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"I’ve already tapped both runners of my exhaust manifold with 1/8" NPT fittings and will be running some back-to-back testing. I’ll report the data here once I have it."
I’ve already tapped both runners of my exhaust manifold with 1/8" NPT fittings and will be running some back-to-back testing. I’ll report the data here once I have it.
I’m using my 99 Spec twins as the baseline/control, and I’ll also be doing dyno runs on a Dynojet in parallel with the sensor logging so I can capture full horsepower and torque curves at the same time.
I’m installing anEMAP (Exhaust Manifold Absolute Pressure / backpressure) sensor on the front runner (pre-turbo, primary side) using the FFE EMAP canister kit with the 5 bar absolute pressure sensor and stainless hardline, and an EGT probe on the rear runner. Note that both runners communicate internally through a balance port, so the pressure is very similar between the two sides. I’m still putting the more useful EMAP sensor on the front runner (the one connected to the primary turbo, which is active most of the time).
I’ll be logging everything live through my FC Master with the I/O Extender.
Once the baseline is done, I’ll also be testing the Sakebombgarage hot-side manifold with BNR CHRAs attached to it. I’ll compare the sensor data (EMAP + EGT) and dyno graphs between the two setups at 14 psi boost, keeping all other mods the same. It would be a true single-variable test if I bolted the stock 99 twins CHRAs onto the SakeBomb hot-side manifold, but that’s honestly a big pain in the ***, so I’ll be comparing two variables: the SakeBomb hot-side + BNRs versus the complete stock 99 Spec turbos.
Looking forward to finally getting some real pre-turbine backpressure numbers on the stock twins versus the SBG hot-side manifold for the community. I’m confident the pressure difference will show positive results, but the real smoking gun for people considering the SakeBomb kit is hard data and I’m glad to provide it.
For reference, I also have one of the best exhaust setups available: Knightsports twin downpipe, FEED twin catalytic converters, and FEED catback (Sonic AS-V). This should help eliminate exhaust restriction as a variable in the comparison.
I love to see more people doing real world testing and excited to see the results. I've got a knightsports downpipe that still needs to go on so I'm glad you have one for the test.
I'm pretty sure Matey and maybe some others in Australia tried dividers between the turbines and made less power as you lose flow area pretty much any way you cut it. It isn't ideal but there is massive swirl out of turbos anyway.
What's so special about the Knightsports twin downpipe?
Theoretically the larger inlet from the turbos along with the twin tubes "Should" flow better than say the HKS or other standard 3" downpipes due to the larger overall volume of the system (specifically speaking for RHD because of the steering shaft issue.) Further downstream as the exhaust cools, the larger piping isn't as necessary as close to the turbos. Having the largest expansion area possible straight out of the turbos is best case. The Huge SMB downpipe would also be a great choice but I believe it may only be able to fit LHD, I don't have any personal experience with it. If I had the time and money I would love to do a downpipe shootout on the dyno to see if there really is a difference between them.
The original owner of SMB, who I bought my downpipe from in 2017/18, did both LHD and RHD downpipes with the bigger bellows. I don't know if the people that produce them now do. Maybe some of our Aussie friends on the forum can chime in, if they know? Obviously, he was limited by steering shaft on the RHD ones. Mine is pretty big on my LHD car. Pictures are after ceramic coating.
Mike
There is still someone manufacturing whatever the evolution of SMB exhaust was after they shut down. I don't know if whoever is making them sells direct or for Marcus specifically, I think he shares them on his page occasionally.
I'm pretty sure Matey and maybe some others in Australia tried dividers between the turbines and made less power as you lose flow area pretty much any way you cut it. It isn't ideal but there is massive swirl out of turbos anyway.
just a divider in the stock shaped outlet would result in a loss of flow.
There is space above, below and toward the unibody if one were to design a new investment cast merge/outlet with cfd modeling, take all available space and require a different downpipe/flange design.
Twin 3" tube v-band downpipe straight off the turbo merge flanges running down back and merging at 2 bolt cat flange like gtr downpipe.
I'm pretty sure Matey and maybe some others in Australia tried dividers between the turbines and made less power as you lose flow area pretty much any way you cut it. It isn't ideal but there is massive swirl out of turbos anyway.
just a divider in the stock shaped outlet would result in a loss of flow.
There is space above, below and toward the unibody if one were to design a new investment cast merge/outlet with cfd modeling, take all available space and require a different downpipe/flange design.
Twin 3" tube v-band downpipe straight off the turbo merge flanges running down back and merging at 2 bolt cat flange like gtr downpipe.
That might work if the car wasn't originally designed in Japan.
I'd argue if you are putting in that much effort I'd rather do modern compound turbos or positive displacement supercharger compounded with large turbo.
No new info here, but I did receive this response from SBG when I attempted to get some some of objective figures to back their claims -- i.e. actual size of the wastegate flapper, demonstrable flow improvement values, etc... on the housing in particular (I'd only be interested in their "DIY" housings as I have a brand-new set of BNR Stage 2s with brand-new housings).
Our stainless steel housing is engineered specifically to resist cracking under extreme heat. We’ve designed the wastegate with a significantly larger flapper door and port, which allows for much better flow at high boost. While this won't necessarily net you more peak horsepower, it greatly increases longevity and provides much finer boost control—especially when paired with a high-flow exhaust system.
Additionally, the center housing features improved flow characteristics over the stock unit. While it is difficult to quantify this as a specific percentage (as it depends on the backpressure of your specific exhaust setup), the efficiency gain is measurable.
