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Technical Questions & Answers - Question It

Fixing what you broke.

Eric Hsu
Jul 3, 2013

Got a burning question or simply need some advice with problems you've encountered while wrenching on your current/future projects? Ask our automotive guru Eric Hsu anything-literally, he's going to answer every single question, as long as it's automotive related.

Got a tech question? Send it to

Turbo Upgrade

I own a stock '04 Subaru WRX. However, the turbo compressor wheel is wobbling, and I'm thinking of upgrading it to a TD05H-18G. Would I need anything additional to install this turbo? The plan is to upgrade the car until it can produce 300-400 hp, but I'm not in a rush to produce that. I just want a turbo that will be able to grow with the mods that will be added on later and would like some advice on this.

02 technical questions answers turbo upgrade Photo 3/6   |   02 Technical Questions Answers Turbo Upgrade

-Luke Sullivan, Bryn Mawr, PA

You can install the turbo as long as it is a TD05H-18G made specifically for a '04 Subaru WRX. When you hear the terminology "TD05H-18G", this is simply a turbo size for the CHRA (center housing rotating assembly). T = turbo, D = D type bearing system, 05 = turbine wheel family, H = high flow, 18 = compressor wheel's maximum flow in m^3/min, and G = compressor wheel design. There are TD05H-18Gs made for many different applications so you would not be able to bolt one onto your Subaru if the housings were configured for a Mitsubishi Eclipse.

You can bolt a TD05H-18G directly on your WRX, but you'll need other supporting parts to allow the engine to make the power: high-flow exhaust system, air filter, injectors (750cc) and fuel pump (255 lph). On top of this you'll also need a better performing intercooler and have your ECU tuned to orchestrate all of these new parts. I'd recommend the COBB AccessPort for this since you'll also be able to monitor key parameters and be able to switch maps for different situations since the AP can hold multiple maps.

The 18G compressor wheel is good for about 300-350 hp at the wheels on pump fuel depending on the parts you end up with and other factors such as build quality and engine health, but you'll be rewarded with a WRX that'll pull you back in the seat pretty good. Make sure to upgrade your brakes, suspension, and tires too. There's no point in having all that power if you can't control the car, right?

Lightened Flywheel

I need to know what I will encounter when rubber meets the road after installing an 8-pound flywheel on a 5,500-pound Isuzu Trooper. This 4x4 five-speed has a 3.2L SOHC engine that makes 170 hp and uses a 25- or 30-pound flywheel. I plan on installing an Eaton M90 supercharger, high-flow exhaust, and cams and port and polish the cylinder head as well as lower the compression ratio. How much horsepower would a stock cast V-6 crank, piston, and rod handle? Someone mentioned 350 hp but I am thinking lots more as the crank has a four-bolt main. I can't find aftermarket forged pistons, cranks, or rods for this particular engine, but if it can handle 450 to 550 hp using stock internals then I don't care.

03 technical questions answers flywheel Photo 4/6   |   03 Technical Questions Answers Flywheel

-David, via

What you can expect are frequent clutch replacements. Since an 8-pound flywheel has a much lower inertia, you'll need to slip the clutch significantly more to get your Trooper to accelerate from a stop. If you're slipping the clutch more, you're going to replace it more often. If you're in a hilly area (e.g. San Francisco), then you're really going to be in for a treat. With an 8-pound flywheel, you probably can't even accelerate from a stop on a high-grade hill in a 5,500-pound car with an anemic V-6. I'm definite your factory flywheel is much heavier than 25 or 30 pounds. In fact, I'll bet it weighs more than 40 pounds. Isuzu designed it this way to make the Trooper easier to drive.

If you're OK with the more frequent clutch replacements, you will be rewarded with faster acceleration. The lighter flywheel takes less power to accelerate and allows the engine to get more of its power to the wheels. I am not familiar with the Isuzu V-6 engines so I couldn't say how much power you can make with the factory components. Keep in mind that even though the engine has four-bolt mains, it also only has four main bearings. Compare that with a straight-six engine that has seven main bearings and maybe you'll rethink how great a four-bolt main V-6 is. I think it is safe to say that your engine can probably handle 40 percent more power with relative ease in stock form. Anything beyond that should be approached with caution. Contact JE or CP pistons for custom forged pistons and Carrillo for custom connecting rods. All of these companies will require samples of factory components to design a custom piston. I doubt you'll find anything off the shelf for the Isuzu V-6. Try Castillo's Crankshafts; they may be able to find you something that can work.

Rotary Virgin

I recently purchased a '88 Mazda RX-7 convertible as my next project car for my club since my '04 WRX has been put to rest (RIP). I'm having some issues finding sites or even stores that might carry specific parts for this car. I'm new to rotaries (as if you couldn't already tell), so any help would be greatly appreciated as I plan to do a drift setup. I just hope you guys don't say, "Step 1: Get rid of the convertible and get the turbo model." Again any help to get me on the right foot so I don't piss off all the hard-core second-gen RX-7 owners would be greatly appreciated.

-Patrick Maguire, Elite Speed Founder

Step 1: Get rid of the convertible and get the turbo model. Truth be told, that's going to be the easiest road to achieve your goals, but if you want to do it the hard way, you'll need to start saving money now. As with most anything, your goals are always achievable with enough of a budget.

