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Here's the official Press Release. The dyno graph is posted here on the website.

FOR IMMEDIATE RELEASE
September 20, 2005

Zzyzx Motorsports Impreza 2.5 RS breaks 300 NA horsepower

TechWorks Engineering (Calgary, Alberta, Canada), Dieman Motorsports (Lees Summit, MO) and Zzyzx Motorsports (Overland Park, KS) conspired to build the most powerful normally aspirated Subaru 2.5L Flat-4 in North America. At more than 300 CHP, the output shatters any previously documented efforts to date.

Utilizing an MD Mustang IMP dynomometer, the engine output hit 235 WHP at 6450 RPM and 209 WTQ at 4600 RPM. "We typically see 233 WHP for a WRX STi, which is rated at 300 CHP, comments Jake Diehl, owner of Dieman Motorsports. "This engine puts down roughly 185 WTQ at 2000 RPM and carries a nearly flat torque curve up to 4600 RPM where it makes 209 WTQ, then tapers off to roughly 185 WTQ at 6500 RPM. Though the peak of 209 WTQ is at 4600 RPM, peak numbers don't readily describe the output of this engine. There is more power under the curve than any stock STi can wish for. Based on the average WRX STi, WRX and 2.5 RS data for our dyno, we're looking at peak outputs of roughly 302 CHP, and 276 CTQ."

The longblock was built entirely by TechWorks Engineering. "The recipe for the engine is less exotic than most would guess.", comments Tom Penner, owner of TechWorks Engineering. This engine uses our off the shelf 11.2:1 CR forged pistons, Stage II SOHC Street cams and headwork to maximize both velocity and flow. We consider this a Stage III engine build as it requires high-octane gas and stand-alone engine management, but simply lowering the compression ratio would still yield impressive output in a more streetable configuration." The TWE headers are a race-only 4-2-1 design, with large primaries. "The design of the headers was twofold: to provide power up top, and to lower dynamic compression in the lower RPMs to avoid torque spikes and detonation.", comments Tom. The trough in the torque curve from roughly 3000 to 4500 RPM is a direct result of the header design.

"I knew we needed to find a different intake manifold as the pre-2005 designs clearly are not meant to make power up top; this is a well documented.", comments Steve Sulatycki, owner of Zzyzx Motorsports. "Looking over the options, it appeared the 2005+ 2.5 RS intake manifold design was clearly superior and I decided to mate a high-flow 65mm throttle body to the '05 intake manifold. I had no idea what kind of numbers we'd be making."

"Once the car made it's first 220+ horsepower pull with very little timing and 11.5:1 AFRs we knew we had a strong motor on our hands. I proceeded to level out the AFRs to a very conservative 12:6:1 AFR and we started making pulls in the 230+ WHP range.", comments Jake. "As this engine was built and is being used for road racing, we stayed with a conservative tune for longevity. This is no dyno queen, and these numbers are real-world, not one-offs."

"The engine makes power everywhere", comments Steve. "This kind of power is useable on the street, at an autocross or road racing. It's perhaps the most versatile power delivery you can ask for and the flat torque curve results in a very predictable and controllable chassis when you have the car at it's limits."

The dyno graph is available at the Zzyzx Motorsports website.

Contact Info:

Tom Penner
TechWorks Engineering
403-288-8568
Tech Works Engineering is Subaru performance, upgrades and aftermarket parts


Jake Diehl
Dieman Motorsports
816-347-1950
http://www.diemanmotorsports.com


Steve Sulatycki
Zzyzx Motorsports
913-706-5496
http://zzyzxmotorsports.com
 

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2000 Subaru Impreza 2.5RS-T
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holy shit! very very very very very very impressive. congrats to everyone who was in on this project. This is very good for the ej25 provin it can make N/A power to compete with the Hondas and others out there. nice job
 

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Nice, I was waiting for the press release. What EM are you guys utilizing? Also, in street for would there be a "package kit" for this. I am getting more and more N/A customers and am generally going with suspension mods for them. This is very intriguing but I'm curious of the costs involved (obviously not for this as it is development time involved) but real world.
 

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00 RS & GSX-R 750
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Stock block and internals? I have a na short block sitting in my garage for an NA build up so this might be a new project for me.

Excellent job though, very impressive. You get a sticky. ;)
 

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Discussion Starter #16
I need to post up technical details on the website, but for now:

1) EMS is LinkPlus

2) '05 mani is not a direct swap. Keep in mind all '05+ use electronic TBs. You need to figure out the throttle linkage, use the '05 coilpack, wires, fuel rail and WRX-style injectors.

3) It's best to contact TWE if you want pricing details on something similar.

4) No 1/4 mi time yet. Probably in the next month or so.
 

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ZZYZX,
So the 05 manni isn't a direct swap but can you go into a little more detail about how that went?

Like, what throttle body did you use? Was it stock and then just bored out? The 05 manifold. was there much custom work done to it? Does the 05 mani physically bolt to the older heads? Did you port and polish the new manifold? What kind of fuel system mods have been done. What injectors are you using? Did the 05 fuel rail need to be modified? He he sorry for the 20 questions. I'm sure I'll have more. Congrats on an awesome job.

cheers

garrett
 
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