Because of the additional material surrounding the wastegate orifice and the oversized flapper, this housing can be ported well beyond the limits of a stock unit. This is especially important for high-boost applications where maintaining precise control is critical.
I'm still very much on the fence. Given how much I'm sinking into my build, it seems a shame to NOT go with their housings... but, the only demonstrable benefit is the wastegate size, which is a big benefit. But they won't qualify how much larger aside from "significantly". They claim "measurable" gains in efficiency but won't claim what those measures are even in a vague way. With a KnightSports Twin Tube and a full 90mm catless exhaust from there, flow would definitely help... at least in theory...
I'm not trying to claim that they're hiding something or anything like that. Certainly nothing nefarious. I think they themselves don't know yet... which isn't exactly confidence-inspiring either. And I don't blame anyone for being hesitant to provide hard, objective claims on performance improvements made to 30yo cars each configured with eleventy-bajillion permutations of mutlipe-owner's mods by this point. It just makes it hard to make a decision as a consumer.
And now with BNR coming out with better CHRAs in both the Stage 1 and Stage 2 variety.... doesn't help with the indecision. May just be better off flipping the Stage 2s that I've got and waiting a few months for both the new BNR Stage 2s and SBGs housings.
No new info here, but I did receive this response from SBG when I attempted to get some some of objective figures to back their claims -- i.e. actual size of the wastegate flapper, demonstrable flow improvement values, etc... on the housing in particular (I'd only be interested in their "DIY" housings as I have a brand-new set of BNR Stage 2s with brand-new housings).
I'm still very much on the fence. Given how much I'm sinking into my build, it seems a shame to NOT go with their housings... but, the only demonstrable benefit is the wastegate size, which is a big benefit. But they won't qualify how much larger aside from "significantly". They claim "measurable" gains in efficiency but won't claim what those measures are even in a vague way. With a KnightSports Twin Tube and a full 90mm catless exhaust from there, flow would definitely help... at least in theory...
I'm not trying to claim that they're hiding something or anything like that. Certainly nothing nefarious. I think they themselves don't know yet... which isn't exactly confidence-inspiring either. And I don't blame anyone for being hesitant to provide hard, objective claims on performance improvements made to 30yo cars each configured with eleventy-bajillion permutations of mutlipe-owner's mods by this point. It just makes it hard to make a decision as a consumer.
And now with BNR coming out with better CHRAs in both the Stage 1 and Stage 2 variety.... doesn't help with the indecision. May just be better off flipping the Stage 2s that I've got and waiting a few months for both the new BNR Stage 2s and SBGs housings.
I think the big thing about the new stainless replacements is just that. We have an option for factory replacement manifolds which are becoming increasingly rare. For many, the performance of the factory or 99 spec turbos are enough, so the stainless manifolds are a welcome item to help keep the twin dream alive. I was starting to sweat it a little and constantly had my eyes open for good shape replacement manifolds to hoard because they are ultimately a consumable item in these cars, now I don't have to do that. Adding ability for BnR will just be icing on the cake for those that want more horsepower than the stockers can support.
This is a no-brainer if you want a twin turbo car. I ran '99 turbos for years on my track car, went through two sets, ported wastegates, etc., no way I'd buy a set if this existed.
Now that Inread that again though, maybe the "improved aero" in the new ones that he is speaking about is just selling them with the SBG housing.
Might also explain why his post talking about the changes several months back disappeared. SBG probably told him to stay quiet.
I think the big thing about the new stainless replacements is just that. We have an option for factory replacement manifolds which are becoming increasingly rare.
100%. But that's the thing. In my case, my BNRs already have a set of brand-new, ported housings. So for me specifically, it's about how objectively better the SBGs are than new OEM.
Now that Inread that again though, maybe the "improved aero" in the new ones that he is speaking about is just selling them with the SBG housing.
Might also explain why his post talking about the changes several months back disappeared. SBG probably told him to stay quiet.
100%. But that's the thing. In my case, my BNRs already have a set of brand-new, ported housings. So for me specifically, it's about how much better these are than that.
If I didn't have that, it's a no-brainer.
If your manifolds are in good shape, I would 100% just run the BnRs that you have and put the money towards something else on the car. That money can be spent on some serious supporting mods or just saved for when the next thing breaks or needs replaced. For my power goals and build of my car, I would be fine with some 99 spec turbos and the stainless manifolds. That being said, if they do release BnRs in the future (sounds like rumors based on hope at this point) and they are just as responsive as the 99 spec and support more HP, then that would be a no brainer for me. My main goal is to keep the drivability and response of the factory system and have 350 whp max most likely. 99 spec can support this but if the BnR can do it more efficiently with less boost then that's the route I would probably want to go.
My perfect setup would be the stainless manifold paired with BNR stage2+. 300-350whp is more than enough for me tbh. And with the car in stock form i can keep it the time-capsule it is.
I ran into Heath and others from the Sakebomb crew at The Thunderhill Open race / drift event this weekend. Got to see and touch these manifolds and associated parts. They look awesome. I will probably get a set when I do my engine this year or next.
Heath also shared a few other top secret things in the works that they will share on the socials eventually but I'm sworn to secrecy.
Check their vendor sub-forum for upcoming Group Buys and product announcements. Looks like they are running a new GB on the Water/Meth injection tanks rn.
It was a fun weekend with @Gadd using his FD as the pace car for the Spec Miata race and a bunch of other rotary brothers racing and hanging out.
Last edited by gracer7-rx7; May 18, 2026 at 01:53 PM.
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