The Works O2 housing is divorced in one way: It will divorce you from $400 dollars...

 

LOL!

I still dont know how my EBAY O2 made such a drastic boost change. Prior to the housing I could barely hold 17PSI at redline. I ran my boost table with 100% in nearly all cells.

After I installed the EBAY tubular O2 housing (which isn't much bigger than stock) my boost skyrocketed. I'm currently running my boost table at 75% and that holds 22PSI in most gears. It even causes creep in higher gears.

Buschur claims if you have an efficient motor you may out flow the turbo thus not being able to hold boost at higher RPM. Does this mean by installing my ebay O2 housing I may have backed up the exhaust flow causing more pressure in the system?

 

Well I am not sure if I missed it I went into skim mode at the argument in the middle.

But for all the people relating this to the subaru downpipes. One of the main points of the divorsed wastegate design is the huge amount of air passing through one side causes a vaccum on the other side essentially sucking the exhaust through the other side. I am not sure if this is how it works but it is how companies claim it works.

The divorsed wastegate design has not shown power gains on subarus I will doubt it will have much affect here.

Ben

 

Thankyou for clarifying my point and also adding some valuable anaysis to this discussion.

From my WRX experience, I found the splitter (divorced) dump pipe design made a measurable improvement to the performance of the turbo. Most noticeable making it spool better. (produce more boost lower in the rev range.) I haven't had the opportunity for testing this on the EVO. Sounds like it is going to be done for me. :-)

Trinydex, I think my description ("...In fact the opposite is true. As the gases head down the exhaust they cool, become more dense (ie. contract) and lose velocity....") describes the process reasonably well. Maybe you just dont get it??? FSUevodudes first paragraph does a better job of explaining it.

 

I wish I had taken the camera out yesterday. We had an EVO here on our lift and I'm not sure what exhaust system it had on it. My guess it was a full Titanium catback as it discolored a really nice blue that I have only seen Titanium do.

Here is what was cool. Just by looking at the tubing on the catback you could see how critical it is to watch the degree of the bends you use and how many are in a system. This is our one big concern when building any exhaust. The straightest most direct route to get the exhaust gases out. On this system yesterday you could see where the extreme heat was built up plain as day. In each bend the outside of the bend was so blue'd from the heat pounding on it internally. On the inside of the bends there was no discoloration at all. The more severe the bend the more blue'ing the tubing had. It was like a visual flow bench.

This particular system (not sure who's it was) had more severe bends and more of them than our system does. I know this topic is about 02 housings but it all applies, it is the exhaust system.

 

you're talkin' about two different things.

an efficient motor will outflow a turbo (COLD SIDE) as in the turbo cannot support the air flow of hte motor by pushing enough air INTO the motor.

what you experienced was your turbo (HOT SIDE) not being able to flow enough, likely because there was too much pressure directly after the turbo. this was remedied once you threw the housing on cuz it alleviated the pressure and allowed the turbine to flow more air which got you more compressed air which got you more boost.

 

you just didn't get how loose language translates into misinformation.

FSUevodude already gave the correct info. if we're talkin' about the velocity of the gas in an exhaust system then the gas is continually losing heat so cross section is the only thing that can INCREASE velocity, with many other factors decreasing it. this is why we see good spool with a stock like manifold because the stock mani inports are smaller than the port of the head. this is consequently where the gases are also hottest.

 

Agreed. And because the cast manifold once heated up, retains heat better.

 

really?

 

OK, this is getting OT but still relates to exhaust discussion. I have found the greater thermal mass of the cast manifold suffers much slighter fluctuations in temperature than tubular. This has been eveident on dyno pulls where the tubular manifold cools considerably when the car is rested between pulls and it seems to take a couple of pulls to get back to the same number. I put this down to some time being required for heat to be pumped back onto the manifold. Cast manifolds dont seem to exhibit this charateristic on the dyno. This is only my own theory and not fact. Please dont read it as such.

Sorry if my previous statement was a poor choice of words.

