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Old 11-29-2003, 08:27 AM   #1
OMAHA2.5RS
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Question Info on TWE header

I've seen a lot of discussion and speculation, but not many testimonials from people who have it installed.
I'd like to know if someone had the usual bolt ons: intake, 2.25 catback, and then added the TWE header (with the stock cat section). What kind of a difference did it make? Are you happy with it and would you recommend it to others?
Thanks in advance........................................... ..........Doug
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Old 11-29-2003, 01:22 PM   #2
Matt Monson
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Doug,
I can't speak from personal experience but have done my homework. I went back and forth on getting the TWE or the Cobb. I think they are the two best headers on the market under $1000 for the EJ25. The dyno#'s that TWE recently posted on their site are of an RS-T with the headers. IIRC they got something like 14hp more. They plan of getting an NA dyno run done in the near future, but it is difficult because they don't have their own dyno and have to travel for dyno days. And until recently they didn't have their own test car to build and swap at will when they wanted to test different things independently.

As for true testimonials, I haven't found many people that actually have them on their cars. However when you find the few people that do, they rave about them. If you shoot an E-mail to TWE they are always happy to discuss their product and its design and construction to aid in your decision. Sorry, I couldn't give you the first hand experience you wanted...
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Old 11-29-2003, 02:47 PM   #3
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I had the header and the hi-flo cat on my car. I also had a JC sports intake, Brullen cat-back, and J-A cams.

I was very happy with the header and would definitely recommend it to anybody with the green. Yaaah, they are kinda pricey, but N/A always is. It made my car sound mean and haul ass. When I put back on the stock headers/cat, there was a noticeable decrease in power everywhere. I was like.. that's it?

Don
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Old 11-29-2003, 02:55 PM   #4
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anyone have the header on an auto RS? worried about fitment issues.
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Old 11-29-2003, 08:41 PM   #5
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why would it make a difference if its auto or manual?

oh ya here is a good testimonial about the TWE headers(I'm still debating getting them or just putting the 900 towards a turbo kit):
http://www.rs25.com/forums/showthrea...threadid=10993
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Old 11-30-2003, 02:55 PM   #6
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Defiantguy - different trannys have different clearence points. Do it doesn't necessarily mean fitting a 5spd will fit an auto. Just like some Down-pipes for WRX's.

Jejunum - You may also want to consider the iON/Brullen header-back or header system set-up. Those will fit both 5spd and auto for sure.
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Old 11-30-2003, 05:53 PM   #7
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Ive been looking at these headers for a while now, I might crack and get them over winter. But I would like to see some N/A dyno numbers with them on. I dont know how thos egains would translate over to my car for instance. And I am guessing it was in comparison to stick headers, Im not sure what kind of gains I would expect over my borlas. Im confident thay are better than the borlas, but I just dont know how much more.

Dan
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Old 11-30-2003, 07:11 PM   #8
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Hi Omaha.

Firstly, I have to say to the vendors, it's prolly not the best place to make marketing insertions or plugs amidst these discussions. I hope that I don't sound offensive.

I run TWE 2.25" headers on a N/A EJ25 '00. There were a few quirks concerning fitment to work out. Especially, the placement of the front O2 sensor, which in the stock location seats hard on one of the lengths of the header. I am prone to a front O2 sensor error causing a CEL, despite replacing the sensor. I'm sure that a sollution would not be difficult, if I ever get around to it. But these headers otherwise seem to perform quite well.

Their sound is intriguing. It still has most of the beloved flat-4 pulse and burble, but it has been smoothed. It takes time to get used to the tuned pipes, which have a few harmonic 'sweet' spots on deceleration, but otherwise seem to enable a more forcefull accelleration throughout the revs, most notibly up high (4200 +). There is a small, but noticible difference in power with a low resistance cat.

I think it complements my cat-back, which is a Brullen (quiet version). PM me if you're wanting more info.
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Old 12-05-2003, 02:19 PM   #9
Section 8
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Quote:
Originally posted by dcoty
Ive been looking at these headers for a while now, I might crack and get them over winter. But I would like to see some N/A dyno numbers with them on. I dont know how thos egains would translate over to my car for instance. And I am guessing it was in comparison to stick headers, Im not sure what kind of gains I would expect over my borlas. Im confident thay are better than the borlas, but I just dont know how much more.

