration, not hostility.

Tried to warn you, but I didn’t heed my own advice any more than you did. So I’ll just back out. Deleted what I could, not to hide anything, but just fix what I now recognize as a mistake. Can’t delete your copied replies though, yet there’s no point having it listed twice either.

If you want to run something specific by me just send a pm. Otherwise hope it works out for you despite my perceptions.

Best wishes.
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https://eliterotaryshop.com/product/...header-flange/

doesn’t state round pipe/tube size, you’d have to inquire about it.
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