Replaced aftermarket header with stock and..

[magicmike]

HOLY CRAP! I have torque now.

I rebuilt my engine a few years ago and at the time I installed a "GT-Spec" header along with a VF-34 and 3" TBE. The motor was blown before I rebuilt it so I didn't have a refference point really for the butt dyno.
AFter discovering an exhaust leak on my $500 dollar header (POS!) I decided to take off the factory cast iron header and up pipe from the engine I'm selling and put that on.

So, here is what I noticed. Before the car seems to struggle a little to get up to speed unless I was totally dogging it. It seemed like the turbo was lagging quite a bit. Now it is definately more responsive and it definately feels stronger at lower RPM's

So, just to let you know, I noticed a huge difference on the ol butt dyno so if your thinking of getting aftermarket headers for the turbo don't do it!

That being said, does someone want to buy an aftermarker header with a broken weld on the up pipe flange? lol

[DLC]

As Mike Shields used to say, and may yet still, some things are just "presents for your car".

There's surely a performance advantage to the aftermarket headers, but not in the average daily use and probably on track.

[93forestpearl]

Very nice.



The only aftermarket manifold I would personally consider is an equal length, twinscroll design with an appropriate turbo.

[kimokalihi]

Are you sure it wasn't just the difference of having an exhaust leak in your header and not having an exhaust leak? I could see that making a big difference in spool up.

[magicmike]

Are you sure it wasn't just the difference of having an exhaust leak in your header and not having an exhaust leak? I could see that making a big difference in spool up.

I see your point. However, I have been driving on this setup for a while and definately noticed a big difference.

The header basically went bad in like 2 days. It broke cleanly at the weld on the flange for the up pipe. so the car was normal one day and loud on the next time I drove it then really loud the next day and then I did the swap. Had there been a rust hole or something like that where the loss would be diminished over a longer period of time I would have to agree with you.

[All_talk]

Equal length and larger diameter headers can make more peak power but the typically focus that power in a narrower band higher up in the RPM range. The stock design was not an accident and has some advantages for most street driven cars. It uses a very direct line to the turbo conserving heat, pressure and velocity. And the un-equal length broadens the power band.

Plus you get that great boxer growl.

Gary

[Legacy777]

I think the only real gain on the USDM stock cast iron header is the JDM stock cast iron header.

From past posts the flow path appears to be a little better. I picked one up from Frank, so we'll see how things work. I'm probably going to get it ceramic coated.

[magicmike]

Equal length and larger diameter headers can make more peak power but the typically focus that power in a narrower band higher up in the RPM range. The stock design was not an accident and has some advantages for most street driven cars. It uses a very direct line to the turbo conserving heat, pressure and velocity. And the un-equal length broadens the power band.

Plus you get that great boxer growl.

Gary

I agree BUT with the stock ej22t heads they lose breath at those high rpms. For my setup I guess it was money poorly spent.

[asc_up]

How about some of the crosspipes that GrimmSpeed.com sells? They're stock manifolds that they port a little bit and then heat coat.

[kimokalihi]

Are you sure it wasn't just the difference of having an exhaust leak in your header and not having an exhaust leak? I could see that making a big difference in spool up.

I see your point. However, I have been driving on this setup for a while and definately noticed a big difference.

The header basically went bad in like 2 days. It broke cleanly at the weld on the flange for the up pipe. so the car was normal one day and loud on the next time I drove it then really loud the next day and then I did the swap. Had there been a rust hole or something like that where the loss would be diminished over a longer period of time I would have to agree with you.

I see.

[Adam West]

I saw a U.K. pub, Japanese Imports, did dyno testing of a bunch of aftermarket headers on an Impreza and none of them offered *ANY* significant HP gains...And none of them were free...car jewelery for sure...

Ceramic coating your stock headers and uppipe is a good thing to do tho.

http://www.performancecoatings.com/

[93forestpearl]

How about some of the crosspipes that GrimmSpeed.com sells? They're stock manifolds that they port a little bit and then heat coat.

The piping itself does not match that of the collectors, whitch is not in your best interest.

Several friend of mine have crept up on 500whp with the factory exhaust manifold, and a shitty Perrin rotated pipe set. Worry about your turbo, and then your heads as far as breathing goes. My GT2871R was making over 300whp on 22T heads with Delta cams and a factory exhaust manifold. The VF11 or TD04 is the single largest restriction in your system, and then heads. Deal with those first before, plus everything required to exploit a 50 lb/min turbo before worrying about the factory exhaust manifold.



I'll quote Cob tuning...

The exhaust system before the turbo and the turbo itself have a greater effect on backpressure than the exhaust behind it. You want the least restriction after the turbo as possible for both top end power and quick spool-up. Careful attention has to be paid to keep velocity high before the turbo and in the exhaust housing of the turbo to spool the turbo up as quickly as possible while not choking off the exhaust gasses on the top end.

The header can be simpler in some ways than a non-turbo header. Bigger dividends can be had by getting the exhaust gasses to the turbo with the least amount of restriction, highest velocity, and the most heat rather than worrying about a tuned equal length design. It would be optimal to make an equal length header, but the packaging of the WRX make a tuned equal length header difficult to design. This helps explain why we usually get near identical results from a factory header when compared to the aftermarket ones we have tested thus far. The factory header gets the gasses to the turbo as quickly as possible and goes a good job of keeping the heat in. Aftermarket headers tend to take a longer path and loose quite a bit of heat in the process. Also, most have a poor collector design that is s a byproduct of the unique packaging of the WRX. In this case a good collector does play a more important role than the length of the pipes. If all of the gasses ram together at a steep angle it causes a lot of turbulence, creates backpressure, slows velocity, and tends to make a mess of things before the turbo, which is the worst spot for inefficiency on a turbo charged car. A good header design would be something like a 4 into 1 design that uses castings or good thermal coatings as much as possible to keep heat in and would also get the gasses to the turbo as quickly as possible. The collector would have to be longer than the ones I have seen and the transitions nice and smooth. The main problem comes from trying to make it package well into the constraints of the turbo Subaru. A well designed header would likely require the header to up-pipe connection to have different flange points than factory, so it would not be as easy to sell in header and up-pipe pieces. The WRX is a hard car to design a proper header for, to say the least. It is very hard to improve what the factory has already done.

The up-pipes duty is to get the collected gasses from the header up to the turbo. The best size is the smallest that does not create excessive backpressure for the intended use. Again, the goal is to keep the gasses moving as quickly as possible while flowing enough gasses to make the desired power. There also needs to be a small amount of flex in the system to avoid cracking, warping, and blown out gaskets. The exhaust before the turbo has a lot of heat differential from one point to the next and adding to that is the fact that different metals have different expansion. This leads to a system that wants to twist, pull and push quite a bit. Without some give, something has to go. The gaskets and welds are usually the first victims. One problem lies in getting flex without having a flex section that is prone to cracking, splitting, and leaking it's self. It is not wise to cure a problem with a part that causes the exact same problem. That would be like sun screen that causes skin cancer.

[GodSquadMandrake]

Interesting. Do you notice if you lost any top end though?
Headers seem like such a tricky thing on Subaru's. On an inline 4 it's a no brainer though.