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April 2014 Question IT

Fixing what you broke

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Catch Cans

There are so many different variations of catch cans sold on the market today, but do they really work? The typical unit only has a two-port (inlet and outlet) fitting to run from the valve cover to the intake, but it's hard to imagine it actually working correctly. Can you set the rumors straight and tell me if this is indeed a good investment as I am looking to install a Cusco-type catch can on my '08 WRX 2.5-liter. I was just wondering about the hose routing, because there are no input or output marks on the nozzles or anywhere on the can and I need to know which line to use from the engine and intake.

-John S., via

If you bought a genuine Cusco catch can for a WRX, it should be application specific. If you bought a universal unit, you should return it and get the application-specific part number because it does make the installation a lot easier and includes instructions. There are a lot of fake parts out there, but you can visit Cusco's website on how to identify fake Cusco parts.

Different catch cans are better for different situations. Some of the more complex units with multiple cans and a bunch of hoses are better suited for cars that spend a lot of time on tracks whereas the simpler single-canister catch cans are better suited to street cars. The Subaru flat-four engines suffer from a lot of oil getting blown out of the valve covers during heavy acceleration because of the position of the cylinder heads. They are very low and close to the oil pan so the oil doesn't always drain back into the crankcase as well as inline-four engines, where gravity plays a big role in draining the head of oil. During heavy acceleration, blow-by gases pressurize the crankcase and cause some of this built-up oil in the cylinder heads to get blown out. In a stock car, this oil gets blown out directly into the turbo inlet. After the addition of a catch can, the oil will collect in the catch can and "catch" the oil in the can. In theory, only the residual gases go back into the turbo inlet.

A catch can is a nice addition and can keep liquid oil from building up in the charge system. For race cars that spend a lot of time on tracks, the necessity of a catch can is critical since there are a lot of high-g situations, a lot of time spent at full throttle, and a lot of blow-by gases flowing through the crankcase. Catch can systems for track cars commonly have multiple canisters for higher oil capacity, better air/oil separation, and have drain-back hoses to allow collected oil to drain back into the crankcase. This way the engine will still have enough oil in the crankcase to keep oil pressure where it needs to be.

All properly designed catch cans are baffled inside to help separate the liquid oil and the air. For a Subaru, both valve covers connect to the catch can via the factory crossover pipe, and this enters the catch can. Inside of the catch can, there is usually a wall that acts as a baffle. The liquid oil that enters the catch hits this baffle and drips to the bottom of the catch can. The residual blow-by gases then exit the catch can and enter the engine from the inlet of the turbocharger. This keeps oil from building up in the charge system (turbo, intercooler plumbing, intercooler, throttle body, and intake manifold) and prevents liquid oil from entering the combustion chambers and causing poor combustion (e.g. knock, misfire).

Ignition Upgrade?

I recently built my turbo H22 Honda 2.2L motor with plans for a coil-on-plug conversion. I've been told that they are good for use in high-boost, high-rpm, or high-compression applications; the increase in spark energy can be seen over factory smart coils. I know some of the older-model cars use MSD 6AL-type boxes or high-output external coils, but what do you think is the best bang for the buck ignition system upgrade?

-Mike, Santa Rosa, CA

Bang for the buck would highly depend on the level of necessity. If you have a simple 6 psi of boost street car engine, a good set of plugs, ignition wires, and a multi-spark box will probably do the trick. If you've built a 40 psi of boost 900hp drag engine, then high current, coil-on-plug coils are probably a necessity. Without any information, it's hard for me to tell you what I recommend. I'm guessing you've built a mild street car engine so I'd recommend running a new distributor cap and rotor, hot external ignition coil, a set of high-performance ignition wires, some NGK Iridium spark plugs (gapped accordingly), and an MSD Digital 6 ignition box (this is 2014, so let's stick to digital). MSD has distributor caps that already have provisions for an external ignition coil. In fact, you could just run all MSD ignition components except for the NGK Iridium spark plugs for an almost one-stop ignition solution. This ignition setup should be fine for over 500 whp. Going to a coil-on-plug solution requires custom wiring, four coils, and an ECU that can control individual coils.

Spark plug gap can vary according to cylinder pressures and air/fuel mixture, but you'll probably want to start off at 0.032 inch and then start gapping them down .003 inch at a time if there's any misfire. It's not uncommon to gap the plugs all the way down to .020 inch for a high boost engine.

Nitrous & Tequila

Being a child of the Internet I've seen Nissan 350Z cars using 150 hp of nitrous to defeat mighty 12-second quarter-mile cars (my main goal is to hit at least low 13 seconds). How safe is that and what would it take to hook all this power down on the tarmac, straight slicks or street tires would still hold up on Second gear? Is it a one-time deal before you blow that sweet VQ35 to pieces, or is 75 or 100 hp a decent daily driven option for a good 375hp cheap build considering I've got a few bolt-ons like a Skunk2 plenum spacer, JWT pop charger, UR lightweight pulley kit, and custom catback exhaust. Or would you rather suggest saving money and go for a blown VQ, maybe a Stillen supercharger?

-Jay, Rimouski, Quebec, Canada

Nitrous is a wonderful thing and is definitely the quickest and cheapest way to get some horsepower out of your engine. I like to think that nitrous and tequila are pretty similar in that they both give your more power, but in both cases, too much can result in disaster. Considering the VQ35 doesn't have the strongest pistons or connecting rods, I'd keep the nitrous under 100 hp with a single fogger nozzle. Add a good clutch, steel flywheel, good gas, and a pair of slicks in the mix and you should be able to run 12s in the quarter-mile. Getting 11s might take a bit more nitrous, but proceed with caution (much like tequila). Be sure to run a colder spark plug too. The stock VQ plugs have a heat range of 5. I recommend running a colder heat range 7 NGK Iridium spark plug.

Beyond 100 hp, I'd recommend a wet direct port setup, which can be conveniently plumbed onto the lower intake manifold. Ideally, you should also log your air/fuel ratio (add a wideband if necessary) to make sure the engine is running safely and run some race fuel if you do not have ignition timing control. Also a bottle heater and blanket will keep your engine running consistently when on nitrous. Hit up the guys at UpRev for their data logging and ECU tuning software if you don't already have it. Of course, a set of forged pistons and rods would increase engine longevity also.

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