Brettus turbo 111 (the ultimate Renesis turbo ?)
 

As the title states ............ this is my attempt at making the ultimate Renesis turbo setup .

I've been running the Greddy system for about 6 years now and learned a heap from maximising that setup (See Brettus turbo and Brettus turbo 11 threads) but figured it was time to do something of my own design.

The engine : will be using my current engine . This engine has been doweled and had rx7 deep apex seals fitted along with increased oil pressure. However , once the turbo system is sorted I plan to refreash this engine as it is down on compression .

The Turbo :
This is a Garrett GT3582r unit . I chose this turbo after considering all the major brands . The main reason I went with it is because of it's relative compactness plus it had the options I was looking for . Other Garrett turbos I looked at ,that would also have fitted, were the GTX3076r, GTX3576r , GTX3582r . I settled on the standard 3582 for a few reasons :

*Discarded the 30 series when I realised they used the same turbine castings and CRHA as the 35 series so size is the same.
*It's more efficient than the smaller X76mm wheel in the range I want to operate it .
*With the design i'm looking at spoolup should be ultra fast , and I figured the smaller 76mm wheel would certainly go into surge without the benefit of a ported shroud. A ported shroud wont fit in a low mount design.
*The GTX3582r ,I felt, was just overkill for my whp goal .
*The cast compressor wheel is said to be more durable than billet when using pre turbo W/M injection.
*It's a lot cheaper than the GTX series

The Brettspeed manifold design :
This is where I'm hoping to make some inroads into making the Renesis turbo a viable alternative to an REW swap .
*Lowmount
*The turbine housing is a 1.01A/R twin scroll fed from the end ports.
*Wastegating will be a single 38mm wastegate through the siamese port .

I'm sure this will raise some eyebrows and create some scepticism . The system has been designed around making this work and I'm excited to see if it does .

Goals :
Reliable 400-450whp
16 psi by at least 3500rpm
Factory drivability


https://cimg0.ibsrv.net/gimg/www.rx8...15a7e564fe.jpg


Turbo on dummy engine .



https://cimg1.ibsrv.net/gimg/www.rx8...916b34c790.jpg
Edited for 4 port solenoid valve


A little more on why i went down this path ...

The 'Achilles heel' of the Renesis when turboed has always been the poor exhaust port flow. The siamese port is particularly poor and I have thought hard about how to improve on that . I even did tests on my last turbo setup where I removed most of the divider in the port. That test proved fruitless.
It occurred to me , why not take the siamese negative and turn it into a positive. The design above wasn't the first one i came up with by any means (and might not be the last) .
I see it as having huge potential it if does work , for the following reasons :

*unparalleled spoolup/response due to very small air volume in the manifold and the twin scroll turbine.
*large turbine housing to reduce backpressure and minimise the amount of air that needs to flow through the wastegate.
*Ability to get more flow out of the siamese ports than previously achieved due to the fact that backpressure at the wastegate can be close to zero if necessary, thereby allowing the siamese port to evacuate gas more easily . It should flow what it needs to flow (up to a point) to achieve the necessary pressure at the turbine.
* The wastegate should flow really well as it has perfectly timed pulses from either rotor and is 100% prioritised. Any restriction to flow should be at the siamese port itself , not the wastegate , even though the WG chosen is small by normal standards .
*no energy sapping major changes of direction for exhaust gases.
*Tubing to turbine does not have to carry gases that go through the wastegate so don't need to be large diameter .

2nd Edit : .Final design after a few iterations :
https://cimg4.ibsrv.net/gimg/www.rx8...77ea1cd838.png





Pasting this summary for those who don't want to go through 85 pages to get to the crux of what was done here ....

Siamese wastegate/twin scroll turbo (edit June 2020)
From data i have I now believe that the siamese wastegate design when used with a high flow twin scroll turbine has several advantages over a more traditional design.
1/The top end power the engine makes is better than anything I can compare it to using a similar turbo and a well setup system . I believe this power advantage is due to there being a lower pressure in front of the wastegate which allows the siamese ports to evacuate gases more effectively. Especially during the last few degrees of exhaust port closing.
2/ Low to mid range power is better than any other Renesis that has a similar top end , and also better than most with less top end potential as well. Mostly due to good spoolup.
3/Improvements in boost control were an added unexpected benefit .
Overall , I would say this design experiment is a success. Major drawback is the difficulty of replicating this result in other setups as it also requires engine port timing modifications to work well.

Bridgeport : (Updated june 2020)
As mentioned above , this modification was very disappointing . I believe I lost somewhere around 20whp across the entire rev range by doing this . A slight reduction in spoolup/response being an added downside. I have subsequently tuned other bridgeported turbo renesis engines and found their performance even worse than I experienced (due to higher exhaust backpressures). My advice is FFS ............................ DON'T BRIDGEPORT YOUR RENESIS !
One surprising side effect that has been beneficial is fuel economy . I get really good fuel economy with a 30% ethanol blend . Mileage being as good if not better than any stock NA Renesis on 100% petrol.

