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 |   |   |  2003 Mitsubishi Evolution VIII - Let It Breathe - Project Super VIII
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2003 Mitsubishi Evolution VIII - Let It Breathe - Project Super VIII

The first round of modifications nets solid results.

Peter Tarach
Jul 10, 2012
Modp 1207 01+2003 mitsubishi evolution viii+cover Photo 1/26   |   2003 Mitsubishi Evolution VIII - Let It Breathe - Project Super VIII

Before Project Super VIII would receive any modifications, some minor housekeeping needed to be done. Anytime you buy a well-used automobile, it’s smart to change out all the fluids. A fresh batch of Eneos Sustina 5W-30 fully synthetic motor oil found its way into the engine, and the transmission, transfer case, and rear differential received OEM Mitsubishi gear oil. There’s a lot of debate online about what oil is best and which ones to use, but from my experience, if you’re using the right weight and specification, then you’ll be fine.

Modp 1207 03+2003 mitsubishi evolution viii+gear oil Photo 2/26   |   2003 Mitsubishi Evolution VIII - Let It Breathe - Project Super VIII

On the cosmetic side, I couldn’t bear the look of the yellow, faded headlights, so after two hours of scrubbing and polishing with Meguiar’s headlight restoration kit, the EVO’s headlights were back to looking as good as new.

With all that out of the way, it was time to focus on the go-fast parts. First thing up was replacing the factory EVO VIII blow-off valve. Mitsubishi used a plastic valve, which may be fine for factory boost levels, but it has a tendency to leak under higher boost pressure. In its place went a Synapse Synchronic DV that is a drop-in replacement for the stock unit. Its compact size makes it ideal for the cramped EVO’s engine bay, and because the DV doesn’t have a diaphragm rather a forged billet actuator assembly, it is capable of lightning-fast response with high flow capability. Not that this engine will ever see 60 psi of boost, but it’s worth noting that every Synchronic DV is tested to withstand that boost pressure.

The EVO’s stock intake box is well designed, but as with any OEM part, there’s always some restriction, and because we’ll be raising the boost very soon, a better-flowing intake was on the agenda. Having run several HKS Suction Kit intake systems on previous project cars, we again chose it for this vehicle because of its excellent fitment, high-quality design, and larger intake diameter. It also doesn’t hurt that it’s one of the best-sounding intakes we’ve ever used. If you like to hear the whoosh of your turbo and blow-off valve release (recirculated, of course), this intake amplifies those noises harmoniously. Getting this intake is still easy even though HKS doesn’t have an official office in the US. Motovicity is HKS’ North American importer and has lots of stock on hand, so if your shop is buying from Motovicity then you’ll have your HKS Suction kit in no time.

Modp 1207 04+2003 mitsubishi evolution viii+eneos oil Photo 3/26   |   A quick flush of all the fluids ensures the EVO is ready to perform at its best.

Arguably the most important upgrade on any EVO is the exhaust system. Having adequate flow for the exhaust gases to escape quickly and efficiently is key to making good power. A after-cat exhaust system is a good start, but if you really want to maximize horsepower gains, then start right at the motor.

The factory exhaust manifold is a durable unit that will last the life of the motor. The problem is that its cast design is limited in flow. Enter Tomei’s Expreme exhaust manifold. After extensive R&D of the factory piece, Tomei has designed a manifold with smooth curves and larger exhaust runners that enhance flow to achieve maximum torque numbers. However, this design still retains a very stocklike appearance, so clearance and heat issues aren’t a problem. The Expreme exhaust manifold is made of aircraft-grade SUS304 stainless steel that Tomei ensures will not deteriorate. As a bonus, it’s about 8 pounds lighter than the factory manifold.

Unlike other tubular manifolds on the market that can be a complete nightmare to install, the Tomei manifold bolts up to the engine just like the stock piece, with adequate clearance to get at all the bolts. It can even retain the factory heat shield. However, a much cleaner and nicer option is the Tomei heat shield that will keep underhood temps to a minimum but look good doing so with its polished stainless steel finish.

Bolting up to the exhaust side of the turbo is an 02 housing that redirects the spent gas fumes down toward the downpipe under the engine. This sharp bend also causes a bit of a bottleneck; although Mitsubishi has done a good job on the design of this piece, there’s always room for improvement. Tomei has increased the inner diameter of its O2 exhaust housing to 2.5 inches over the factory 2.1 inches, and as with its exhaust manifold, Tomei uses SUS304 stainless steel to manufacture the pipe, reducing weight by just under 3 pounds over stock. An often overlooked item on the Tomei 02 housing is the turbo mount bracket. Cracks that develop in tubular exhaust components are usually a direct result of not enough support of the turbo setup. Tomei’s design incorporates the factory mounting bracket, reducing fatigue and stress and increasing the life of the parts.

