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)


Making sure the reads are the right size

Will put a 2 nuts on the rear and tight into the front iron after stacking the rest

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.

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.


This had seen better days. Need to clean it up and use pieces for the mockup.




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.

 

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.



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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.


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.

Filter that got removed.

Working on the BNRs. Lots of little things to mess with due to the custom lines and excessive LIM.

Turbos out my crush washers were imperial vs metric and needed to be enlarged to fit on the banjos.

Oil drains attached.

Apparently the fresh oil OMP adapter was never intended to be used with twins. Oil train interference.

So I deleted it.

And then had second thoughts overnight and added the OMP back, but without the dress oil adapter (for sale if anyone wants it)

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.

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.

Then the next issue, excessive intake sits further forward and no clearance for the sequential hardlines.

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.


OMP injectors with fresh lines, using the old style injectors.

Lines

New oil feed without needing the little filter, came out nicer than the last one

No turbo oil filter thanks to the Race Only filter adapter

Good clearance for oil line between LIM and secondary turbo intake pipe

Mocked up with intakes

Drilled holes in the heat shield for EGT access


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.


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.

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.

 

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.

 

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.







The stock setup is so much better. More organized chaos.

 

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.

 

Update on the silver BNR twins car. Swapped places with the 4 rotor car so I can try to get it running and usable before the 4 rotor engine comes in.

trying to chip away little pieces at a time now that the engine is in. Today I put the ABS and brake lines in. Also put in the DBW mount from z precision and a 2015 Camaro pedal. Fit really nice.

Wanted to put in the AC/Power steering bracket and the accessories but realized I can’t put those in and still be able to hook up the wiring to the crank sensors. With all the modifications I’m doing I decided to make my own harness, so taking the opportunity to switch to the FFE trigger with hall sensor. Will make it so that can be installed and the wiring hooked up last. Also ordered the DBW and adapter. Once all that’s in I can figure out where to mount the fuel regulator/damper and flex fuel sensor and plumb it all. Trying to make everything easily serviceable, and need all the parts here. Also got the Prometh solenoid so I can find a spot to mount that as well.

unfortunately I spend more time cleaning little parts and then determining whether to paint them, and then I procrastinate…



Cleaned up before it goes in the garage. It looks good from 20 feet but really needs a paint job.

Has the 4 rotor bumper on just because I needed a place to put it.

Z precision mount

Camaro pedal

New charging harness ready to go on

Abs

Lines

Fuel components and rebuilt brake master cylinder


Solenoids for each car, and only bought one pump. Will get the others when the other cars are closer to running.