BULLSH*T!!!!!!! They create better/more smooth exhaust flow which gets to the turbo quicker = less lag. Especially if you get rid of a cat. Mine spools way quicker w/o the cat in the up pipe.


Nick

 

No lag on mine as well. You do tend to loose a little power lower in the rpm band, but more than make up for it in the mid to high range. That has been my experience.

 

They don't cause lag persay..

You lose power ehrn off boost, but this is easy to understand..
When off boost, our EJ20 is like a normally aspirated engine, and we all know that NA engines NEED backpressure for torque...
Well, aftermarket headers reduce backpressure, and hence, we lose torque downstairs..

On the other hand, when on boost, our EJ20 acts like just about any other turbo engine.... They hate backpressure...
The aftermarket headers reduce this back pressure, which in turn creates more power while on boost.

Most people interpret the loss of low end grunt as lag, but it isn't... since you have reduced the backpressure in the system, you now have less low end torque... As a result of the loss of backpressure though, you are able to make more power upstairs...

 

Have to remind people again... HEADER not headers

 

Also the header that are sold are stainless steel not cast so heat is not held in the header to the flow to the turbo like the stock one did. Heat is energy and to keep that energy you have to contain it some how. Header wrap!! When i come across this thread on Nabisco were some guy is testing different header. It talks about why you should wrap them in more detail than my knowledge.

 

Mario is correct. Header wrap on SS tubular header is a must. Especially on Subaru's where the header cools down very fast due to its location.

Explanaion is simple.

Hotter exhaust gas has higher velocity than colder exhaust gas.
Higher velocity = faster spool up.

 

If you want to be polictically correct, it is actually called Exhaust Manifold. ha ha ha

 

Here are two technical papers on exhaust system design as it applies to turbocharged engines. One paper is hosted on Cobb Tuning's site, the other paper is on Vishnu Performance's site.

Both say to keep exhaust gas velocity high before the turbo, which means using a slightly smaller diameter tubing than is ideal for maximum flow, while reducing backpressure after the turbo to as little as is practical, given the constraints of the car chassis.

When using heat wrap on exhaust components it couldn't hurt to ask the manufacturers recommendation. There have been cases reported more than 15 years ago in Hot Rod Magazine where the wrapped header tubes retained so much heat that the welds cracked on normally-aspirated high-output V8s. I don't recall the details and it would make a difference whether it occurred on a street engine or a NASCAR motor being run at 8000 RPM for extended periods of time. In any case, heat wrap and ceramic coatings can be very effective at maintaining velocity.

--
0==WW==0
"…axles of evil…" - george w. bush

 

I did not use wrap but I did get Jet Hot 2000 applied. A 2450 degree finish inside and out. I didn't want it wrapped due to the location {down by the pavement }. It will pick up a ton of road gunk and trap moisture and has the potential to rust out the manifiold.

http://www.jet-hot.com/index.html

 

This is a bit of a contradiction to be honest.... If the wrap is trapping the heat in the metal, why is there still a concern of moisture being held against the pipes?? Any moisture near the pipes would evaporate...

Also, if the header is made of stainless steel, there shouldn't be a worry of rust, since stainless steel doen't rust..

 

You shouldn't worry about losing low end after adding an aftermarket exhaust manifold on STi. The car itself has a lot of torque already. Manifold will actually help the car spool up faster and gain considerably amount of top end.

 

Ditto on what jigga said.


But a small thing your not thinking about Hummer is that splash gaurd under your engine if you really think that water and dirt will ruin the header.


Do you think that a Jet coating and header wrap combo would maybe be a little more effient?? Or maybe just a little overkill??

 

Thank goodness. I recently picked up a Maxim Works header.

 

You are probably right about the heat evaporating the moisture. However, stainless steel will rust. It is less likely do so so than "regular" steel though.

Jet-Hot and wrapping seems an overkill to me though. I read a lot of posts about wrapping header{s} before getting the coating done and I convinced myself not to coat and wrap. It probably does not matter either way {shrug}.