 

yeah i'm not tryinna bust yer nuts, there's just caveats when you're talkin' about fluids.

i actually asked because there's several groups of thought on this.

everyone know that intercoolers with more sink mass transfer more heat. and in upper echelons of racing they tend to make thin tube headers because the thin tubing keeps the heat sink effect from taking away too much heat to the surroundings.

now i think your cast manifold analysis is correct. i think in this case it has more to do with the material, what the cast manifold is made of does not transfer heat as readily as what the ss headers are made of! so with cast mani you win and you get hte strength.

 

I understand what you are saying but how do we know that the O2 housing didn't restrict flow thus killing efficiency. Its alot like throwing cams into the mix. Prior to cams I could easily hold 20PSI to redline. Then I did cams and I could barely hold 17PSI because the motor was flowing alot more air.

You are saying it couldn't hold 17PSI because there was alot of pressure from the exhaust side? I'm saying its now alot higher than before because there is a restriction and its now easier to hold that PSI.

I wish I had a way to take MAF reading to tell which one provides the highest flow.

 

you will not make boost if there is a restriction... you only make boost when there is freeflow across the turbine. this is the same reason why boost creep happened in 2g dsms after you relaced the o2 housings.

the turbine becomes more efficient and what was suitable boost control pressure before is no longer suitable because at that same pressure so much more air is now flowing.

it only gets worse when the engine breathes better, tehn the turbine becomes a bottle neck and you create a huge pressure after the turbine and it becomes harder to maintain an efficient operation and hence it becomes easier to experience knock. this is like the 9.8 to 10.5 increase in power through tuning.

your cams reasoning is flawed czu you're mixing up intake and exhaust again. when you throw cams in you have a hard time battling boost taper (holding 20) because the motor can outflow the compressor wheel. the cold side can't move the air anymore.

this is different from the hot side not being able to move the air. when the hot side can't move the air you experience lower knock threshold and less efficient turbine operation which eventually translates into inefficient compressor operation.

there's two ends to this.

here's a better example... say i had a stupid turbo, it's a 16g35, has a 16g cold side and a 35r hot side. this turbo can move all the air post combustion, no prob. but you will get mad boost taper because the cold side can't shove enough air in.

conversely if you have a 30r 10.5, a 30r compressor side with a 10.5 hot side then your compressor can flow all kinds of air, you won't get taper but you will not be making power because your turbine side is corking up all the power. if you swapped that 10.5 out for a full 3076 then your boost would skyrocket cuz your turbine is actually flowing and moving the compressor wheel more.

so what we're seeing with the o2 housings is the second example... you're alleviating some pressure post turbine, so it makes the compressor work better too and it also gets you some power simply becuase you're reducing pumping loss. but the precept to all this is that you're lowering the post turbine pressure, creating a larger pressure differential across the turbine.

 

It wouldd be nice if WORKS responded to this thread about their product. I would like to know why they designed it without the divorce and what tests they ran on it.

 

False. The turbine does not "move" air, it simply transfers the kinetic and thermal energy in to work that is used to spin the turbine and compressor wheels. You are looking at it the wrong way. The compressor is the "boss" of the system, whatever shaft speed that the compressor needs to produce a certain flow rate and pressure ratio it gets (as long as it is physically capable of providing that amount of air) by the wastegate controlling the airflow though the turbine. With a small compressor, it will have to spin faster than a larger compressor (i'm sure they're exceptions, but generally) and therefore the turbine will also have to spin at that same speed. At that speed the turbine efficiency is very low and causes a larger pressure differential between before and after the turbine. The turbine does not cause an increased pressure after the turbine like mentioned earlier in your post, but like my above post said, it works with a pressure differential, pressure after the turbine will be multiplied (by the turbine's pressure differential at that shaft speed and certain flow rate) into pressure before the turbine.
This causes the engine to have more back pressure which causes increased reversion and pumping losses, these are not desireable for many reason, but mainly more detonation and less power. The compressor just causes the turbine to decrease the performance because it is very inefficient at that speed that the compressor needs.

An O2 housing has absolutely no effect on the thermal efficiency of the compressor. It decreases the pressure after the turbine which in turn decreases the back pressure to the engine. This drop and pressure causes the engine to "breathe" better and for the compressor to be able to operate at the same speed, but to produce more boost because of less back pressure within the system. (note that the compressor is pumping air at the same pressure and mass flow rate as before)