Low Mount Twinscroll Turbo Concept for EJ25

Starting a new thread to continue an old one that's now going in its own direction.

 

Start here:

http://legacygt.com/forums/showpost.php?p=5333543&postcount=180

 

February 11, 2016:

 

I've had this bug in my mind again, now that I'm starting to get my mojo back

 

My drawing from June 3, 2010:

http://legacygt.com/forums/attachment.php?attachmentid=224582&stc=1&d=1455176480

 

My drawing from Nov 30, 2010:

http://legacygt.com/forums/attachment.php?attachmentid=224583&stc=1&d=1455176480

 

My drawing from January 31, 2016:

http://legacygt.com/forums/attachment.php?attachmentid=224584&stc=1&d=1455176629

 

I've come up with a more elegant design since, excited about it.

 

The standard of design is simple:

1) Twinscroll T4.

2) 2.5" radius 1.75" OD pipe.

3) Equal length.

4) Not having to cut anything.

5) No meaningful change to road clearance (my car already has only 5.5")

 

That's all for now.

 

February 15, 2016:

 

Progress. Symmetrical on X and Y, which is certainly more elegant, but TBD whether it offers the best fit for the specific EJ25 oil pan constraint.

 

HexMods Header Merge Collector v0.2:

 

http://legacygt.com/forums/attachment.php?attachmentid=224786&stc=1&d=1455525321

 

 

And:

A nice reply from mwiener2:

http://legacygt.com/forums/showpost.php?p=5336839&postcount=184

Worked myself ragged this week, so no new CAD renderings or other major hobby progress.

Though I did do a couple small things toward this end:

 

1) Calculated over 20 variants of this design. So far you've seen two. Fortunately several are impossible or impractical. I will do a bit more CAD work on this to work out the viability of tighter pipe radii, but will hopefully by then have picked a turbo and will be able to jack it up into place and measure more exactly. Then it will be the practice of going through all the variants and determining the optimal design(s).

 

2) (Digitally) measured some turbos to see what will fit relative to what else. So far just Borg Warner. This isn't exact, but it's close and quite helpful:

 

http://legacygt.com/forums/attachment.php?attachmentid=225096&stc=1&d=1455956285

 

As far as I can tell, the Borg Warner EFR 9180 is only an inch bigger around than the EFR 7670.

 

The S200 & S200SX are roughly the same size as the newer EFR 7670.

 

I am (for the time being) planning to use a S200 or S200SX with External Wastegates.

 

There are many options, I will narrow it down soon. Really wanting to stay under 50lbs/min of flow to keep boost threshold reasonable.

 

The design goal is for an EFR 7670 to fit. There's no telling yet on the bigger frame EFR turbos.

Do EFR IWG twinscroll. Less plumbing and parts.

Subd for interest

What would you run for an oil scavenge pump for the turbo oil drain?

This looks fantastic. I wish you all success in this endeavor. I've thought about it a lot too. And, I second an EFR twin scroll : ). It would be awesome if someone could manufacture a cast piece that the header tubes could merge into in lieu of individual pipes.

Do EFR IWG twinscroll. Less plumbing and parts.

 

Iteration 1 will be IWG. Then the plan is to figure out EWG. There are many reasons for this. Would make compounding a lot easier. Would of course allow a greater selection of turbos and A/Rs.

But to say it would be complicated and crowded is an under statement.

 

What would you run for an oil scavenge pump for the turbo oil drain?

 

Electric scavenge pump, with T'd breather.

 

Mike what is your setup?

 

This looks fantastic. I wish you all success in this endeavor. I've thought about it a lot too. And, I second an EFR twin scroll : ). It would be awesome if someone could manufacture a cast piece that the header tubes could merge into in lieu of individual pipes.

 

Thank you

I've played around with that idea too. Not a cast piece, but either

-CNC merge collector,

-CNC merge collector made in slices and bolted or welded together,

-Thinner laser jet layers stacked on top of each other,

-3D Printed (but WAY too expensive).

 

But each time I end up right back at clever and feasible notched pipe elbows.

 

Fact is not enough of these would ever be sold to justify a lot of scaled production techniques, nor would they be exceptionally beneficial to the end product's function.

That all makes sense, but there is so much elegance in the low placement to reduce all the piping lengths. We can all just live vicariously through those of you who can make it work for yourselves [emoji1303]

 

EFR also has the possible advantage of clocking the compressor housing and IWG actuator more easily, if that ends up helping out.

Seen this? Not TS, but a good example of how things fit down there.

Seen this? Not TS, but a good example of how things fit down there.

 

Beautiful build, but not applicable unfortunately. since it's a 5th Gen there is enough room under there to host a dinner party for extended family.

 

You'll see once I post mock-up photos, or instead look at mweiner2's pictures, there is barely enough room under a 4th Gen to put just a turbo laterally, and certainly not enough room to put a straight merge collector. It is by all measurers same thing different application as what has been done for the last two decades.

Thank you for sharing though, I had not seen it

I've run into a new problem... 1am last night took a few minutes to plug all the Borg Warner Turbo part numbers into eBay, and they are not readily abundant like they use to be in anti-surge compressor housing form. There are lots of standard compressor housing options, but those housings move the surge line pretty far to the right, so much so that I'm not confident they would operate to their potential without surging. I'll check later, don't really have the time now to run those numbers.

If things stay exactly as they are, then I might be buying an EFR 7670 IWG after all, purely out of cost/benefit. I'm not the type to spend $2000 on what could be done 90-95% the same for $1000, at least on my own car where horsepower result is concerned. Some of my customers have been happy to spend an extra $1000 to get an extra 5-10% relative sub-increase and that made sense for them, so not knocking it either.

