j200pruf

iTrader: (4)

I have been trying to find out the size of the stock turbine housing (for a S5), the answer I got was a 1.00 t3. If this is the case wouldn't hybrid turbos be comparable to a gt35(minus the gt40 compressor)?

RacerXtreme7

iTrader: (2)

NO, the GT35 has a bigger turbine WHEEL which effects flow as does A/R. The inlet on s4/s5 area wise if measured perpendicular to flow rather then the skewed mating flange, you'll find its smaller then even a T3 inlet flange.

~Mike................

BLUE TII

iTrader: (9)

GT35R to stock TII hybrid is a closer comparison than one might think judging by price and forum hype.

Amazingly enough, if you put a TII hybrid turbo w/a 60-1 HiFi compressor on a long runner divided manifold w/ large external wastegate you will have the same 400RWHP @ 15-17psi and the same or better boost response than the GT35R

If you search the AUS forum you will find a member who did this w/ S4 hybrid and made the 400RWHP and his dyno plots have insane low end.

The key is a huge wastegate w/ good flow to its runners so top end flow is not limited by the turbine housing.

The Impact exhaust wheel on the HT18 (designed by Mazda and Hitachi for the rotary) is better suited to the sharp rotary exhaust pulse than the GTQ that was computer modeled for the smooth flow of an equal length collected 4 cylinder and up engine.

If you need more flow prior to wastegate opening (to prevent "choke" on a high overlap ported motor) a larger T4 turbine wheel in the TII Hybrid is becoming more popular, but can lead to overspeeding the rotating assembly as the high exhaust velocity in the small turbine housing hits the larger exhaust wheel w/ more levarage. Wastegate design or exhaust restriction becomes key in boost control.

Even a well set-up hybrid on stock manifold can better a GT35R or 500R in power and boost response, it is just that those who go the stock hybrid route don't usually do a good set-up.

j200pruf

iTrader: (4)

Awsome, so Ian when you had the problems with boost creep (when you had the 3.5" exhaust) do you think that if you had that 60mm wastegate on tube mani it would have dealt with the creep unlike it did when added to the turbo housing?

I know I should search but does anyone have some specs on the exact size of the S5 turbine housing/turbine wheel?

Thanks
-Justin

BLUE TII

iTrader: (9)

[I]when you had the problems with boost creep (when you had the 3.5" exhaust) do you think that if you had that 60mm wastegate on tube mani it would have dealt with the creep unlike it did when added to the turbo housing?{/I]

Exactly, a direct path to the wastegate would have eliminated boost creep.


I ported my manifold and turbo housing out up to the wastegate runners to promote WG flow and now run the 3.5" exhaust again w/ zero boost creep.

Full boost comes on same 3,400rpm 5th, but I did lose some boost response in low RPMs from reducing the factory velocity stack in the manifold leading to the turbo. Now in 5th I get 1-2psi by 2,000rpm, 4psi ~2,500rpm, 8 psi ~3,00rpm and full 15psi 3,460rpm.

Power comes on very suddenly at 5,000rpm and I have to more than double the amount of fuel added every 500rpm. I guess that is when the overlap starts working- I haven't yet checked exhaust backpressure yet to see if I am actually hitting crossover (intake manifold pressure higher than exhaust manifold pressure).

I am thinking if I step away from the stock turbo/manifold I want to do a NA style header w/ a giant WG on the collector and 2 up pipes close to the exhaust port to velocity stacks and into a small divided turbo housing with a big exhaust wheel.

High exhaust velocity hitting a high leverage wheel, but with enough open area not to create too much backpressure and choke = fast spool. Once the wastegate starts flowing it can stop overspeeding of the rotating assembly because flow favors WG and you get the benifits of scavenging from good header design.

Basically, I thinking how to lower the rpms of the dramatic surge of power I get at 5,000rpm or how to get crossover on a small turbo for the best compromise of spool and top end power.

j200pruf

iTrader: (4)

What size do you mean when you say small .82 T3 T4?

BLUE TII

iTrader: (9)

Yes, in that long runner "header style" WG scenario I would like to try a 1:00 AR T3 divided w/ T04 "P" trim exhaust wheel- new T04B dual BB w/ 60-1 comp.

I might just have another try at the S5 hybrid though. Grind open turbine housing to weld up stock WG ports and weld in a couple of wastegate runners right at the turbine housing to manifold flange- so it is a straight shot out of the mani to the WG.

That way I could leave the stock velocity stacks in the mani for that 8psi boost by 2,500rpm and not get the boost creep.

Could always fit a To4B BB section in the stock turbo housing when the hybrid dies.

bobybeach

The hitachi turbine is similer size to a stg3 t3 wheel. The hitachi turbine if clipped or back cut will flow similer to a small t4 but you will loss a lot of responce.

The stock housing however is ideal with turbine upgrade. I have personaly run...

S5 hitachi high flowed with small to4b compressor with stock turbine wheel and stock manifold.

Later i upgraded with a S4 medium to4b compressor along with p trim turbine on custom header. using stock ported wastegate on the s4 housing i was abble to hold .4bar with 2.5" exhaust.

I have also run the s4 housing with large T-58 compressor @ 1.1bar boost. Again using stock ported internal hitachi wastegate with larger p trim turbine fitted i was still able to hold .4bar boost.

I dont think you can compare the hitachi turbine to a gt35. but the stock housing and core can be carried to very high levels of power with turbine and compressor upgrade that could better compare to a gt35 or full t4.

I am know running full t4 with external, but only because i feel my target power levels (400-500whp+) are beyond the stock housing now.

I must admit i was suprised just how far i could push that litle .84 internal wastegated hitachi housing matched with compressor combos like the t-58.