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Automotive Technical Questions & Answers - Question It

Fixing what you broke.

Eric Hsu
Jan 18, 2013
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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

200SX/RS13 Turbo Dilemma

I own a 200SX/180SX with the CA18DE turbo engine, Garrett GT28 turbo, Dictator fuel management system (local system) and Autobahn88 front-mount intercooler kit. On the dyno, the setup makes 278 hp at 1.1-bar boost. I’m very happy with it, besides the clutch burning out. Now my plan is to build the strongest CA18DE turbo engine in South Africa. The strongest one we know of here makes 275 kw (369 whp). I’ve already imported Wiseco pistons, Eagle K1 rods, Splitfire coil packs, a Cometic gasket set, and a fully worked head with Kelford cams, Tomei Powered double valve retainers, stainless valves, and solid lifters. I’ve also imported an Autobahn88 bottom-mount turbo manifold and plan to purchase an intake manifold.

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What turbo should I use? I don’t mind a bit of turbo lag; as long as it’s fully spooled up by 4,500 rpm, I will be more than happy. I’ve been contemplating using the new Precision Turbo GT30 with billet wheel and internal wastegate to address the previous turbo’s inefficiency from 6,000 rpm to redline.

Groete Reinhardt
Rautenbach, South Africa

The parts you have should definitely prepare it for the additional power. The CA18DET can make good power, but that’s never been its problem. The CA18’s weakness is the head gaskets. Aftermarket head studs, a metal head gasket, and surface grinding the sealing surfaces will go a long way to improving the head seal, but the cylinder head suffers from a lack of stiffness and water passages that prevent the CA18 from making big power for sustained periods of time. Outside of that, a GT30 should easily do the trick and spool by 4,500 rpm, but you might even consider a Garrett GT2871 52 trim or BorgWarner EFR7064 for something that will spool even quicker and still be capable of more than 275 kw. The GT30 might also help to keep the cylinder head seal together since it will make more power at lower boost, but will be slower responding (although still hitting full boost below 4,500 rpm).

Turbo Perfection

I have a stock Subaru WRX. The turbo wheel is beginning to show age and wobbling. I’m thinking of upgrading it to TD05H 18G. Would I need any additional parts to install this turbo? The plan is to add parts until the engine can produce 300-400 hp. I am looking for a turbo that will be able to grow with the mods that I will be adding later down the line.

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Luke Sullivan
Bryn Mawr, PA

An 18G compressor wheel is really only good for 350 hp at its limit so if you’re happy with that, it’ll be a good turbo for the job. The TD05H 18G will bolt right on, but to extract everything you can from it, you’ll need a larger-diameter downpipe, a higher-flowing exhaust, and an upgraded intercooler. If you ever pull the engine apart, I’d also recommend a set of mild cams from Kelford or Cosworth. What’s nice about the TD05H 18G is that it is cost effective since it is built on Mitsubishi’s OEM Subaru housings.

Eclipse 2G Questionnaire

I have a ’95 Eclipse GS. Before I bought it, the engine and trans had been swapped to the ’98 GS setup with the ECU swap as well. Not too long ago, the ECU went bad, and jacked everything up. I’ve been looking for a new engine and trans, but have been coming up short around these parts. (I live in the middle of Tennessee.) I’ve called all the junkyards and salvage yards within 50 miles, and the closest I could find is a ’00 Eclipse GS 4G64 engine and trans. I know that engine and trans came in the ’95-99 Spyder Eclipse, but I was wondering how hard it would be to swap? I know it is a bigger engine, and I would have to change the engine ECU. What about the trans ECU? And I know I’ll need new engine mounts. Both are automatics, so I don’t think I would have much of a problem in that respect. Most people would just buy another car, but I really like the 2G Eclipse, and would rather keep it than buy something else.

David Martin, via

I believe your ’95 GS has a Dodge 420A engine in it. The 4G engines have totally different engine and transmission mounts—so different that even the sheetmetal welded onto the framerail for transmission and engine mounting are completely different. Your best bet is to locate another 420A engine and drop it in since it would be a 100 percent drop in without any additional hassles. Try for a huge database of used auto parts. Many of the junkyards will ship nationwide, so being in the middle of Tennessee shouldn’t be an issue anymore.

Swap Time

I drive a ’04 WRX and am running an STI 2.5L block with WRX 2.0L heads. I want to upgrade to the Cosworth STI heads. I was hoping you could tell me how I could make this happen. Do I need the ’04 STI ECU? Are there any other issues I need to address, such as the STI fly-by-wire? These are a few issues I have been trying to figure out, not to mention the AVCS. My car is currently running on an EcuTek tune, 264-degree camshafts, as well as PPG straight-cut trans gears.

Jason Hall, via

Your best bet would be to get a JDM ’01-04 EJ207 engine harness and ECU, which will give you the ability to control the AVCS without having to switch to a fly-by-wire throttle. Using a U.S. ’04 STI ECU would require some additional wiring, a new throttle body, and a good deal of time figuring it all out. EcuTek does support the JDM ECU as well, but I believe you’ll need to buy a new license for it. You’ll also need to get a new set of cams if you are going to switch to the Cosworth EJ257 heads. I’d recommend a set of Cosworth 278/274 JDM STI cams to go with those heads.

Air/Fuel Ratio

I have an automatic ’08 Scion tC that feels like it’s running a little rich. As far as engine mods, the car has a cold air intake, 4-2-1 header, full, header-back exhaust, along with a throttle-body spacer, and an underdrive pulley. Would any of these cause rich fuel conditions? Also, would a piggyback or stand-alone ECU net me any gains as far as horsepower or mpg? Would either of these lean out my air/fuel ratio?

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Anonymous via

Air/fuel ratio isn’t anything that you can play the guessing game on. Short of having a black exhaust tip stained with soot, you may not be guessing correctly. I’d recommend a wide-band air/fuel ratio monitor from Innovate or AEM to make sure your car’s running correctly. The combination of the CAI, header, and cat-less exhaust will surely require some fine-tuning to optimize air/fuel ratio and timing. Check out Greddy’s E-Manage for the Scion tC. They’ve done quite a bit of piggyback development work on the tC during the development of their turbo system that would apply to even a normally aspirated tC. There is definitely some horsepower to be made through fine-tuning, but it’s unlikely that your mpg will change much since the factory ECU handles that quite well already.

Old-School Present

My wife surprised me with a ’82 RX-7 GSL as a welcome home gift when I returned from military deployment. I think she bought it for me because she really hates my Mercury Capri XR2. What would be the best way to tune it to boost a gain of 30 to 40 hp, or swap the 1.1-liter for a 13B out of a FC3S?

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PO3 Michael Alexander
Port Hueneme, CA

I also owned a ’82 GSL and to this day still consider it one of my favorite cars. You’ll have a blast in it with the right parts. You can pick up 30 to 40 hp pretty easy with the 12A engine. Call up Racing Beat for a set of headers and a bolt-on exhaust. Then get a Mikuni side-draft carburetor kit from Mazdatrix to get more air and fuel into the engine. Boom! You just got yourself 30-40 hp with a little turn of the distributor for additional ignition advance. Another good mod would be an ACT clutch and a lightweight Racing Beat flywheel to round out the package and a whole lot more fun. Don’t get carried away with that redline buzzer!

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