I'm using the "crazy saltflats motorcycle guy" oil pump with bronze gears. There's just a hose from the turbo drain up to the pump. I've got a filter and a check valve before the pump. I also have a check valve on the oil feed. Pump runs for one minute after engine shutoff. No issues in 5 years.

 

 

I happen to have an EFR 7064 TS IWG with anti-surge housing. It's never used and I would let it go for a really good price...

Made a bit of progress tonight (couldn't fall asleep):

 

Drew the collector in 1.63" OD 1.63" radius (centerline) elbows, and the vertical clearance from the top of the flange is only 2.4", or 2.9" when you count a 1/2" thick T4 flange. Would prefer for it to be 3/8" thick since every bit counts here, but this leaves room to spare. I now know this concept will work.

 

This version is a symmetrical reversal of the previous mockup, where the far side elbows go to the outside instead of the inside. There is some unnecessary and undesirable pipe merge overlap before the pulses have been directed completely down into the turbine housing, so there would be a bit of reversion / inefficiency. I just wanted to see what it would like like since symmetry is a bit more elegant. And it let me test pipe angles and clearances with this new radius specification.

 

http://legacygt.com/forums/attachment.php?attachmentid=225618&stc=1&d=1456567232

 

See how the pipes merge:

http://legacygt.com/forums/attachment.php?attachmentid=225616&stc=1&d=1456567232

 

http://legacygt.com/forums/attachment.php?attachmentid=225617&stc=1&d=1456568854

 

 

 

 

Now separately, turbo selection time is coming up this coming week.

 

Mike is offering to sell me his EFR 7064 T4 Twinscroll IWG.

 

Boost figured at 23psi (93 pump gas, conservative timing).

1=2000 rpm

2=3000 rpm

3=4000 rpm

4=5000 rpm

5=6000 rpm

6=7000 rpm

http://legacygt.com/forums/attachment.php?attachmentid=225619&stc=1&d=1456568854

 

Pros:

B2 footprint will allow me to get a better idea for the fitment of the bigger EFRs.

Zippy around town, which is most of my driving (with this car).

IWG will save a lot of early stage development headache.

Very compatible with E85 (better at higher PR).

Better in every way than my comparably arcane 20g.

 

Cons:

Power will drop after 6000rpm as boost will need to be reduced (the only real con on this list).

I know the EFR7163 exists and this will bother me slightly, but it will be fine.

EFR is still expensive, but then again so are wastegates and the extra fabrication to plumb them.

Still needs to be water cooled, or at least it's "recommended".

 

That's all for this week, have lots more wrench turning ahead for the immediate future.

EFR 7064 is on the way!!!

 

Thanks to Mike at 5250 Performance in Colorado!

 

And a side note, thank you of course to Geoff at Full Race for always being a 100% positive and helpful person with my efforts. You would think lots of true turbo header experts would have risen over the last decade in the Subaru market, but after all these years he's still among the top on a very short list of people who truly know what they're doing with development. If you have to ask, just order an EFR 7163 Full-Race kit already!

Love it

Turbo arrive yet?

 

 

I have had some bad dealings with Full Race... To the point that I will no longer do business with them. Nothing against Geoff personally, I'm sure he doesn't know about what happened.

 

Order a kit from Full Race, wait 1 month for delivery.... Then wait 2 more! Long time to wait for jigged and robot welded parts.

 

5250 Performance now builds Stock and Rotated location EFR kits in house becauue Full Race could not deliver.

subscribed.

Turbo arrive yet?

 

5250 Performance now builds Stock and Rotated location EFR kits in house becauue Full Race could not deliver.

 

Not yet.

 

I saw you have a former NASCAR fabricator on staff now. Great to have such a person!

subscribed.

 

This.

Re the TS/SS debate, is the paired EWG used allowing exhaust cross-flow, making the headers more like a 1.5 scroll header config?

Re the TS/SS debate, is the paired EWG used allowing exhaust cross-flow, making the headers more like a 1.5 scroll header config?

 

The Borg Warner Twinscroll IWG Turbine housing has the two scrolls' wastegate passages separate until their entry into the post-turbine exhaust stream:

 

http://www.rx7club.com/attachments/single-turbo-rx-7s-23/569158d1447779342-bw-8374-boost-creep-check-borgwarner-efr-8374-turbo-content-9.jpg

 

http://www.full-race.com/store/images/full/borgwarner-efr-8374-turbo-content-11.jpg

Thanks for the clarification & pics.

Are the merge pipes welded together, then welded to the flange through the ports on the flange?

(intrigued fabrication student here)

Thanks for the clarification & pics.

Are the merge pipes welded together, then welded to the flange through the ports on the flange?

(intrigued fabrication student here)

 

The plan for now is to weld pipes 1 and 2 together, separately weld pipes 3 and 4 together (so there's 2 separate solid pairings), then weld each pairing to its respective flange volute opening. The plan there is to weld the inward-facing sides on the inside of the T4 flange openings (the inside being where the hot gases flow through), and then weld the outer 3 sides of each pairing to the outside of the flange (which is the more conventional way).

Can't wait to attempt something of this stature, currently on book 2 arc so it's going to be a while. Are they multi pass runs, eg root then fillets or stringers?

Can't wait to attempt something of this stature, currently on book 2 arc so it's going to be a while. Are they multi pass runs, eg root then fillets or stringers?

 

I'm going to send the tacked manifold out to a professional tig welder, so he will make the final call based on what he believes is needed.