Dan
Dan,

They will be better than what we are running. Due to the firing order fo the Subaru engines, the header doesn't have the effeciency of exhaust pulses 180 degrees apart (there is no way of doing that unless you run pipes under the motor). What we see are the benifits of an excellent flowing tublar exhaust with a good part of the scavaging ability of the 4 into 1 TWE design. Also piping diameter is the same, which most headers are only 2.25, which isn't all that great. Fluid dynamics tells me that the Burns Stainless collector is far superior to the cheezy (yet beautifly welded) merges on the header that you run now.

You might not want to buy it, I can tell you from first had experiance that your header is goingt o be a REALLY hard sell, unless you can handle loosing alot on it.

Greg
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Old 12-05-2003, 04:06 PM   #10
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I can find some local people to sell it to, I am prepared to lose some money on them. But I am leaning more and more towards these headers though. I might as well do it right if every hp counts right? And I bet the gains would be there. I have seen that the design is far superior to others. if you were me would you have already gotten them on my car by now? Thanks for the help!

Dan
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Old 12-05-2003, 04:30 PM   #11
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I would already have them if I didn't want to get my project engine underway.

Make sure that you order the one you want (HO). THere are two different sizes (SS, and HO).

Greg
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Old 12-06-2003, 12:42 AM   #12
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Default Headers

Why not checkout the MRT's. I felt substancial gains with these and the high flow cat and brullen catback. The car felt like it was lighter, (ie. more power). Rust, maybe 3 or 4 years. But for $340 with cat it's a bargain!! The only negative I've seen so far was going through O2 sensors. I'm on my 3rd, but no CEL's. Good luck, Keith
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Old 12-06-2003, 12:05 PM   #13
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Thats it too, Im (as well as others looking into this) a liitle confused as to which comoany to go with! I cant decide between all the equal length headers. I browse every review on equal lengths I can.
Dan
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Old 12-06-2003, 02:45 PM   #14
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MRT are Just like the SYMS design, they are not as effective as they could be becasue the cylinder firing is wrong for the way that the cylinders are joined. They do not opperate as equal length designs becasue the wrong cylinders are joined. Its as simple as that. They proved gains, but if you used the same primary lengths and diameters and jointed the correct cylinders, and thested then back to back with the SYMS or MRT offereing they would be superior. The cross over helps the MRT but while it smooths the torque curve, it doesn't make up for the lost peak where the length of the primaries make a difference.

Purchasing the MRT when the syms is on your car is a dumb idea. It is a a 2.25" ehaust, it will deteriate.

THe only true tuned exhaust header with equal length primaries will be the 4-1 design with out running pipes all over under the engine. There is only one place that makes one this way, with no competition of yet.

The 2.25" comments do not pretain to those with engines with bolt ons. 2.5" will be better for a car with head work and cams with asperations of raising redline.

There are physics involved in exhaust tuning, simply making the tubes the same length, does not make a tuned header. You need the correct exhaust ports to obtain exhaust pulses in the right order. Any 4-2-1 headers that do not join cylinders from the OPPOSITE side of the engine are not "correct" and are giving up power. Again, on the Subaru motor it is really hard to make the correct pairings, so you go to the other design, which is the 4-1. This method fits. You either use it or you don't.

2 years ago, the SYMS was the best header for cars with modified top ends, now its not.

THere are no other choices for power production. You will buy what ever you want. If you listen to your wallet, there are plenty of choices that are superior to the stock header design, and only 1 superior to the SYMS. You either buy it or you keep what you have. Everything else is is a waste of time and money for your car.

Greg
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Old 12-06-2003, 05:11 PM   #15
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With the introduction of the Cobb as a 4-to-1 system, it and TWE should be better than the SYMS if what you say about firing order is right.

Im still waiting for the Cobb flow charts to be certain but they look quality. TWE is the only turbo compatable one though so it will never lose its place for that at least.
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Old 12-06-2003, 09:09 PM   #16
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Wow, Section 8, masterfully worded, a very nice treatise.
I bet'ya the "smoothed" pulse-quality of a set if equal lengthed tubes would especially boon a turbo, eh?
To those who may wish to futher mutate into the 'aftermarket F/I' crowd, I have to say, the high temperature ceramic coating of the TWE is really quite impressive. It's well suited to forced induction temperatures.
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Old 12-07-2003, 01:02 AM   #17
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I forgot abou the Cobb header.

Yes, it has the desired qualities. It is a little long in my opinion though (shorter primaries have less time for wave reflection, making the "tuned" region of the rev range higher. Longer primaries will work better at a lower RPM).

I would imagine that the Cobb header was designed in conjunction with a stock redline, and probably took the street cams and stage 1 heads into consideration. It would likely work as an excellent package for the bolt on enhanced motor.

