.64 or .82 turbine housing?

[Jarods7920]

I am going to be uprading the turbo on the car soon and was wondering what your opinions on the turbine housing should be? I am not looking for an all out monster so i am think the .82 will be a bit too large. The turbo that i am using will be a journal bearing turbo as well. It is similar to the 3076 and the s256, but better and newer techonolgy. I just dont want to let the cat out of the bag as to what i am using just yet. Thanks a lot

Jarod

[subparpunk03]

Whats the car going to be used for? Dyno queen or Drag strip I'd go with the larger A/R. From what you're saying I think a .64 A/R would do nicely. I'm basing that on the 10 minutes I spent reading the explanation of what an A/R is on turbobygarrett.com so take it FWIW... I am by no means an expert on this and really just getting started learning how the turbo construction affects its performance.

I picked up Randys old 3071 and i'll be leaving the turbine housing a/r the same and maybe bumping up the compressor housing A/R to eek out just a liiiitle bit more from it.

[Jarods7920]

Originally Posted by subparpunk03 Whats the car going to be used for? Dyno queen or Drag strip I'd go with the larger A/R. From what you're saying I think a .64 A/R would do nicely. I'm basing that on the 10 minutes I spent reading the explanation of what an A/R is on turbobygarrett.com so take it FWIW... I am by no means an expert on this and really just getting started learning how the turbo construction affects its performance. I picked up Randys old 3071 and i'll be leaving the turbine housing a/r the same and maybe bumping up the compressor housing A/R to eek out just a liiiitle bit more from it.

dop you have one of the atp turbos? What is the ar on the turbine housing. The car is just a more fun DD. All around fun is what i am looking for.

[subparpunk03]

I have the ATP 3071. The A/R on the compressor side is .50, and not 100% sure what it is on the turbine side, I'll have to check when I get home. The turbine side is harder to upgrade b/c I want it to stay bolt on style...

[ATE BALLER]

Better/newer technology than the BW S series turbos? I'm pretty sure the extended tip is the latest/best thing to hit the turbo industry in a loooooooong time, so please let me know what you're talking about.

[medieval]

One of the problems the Mazdaspeed has is reversion. Many are going down the route of running a larger compressor side turbo (ATP turbos) while still using the stock turbine configuration. To make it simple, the stock turbine A/R in relation to the compressor is causing some issues that many are not looking at. In layman's terms, you can only flow as much as the turbine will allow regardless of how big you get on the compressor. Since our motor is a 4 stroke, valve overlap is present. With that being said, so will reversion. This is why many are falling below the 400whp mark.

Manifold design:
A turbo uses the energy present in the exhaust pulse to produce boost, so the faster and more efficiently the manifold can deliver exhaust pulses from each cylinder to the turbo, the quicker the turbo will spool up and produce boost.
The idea behind keeping each exhaust pulse separate to the collector is to maximize efficiency to control and minimize the turbulence created when the exhaust pulses merge.

Uncontrolled turbulence equals lost energy. Lost energy is when the exhaust gas pulses lose their direction and cannot deliver full and controlled punch to the turbine.
A turbo manifold design that creates turbulence inside the manifold causes reversion, energy loss and increased exhaust gas temperatures. (The added heat will burn exhaust valves)
Reversion is a normal condition in a 4 stroke engine. It is most predominant in higher horsepower engines. When the piston reaches top dead center (TDC) on the exhaust stoke, there is valve overlap.
The exhaust valve remains open for a short period of time as the piston is going down on what is called the intake stroke. This causes a negative pressure pulse (vacuum) in the turbo manifold that is drawn back into the combustion cylinder (reversion).

The effects of reversion:

The engine becomes prone to detonation.
The engine power decreases due to charge contamination.
Charge contamination occurs when hot, thin exhaust is pumped back into the combustion chamber when the manifold cannot exhaust it efficiently. -properly.

Testing shows a log style manifold has roughly a 3-1 pressure ratio (3 psi of exhaust pressure Vs 1 psi of boost pressure)
Simply put, your exhaust pressure is much greater than your charge pressure (boost). During the overlap period, exhaust is forced back into the combustion chamber.

