So, you're saying that as the gases cool down and contract they need more space?

 

Hotter gas is moving faster ..... less pipe

Cooler gas is moving slower ..... more pipe nice to have.

Still not maxing out the stock O2 though.

 

I still don't follow your logic here ...

Hot gas expands and takes up more space. That makes me think it would benefit from a larger pipe diameter. The gas would contract when it cools taking up less space ...

I'm not sure the exhaust velocity would change if the gas temp changed since it's being pushed out of the engine by the pistons and they don't care about exhaust temp. The temp at the tailpipe shouldn't affect the velocity at the head.

I'd really have to see some actual tests and numbers to follow your logic.

I will agree that a 16G or 20G isn't "maxing out" the stock O2 housing. However, restriction exists before you reach the absolute limit of flow in an exhaust system. If there is any restriction at all then there is power to be made ... and there is ALWAYS restriction.

 

Yes that confused me as well. Hopefully its just a phrasing issue that he will clear up .

 

I don't care about hot gases and exhaust pipes. I would like to see one single dyno where the tubular O2 made more HP at the same boost level. Just one.

 

Jeff, maybe you haven't seen you've wanted to because it's rare for someone to just change their o2 housing (turbo outlet pipe). I got one and was planning to install it the same time as my turbo as it seems the outlet pipe is a lot of work.

I think changing out the outlet pipe is the same as going from stock cat to high-flow or straight pipe. Have you seen someone that went from stock cat to straight pipe run exact same boost before and after?

Chamama, I think the Tomei exhaust manifold was supposed to increase spool time, or maybe that was just for silvias. Did you change your boost control around spool up or leave it the same as before the manifold?

 

I did not change any boost settings. Maybe because I installed the manifold and O2 together, I didnt see much loss in spool due to manifold only. Here is a graph of FP WHITE installed log.

 

Oh sorry. I meant spool time should go down. You should get full boost onset sooner.

If you didn't change any boost settings maybe you should try. Could start spooling sooner than you are.

 

the Tomei manifold should give stock-like spool ...

 

Here I fond a pic of the outlet pipe. The wastegate mouth is huge huh?



Wastegate path on the left, exhaust path on the right.

 

The puck is only about 40% of that size though ...

 

It's the size of the wastegate hole that converges back into the exhaust that matters.

 

Why would the spool up change? During spool you aren't even close to out flowing stock parts. Spool will not change with the O2.

If the stock O2 is a restriction and the tubular adds HP on average we should be seeing people with stock O2 running 1-2mph slower in the 1/4 mile. That isn't the case.

The only good thing it has to offer is reduced weight.

 

Jeff, I never said the turbo outlet would change spool-up.

I read this Japanese guy's website where he reviewed the Tomei outlet pipe. He said the boost became more stable after installing it. I'll show you the page if you want (it's all Japanese though).

Now that I think of it, I get unstable boost curves. Even though my WGDC curve is gradually ascending my boost/load will fluctuate up and down. That's one more test I can do after I install my turbo outlet.

 

If it reduces back pressure then it could, much like upgrading the exhaust or moving from a Cat to a TP.

I'm neither agreeing or disagreeing with an 02 changing spool though.