Strokecharged RX8 V2.0
 

I bought John’s RX8 13B-REW last year with the intention of using it as a test-mule for some future mods I want to try out. It had all the basics in place to serve my purpose without me having to go through all the trouble and the price was fair. Here’s the link to his thread:

https://www.rx8club.com/rotary-swaps...2/#post4655521

The intention is to stay with the current junkyard REW engine to start. It will eventually change from the current bridgeport configuration, but for now it seems to be unbreakable. So figure I might as well take it as far as I can before dropping the cash on a serious engine build when that day comes. This will be going in quite a bit different direction than where it is now though.

One big change will be swapping out the high-forward mount Borg Warner S369 SX-E turbo system with a low mount Garrett G30-770 1.06 T4. I’m shooting for lowend response/torque with wide powerband range and not expecting to need more than low-mid 60 lb/min compressor flow (460 - 500 whp). The G30-660 comes up short of that and the larger wheels of the G30-900 will hinder response; the -770 seemed like the best Garrett selection. I might have considered the G35-900 if there was a tighter A/R T4 option, but with the 1.06 A/R currently being the only choice it will be too top end oriented (550+whp).

To handle the anticipated torque level another big change will be retrofitting the drivetrain with a CD009 6-spd transmission conversion (Nissan 370Z version), PPF delete, new driveshaft, and an OS Giken LSD with 3.727 ring/pinion. I plan to retain the RX8 differential and axles because imo the weight savings for the Ford 8.8 conversion isn’t that significant and it still uses the RX8 axle stubs that are the weak link in the factory rear axle assembly. So I just don’t see it being worth the cost and fabrication effort.

https://cimg3.ibsrv.net/gimg/www.rx8...c1d200677.jpeg


Currently this car still has the factory suspension, which with a 30 psi boost level makes for a bit scary nose up, rear squat situation under WOT. Initially I’ll be putting a set of Koni STR.T Orange non-adjustable shocks on it with Mazdaspeed springs and spherical shock mounts, but eventually it may get an old set of Koni 2812 race coilovers on my shelf thrown on it. I have a collection of various swaybars as well. The suspension isn’t really my goal with this car though. I already know what’s needed for that and the development intention is more for engine and drivetrain purposes. Another mod will be converting it from DSC to non-DSC, which presently the DSC system is faulted out for some reason and the ABS is not functioning.

Currently the engine is supported by an older Adaptronic Select ecu piggybacked on the Mazda ecu. It works fine for what it is, but will be swapped out for the newer and more feature-oriented Modular ecu. Everything else for fuel system, AI, etc. already exists. There’s more to come, but it can be addressed along they way. This will be a bit slow because I want to finish up my other NA Renesis RX8 for competing in DSP for 2022. That needs to be my primary focus initially.
.

Team,

Do you have a thread for your NA Renny? Would love to see the build and hear about your past and upcoming seasons.

There is info about it scattered throughout the DSP Racing thread, but no dedicated thread.

So the G30-770 shipped today. I already had the 1.06 A/R divided T4 turbine housing and have a super-short low-mount manifold worked out. I won’t be able to finalize it until I can confirm the position of the bottom of the REW exhaust ports relative to the top of the subframe using the Banzai REW swap mount brace. Honestly though I’m not a fan of the Banzai swap mount due to it using the OE style engine mounts, but am unsure if I will change it out or possibly modify it to get rid of those.

Anyway some info, not anticipating having any issues achieving the power goal running 18 - 25 psi boost on E85 without AI. The numbers are pretty much right in line with an EFR8374 wrt that power range, except in the smaller Garrett “7160” G-series package that will hopefully respond and spool better


https://cimg6.ibsrv.net/gimg/www.rx8...58b1bbb67.jpeg
.

https://cimg7.ibsrv.net/gimg/www.rx8...f7616371d.jpeg
.
https://cimg6.ibsrv.net/gimg/www.rx8...bc224bf4a.jpeg
.
https://cimg7.ibsrv.net/gimg/www.rx8...8339e5ab9.jpeg
.
https://cimg9.ibsrv.net/gimg/www.rx8...c7351c7e6.jpeg
.
https://cimg0.ibsrv.net/gimg/www.rx8...c44802eb1.jpeg
.
https://cimg9.ibsrv.net/gimg/www.rx8...7325951b8.jpeg
.
https://cimg6.ibsrv.net/gimg/www.rx8...5015d3908.jpeg
.

