What he said :)

Yeah I recommend reading the thread first :yesnod:

I'd take as a compliment. Are you in a town of like 300 sheep fuckers?

I have a secondary radiator , rx7 depth unbreakable apex seals , and water meth .

Plus dowelling soild corner seals and a few other things.

Hahahahaha, you're thinking of my neighborhood - it's much colder down here in the South Island :smoker:

Brett's town does have a reputation...for teenage parents, so I think they were still calling him the oldest teenager Dad :yelrotflm

Did some testing with an open wastegate tonight and found my muffler is a serious restriction . Lost 5-6psi in turbine backpressure at 10psi boost and gained significant power . If i can improve my exhaust system to this level I'm thinking 400whp will come at a lower boost pressure than I thought possible.
The sound of the vta wg was ............................ absolutely nuts !


https://cimg0.ibsrv.net/gimg/www.rx8...c7d7693bb1.jpg


VTA WG at 9psi boost

I originally had mine vta and she was a screamer lol. I loved it wide open, was good for scaring kids and grannies at crosswalks downtown, but part throttle got to be obnoxious....

Yeah , mine is not a pleasant sound at all , coming straight off the siamese is maybe a little different. Kinda sounds like a hammer being bashed around inside a can. Perhaps with some pipe length and a little resonator ............

Ouch! Yeah that probably hurts the ears! Mine was a little farther away, right off the rear end of the manifold. PTP had designed it to dump back in just pre-cat but I hacked it off and had the entry welded closed. Sounded like a screaming banshee going through the tunnels downtown. I once got the "shoosh" sign and stink eye from a little old lady I drive past when she wound up next to me at the light :lol: I like it much better recirc'ed but sometimes I miss being able to let loose an ear piercing shriek:)

...and by contrast, while running at the same 9psi of boost pressure, this setup produces 100whp more than my Greddy turbo setup ( :puke: ). Comparing the two, the only significant difference on the cold-side is the compressor wheels, where Brettus' is approximately 15% more efficient at my max flow rate. So the majority of the gains are from the well-sorted hot-side.

Seeing Brett's figures has motivated me to do a direct comparison of the same turbo running T25 vs. T3 turbine housings.

I wouldn't be taking too much notice of the 380 .... but it's certainly looking pretty darn good .
The porting and siamese sleeve mods have to be helping get these numbers also.

Jimmy where your pulling boost pressure from makes a differance too. I think Brett pulling it from his uim. Are you pulling from there or the turbo?

^^^ I'm also taking boost from the UIM.

Driving home today I did a test in 5th gear ........... 10psi at 3000 rpm :yesnod:

Doing a comparison between the backpressure in the front scroll (which has flow from front port plus siamese ports) and rear scroll (rear port only) of my 1.01 AR divided turbine housing. Both of theses tests done at 12.5psi which is reached somewhere before 4000rpm.


....................Front scroll ......................rear scroll...................... mass airflow g/s
3000..................5........................... ..........4..............................101
4000.................11........................... .........9..............................184
5000.................14........................... ........13..............................248
6000.................18........................... ........17..............................296
7000.................24........................... ........22..............................362
8000.................30........................... ........27..............................390

Expecting backpressure to drop to just over 20 peak once i get a better muffler setup installed. Good to seee the variance in the zone where detonation is most likely (4500-6500 ) is minimal.

It's taken a bit of time to digest this info, along with the odd Xmas mince pie, and I believe these results show that your original manifold design with the center port plumbed only to the waste gate should show performance results (whp) very similar to those from your current design, which has center and front port sharing one of the divided scrolls into the T3 turbine housing.

With the waste gate venting a very small portion of center port exhaust gas at low rpm vs. a large portion at high rpm, I'd expect the variation in front to rear scroll pressures to be greater at low rpm if the center port exhaust gas was contributing much to the exhaust back pressure. Since there's not a huge pressure difference between front and rear scrolls, it shows that the center port isn't contributing much to exhaust pressure at any rpm, so moving from your current manifold design to your original one shouldn't impact performance much at all.

This is good news for those wishing to adopt a low mount divided T3 setup as plumbing is a fair bit easier (relatively speaking) without needing to plumb the center runner back into another manifold runner/collector.

I would agree with you if i hadn't already tested the two designs side by side and found the extra tube actually increased midrange torque.

I expected the same results you did ..... have been trying to think why it didn't quite work out that way (The bigger differential at 4000 was there but i expected more ). All i can come up with is the old nugget ..... air will take the path of least resistance. I think there is a balancing that takes place as pressure increases on the siamese side.

I'd forgotten about your VD comparison between designs. Here they are:
It looks like we're talking an improvement of just under 10% torque in the 4-6.5krpm range if the center port is plumbed into the front runner. OK, so 10% performance difference is actually quite a lot, and we can't see this much accuracy from the exhaust pressure readings as they only read to the closest 1psi, (12% accuracy at 5krpm).

Brett, based on this, are you thinking that the best divided T3 manifold is per your current design? For my divided manifold design, if I were to plumb in the center port I was considering splitting the center runner after the WG so that it feeds half into each scroll. This would provide even exhaust pressure on both scrolls, so in theory would provide the most efficient flow path for exhaust out of each combustion chamber. Your thoughts?
All runners must be equal length of course, which makes fabrication an absolute bitch!

390g/s.... Is that all? :p: kidding... :) looking good!!!

nice!! i just broke the 344 g/s mark at at 6000 rpm

390 at 12.5psi ............. not a bad starting point :)

I think a better design would feed both sides and have equal priority between wastegate and turbine . How you could get that in beats me though .

looking fantastic!!!

Just playing around with matchbot and allowing for a free flowing exhaust gave me these numbers as a comparison . My thoughts are that 4000 and below is pointing to the benefit of the twin scroll whereas 5000+ is highlighting my restrictive exhaust . Hoping with that rectified the backpressure will line up with matchbot and the variance between scrolls at peak will be close to nil .


.................Front scroll ..........rear scroll....RS no muffler..Matchbot............ airflow g/s....matchbot g/s
3000..................5........................4.. ............3..................4.1................ .....101............97
4000.................11.......................9... ............7.................8.8................. ....184............170
5000.................14......................13... ...........9.................11.2................. ....248............229
6000.................18......................17... ..........12.5..............13.3.................. ...296............302
7000.................24......................22... ..........17................16.7.................. ...362............354
8000.................30......................27... ..............................19.1................ .....390............385

Matchbot FWHP is at 450 which is lining up nicely with my test with a VTA wastegate.
Also worth noting is that I've had to drop BSFC to get the numbers to line up .......... I think this could be significant .

I'm dumb, can you expand on this?