12a-Bug

Hey people, I have a 1985 12a with a street port, racing beat intake and a holley 650. I wanted to know, I just bought this cutom turbo, and i trust the people who sold it to me, but I want your input as well. Its a T04 B. Its an O-trim, has a .69 a/r, and he said it has a V2 compressor wheel. What can you tell me about this turbo? and is it good for my setup? Im going for 300-350 hp. he says my turbos max is 400 hp. Let me know if you need any more info or pics.

jwteknix

i would say any thing under and .84 a/r is too small

12a-Bug

That's way too big! That's just going to tear my motor apart. These 12a's don't rev as high as a 20b.

mazdaspeed7

Rotaries require much larger a/r's than piston engines. .84 is typically the smallest you will see on a rotary, with most people running larger. That sounds like a honda turbo.



It will probably work fine for your application, but you may see power falling off on the top end from the small exhaust housing, even on a 12A. Also, dont expect much more 300 whp out of it.

Liborek

Is seller familiar with rotary engines? Are you sure that for given money, you couldnīt pick something better? Iīm not bashing you, its just pity when someone buys turbo that isnīt as good for given combination when there are so many options



V1/V2 compressor can push as much as 52 lbs/min around 2.5 PR - roughly 22 psi. Which on good engine can be as much as 440-450 HP@cranck. At 2 PR - roughly 15 psi, can push 47 lbs/min so around 400 HP. So potential is really good.



Turbine is different story.

O-Trim has same major diameter as P-Trim. But exducer is much smaller.



Turbine Major:

P-Trim 74,2 mm

O-Trim 74,2 mm

Turbine Exducer:

P-Trim 64,6 mm

O-Trim 58,3 mm



Compressor matches turbine quite well, but turbine housing is simply to small for given wheel. It will probably work. But with quite high backpressure. Usually, for rotary application, this compressor is mated to P-Trim turbine with turbine housing around 0.8x A/R.

12a-Bug

He originally told me he was going to give me a p trim. But when I called to get the info written he said o trim. Maybe he got confused? And yes they do have PLENTY experience with rotaries look up the black mamba. These people are called Mike-Turbo. Maybe you've heard of them

mazdaspeed7

Heres a thought: why is he the only person pushing those turbos for rotaries? Did he stumble upon something that goes against what every reputable tuner in the country is doing? If so, he should have no problem qualifying it.



I have heard of people running overly small turbines and very large wastegates on a rotary as a way to get good boost response out of large turbos. But the backpressure on that setup will still be higher for any hp level than a properly sized turbine, and that backpressure will make the engine much more sensitive to the porting and tuning. Basically, it works well in a narrow envelope where everything is right, but outside of that it will perform below what a typical setup would.

Liborek

As I already said, it will work for your intended power level.

Donīt get fooled by name and some race cars, as in any other company, their main interest is profit. But I donīt want to assume. It depends on your goals. Transient response, part throttle torque etc. will benefit from smaller hot-side.



There is interesting thread on evil forum about autoX FD. 13B-REW stock port, Precision 55mm billet compressor, GT35 turbine in 0.63 A/R housing, and 360 whp on DynoDynamics(back to back tested against dynojet, reads 15% lower) at 19 psi boost.

NOTE: turbo dimensions are roughly comparable to yours.



This car has mountain of torque, 350 lb.ft by 3800 RPMs, boost threshold under 2000 RPMs and over 350 whp between 5300-7000 RPMs. Of course, thanks to tight turbine, power takes dive after that point despite boost holds at 19 psi to 8000 RPMs, where power is only 200 whp.



So You see, its application dependent.

12a-Bug

True. I understand what you all say. I'm just making sure. What I'm building is going to be a weekend cruiser and occasional track days. And of course, put these ricers to shame. Lol. Even if I am pushing 300-350 that's just about the same power to weight ratio of a gt500kr, Abd if I push to 350, it's comparable to a zr1. That's ****** scary. Either way, I'ma be a happy camper when it's done lol

Liborek

Just make sure to have very free flowing exhaust - literaly with zero backpressure. It will lower pre-turbine pressure with turbine expansion ratio magnitude. Very overlooked but determining factor how efficient whole setup is.