Good choice for your goals IMO. The 770 is probably the first turbo out there to seriously challenge the 13b domination of the 8374 in that power range. Will be really interesting to see if you can get the same or better response . My feeling is that it will fall short on spoolup but be slightly superior up top.

I’m willing to let that play out rather than address it now.

However, I updated the previous post above with the addition of the EFR8374 compressor map. The different map scaling and resulting appearance differences requires paying close attention to the values. The one thing I’ll point out is that Turblown has mentioned hitting surge trying to boost as early as possible with the 8374, but in addition to seeing how similar the compressor maps are to each other for the goal, the notable difference to take away with is the Garrett map extends further over to the left to provide more potential low rpm surge protection.

We’ll have to wait and see how it pans out in reality, but based on your own results and understanding the differences between a Renesis and an REW I’m quite hopeful. :)
.

Why do you see 70% efficiency as being so important ? I would have thought actual operating range of the turbo/engine combo at various PRs would be more critical.

It’s a viewpoint that Howard put forward on RX7Club that I came to agree with

Efficiency matters, that’s why these turbos do what they do compared to those in the past, and with a lot less zoom-zoom-boom end results too if applied properly. It’s not just the compressor, but turbine efficiency as well and the things that can be done to optimize the full potential available. Honestly your comment surprises me in that regard.

the 8374 compressor is slightly better wrt peak efficiency, but 1% or 2% compressor difference between these two turbos is going to be minimal, particularly wrt other influences. The -900 compressor shines a little brighter both in peak efficiency and width, but offers no advantage to my goal, even works against wrt response. Keep that in mind. Because contrary to what you stated earlier, the 8374 actually has more top end potential and is more in line with the -900. I’ve seen 575 whp on a 13B with the EFR, the -770 will never get there, but on paper the -900 can.

But wrt Pr for the range being discussed, they’re almost identical for this application. So seems a bit mute on that particular point.

There are other factors too. The EFR GammaTi exhaust wheel may be light, but it and the compressor wheel are quite a bit bigger radius than the Garrett. Hence why I point out it’s a 7160 to provide a direct reference comparison to the 8374. MOI = mass x radius^2. Therefore the radius has a greater influence on inertia than mass. So the weight alone is not always revealing. It really depends on how the weight is distributed relative to the radius. Garrett not only kept the radius short with an extended width profile, but the stronger though heavier Mar-M material can be thinner out at the tips and still take a lot more heat.

Then there’s the things not being discussed. Not all the cards are out on the table yet, or will be obvious to see, or readily revealed in every instance, but let’s not put the cart ahead of the horse.
:)

I didn't explain properly what I meant by that . Sure the 8374 has more ultimate power potential, but in the operating range you were looking at IE the 450-500whp range the G30 should operate at slightly higher efficiency. That's what I meant.
I still think the 8374 will spool faster ... unlesss you have access to actual moi data ... even then I think you are underestimating the effect of the extra revs the G30 has to attain for the same mass flow. Will be interesting to see anyway.

No problem, the results will be what they are. And with the current junkyard BP engine that is likely even. Yet again, I can appreciate your view based on the information you have. :)

ps: mass flow through either is the same; EFR is passing through 65mm exducer, G30 is passing through 55mm exducer. Neither wheel is accelerating from zero, but from the rpm of the resulting velocity generated from the same given flow rate through either.
.

True , but whatever the starting rpms are, the G30 still has to accelerate through significantly more rpms to achieve the same mass flow. That's the tradeoff of going with smaller wheels and achieving lower MOI . It does achieve faster spool but I'd argue not as effectively as what Borg Warner did with lighter turbines. looking at the results from around the world with these G series turbos it seems to me like , yes they are better, but not by the margin that you or I might have hoped. They aren't outperforming the EFRs. Not on any platform that I've looked at anyway.