The turbo FC (second-generation RX-7 chassis code) engines have components in them that are specifically designed for turbo use. The rotor housings use different chrome plating, the stationary gears are made from better materials, the oil pressure is higher, and the port configuration is capable of more flow in stock configuration. But you can successfully turbocharge a non-turbo FC engine for street and drift use. Its reliability will depend on how well the engine is built or how healthy it is. Most important will be the ECU you choose and how well it is tuned as well as the quality of the components you choose.

Most aftermarket FC turbo upgrades are out of production these days. Even if you pieced together a turbo upgrade intended for a turbo engine, there's a slim chance it would fit your non-turbo engine. The non-turbo engine has a six-port configuration and the auxiliary port actuators occupy the same space as the turbine housing or downpipe would typically. You can remove the actuators and wire them shut, but your engine will suffer some low rpm torque loss.

Building an FC can be a pretty expensive undertaking if you aren't a fabricator. On top of the turbo and its associated components, you'll also need a front-mount intercooler, a high-flow exhaust system, an upgraded fuel system, and a stand-alone ECU (e.g. Haltech, ViPEC). Then let's not forget the brakes, suspension, and tires to control all of that power. However, there's absolutely nothing that feels like a healthy turbo rotary in the tuning world. I built my Turbo II back in '92 in my dad's garage, and I still remember the first time I ripped through the gears after tuning it. The feeling was absolutely amazing, and even after all these years I still have yet to find an engine platform as enjoyable as a turbo rotary.

Back in '92 we were able to buy upgrades from companies like HKS, Greddy, and even Cartech. In 2013 parts for the FC are much harder to find. I'd recommend contacting Racing Beat for chassis and suspension goodies. Try Mazdatrix for engine-related upgrades. Both of these companies have been racing and building rotaries long before I had my driver's license and their experience with the FC platform is something that you could definitely benefit from.

Tuning For Power

I plan to turbocharge my '01 Tiburon in the near future. I have a new block and head, which will get upgraded internals before I put it in the car. Can a stock ECU for a '01 Tiburon be reflashed to run 7-9 psi for a daily driver. If not, which ECU would you recommend? Also, should I shy away from the eBay turbo kits for my car?

-Anonymous, via

The whizzes over at Evoscan in New Zealand developed a software package that allows reflashing of the Tiburon ECUs. The software is open source so there is probably a small community of people successfully flashing the ECUs. Whether or not the ECU can support 7-9 psi really depends on the size of the open source community, but it is a possibility. It's likely that you'll get more reliable performance, however, from a properly tuned stand-alone ECU such as an AEM or Haltech. The stock ECU code was never intended for boost.

Not everything on eBay is junk, but a lot of it is certainly from China. Chances are a $300 turbo kit isn't going to work very well for very long. Remember that if it sounds too good to be true, it probably is. Just be sure to stick to quality parts with proven performance whenever possible.

Tucked Brake Line Functionality

I've been working on an AE86 for a while now and have almost gotten where I want; however, I'm curious about my brake lines. I have upgraded the stock rotors, pads, and hoses to performance bits, but I am looking at upgrading the master cylinder. Rather than buying an OEM master cylinder I was looking at a kit that includes the brake booster delete, but I'm curious on how to replace the brake lines. I would like to tuck them if possible, and include an in-cabin proportioning valve. Do you have any recommendations as to the size hose to use or a preferred company to get the fittings/hose? I want a bit of a stiffer pedal feel, but I don't want it to be wasted when I actually hit the brakes.

04 technical questions answers brake master cylinder Photo 5/6   |   Technical Questions & Answers - Question It

-Chris P., via

Manual brakes are for race cars and old, small lightweight cars, like a Lotus Europa. The AE86 is light, but it isn't that light. Remember Initial D is a cartoon and your name isn't Takumi. It will still be very difficult to drive on the street with manual brakes. It will also be dangerous in an emergency situation.

But should you ignore my warning and foolishly try anyway, you'll need to use 3/16-inch tube for hard lines. You also have the option of using -3AN Teflon-lined hoses and M10x1.00 metric inverted flare adapters.

You didn't mention anything about the configuration of this new unassisted master cylinder, but you'll simply need to split the brake lines using a T-fitting with one leg going to the front brake tube and one going to the rear brake tube. You can run a cockpit mounted inline proportioning valve on the tube that goes to the rear brakes and that should proportion the system.

Missing Car

Hi Eric, I was having a look through the section on the cars you own/have owned and I noticed the lack of an R34 Skyline GT-R-most notably, the one that won the Best Motoring American Touge challenge several years ago.

05 technical questions answers brake R34 skyline GT R Photo 6/6   |   05 Technical Questions Answers Brake R34 Skyline GT R

-Sol, England

That was a customer's car of XS Engineering, the tuning shop I used to own. As much as I would have loved to say it was mine, it was not. It belongs to my friend Kim Johnson and still does. Call me old school, but I still prefer BNR32 GT-Rs and still have mine. Johnson's car still runs mostly unchanged from that episode of Best Motoring's American Touge 2. In fact, it finished in Second Place with Tarzan Yamada behind the wheel just barely behind an R35 GT-R in the 2011 Modified magazine AWD Shootout. Johnson's car is proof that a properly built, extremely high-performance car can last over 10 years even when driven in anger. The build has to be planned correctly, the tuning right, and maintained, of course. This would be no different than any high-maintenance chick, right? If you want your hot chick to last 10 years, you're going to have to maintain her too!

By Eric Hsu
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