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Ski-Doo dealer CJ Motorsports of Booneville, N.Y., brought us this pre-production demo 4-TEC 1200 4-stroke to dyno test. At press time the production versions had not even begun to be built, but we can still draw preliminary data from our test.
4-stroke fuel consumptionLike the E-TEC we tested earlier in the year, the 4-TEC has a fuel bypass EFI system. Fuel is sent to the rail and excess fuel bypassed back to the tank via a 58 psi blow-off bypass regulator. Because of this, we needed both dyno fuel flow meters. One was used to measure gross fuel flow from pump to rail, then the bypassed fuel is deducted and the difference is what's consumed by the engine.
To measure approximate fuel efficiency at cruising speed, we warmed the engine, I set the dyno computer to hold the engine steady-state at 6,700 rpm and gradually opened the throttle while measuring data points. This showed us sub 0.40 lb./hphr BSFC (Brake Specific Fuel Consumption) in the midrange, which should afford 4-TEC riders much lower fuel consumption compared to most 2-stroke sleds, most of which have a BSFC usually between 0.60 and 0.75 lb./hphr in the midrange.
Dyno it up!We completed several full throttle dyno tests with varying coolant temperatures and warm oil. While fuel flow remained constant from cool engines to hot, peak horsepower varied considerably. This is most likely from ignition timing being altered by the ECU depending upon coolant temp. On 4-strokes, engine temps and airflow are not interlinked like they are on 2-strokes. After completing all our pulls, the 4-TEC showed its lowest peak horsepower (130), when the coolant gauge was at its highest and just before the hot engine "fail-safe" rev limiter kicked in. The engine showed its highest horsepower, 137, with the digital coolant gauge needle about halfway from cold to hot. When run moderately above or below halfway on the coolant temp gauge, or how a normal operator would ride the sled, peak horsepower ran between 134 and 136.
Shown here are the dyno results for the 4-TEC with the coolant needle on the digital gauge hovering slightly below 50%. Note the flatness of the horsepower curve or plateau. This is unlike the '08 SDI we dyno tested that could lose major horsepower and acceleration if it lost a few hundred revs due to snow conditions.
Also for those power junkies who are planning to mate this engine with a turbo or supercharger, we closely observed the fuel flow meter reading. This showed that the stock fuel pump should support close to 300 observed, not corrected, horsepower. So, targeting this engine for 200-250 corrected horsepower should be no problem for the stock fuel pump. There is a rev limiter at just above 8,500 rpm though.
One other test observation: the stock exhaust header is a three into one unit that tucks closely to the cylinder head, probably to enable it to clear the steering post in front of the engine. The shape of this header reminds me of the driver's side exhaust manifold on my first car, a '59 Ford 292. Perhaps some meaningful power can be added to this engine by creating a more fashionable equal length header/collector into either the stock muffler or a more free-breathing muffler. But noting the lean mixture of the stock EFI with the stock exhaust, adding airflow will likely require a Boondocker-like fuel tuning device to add fuel to maintain a safe A/F ratio. If boosting performance is your desire, there is plenty of room up front for turbochargers and intercoolers!
More info:
www.dynotechresearch.com