IMO you’re overlooking plenty in that assessment, but ok. I only really responded more for those who can’t see the holes in such an argument. Even though I have an ME degree intending to focus on turbomachinery design, I can concede not being an expert in the field since life choices took me in a different direction.
.

expanding on that part of the conversation, I get what you’re saying and am not really in total disagreement with it. My feeling is that if I had the -900 compressor that would be a more valid apples-apples comparison. So in my mind the decreased compressor loading plays into the response factor some, plus I’m trying to accomplish some other features taking advantage of the packaging differences that help to spool and spin up the turbine faster. So it’s not all about just a direct turbo comparison either.

I do wish there was a slightly tighter A/R divided T4 housing option though as a back up plan, but am stuck with 1.06 as the only current option. However as a slightly smaller performance-factor turbo with twin scroll on a 13B REW divided exhaust manifold there is potential in my mind, but not much results for others to judge against. In fact the only divided T4 Garrett rotary engine result I’m aware is Rob Dahms G42 20B, which is a 1000 whp monster.

So I hadn’t seen it mentioned anywhere much, but Borg Warner did release a new EFR8370 at PRI; essentially a compressor upgrade for the 7670 turbo. Without a more suitable turbine housing it may have flow/emap issues on a 13B though. If anything the equivalent to the G30-770 would be an EFR7974; slightly smaller compressor paired with the 8374 turbine.
.

I think it's good that you are trying something new .... the EFRs have had all the glory on 13bs for some time now.

Team, which trans swap kit will you be using? Quickly searching they are very expensive aside from Collins adapter kit $700 USD.

Skimming/searching strokers thread, he was using the stock 5spd? I'd be interested to see what you come up with for the whole trans situation if you stick with the CD009.

It was from a group buy on RX7Club and was so far a one time deal

there’s this kit from Fisch Racing in Canada, but these are all for an RX7.

So you have to supply your own trans/diff supports and driveshaft if using on an RX8.

https://fischracingtech.com/products...adapter-system
.
.

G30-770 supercore received from ATP Turbo; pics added above.

seems slightly smaller than the EFR7163 compressor, but that may be due to the integral BOV on the EFR cover.

Also received the non-DSC ABS conversion parts from HufflePuff.
.

some comparison photos; EFR7163 0.85 IWG on left, Garrett G30-770 1.06 EWG on right

just fair warning that getting the G30 1.06 twin scroll turbine housing v-band mated to the CHRA is a son of a gun, pretty much an interference fit that will only go on in one position. There is zero space left, couldn’t possibly be any more compacted.

but with the super short turbo manifold design it will be equal length, as direct-coupled as possible to the engine ports, and just does fit. I’m probably going to test on Stroker’s manifold first before mine is fabricated.

Little bit of a setback; the person where I store RX8 #3 and who’s shop I was going to use for fabrication unexpectedly passed away last Thursday. He went into the hospital for a kidney issue and just died the next day. Seems a bit suspicious even (wrt the hospital). He was a good man, may he rest in peace. Good reminder that nobody knows their day or hour when it comes unexpectedly like a thief in the night …


https://cimg9.ibsrv.net/gimg/www.rx8...db1414c04.jpeg
.
https://cimg0.ibsrv.net/gimg/www.rx8...d0e61d0ba.jpeg
.
https://cimg1.ibsrv.net/gimg/www.rx8...0edc05fc0.jpeg

.
edit:

Here’s the EFR7163 converted with SX-E compressor cover and 1.22 A/R EWG divided T3 turbine housing. Full assembled with the aluminum CHRA option it weighs just under 16 lbs and is very compact. This is more likely to end up on a Renesis engine project, though I may try to put it on the REW just to see what happens. :suspect:


https://cimg9.ibsrv.net/gimg/www.rx8...849a9405e.jpeg

.

should have posted this here instead:

Received the hybrid “S262 SX-E” (8370 in EFR terminology); a Borg Warner S257-SXE converted to the S362 SX-E compressor wheel along with a 1.22 A/R divided T4 housing, except it’s a T4 flange with T3 ports. There was nothing on the turbo specific page indicating this, but it is stated in the BW S200SX-E literature, so my bad. In the turbine housing only section it states this along with offering to port it put to full T4 port size. It’s a $90 service fee; they are porting one and will ship for me to swap and return the other.