Modp 1207 07+2003 mitsubishi evolution viii+headlight restoration kit Photo 4/26   |   Cloudy and yellowed headlights are restored to like-new conditions with Meguiar’s Headlight Restoration kit.
Modp 1207 09+2003 mitsubishi evolution viii+diverter Photo 8/26   |   The Synapse Synchronic diverter valve is the perfect replacement for the Mitsubishi plastic BOV.

The Tomei downpipe that connects to the 02 housing is 2.75 inches in diameter, which Tomei maintains is the best size for performance gains throughout the entire powerband (Tomei has more than a year in R&D on this). It too is made of SUS304 stainless steel, and unlike the factory piece has a flex section built into it to reduce vibration transfer from the engine into the exhaust.

Modp 1207 10+2003 mitsubishi evolution viii+installed diverter Photo 9/26   |   The Synapse Synchronic diverter valve is the perfect replacement for the Mitsubishi plastic BOV.

Keeping the factory catalytic converter would prove futile in maximizing power potential. In its place went the cream of the crop, Tomei’s uber light titanium test pipe that tips the scale at a feather light 1.76 pounds. Considering the OEM cat weighs almost 12 pounds, the weight savings are huge. The downside is that the environmental impact is bad, but because this car doesn’t see daily use (it will be more track oriented), we can justify it. Eventually, a high-flow cat will find its way onto the car, but for now, it’s all about power, and there’s no better way to get that then with a 3-inch titanium straight pipe.

As you can already tell, weight reduction is just as important as horsepower since both go hand in hand. The lighter the car, not only the faster it will be but the better it will handle and it will stop shorter, wear tires slower, and so on. That’s why there’s only one system on the market that weighs in at 10.7 pounds and costs just over $1,000—the Tomei Expeme Ti after-cat exhaust.

Replacing the factory exhaust with the Expreme Ti nets a 24.6-pound weight savings, but that’s just half of the equation. This exhaust is built for total performance in mind. Therefore, bends have been minimized and a high-flow, canister-style muffler is used. To keep noise levels at a reasonable decibel, long-fiber wool threads are incorporated into the muffler. The system also features thin-walled, 3-inch, titanium piping with slip-fit joints to save every ounce of weight.

Modp 1207 11+2003 mitsubishi evolution viii+hks intake Photo 10/26   |   The HKS suction kit is a complete replacement piece for the EVO’s stock intake, and using its patented mushroom filter and larger-diameter intake pipe increases airflow to the turbo.

The Expreme Ti is the best bargain for a truly performance-oriented exhaust that weighs next to nothing, and it looks like a million bucks. The quality of welds and overall craftsmanship is second to none.

We should also add that Tomei really looks out for the DIY user when it comes to installing its parts. Every part came with all the necessary gaskets, washers, nuts and bolts, so you don’t have to reuse the old factory hardware. This and the overall time and care that goes into designing Tomei’s products is why we can’t help but write all this praise, but you don’t have to take our word for it because the dyno can back it up.

That’s where my good friends at Road Race Engineering come into play. I headed to the facility in Santa Fe Springs, California, to have the EVO strapped onto the Dynapack dyno and see what kind of numbers it would make. The results proved yet again how well turbo cars respond to exhaust and intake mods. A peak 35 whp and 16 lb-ft of torque were made with the Tomei components and HKS intake over stock. However, that’s with a completely stock ECU tune. After Mike Welch played with the fuel, timing, and boost maps, the EVO produced 273 whp and 288 lb-ft torque. And there’s more to the story. Those numbers are a bit low for what we were expecting, but that’s because the stock fuel pump was maxing out meaning that’s it for this round.

Modp 1207 12+2003 mitsubishi evolution viii+installed intake Photo 11/26   |   The HKS suction kit is a complete replacement piece for the EVO’s stock intake, and using its patented mushroom filter and larger-diameter intake pipe increases airflow to the turbo.

We’ll be back soon with adequate fuel upgrades and much more in the never-ending quest for additional horsepower.


Irvine, CA 92614
Tomei Powered USA, Inc.
Lake Forest, CA 92630
Road Race Engineering
Santa Fe Springs, CA 90670
Synapse Engineering
San Diego, CA 92121
By Peter Tarach
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