A 4-1 pyramid collector manifold is superior to a log manifold style, non-collector style, and cast manifolds for the simple fact that turbulence is limited to one point instead of two, maximizing the energy potential. This can result in faster turbo spool up, and potentially more energy to create boost.
Besides minimizing the lost energy, reducing turbulence also has another desirable effect: the creation of a freer flowing exhaust path for the engine.
We all know the freer the flow the more HP you will make. A properly designed collector style manifold will help evacuation of exhaust gasses from the combustion chamber and minimizing energy loss that is normally lost in this process.
This also means more of the exhaust gas is expelled on each exhaust stroke of the crankshaft, which is known as cylinder scavenging.
You must maintain exhaust pulse velocity from the cylinder head to the collector in a manifold. This is done by designing a properly sized collector in relation to the primary runner diameter.

The design of the collector itself can dictate what happens to the exhaust pulses after they reach the collector. The shape and length of a collector, in relation to the secondary runner, can promote a venturi effect, which positively affects the velocity of the exhaust pulses heading towards it in the primary runners.
Individual exhaust pulses reach the collector at different times due to the way that a four-stroke engine works. For one rotation of the crankshaft, while one pulse is entering the collector, other ones are at different points along the primary runner lengths of a manifold. When a pulse enters the collector, it expands due to the greater volume found there in the collector (now a low pressure).

The localized expansion of this exhaust pulse creates a suction effect on the other primary runners that converge at the collector, thus further helping the exhaust pulses in those runners to maintain as much velocity as possible.
However, just like how the exhaust pulses under pressure in the primaries seek out the relatively low-pressure collector, the pulse that is expanding in the collector will try to enter the other primary runners at the collector.
As the expanding gas from the primary enters the collector the other primary exiting would then present a restriction to the pulses moving down the primaries, instead of helping them. (Reversion)
Thus, a necessary component in the collector is an anti reversion wall (4-1 Pyramid).This is the wall (the pyramid) present in the collector design that presents a barrier to the expanding gas in the collector, discouraging it from entering the other primaries.
Keeping the expansion in the collector and not in the other primaries that are trying to deliver their exhaust pulses helps low back pressure and restrictions. Thus, a collector must be much more than just a meeting place of the individual exhaust pulses. Without a 4-1-pyramid collector or equal to, the collector can actually slow down the exhaust pulses in the primaries. Slow it down and you make it hard for the engine to breath freely.

If we keep it basic and look at just restriction ideas you will see why a tubular manifold with a 4-1 pyramid collector will create less resistance and make more power day in and day out (if designed right). Less restriction means more power.

[subparpunk03]

Thats all well and good about the manifold design, but I'm confused at what point you are trying to make about the A/R size?

[SSinstaller]

The .64 ar turbine housing will spool slightly faster, but flow less than .82 ar turbine.. Do you want top end HP, or a broader torque curve??

[Jarods7920]

Originally Posted by ATE BALLER Better/newer technology than the BW S series turbos? I'm pretty sure the extended tip is the latest/best thing to hit the turbo industry in a loooooooong time, so please let me know what you're talking about.

Well the turbos have only been out since february. I have yet to see definative proof of what this "extended tip" technology does. It claims that it spools up faster. maximizes flow...etc, yet when it was compared to a GT3076 it seemed they were right on par with each other, but the 3076 spooled a few hundred RPMs sooner. If you have more information than a regugitated answer from another forum i would love to hear it. Here is the comparison i found FWI.

s256vs3076R
Turbo shootout results: BW S256 vs GT3076R - Honda-Tech

[Jarods7920]

Originally Posted by SSinstaller The .64 ar turbine housing will spool slightly faster, but flow less than .82 ar turbine.. Do you want top end HP, or a broader torque curve??

I am looking for the most area under the curve...i am not really concerned with huge power numbers. I want what is going to be the most fun to drive and have the most usable power curve.

[SSinstaller]

Originally Posted by Jarods7920 I am looking for the most area under the curve...i am not really concerned with huge power numbers. I want what is going to be the most fun to drive and have the most usable power curve.

Go with the .64 AR turbine housing then, you can always buy a new turbine housing if your goals change.

[Jarods7920]

Originally Posted by SSinstaller Go with the .64 AR turbine housing then, you can always buy a new turbine housing if your goals change.

Ha ha ya the only problem the housing i am running is pricey! Its 239 plus shipping!

[ztuner]

If this helps the larger a/f will promote lower egts an reuce the propensity for reversion at the expense spoolup. I' do the bigger housing just for that reason.

Harry