so I never looked at those small BW turbine plots before, but after just reviewing it am now concerned that you may have overestimated their flow capacity. The 58mm 0.85 A/R is tighter than I had anticipated. It looks to me like they could have been parallel and still spool easily. What was your power goal again?
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Around 450. I have stock seals.

They definitely would have worked well in parallel. And I even made a delete pipe for the egate in case the sequential system doesnt add value.

I'm thinking the transition will be a bit different than stock. Secondary turbo might not need to kick on until 6k rpm. But I really have no idea yet.

Also, if you are looking at the compressor maps, I have SXE covers, so 10%-20% more flow. This efr range is pretty old now, and the SXE had a decent flow improvement especially on these smaller frames. Was not the case on newer versions like the 9280, which had the benefits of the SXE cover built into it.

sorry, ran some quick numbers and not as bad as I had initially projected.

It should be fine for that power level, but I’m think sequential may be too much for surge.
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Meaning the first turbo will overspin too quickly? Or are you thinking it will boost so quickly but not flow enough air and therefore cause weird pulses?

based on the numbers I was using it was suggesting anything over 6 psig boost @ 3000 rpm was going to surge. At 4000 rpm, 19 psig was ok. I didn't explore between the two. This was looking at a single turbo @ 1/2 volumetric capacity, which would be equivalent to a parallel system (sequential valve open). The numbers used for plotting it matter, but likely how much air you can bypass in sequential mode at low rpm is going to matter a lot.

It’s a projection I never attempted before and somewhat unsure of, but even when you consider the idea of running a 13B with a single EFR 6758 0.85; which is equivalent to the sequential valve closed, is why I was always theorizing about a parallel system. The primary turbo with a larger A/R housing might be advantageous, but I’m not aware of one for the 6758. Or at least not with a V-band inlet.
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I guess time will tell. The whole thing is a bit of an experiment. There was a set of the next size up B1 frame efr for sale on here not long ago. I almost got them so I could swap and test but then I would have had to buy new housings and stuff. So I figured will try this out and if it doesn't work well, can either run parallel or swap turbos.

Main regret I have so far is the internal gates. I thought it would save space and make this easier to build. But the actuators take up space in all the wrong spots (without the actuators I could have mounted the secondary turbo much further back making it a lot easier to work on). And turns out there is plenty of room down in the runners to mount wastegates.

so I looked around and the only option I knew of and couldn’t find any reasonable alternative to would be a larger EFR 7163 with an aftermarket cast iron T3 open scroll 1.06 A/R or T3 twin scroll 1.25 A/R for the primary position. I understand you already have what you have and that’s how it goes, and we’ll see how that goes, but maybe a consideration for someone else down the road. Because even as a single turbo, an EFR 7163 with the aftermarket T3 TS 1.25 should theoretically be capable of 450 whp on it’s own. Though higher emap as a single as well on the top end. The calculated numbers suggest that the TS 1.25 A/R could do 25+ psig @ 3000 rpm though, but only 10 psig @ 2500 rpm in full 13 exhaust flow rating i.e. sequential valve closed.

forgot to note that unfortunately those housings are EWG only.
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A few 4 rotor updates.

Ordered some threaded rod so I can hold my mock-up block together. And took apart an old block I got about 10 years ago so I can get the extra intermediate plate and housings I need. Also made longer dowels to stack it.

Then, cut into the eBay 2jz intake plenum to get it ready for a new end plate with 8 runners instead of 6. Size is about perfect for the 4 rotor. Laid it on the 2 rotor to give a sense of the size. I was really surprised by the level of quality. Good thickness aluminum sheet formed, and great weld penetration (I’m guessing there aren’t many of these cut open for weld inspection)

https://cimg7.ibsrv.net/gimg/www.rx7...b1473edc7.jpeg
Making sure the reads are the right size
https://cimg9.ibsrv.net/gimg/www.rx7...924f13bfe.jpeg
Will put a 2 nuts on the rear and tight into the front iron after stacking the rest
https://cimg1.ibsrv.net/gimg/www.rx7...fc0cf19b9.jpeg
Long Dowels from Amazon which were a hair too thick. Put them on a drill and sanded them down quickly. Perfect fit in the block to hold everything aligned while I work on intake and turbo manifolds.
https://cimg2.ibsrv.net/gimg/www.rx7...65ccd883d.jpeg
Cut to size, basically it’s long enough so each end lands in the middle of a housing, so you can stack a portion of the block, add the next dowel, and stack the rest. Then cinch it up with the threaded rod.
https://cimg5.ibsrv.net/gimg/www.rx7...bcf763fe1.jpeg
https://cimg4.ibsrv.net/gimg/www.rx7...45459c953.jpeg
This had seen better days. Need to clean it up and use pieces for the mockup.