For more agressive set ups, shorter primaries and a larger dump would be better. It doesn't say anywhere on Cobbs site what the final diameter of the header is. I'm sure that someone knows, or obviously Cobb will tell you if you ask.

The extra length of the Cobb header is a bonus in terms of cost versus value. you son't need to purchase a cat pipe, its on the header (with or with out catylist).


Turbo charged 4 cylinder engines have all kinds of weird things going on. You would think that a steady flow of exhaust would be better, but its not. The turbo actually likes pulses as proven by the awesome performace of a twin scroll turbo. It keeps 2 different pipes seperate all the way through the turbine. This is different than a odd length header sending oddly timed pulses to the turbo, but maybe not all that different. This goes in line with various headers making more power, its just a more efficient header, with no direct influence on the turbo itself. I don't hink any header claims that it will spool your turbo faster, just that you will se power gains, particularly in the upper rev range. I don't know how it works, but the seperate pulses in a twin scroll turbo spool it very quickly for the size of the turbo. I suppose that it might be related to the inerta of the turbo, it gets hit harder with exhaust gas and speeds up quicker, but is able to keep its speed until the next pulse hits, but this is just out of my ass. I have always understood that turbos work on a pressure differential, the more pressure inside the turbo means that it wants to escape faster and pushes the turbo faster until the hole that the exhaust gas is exiting reaches the speed of sound and can no longer flow any more CFM. Twin scrolls opperate under the same fluid dynamic laws, but take advantage of different forces, or maybe better advantage of the same force.

Either way seperate pulses via twin scroll is the way to go, its just not available to everyone yet.

THis in my last post:

Quote:
The cross over helps the MRT but while it smooths the torque curve, it doesn't make up for the lost peak where the length of the primaries make a difference.
I meant to say:

... It doesn't make up for the lost peak power where the PAIRINGS of the primaries make a difference.

Greg
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Old 12-07-2003, 01:11 AM   #18
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Oh and as far as a weird timed pulse header, versus the equal lenght header on a regular turbo. Thats a question for the dyno. I would imagine that different turbos would be more sensitive on way or the other, and there are trade offs as always. For the biggest number possible 4-1 seem to be making the most power, but you can change things to take advantage of the strengths of a header, with management, boost and different wheels on the turbo. Maybe there is no difference if you were to maximize everything related to it.

Greg
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Old 08-28-2009, 02:14 PM   #19
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ebay headers with stock catback?
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Old 08-28-2009, 02:28 PM   #20
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Wow!

You win!

...bumping a 6 year old thread.

Lots of info already exists. The gist:

-Cobb (and OBX and Rallitek copies of it) and TWE designs are about the same. Both are a 4 to 1 design running a 1.625-1.65 OD primary of length of around 40". For our cars, this is pretty much the ideal.

-The header does most of the work involving what happens at the combustion chamber (along with intake manifold and cams). What happens after the header is less of an influence. As you step to bigger exhaust, you will see tiny gains in top end power for each step up. A 2" pipe is needed which is around what stock is. A 2.25" is better, simply guarantees no (minimal) constraint up to redline. 2.5" and bigger doesn't do much and would only be useful if redline was significantly higher, think 8k rpm, i.e. building a race engine.
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Old 08-28-2009, 08:29 PM   #21
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lol thanks... i got installed no problem. but noticeable gain
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Old 08-29-2009, 08:29 PM   #22
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The header alone will give you around 5-10 ft-lb. It will also allow for a little more aggressive spark timing which will yield a touch more.

The key is not to expect vast gains from mods on a NA platform. It simply doesn't happen. I mean efficiency is pretty decent to start with. You have two options. You can improve efficiency over the current power band, gaining 20-30 ft-lb. total over stock. Or you can do the same but move it up higher in the power band creating high hp. The problem is you lose low end efficiency, so you may be down 30 ft-lb. putting around. If you want to make the engine run to 8k rpm and make 180-200 (crank) ft-lb up there, you'll have high hp. However, it's a ton of work, basically a full engine rebuild to support the rpms and flow. What we most do is simply keep what we have and simply improve efficiency over a wide power band. You're just limited to around 20-30 ft-lbs. though, and top end hp doesn't go up much either. You end up with a better engine but still an engine that feels very similar to stock, just better everywhere. The only way you vastly get a different engine is to completely redesign it, mainly up peak rpms and move the torque band up there or go forced induction and go around the displacement limit. Those are your two options.
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