Half bridge turbo engine build, oppinions/advice wanted
 

I'm building a new motor for my FC and I'd like some tips/advice from you guys, especially from those with actual experience.

This is will be for a 95% street build, might hit the drag strip once a year. This is a just for fun car and i probably wont put more than 1000 miles a year on it. I would like to see 400+ at the wheels but number isn't too important. I want the half bridge port for the idle, any benefits or consequences aside.

as far as the engine itself, I'll be using a 13bre rotating assembly, a combination of s4/s5 tii irons and whatever housings i have that are in the best shape of the 5 blocks I have to tear down. Im planning on a mild streetport for the center iron and a mild bridgeport similar to those outlined by BDC. Exhaust porting will be done, probably nothing too aggressive.

I will likely use either my current td06 greddy turbo or a slightly larger garret t4 I have lying around.

planning on using an adaptonic ecu.

what is the golden standard for seal kits/apex seals these days?

what other things should I be looking into?

if it was mine, i would do the following:

i'd run whatever iron are nicest, preferably with a big S5 rear. use the S5 tension bolts.

if you have them run the FD stat gears and larger thrust bearings. if not its ok

the 8.5:1 rotors are better for this kind of build, they will make more power everywhere.

keep the exhaust porting mild, the stock ports are already pretty good, less is more here.

i would get it up and running with the TD06, but it'll want the larger hotside

as far as rebuild kits go, if you're going to tune it so it doesn't knock, you can't beat Mazda's stuff. if you are going to tune it so it knocks, then use something else

I'm hoping out of the block I tear down, one will yield a good s5 rear iron, otherwise I'll source one. I have a collection of 89+ tension bolts ready to go as well.

I believe I have Cosmo stat gears, iircc they are similar to the FD's?

On my current motor I'm running 9.4:1 with the td06 and the response is hard to argue with. I know the 8.5's are best for big boost and safety, I figured the 9.0's would be a fair compromise for my power goals. Is that incorrect thinking on my part?

Since its a street car, pump gas will be a must, so I'll likely be running water/meth to combat knock.

as far as tuning it will be going to the local rotary specialty shop synaptic 3. They're been around for a long time and do great work. Timing and fueling will both be aimed at safety.

okay so mazda seals are still the go to, good to know!

nope, as long as your power goals aren't too crazy it'll be fine

Okay, i had figured as much since many FD guys are hitting the 400 mark on stick rotors. I should have a good set of 8.5 rotors if they will actually make more power across the board as you suggested. Care to share your thoughts A bit more in depth on the matter?

I have intake and exhaust streetport templates from pineapple racing, should these be appropriate for what I'm looking for?(conservative half bridge as well)

there are a few reasons the 8.5's make more power than the 9.0. how much of each reason depends on the setup.

1. the rotary is unique in that the air/fuel mixture needs to travel inside the engine. it seems when the rotor is at TDC in the compression stroke, the bigger combustion recess has more room for flow, so it is thought to flow better.

2. the chamber is 654cc at BDC, at TDC with a 9.0 rotor the chamber is 72.66cc. TDC on the 8.5 rotor is 76.9cc. the 8.5 rotor gives you 4.28cc more room for air/fuel. all other things being equal, density, pressures, etc, more air and fuel = more power. 4.28cc is not a lot more power, but effect is there.

3. on pump fuel, it is possible that you can be closer to an optimum tune (MBT), with the lower compression rotors. with the higher compression rotors you may need to tune to avoid detonation. an extreme example i saw an FD that was dynoed back to back with 9.7 rotors and 9.0 rotors, and the 9.7's were down 50hp. they had to compromise the tune so much to run the 9.7's that they lost any potential gains, and then some.

in closing #3 is the big obvious one, but 1 and 2 matter also to varying degrees.

I can see the flow argument in point 1, but I would think that the difference would be very small, especially in a turbocharged application where flow isn't so critical.

As far as point 2, the extra chamber volume is a valid point, but that extra volume is probably little more more significant than the increased pressure gained but the higher compression rotor.

I'm right with you on point three, but that's the case of 9.7s to 9.0s, not 9.0s to 8.5s. Were I shooting for huge power numbers I realize that lower compression would quickly become very important, however at 400 hp is the same true?

Not calling you wrong in any of these cases J9, I really appreciate your input. I'm just trying to better my understanding around my build.

Finally starting to get to around to this build.
Here is how it's looking so far:
13bre rotating assembly
s4 tii front iron -modified pineapple racing bridgeport
s4 tii center iron -modifies pineapple racing streetport
s5 tii rear iron -modified pineapple racing bridgeport (still looking for this one)
s4 tii housings -pineapple racing streetport
FD flywheel
ACT HD pressure plate and sprung 6 plug clutch disk
Oem 2 piece apex seals/ springs
FD corner seal springs
OEM corner seals
OEM side seals/ springs
OEM coolant seals
turblown stud kit

Most likely going with the adaptronic modular s4 pnp for an ECU.

sticking with my Greddy TD06 turbo kit. I may or may not swap the turbo out for T04S.

The end goal is still to make this a fast reliable street car that braps.

Pay special attention to your rear iron as not all s5 irons were thick cast. They will all have the triangular support underneath the oil pedestal that makes the dowel casting more structurally sound compared to s4, but not all were thick cast around the dowel area itself.

OEM engine harness? if so, why would you risk such setup on a crusty harness?

Definitely paying attention for that brian skotch.

Knonfs Yeah, OEM NA harness, it's still pretty pliable actually. I've considered going with the wire in, but it's a fair amount of time and expense for something that's doing the same job. Were it anything like the harness I had in my FD I would have absolutely replaced it with a new one.