https://cimg7.ibsrv.net/gimg/www.rx7...797c73660.jpeg
https://cimg9.ibsrv.net/gimg/www.rx7...33f6b2918.jpeg
https://cimg1.ibsrv.net/gimg/www.rx7...b7e6eeefd.jpeg
I initially started drilling holes to cut it out on the thick plate to remove the 6 runners in one piece, then smooth the edges and weld a new plate with the 8 runners to it. Got about halfway done and decided just to cut off the entire backplate and weld the new one with 8 runners directly to the plenum. Think this will look cleaner.

https://cimg2.ibsrv.net/gimg/www.rx7...48d4a3c68.jpeg
https://cimg4.ibsrv.net/gimg/www.rx7...f9df4f2e4.jpeg

stumbled across this recently; Sato-san at RS-Pantera built this TT FD3 setup with a pair of Garrett GTX-3076 turbos. As I understand it, he ported the irons to the Cosmo port size and it made 650 ps at only 19 psi boost. I’m assuming using their 8.3 CR modified T2 rotors too.


https://cimg4.ibsrv.net/gimg/www.rx7...30b0ed30d.jpeg
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interesting, same but older HKS version (GT3037S) of the 3076 turbos above on an FC twin turbo setup

https://www.rx7club.com/time-slips-d.../#post12590230
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A few updates on the silver BNR car. Need to get it running for the summer and clear up space in the garage so I can finish the others.

https://cimg3.ibsrv.net/gimg/www.rx7...b63af99ab.jpeg
Switched over to the Race Only oil filter adapter which has 3 -6AN ports which are post filter, so you can run straight full turbos. It meant I needed to redo an oil line, but I was able to remove a small turbo oil filter to simplify things.
https://cimg4.ibsrv.net/gimg/www.rx7...2ab3e992a.jpeg
Filter that got removed.
https://cimg7.ibsrv.net/gimg/www.rx7...c0fabc61b.jpeg
Working on the BNRs. Lots of little things to mess with due to the custom lines and excessive LIM.
https://cimg6.ibsrv.net/gimg/www.rx7...0d79ac124.jpeg
Turbos out my crush washers were imperial vs metric and needed to be enlarged to fit on the banjos.
https://cimg8.ibsrv.net/gimg/www.rx7...4d5759d86.jpeg
Oil drains attached.
https://cimg0.ibsrv.net/gimg/www.rx7...a2e46035f.jpeg
Apparently the fresh oil OMP adapter was never intended to be used with twins. Oil train interference.
https://cimg2.ibsrv.net/gimg/www.rx7...de7295d1f.jpeg
So I deleted it.
https://cimg9.ibsrv.net/gimg/www.rx7...91289b171.jpeg
And then had second thoughts overnight and added the OMP back, but without the dress oil adapter (for sale if anyone wants it)
https://cimg3.ibsrv.net/gimg/www.rx7...167b06d69.jpeg
Went to fit the y pipe after vapor blasting. And it was hitting my coolant line, which was odd because I made it specifically for this. Thought I was going crazy.
https://cimg5.ibsrv.net/gimg/www.rx7...5c24c186c.jpeg
Then I remembered I was using the 99 spec Y pipe. Pulled it out of the box, and apparently it’s a slightly different shape and fit fine.
https://cimg7.ibsrv.net/gimg/www.rx7...82ffb4931.jpeg
Then the next issue, excessive intake sits further forward and no clearance for the sequential hardlines.
https://cimg8.ibsrv.net/gimg/www.rx7...d961f1668.jpeg
So I cut off the vent line section and bent the rest. Will just run a long silicone line for the vents. Note to self, using the twins with aftermarket parts not intended to use with twins causes a million chain reactions haha

Then I got the twins fully installed and torqued down. Unfortunately I had to do this twice because I forgot one of the heat shields bolts to the rear of the turbos. Also put in a new reverse switch on the trans due to wires being old and broken, also a new seal on the tail shaft, had this kicking around from when I rebuilt the 5th gear synchro about 14 years ago and forgot to put it in. This is the trans from the black car getting the 4 rotor. Idk the condition of the trans from the silver car so not bothering with it.