Turbo : (updated June 2020)
I have tried a few different combinations of turbine housing and compressor wheel in the GT3582r base turbo .
In the final analysis I saw only minor improvements going from the stock GT 35r wheel to a billet GTX3576r wheel and then to the GTX3582r.
I found the larger 1.06 AR twinscroll turbine housing to be superior to the 1.01 and the 0.83 in almost all respects
The slightly better spoolup of the 0.83/1.01 did not translate to more power at the wheels in lower rpm ranges as you would expect in a more traditional manifold design.

To date (June 2020) there have been not been any faster spool (specifically BW EFR series) top mount turbos that have exceeded the power band of this setup.

E30 :
Running this compromise blend was a biggie and I would recommend it for anyone running similar boost in a Renesis . I think it's been a great compromise between fuel consumption , fuel system requirements and octane for a street driven Renesis running over 14psi boost.

Two stage exhaust system :
After my latest modification to this I would have to say that I would definitely do it differently if I was starting over . The simplest and cheapest thing I could have done would have been to just go straight to a 31/2" exhaust ...perhaps split into 2x 3" mufflers at the rear .
That said , the setup does produce a unique sound for a Renesis that I really like . It is no longer obnoxiously loud nor is there any drone at highway cruise . Not worth the expense though , I have to say .

Great stuff.

What I'm afraid of it that exhaust is going to be too much of an restriction. At intake side, you'll have pressurized air, making it more dense, but after combustion pressure is lower, and volume is around double. Exhaust bends inside block, if I was to guess, does not look like its made to take massive amounts of flow, with its angle.

I'll definitively stay tuned to see how this goes. It's fantastic that you put so much time and effort into this!

Have thought about this a lot and initially had the same concern . However , there are a couple of things about the design that have led me to think it will flow way more than in any other design .

Oh yeah baby another Brettspeed project.

Not sure if I'm clear on your intent.

Are you sending only the end ports to the turbo and dedicating the siamese port for wastegate flow only?

Yes ... that's the idea .

hmmmm ... will have to mull that one over some. Not so sure that's a good idea under some conditions.

I've done a shit ton of mulling and the more I mull the more confident I get ... heh.

have heard your hubris before, lol ... :p:

It will probably be fine. Only worry is the slightly higher back pressure causing hot spots, but WI will take away that danger. It also lets you use a divided housing.... yeah I love the concept. Make sure to use lots of water. ;)

Well put it this way ........
I wouldn't spend money on it if I didn't think there was a good chance it will work ,and if it does , it could be significant . So I'm prepared to take the risk .

Do you mean from the restriction of the siamese ?

if it stays closed for too long i.e. no flow, I'd be concerned about the temps the seals traveling that path will be abused by

It only needs to be closed while the turbo is spooling up ;)

I can control the WG with vacuum ,to stay open under cruise conditions .

Yeah it's the restriction from closing the siamese. I wouldn't be worried about it, but I would keep a heightened awareness of it while tuning.
Have you tried it yet? It's lovely.

I'm confused.

If the siamese can't flow enough , my concern is that I'll get boost creep as the turbine needs what it needs and will speed up the turbo if it gets too much back-pressure.
My hope is that , as there is no back-pressure on the siamese side , those ports will flow more . The WG can almost provide zero back-pressure if that is needed to allow the siamese to flow enough.


Have not tried opening the WG with vacuum yet ..... the trick will be in using a small spring and whether the EBC will get enough control with that spring in place.

Hopefully it can flow enough to prevent overboosting.

otherwise kudos for the novel idea.

and ... :yelrotflm

Is this the first application of a divided housing turbo on a renesis?

I believe so .

Very very cool. The benefits....:D:

I take it this is a contributing factor to your goal of 16 psi by 3500 rpms? (And carefully selected parts inside that monster of a snail)

Absolutely ... The divided housing (albeit a large A/R )and small volume manifold should make it spool like no other Renesis .

Brettspeed needs to start production of this little beauty.

Been crawling through your 11 thread, and the subsequent fuel pump thread. Thanks for all the great info. Your trial and error helps the rookies (me!) learn.

I'm running a 4psi spring and force it closed to as high as I want with the EBC. Not a problem, just involves some creative plumbing. The siamese port should flow enough to prevent boost creep if you run a EBC with a low pressure spring. The real problems come from full pneumatic boost control systems with bad plumbing, closed loop with electronics makes most of that disappear.

Posted a picture of my WG plumbing on my build thread. Dunno if it's how you're doing it Brettus, but I like how it's worked out for me.