Tech Works Engineering Tech Works Engineering 2.5 RS Super Stock Exhaust Manifold
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9.0
Description:
Equal length Header/Exhaust Manifold for 2.5 RS Impreza
Author
Review Date: Mon November 17, 2003
Would you recommend the product? Yes |
Price you paid?: None indicated
| Rating: 9
Pros:
The header is tuned and equal length to provide excellent throttle response within the stock rev-limit.
Cons:
Its difficult to clean mud out of all the bends.
About the Reviewer
My past experience comes from 5 years of Formula SAE design and 2 years of Solo II in Calgary. This past Solo II season I was sponsored by TechWorks Engineering Inc. (TWE) in a bid to win the Canadian National Autoslalom Championships (CNAC). In August I finished 2nd at the CNAC in D Super Stock and definitely attribute that success to the help that I received from TWE.
I’ve been running TWE components on my car for the last year in various configurations. I have run the High Output Cat Section, Mid-Pipe, Stainless Steel Muffler Section, and Carbon Fiber Tip with a modified Version 2 Superstock Header.
Additionally the car is setup for Autocross with the P1/KYB suspension, STi Strut Mounts, FHI 20mm Rear Sway Bar, Whiteline Sway Bar Mounts and Endlinks, and Kumho Victoracer Tires on the stock wheels. This is a well prepared car for CNAC DSS (although still requiring refinement), but would be considered under prepared for STS.
Header Review
The TWE Superstock Header is an equal length 4 into 1 header with the primary pipes tuned to produce power within the stock rev-limit of the car. Since the stock start and end points for the header are maintained, the primary tubes twist to reach their endpoints at the merge collector. This compromise has caused minimal interference with my sub-frame which was hardly noticeable until I installed a front strut tower brace.
With the car configured with the complete exhaust system from TWE, there is a noticeable power gain throughout the power band. What is most noticeable is that the car pulls to redline without any hint of peaking, indicating that I should raise the rev-limit to take advantage of further power. From 4000 rpm to 6200 rpm the added throttle response enhances the drivability of the car on a Solo II course. For CNAC, the stock air filter housing was removed and an oversized K&N cone filter was attached directly to the throttle body. The improvement from this last minute modification was dramatic and continued to draw more power from the exhaust modifications.
The car that I lost to at CNAC was a 2001 VW GTI 1.8T chipped to 220Hp. This leads me to suspect that my Impreza is making about 190 Hp. This was somewhat confirmed with a 16.5 s ¼ mile time at Calgary’s Race City Motorsports Park, where a stock 2.5RS runs in the mid to high 17s.
Since the end of the Solo II season the stock exhaust was reinstalled for a comparison, and at first glance was not bad for city driving. When giving the car more throttle, the response was much slower that with the TWE setup. Currently the car is stock with the TWE header in place, and again there is a noticeable improvement in throttle response.
I have tried the following combinations of the TWE exhaust components with the remainder of the system stock for periods of at least 4 weeks at a time:
• muffler section & mid-pipe
• muffler section, mid-pipe & header
• muffler section, mid-pipe, cat section & header
• muffler section, mid-pipe, cat section, header & cone filter
• header
Replacement of any of the stock components enhances the response of the motor, however the car never really breaths easy until the header is involved in the system. I will continue to run the header alone for this winter unless I am involved in further component testing as I feel that it is the best compromise for daily street use/comfort.
I’m sure that I have left out details that may be of interest to the board, so please feel free to ask me about anything TWE that I have posted here.
Sincerely,
Ryan Warrington.
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