https://cimg3.ibsrv.net/gimg/www.rx7...03e26761c.jpeg
OMP injectors with fresh lines, using the old style injectors.
https://cimg4.ibsrv.net/gimg/www.rx7...2cf0ec81d.jpeg
Lines
https://cimg5.ibsrv.net/gimg/www.rx7...fbd7484ae.jpeg
New oil feed without needing the little filter, came out nicer than the last one
https://cimg6.ibsrv.net/gimg/www.rx7...06def0338.jpeg
No turbo oil filter thanks to the Race Only filter adapter
https://cimg7.ibsrv.net/gimg/www.rx7...38dc946e5.jpeg
Good clearance for oil line between LIM and secondary turbo intake pipe
https://cimg8.ibsrv.net/gimg/www.rx7...e32a572ab.jpeg
Mocked up with intakes
https://cimg9.ibsrv.net/gimg/www.rx7...7a72d31de.jpeg
Drilled holes in the heat shield for EGT access
https://cimg1.ibsrv.net/gimg/www.rx7...295baecba.jpeg
https://cimg3.ibsrv.net/gimg/www.rx7...837038908.jpeg
Finally torqued back down after removing them to fit the heat heat shield. Was a pain, but came out ok after some trimming and had to hammer the rear of it to clear the excessive LIM.
https://cimg4.ibsrv.net/gimg/www.rx7...6ace45765.jpeg
https://cimg5.ibsrv.net/gimg/www.rx7...d91d3f431.jpeg
You can also see in the bottom left, had to grind down on the head of the left banjo bolt for the coolant feed. These bangis fittings are thicker than stock, and my downpipe also has a heat shield, so they were interfering. Glad I test fitted the downpipe before I put the motor in the car.
https://cimg0.ibsrv.net/gimg/www.rx7...9fa64f608.jpeg
Ready to go together and get installed in the car!

Engine and trans in. Waiting on a new vacuum chamber before I put all the accessories on. But now I can get started on intercooler, radiator, plumbing and wiring.

when I was putting the thermostat in, I found something odd. The mishimoto thermostat rubber seal is smaller than OEM and didn’t seat in the housing, luckily I had bought a seal from atkins, inner diameter fit the mishimoto thermostat fine, and had the larger outer diameter and fit the housing nicely. Always some weird little nuance with aftermarket parts. If I hadn’t of changed a thermostat before I would have been very confused.

https://cimg4.ibsrv.net/gimg/www.rx7...5b0eaa090.jpeg
https://cimg5.ibsrv.net/gimg/www.rx7...3349c5bfa.jpeg
https://cimg6.ibsrv.net/gimg/www.rx7...61ffe54dc.jpeg
https://cimg7.ibsrv.net/gimg/www.rx7...3ca03d976.jpeg

Amazing work Bro! I have the RA OMP Adapter as well. It stretches the oil lines a little but not too much.

I will use when I go single, I will also have to cut and extend the stock oil return hard pipe.

Amazing work, by the way - Amazing Job !!!

Thanks man. Looking forward to more updates on yours. Here is another reminder that sequential twins is a poor financial decision in case you need one haha. Although I can’t believe they still make these. ordered on Friday, delivered on Monday, not bad.


https://cimg5.ibsrv.net/gimg/www.rx7...f01d0fe88.jpeg

Awesome work!
That engine is looking all business!

Thanks.

I did some searching but didn't see anything conclusive that wasn't really old. I have a haltech ECU going on this car, my wastegate and pre spool solenoids have broken nipples, and I haven't bought new rubber lines with the pills in them yet. Does it make sense to go with MAC valves for boost control? Most sequential boost control threads for sequential are about how to enable the PFC to control it with the stock setup.

https://www.rx7club.com/group-buy-pr...ispreloading=1
Check that thread and the thread before it from saxyman about using mac solenoids. It is doable.

My experience with the PFC and stock solenoids is that it doesn't do a great job of boost control. I had to add a boost controller (Greddy) to keep it from spiking and creeping - especially in cold northeast weather.

I would hit up Jack Cecil of Horse Power Logic. I think he had his sequential RZ dialed in with stock solenoids and Haltech Elite IIRC.

I have personally used dual mac valves and stock solenoids on the Haltech Elite to control the twins. They both work fine. I started out with the Mac valves and the upgraded solenoid rack. I later moved back to all brand new stock solenoids with the stock rats nest as I re-installed all emissions equipment. If anything I would say the stock solenoids are responding to changes a little bit better, but its negligible.

I think I would want to keep the stock solenoid rack just for cleanliness if that is the case. I wouldn't want to have to mount the mac valves somewhere else in the bay and be an eyesore or make a cover to hide them.

Thats exactly what i had done. Never loved the setup, but it worked.

https://cimg1.ibsrv.net/gimg/www.rx7...2ae262d77.jpeg
https://cimg4.ibsrv.net/gimg/www.rx7...f01957652.jpeg
https://cimg5.ibsrv.net/gimg/www.rx7...ae9973e92.jpeg
https://cimg8.ibsrv.net/gimg/www.rx7...55c4e4b43.jpeg


The stock setup is so much better. More organized chaos.
https://cimg2.ibsrv.net/gimg/www.rx7...454538972.jpeg

Wow, that turned out super clean with the piping restored as well.

Thanks John, good to see you still kicking.

I'll go with the mac valves. My solenoids are going over by the ABS, given where the boost control/prespool needs to tie into, i think I'll put them somewhere around where the normal solenoids would go.