So the S362 compressor wheel in the S200 cover is supposedly good for low-mid 70-ish lb/min flow; which theoretically is low-mid 500 whp on a 13B and the 70mm turbine wheel with 1.22 A/R housing is on par with an EFR8374 0.92 A/R turbine flow to support that (~28.5 lb/min), yet be responsive still at low rpm. Looking forward to see how it pans out overall and in comparison to the G30-770.

The compressor is on par with the EFR7163 SX-E cover I posted elsewhere, but the turbine housing is quite a bit larger and heavier. The full assembly weighs just under 24.5 lbs total, or about 50% more than the hybrid EFR7163 assembly I’m working with on another project.


https://cimg9.ibsrv.net/gimg/www.rx8...761fd82b9.jpeg

.

I should wait and see how this pans out before buying the 8374. If the response is the same then maybe I can package this turbo a little better in the low mount position and retain my omp. What's your time frame on getting this finished up? If it's like me, it's going to be years. Hopefully not.

They’ll be shipping me the T4 size ported turbine housing next week. It’s a $90 service charge that I’ll gladly pay than hassle with match porting it myself.

I’m thinking it will be close to a direct bolt-on for the forward mount BW S369 SX-E setup that’s on there now. Needs a different silicone adapter between the compressor discharge and IC piping, but the turbine housing flanges are the same. Different compressor inlet connection, but I have the necessary 3.5” inlet air filter for it already. Worst case I may need to have one end of the downpipe lengthened slightly. Won’t know for sure until I swap it on there.

You should be able to get the S362 SX-E in the low mount position with an REW, but the manifold influences that a lot. The hybrid conversion of the S200 does make it cost ~$200 or so more than the S362. I’m anticipating it being more responsive (smaller heavy metal turbine wheel = less MOI) and easier fitment with the super short turbo manifold I’m working on. In this form it’s about the same height and width of the Garrett G30-770 1.06 T4, but slightly longer between turbine and compressor housings due to the larger BW CHRA.

.

This is Awsome, makes my Johnson tingle.
Can’t wait for the results.

hopefully … eventually … did receive the ported BW S200 turbine housing this past weekend, but haven’t gotten to it yet.

The engine wouldn’t crank and I assumed the battery was dead again. So I pulled it out last night and brought it home to put on the charger … and the charger indicated that it was still mostly (3/4) charged. Now I have to try and figure out if a fuse or worse is blown. Which it doesn’t help that it’s loaded in the trailer. Suffer it to be so. 😑
.

Oh man I hate when they die in the trailer. Mine did it once. I couldn’t get the door open far enough to open the hood or get inside windows were up. Had to fashion a broom stick and hook to pop the hood.
I really wanna super charge mine but man the cost is quite high for the Dna kit. Trying. To tighten my belt in the coming years. Have a gt 500 coming I need to build.
I’ll just have to live through your build.
Your setup sounds like exactly what the Rx needs

Was finally able to troubleshoot the electrical power issue; dangest thing too. Battery is in the trunk and fully charged, feeding electrical power to an added fuse block in the engine bay, then distributes out from there. No power at all though like the main 120A fuse was blown, but it looks absolutely fine.

Probed the added fuse block and it has battery voltage coming in, but there are three 100A fuse legs across it, with only two distribution legs being used on the discharge end. One leg feeds battery power to the 120A main fuse, but power wasn’t getting across it for some reason even though it has no appearance of being blown. Even down inside the capped ends there’s not any burning etc., like it lost continuity internally, but nothing is loose or moving around inside of it. Kind of baffling really. :dunno:

https://cimg7.ibsrv.net/gimg/www.rx8...2d5642d0c.jpeg


so I just pulled the fuse on the 3rd leg, essentially a spare since it wasn’t being used, and all the power is back after I swapped it over. Work’s been crazy and I didn’t have time to mess with it further, but at least I can get the car out of the trailer and moved around where things can start progressing.
.

Good deal. That fuse looks ok to me but clearly it is not.